Advanced characterization of organic and hybrid materials

Resume : Charge transfers (CT) states play a key role in organic solar cells (OSC). In this presentation I shall demonstrate how we can use time-dependent photoluminescence measurements to identify the contributions of static and dynamic disorder in charge transfer states and their spectra. Notably, from the temperature and time dependent linewidths of absorption, fluorescence, and CT emission, we infer the static and dynamic contributions to the total disorder. We discuss the role of spectral diffusion in this process. The impact of intermolecular interactions and excited state delocalisation will also be addressed.

Resume : Thermally-induced degradation in bulk-heterojunction organic solar cells (OSCs) is an obvious barrier to the fabrication of stable devices. Thus, practical approaches and strategies need to be identified their inherent thermal instability. In this work, the thermally induced degradation of the most commonly used system PM6:Y6 is investigated by varying temperatures and different exposure conditions. The degradation pathways have been identified by applying several opto-electrical and spectroscopic characterizations methods. Due to the reduced charge carrier mobility and extraction probability, the thermally degraded device exhibits significant losses in the open-circuit voltage (VOC) and fill factor (FF). Furthermore, the field dependence of charge generation, charge extraction, photo-generated charge density, and charge recombination dynamics in solar cells were studied by the time-delayed collection field (TDCF) optical-pump electronic-probe technique. By using all the analyses, we can explain the significant recombination process that dominates device performance and thermal stability. Finally, device simulation by SETFOS of the current-voltage (J-V) characteristics was used to confirm experimentally determined thermally induced degradation.

Resume : Polymeric non-fullerene acceptors offer the potential to restrict the self-aggregation that is typical for small molecule non-fullerene acceptors, which potentially yields this fine structured morphology, but phase separation is seen to be restricted. To be able to understand this, we studied a blend of the donor polymer PBDB-T and the polymeric acceptor PF5-Y5 to investigate the molecular interactions in solution in a joint experimental-theoretical spectroscopy study. Solar cells prepared of this blend have reached power conversion efficiencies of over 14% (1). From absorption spectroscopy of the PBDB-T: PF5-Y5 blend solutions at increasing temperatures, combined with concentration-dependent fluorescence spectroscopy and excitation spectroscopy, we could conclude that in addition to temperature-induced disaggregation of both donor and acceptor polymers, donor-acceptor complexes are formed in dilute blend solutions of PBDB-T and PF5-Y5. The formation of the donor-acceptor complexes competes with the donor and acceptor self-aggregation and the solvent environment is found to influence these interactions. Our results show also that the donor-acceptor polymer complexes are stabilized in more polar solvents. The near IR-region of the absorption spectrum could be matched with the calculated electronic excitations of donor-acceptor complexes of PBDB-T and PF5-Y5 oligomers. These pre-formed donor-acceptor complexes in the solution can be expected to have important consequences on the resulting film morphology. These insights are also expected to direct the future design of compatible donor-acceptor polymer pairs for high-performance all-polymer solar cells. (1) Fan, Q.; et al., Energy Environ. Sci., 2020, 13, 5017.

Resume : Organic solar cells based on ternary active layers can lead to higher power conversion efficiencies than corresponding binaries, and improved stability. The parameter space for optimization of multicomponent systems is considerably more complex than that of binaries, due to both, a larger number of parameters (e.g., two relative compositions rather than one) and intricate morphology?property correlations. Most experimental reports to date reasonably limit themselves to a relatively narrow subset of compositions (e.g., the 1:1 donor/s:acceptor/s trajectory). This work advances a methodology that allows exploration of a large fraction of the ternary phase space employing only a few (< 10) samples. Each sample is produced by a designed sequential deposition of the constituent inks, and results in compositions gradients with ?10000 points/sample that cover about 15%?25% of the phase space, with the capability of modifying the covered zone with simple changes in deposition parameters. These effective ternary libraries are then colocally imaged by a combination of photovoltaic techniques (laser and Solar Simulator light photocurrent maps) and spectroscopic techniques (Raman, photoluminescence, absorption). The generality of the methodology is demonstrated by investigating multiple ternary systems, like PBDB-T:ITIC:PC70BM, PM6:Y6:PC70BM, and P3HT:O-IDFBR:O-IDTBR. Complex performance-structure landscapes through the ternary diagram as well as the emergence of several performance maxima are discovered.

Resume : One of the main challenges in the development of high power-conversion efficiency halide perovskite solar cells (PSCs) is the inevitable defect formation during the material processing. This involves the shallow and deep state within the material bandgap that trigger the carrier trapping/detrapping and non-radiative recombination processes, reducing energy conversion efficiency. This makes understanding the distribution of tapping states and their effect on charge dynamics in perovskite devices fundamentally important and carrying substantial relevance for optoelectronic applications. Although significant research efforts have been dedicated to explain these physical phenomena by the commonly used tools, limitations still remain, such as, the undetectable non-emissive traps and inaccuracy due to the low signal of trapped carriers. Herein, we report the first application of the continuous-wave and impulsive pump-push-photocurrent spectroscopies to observe in real time the dynamics of carrier trapping in lead-halide perovskite solar cells. We have investigated how the external factors (e.g., temperature and electric field) impact the photovoltaic performance in PSCs via the trapped carriers. In particular, besides the further insight into realistic operating conditions, the temperature dependent measurement allows us to observe the thermally assisted trapping/detrapping and determine the trap activation energy finally. Through the systematic experimental study, we have successfully correlated the device performance with the kinetics of trapped carriers proposing new design rules for stable PSCs with high performance parameters.

Resume : The dynamic response of metal halide perovskite devices shows a variety of physical responses that need to be understood and classified for enhancing the performance and stability and for identifying new physical behaviours that may lead to developing new applications. Beyond the well-established characteristics of regular impedance arcs, we address the appearance of inductor effect at high voltage in perovskite solar cell. The impedance spectra announce the type of hysteresis, either regular for capacitive response or inverted hysteresis for inductive response. We present a physical model in terms of delayed recombination current that explains the evolution of impedance spectra and the evolution of current-voltage curves.1,2 (1) Bisquert, J.; Guerrero, A.; Gonzales, C. Theory of Hysteresis in Halide Perovskites by Integration of the Equivalent Circuit, ACS Phys. Chem Au 2021, 1, 25-44. (2) Guerrero, A.; Bisquert, J.; Garcia-Belmonte, G. Impedance spectroscopy of metal halide perovskite solar cells from the perspective of equivalent circuits, Chemical Reviews 2021, 121, 14430?14484.

Resume : Large-area, low?cost and highly sensitive high energy radiation detectors are of great interest in the fields of medical diagnostics, dosimetry, industrial inspection, and security. State?of?the?art solid-state X? and gamma?ray detectors for large-area applications based on silicon (Si), amorphous selenium (a?Se), and cadmium zinc telluride (CdZnTe) are difficult to scale up, and have high operating voltage [1]. Recently, lead?halide perovskites emerged as an auspicious novel materials family for X? and gamma?ray detection thanks to strong absorption of ionizing radiation, high charge carrier mobilities, long exciton diffusion, long charge carrier lifetime, and excellent optical properties [2]. Perovskite can be deposited by solution at low temperature constituting a great alternative for the production of large-area low-cost sensors. X-ray Nanoanalysis uses focalized synchrotron radiation combined with techniques like X-ray fluorescence (XRF) and X-ray induced current (XBIC) to probe materials and devices at the nanoscale. Using a precise positioning system is possible to scan an area of interest obtaining a map with nanometer resolution. The ID16B beamline at the ESRF provides a nanobeam spot size on the sample down to 50nm x 50nm. The detectors and instrumentations available in the end station enable the user to perform several experimental techniques at the same time [3]. We used the nanofocused beam of the ID16B beamline at the ESRF to acquire simultaneously XRF and XBIC signals from novel perovskite thin-film X-ray detectors in order to study the relation between composition and electric transport at the nanoscale. In perovskite solar cells Phenyl-C61-butyric acid methyl ester (PCBM) is often used as electron transport layer and its good performance is associated with trap passivation [4]. Here we used 2-fold X-ray nanoanalysis to visualize the effect of PCBM on methylammonium lead iodide (MAPbI3) perovskite nanocrystals. The same Perovskite/PCBM blend is used for X-ray detection. The polymer permeates the nanocrystal layer passivating the surface traps enhancing the detection performances reaching a sensitivity as high as 2270 µC Gy?1 cm?2 under 40kV X-ray, at 4V bias [5]. The combination of the elemental distribution and XBIC signal allows to understand how PCBM passivates charge traps located at the grain boundaries improving the performances of the perovskite layer for ionizing radiation detection. In samples with only MAPI3 nanocrystals, we observed higher photocurrent along the grain boundaries than in the middle of the grains. The passivation of defects by PCBM increases the charge collection from the middle of the grain. The comparison of the XRF and XBIC signals shows a higher correlation between fluorescence intensity and current signal in the case of MAPbI3/PCBM blend than perovskite only devices.

Resume : In perovskite solar cells (PSCs), trap states are considered one of the main factors limiting the device performance (e.g., open-circuit voltage and short-circuit current) as they reduce the mobility of photogenerated carriers and cause trap-assisted recombination [1]. In such a case, trap passivation becomes a popular method to boost device performance, and reports show that passivating surface traps of perovskite become more effective than passivating their bulk traps. Material scientists attribute the better effect of surface passivation to the significant reduction of trap density in perovskites since the majority amount of traps state are considered located at the perovskite surface. We report a pump-push photocurrent spectroscopy study, which is able to trace the dynamics of trapped carriers using a delayed infrared push pulse to bring carriers from defect states to the conduction band. We found that the trapping time as well as recombination time for trapped states are dominant factors towards the device performance of PSCs[2]. Via investigating the lifetime of FAPI solar cells with and without surface passivation, we observed that carriers in surface traps recombine much faster than that in bulk traps, illustrating that surface defects have a much higher possibility to re-trap carriers generated under continuous light illumination. With such a clearer understanding of the trapped carrier dynamics, we anticipate our assay to be another starting point for material scientists to further improve existing PSC performance. [1] F. Gao, Y. Zhao, X. Zhang and J. You, Advanced Energy Materials, 2019, 10, 1902650. [2] A. Bakulin, A. Rao, V. Pavelyev, P. van Loosdrecht, M. Pshenichnikov, D. Niedzialek, J. Cornil, D. Beljonne and R. Friend, Science, 2012, 335, 1340-1344.

Resume : The class of benzothieno-benzothiophene (BTBT) type molecules are among the best performing active organic semiconductors in organic thin film transistors. Functionalization of this molecule by a phenyl group on one terminal end and a decyl group at the other end results in an asymmetric molecule (Ph-BTBT-10). This asymmetry induces specific thin film forming properties and unique crystallographic features substantially different from organic semiconducting molecules which have symmetrical shape. The first outstanding observation is related to the thin film formation starting from the first monolayer up to device relevant thin films. The equilibrium bulk structure is formed just within the first monolayer and a metastable phase is found at later growth stages. This sequence is reversed to frequently observed substrate-induced polymorphism. An explanation is based on kinetically driven cross-nucleation. [1] The second interesting observation is related to crystallographic defects within thin films. Crystallisation far from equilibrium, e.g. by crystallization from melt or gradient crystallization, causes systematic broadening of X-ray diffraction peaks. The sequence of peak broadening can be explained only in case of introducing crystal defects caused by inverted molecules incorporated into the crystal structure. [2] Healing of the defects is obtained by annealing of the films towards a phase transition into a liquid crystalline state. This process is observed irreversible. We report also on the utilization of the smectic E phase for obtaining highly ordered crystallographically thin films for transistor application. [3] Finally, device performance is reported on uniaxially oriented crystals prepared by blade coating. [4] [1] S. Hofer et al., J. Mater. Chem. C 125, 28039-28047 (2021). [2] S. Hofer, et al., Chem. Mater. 33, 1455?1461 (2021). [3] S. Hofer, et al., Liquid Crystals 48(13), 1888-1896 (2021). [4] A. Tamayo, et al., J. Mater. Chem. C 9(22), 7186 ? 7193 (2021).

Resume : Based on novel conjugated semiconducting polymers, organic solar cells are an interesting alternative to conventional silicon based solar cells as they feature new possibilities in fabrication and utilization. Using wet chemical processing, they can be manufactured with large-scale production methods such as roll-to-roll printing. They are light-weight and flexible, which offers novel ways for building integration of use in off-grid applications. However, in terms of large-scale usability, one of the major challenges for polymer-based organic solar cells is to overcome their relatively short lifetime, as compared to their inorganic counterparts. To gain a deeper understanding of organic solar cell degradation with respect to changes in the active layer morphology, we present operando studies during the first hours of operation. The studies reveal information on both, its evolving current-voltage characteristics and the changes of the active layer morphology in the organic solar cells. For that purpose, advanced x-ray scattering methods (GISAXS / GIWAXS measurements) and current-voltage (IV) tracking of the operating solar cell are performed simultaneously to gain fundamental understanding. Starting from an optimized morphology of the active layers in terms of highest device efficiencies, depending on the donor-acceptor system, different morphological degradation pathways are identified. Either a mixing or a demixing process can occur during degradation and cause changes of the active layer morphology. The altered morphology is less optimal for charge transport through the active layer due to poor percolation in a too fine morphology or a poor splitting of excitons in a too coarse morphology. Different examples for both degradation pathways will be discussed. Moreover, the impact of additives on device performance, stability and degradation pathway will be investigated. References [1] Schaffer, C. J.; Palumbiny, C. M.; Niedermeier, M. A.; Jendrzejewski, C.; Santoro, G.; Roth, S. V.; Müller-Buschbaum, P. A Direct Evidence of Morphological Degradation on a Nanometer Scale in Polymer Solar Cells. Adv. Mater. 2013, 25, 6760? 6764. [2] Wang, W.; Schaffer, C. J.; Song, L.; Körstgens, V.; Pröller, S.; Indari, E. D.; Wang, T.; Abdelsamie, A.; Bernstorff, S.; Müller-Buschbaum, P. In Operando Morphology Investigation of Inverted Bulk Heterojunction Organic Solar Cells by GISAXS. J. Mater. Chem. A 2015, 3, 8324? 8331. [3] Yang, D.; Löhrer, F. C.; Körstgens, V.; Schreiber, A.; Bernstorff, S.; Buriak, J. M.; Müller-Buschbaum, P. In-Operando Study of the Effects of Solvent Additives on the Stability of Organic Solar Cells Based on PTB7-Th:PC71BM. ACS Energy Lett. 2019, 4, 464? 470. [4] Yang, D.; Löhrer, F. C.; Körstgens, V.; Schreiber, A.; Cao, B.; Bernstorff, S.; Müller-Buschbaum, P. In Operando GISAXS and GIWAXS Stability Study of Organic Solar Cells Based on PffBT4T-2OD:PC71BM with and without Solvent Additive. Adv. Sci. 2020, 7, 2001117. [5] Wienhold, K. S.; Chen, W.; Yin, S.; Guo, R.; Schwartzkopf, M.; Roth, S. V.; Müller-Buschbaum, P. Following in Operando the Structure Evolution-Induced Degradation in Printed Organic Solar Cells with Nonfullerene Small Molecule Acceptor. Sol. RRL 2020, 4, 2000251.

Resume : We have employed x-ray grazing incidence diffraction (GIXD), x-ray specular reflectivity, and Vis reflection spectroscopy to follow phase transitions in spin-coated thin films of the high mobility organic semiconductor 5,11-Bis(triethyl silylethynyl) anthradithiophene (TES-ADT). The phase behavior of the films is studied both during aging in an ambient atmosphere and during thermal annealing. The as-deposited amorphous films progressively transform towards monoclinic and triclinic alpha phases on the time-scale of several days. Furthermore, using GIXD, we determine the temperature dependence of lattice parameters of the alpha phase and the structure of the high-temperature beta phase. Surprisingly we find that the transformation from the alpha to the beta phase takes place only for films thicker than approximately 70 nm at 130 degC. Instead, for layers thinner than this critical thickness the films become amorphous above the same transition temperature. We attribute the observed thickness hindered phase behavior to the interplay between the surface and the bulk energies of the competing phases. Additionally, the combination of x-ray scattering techniques and Vis spectroscopy allows us to show the two-step nucleation character of the alpha to the beta phase transition. Here, the beta phase nucleates from the intermediate amorphous phase.

Resume : Conjugated polymer blend, such as poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), play a vital role as blocking layers and electrodes in organic solar cells. Especially in combination with structural biomaterials, such as cellulose nanofibrils (CNF), novel applications in flexible devices become possible. Here, spray deposition, as a facile and scalable layer-by-layer (LbL) coating technique, has been successfully applied to fabricate tailored CNF films [1]. Their nanoscale structure and response to external stimuli as well as long-term stability is crucial for their application. Hence, we use a combination of grazing incidence neutron and x-ray scattering to elucidate the molecular and nanoscale structure of these novel hybrid materials and to correlate this with their optoelectronic functionality. To start with, we investigated the nanostructure of CNF films of varying thickness, observing a morphological gradient in length scales throughout the film thickness [1]. With neutrons being highly sensitive to water content and CNF being hygroscopic, we successfully investigated the response of different charged, ultrasmooth CNF films to cyclic humidity changes [1]. This allows for uniquely characterizing the nanoscale, hierarchical, nanoporous structure of these films. In a next step, we filled the existing voids with a semiconducting conjugated polymer blend, used in organic electronics and [2]; we characterized their performance under cyclic stability conditions of this novel conjugated-polymer-CNF-based electrode concerning conductivity under humidity changes. The resulting electronic changes were directly correlated to the reversible nanostructure changes. As a step toward tunable plasmonic sensors and plasmonic electrodes, we investigated the thermally induced band-gap tuning of silver-nanoparticle-CNF hybrids; here, the CNF template guides the synthesis the silver nanoparticles at the CNF interface [3]. [1] Brett, C. J. et al., Macromolecules 52, 4721?4728 (2019). [2] Brett, C. J. et al., ACS Appl. Mater. Interfaces 13, 27696?27704 (2021). [3] Brett, C. J., Adv. Electron. Mater. 7, 2100137 (2021).

Resume : Organic semiconductors (OSCs) are promising for thin-film transistor applications as they potentially offer distinctive advantages over their inorganic counterparts, particularly in terms of their properties, processing techniques and cost-effectiveness. Small molecules with extended aromatic core and solubilizing long chains are budding candidates for solution-processed organic semiconductors. However, as small molecular OSCs are held together by weak non-directional van der Waals force, they tend to exhibit many alternative packing arrangements with differences in structure and energy leading to polymorphism. The utilisation of solid surfaces (substrates) as a nucleation or crystallisation mediator was a strategy used to identify new thin-film phases. We could successfully demonstrate that defined innovations in the experimental protocol (like the choice of solvent, temperature etc.) can promote tuning between polymorphs as different local energy minima become accessible. Among the various OSCs, small molecules with[1]benzothieno [3,2-b]benzo thiophene (BTBT) cores are identified as the best p-type semiconductor. Here we investigated the crystal structure solution, film-forming and charge transport properties of FD44 (OEG BTBT), a BTBT derivative. Also, extensive investigations carried out by altering the experimental protocols employed in the fabrication of thin films at the vicinity of a substrate revealed four new thin-film phases. Specular and grazing incidence X-ray diffractions were performed using in-house X-ray equipment and synchrotron to determine the crystallographic structure within the thin films. Furthermore, our detailed investigations helped us in understanding the origin and stability of these new polymorphic forms and thereby gain control over the conditions that led to their formations. Controlling the polymorphism of OSCs within thin films is crucial because they form the active channel layer in most organic electronic devices, and dramatic variations in charge transport can be induced even by small changes in the molecular packing.

Resume : The film morphology in the active layer of non-fullerene acceptor organic solar cells is key to their high performance. Numerous studies of nanostructured donor-acceptor blend films by scanning probe microscopy techniques have resulted in surface topography images without resolving the actual distribution of donor and acceptor molecules. Scanning X-ray Transmission Microscopy (STXM) has been a valuable synchrotron-based technique that made it possible to image the composition of donor-acceptor blend films with resolutions below 50 nm. STXM imaging was particularly successful for polymer-fullerene blends, thanks to the distinct X-ray absorption resonance of the fullerene cage. Unlike fullerenes, the non-fullerene acceptors are more difficult to chemically distinguish from the donor polymers in the bulk heterojunction films. The AFM-IR technique combines the high resolution of scanning probe microscopy with the chemical fingerprint of infrared spectroscopy. I will demonstrate for some examples from organic photovoltaics that compositional variations in the non fullerene acceptor blend films can be mapped in great detail and with low beam damage. I will furthermore show examples where AFM-IR could reveal changes in metal halide perovskite films upon degradation in air. The results demonstrate the potential of AFM-IR as a high-resolution and non-destructive chemical analysis technique for emerging photovoltaic materials.

Resume : Semiconducting organic molecules are revolutionizing the electronics world by providing new and easily adjustable materials for various opto-electronic and bio-electronic applications [1]. Benefiting from recent developments, neurostimulating prosthetics to restore light sensitivity of degenerated retina will eventually be conceivable. The functionality of this concept has already been demonstrated using a small molecular squaraine dye (SQIB) as active material [2]. For such optoelectronic sensing, however, it is essential to acquire a fundamental understanding of the underlying processes and mechanisms such as the generation and nature of the molecular excitons [2, 3]. N-alkyl anilino squaraines have been shown to exhibit strong excitonic intermolecular interactions, without the SQIB-typical formation of a self-assembled crystalline micro- or nanotextured morphology [3, 4]. Molecular aggregates with short intermolecular distances combine short-range intermolecular charge transfer (ICT) interactions with Frenkel excitons providing a striking feature of these n-alkylated anilino squaraine dyes [4, 5]. Here, we investigate the structure-correlated excitonic properties in photoactive thin-film semiconductors for bio-optoelectronics using known non-chiral (nBSQ, nOSQ) and two new structurally related chiral anilino squaraines (nOCi-SQ, nCi-SQIB). Functionalisation with enantiomerically pure citronellyl-derived residues ensures the analogy to the corresponding n-alkylated compounds and additionally offers the investigation by Mueller matrix polarimetry [6] due to an emerging excitonic chiral dichroism (CD) [7]. This allows a systematic and fundamental study of the structure and chirality correlated excitonic properties approaching a quantitative understanding of excitation pathways. [1] Irimia-Vladu, Glowacki, Sariciftci, Bauer (editors): Green Materials for Electronics, Wiley-VCH, ISBN 9783527692958 (2017). [2] Abdullaeva, Balzer, Schulz, Parisi, Lützen, Dedek, Schiek. Adv. Funct. Mater. 29 (2019) 1805177. [3] Balzer, Abdullaeva, Maderitsch, Schulz, Lützen, Schiek. Phys. Status Solidi B 257 (2020) 1900570. [4] Zablocki, Schulz, Schnakenburg, Beverina, Warzanowski, Revelli, Grüninger, Balzer, Meerholz, Lützen, Schiek. J. Phys. Chem. C 124 (2020) 22721?22732. [5] Hestand, Zheng, Penmetcha, Cona, Cody, Spano, Collison. J. Phys. Chem. C 119 (2015) 18964?18974. [6] Arteaga, Ossikovsky. J. Opt. Soc. Am. A 36 (2019) 416-427. [7] Balzer, Schumacher, Matiello, Schulz, Zablocki, Schmidtmann, Meerholz, Sariciftci, Beverina, Lützen, Schiek. Isr. J. Chem. doi: 10.1002/ijch.202100079.

Resume : Organic semiconductors are an interesting materials family for number of technologies including solar cells, LEDs, transistors and sensors. The fundamental premise of organic semiconductors is that synthetic chemists can generate materials with properties “on demand”. Unfortunately, even if this became a reality, we would not know what to order! Indeed, while organic semiconductors have been around for a while, the preeminent role of the microstructure in governing their properties is far from understood. In this seminar, I will emphasize the role played by structure at different length-scales and how charge transport is a complex multi-scale phenomenon. We use charge-modulated IR spectroscopy to measure the delocalization of charges in crystallites. Correlating carrier mobility to charge delocalization highlights the importance of mesoscale film properties, such as the connectivity of aggregates by tie-chains. As a result, we study the mesoscale organization of polymers using new techniques in the transmission electron microscope and complementary X-ray diffraction measurements at the synchrotron. By combining these techniques we are able to study the microstructure across a range of length-scales in real space and reciprocal space. Microstructural analysis at these lengthscales coupled with charge transport theory allows to better understand the role of defects. Thus, such multiscale stu

Resume : Obtaining accurate thermal conductivity measurements is challenging for any material, but particularly where the amount of material is small or its thermal conductivity is low. Thermal conductivity measurements are therefore not straightforward for thin films of organic and hybrid thermoelectric materials. In this presentation I will present our work on pseudo-steady state 3-? measurements of thermal (and thermoelectric) properties of doped polymer [1] and halide perovskite films [2-4]. I will demonstrate the ability of the technique to detect changes in thermal conductivity due to doping-induced morphology changes in polymers [1], electronic contributions to thermal conductivity [3] and phase changes [4]. I will also show how the technique can be applied to thin films with anisotropic in-plane thermal conductivity [1]. Many models of thin film thermal conductivity measurement neglect the effect of nanoscale topography on the measurement. I will present computational and experimental data quantifying the effect of topography on extracted values of thermal conductivity, and will identify regimes where we can have confidence in our results and regimes where we would need to apply correction factors. [1] High thermal conductivity states and enhanced figure of merit in aligned polymer thermoelectric materials. T. Degousée et al., J. Mater. Chem. A, 9 (29), 16065-16075, 2021. [2] Substitutional doping of hybrid organic-inorganic perovskite crystals for thermoelectrics. W. Tang et al., J. Mater. Chem. A, 8 (27), 13594-13599, 2020. [3] Enhanced control of self-doping in halide perovskites for improved thermoelectric performance. T. Liu et al., Nat. Commun., 10 (1), 5750, 2019. [4] Unusual Thermal Boundary Resistance in Halide Perovskites: A Way To Tune Ultralow Thermal Conductivity for Thermoelectrics. T. Liu et al. ACS Appl. Mater. & Interfaces, 11 (50), 47507-47515, 2019.

Resume : The thermoelectric properties of polymer semiconductors vary significantly with the structural order and carrier concentration. Within this context, mixing a given polymer semiconductor with a guest material is of significant interest as it opens new pathways to fine-tune the structural order, morphology, and even the energy landscape. In this work, we present a combinatorial study of the thermoelectric properties of mixtures of various guest materials with the host workhorse polymer poly[2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene] (PBTTT). By varying the composition and employing thickness gradients, we effectively characterize nearly 200 samples thanks to locally resolved measurements. We find that mixtures of PBTTT with 10 wt% - 15 wt% of poly(3-hexylthiophene-2,5-diyl) (P3HT) as the guest material have up to a 5-fold higher power factor compared to pure PBTTT, leading to zT values around 0.1. Then, through spectroscopic analysis of the charge-transfer species, structural characterization using GIWAXS and AFM, and Monte Carlo simulations, we find that our results are due to P3HT promoting long-range electrical connectivity and low disorder while both materials also share similar HOMO levels, ensuring electronic connectivity.

Resume : Thermoelectric (TE) generators are considered a promising technique for heat waste recovery as they enable a direct conversion of a temperature gradient into electrical power. Especially polymer based organic thermoelectric materials are very advantageous, offering a wide range of applications as these materials allow a large scale, low-cost solution based processability of low or non-toxic, lightweight, and flexible TE devices. The blend poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) is a p-type semiconductor, which gained high interest as TE material. In recent years, research was focusing on the further improvement of TE properties of PEDOT:PSS with different treatment approaches like addition of surfactants, high-boiling-point solvents, acids and bases or inorganic salts. Very promising is the post-treatment of PEDOT:PSS thin films with ionic liquids (ILs), as two important TE parameters, Seebeck coefficient (S) and electric conductivity (?), can be increased simultaneously. To understand the respective underlying effects, we post-treated PEDOT:PSS thin films with three different ILs in varying concentrations and investigated the film properties with diverse techniques. With UV-Vis spectroscopy, we were able to directly correlate the increase in S with a change in the doping level of the PEDOT chains. While the increase in ? is mainly caused by a morphological rearrangement towards an optimized PEDOT domain distribution, which we demonstrated by performing grazing incidence small angle X-ray scattering (GISAXS) and conductive atomic force microscopy (c-AFM) [1]. However, to make these PEDOT:PSS thin films usable in future commercial TE devices it is indispensable to also investigate the performance of these materials for their long-term stability under different ambient conditions, like elevated temperature or increased humidity. Therefore, we performed in-situ GISAXS measurements using a custom-built chamber in which we can heat the ILs post-treated thin films to different temperatures or expose them to a certain humidity, while simultaneously measuring the thin film conductivity. With these in-situ GISAXS investigations and combined with additional measurement techniques like for example in-situ UV-Vis, we are able to investigate the morphology and doping level evolution during operation of thermoelectric PEDOT:PSS thin films under different ambient conditions [2]. These studies give an important insight and understanding of the impact that the operation environment will have for future PEDOT:PSS based TE devices in terms of long term stability. References [1] A. L. Oechsle, J. E. Heger, N. Li, S. Yin, S. Bernstorff, P. Müller-Buschbaum, Macromol. Rapid Commun. 2021, 42, 2100397. [2] A. L. Oechsle, J. E. Heger, N. Li, S. Yin, S. Bernstorff, P. Müller-Buschbaum, to be published

Resume : 2D layered hybrid perovskites have recently attracted an increasing interest as active layers in LEDs and UV-Vis photodetectors. 2D perovskites crystallize in a natural self-assembled quantum well-like structure and possess several interesting features among which low-temperature (< 100 °C) synthesis and low defect density. We present in this work solid-state ionizing radiation direct detectors based on the 2D layered hybrid perovskite PEA2PbBr4 (PEA = C6H5C2H4NH3+) deposited from solution using scalable techniques and directly integrated onto a pre-patterned flexible substrate in the form of micro-crystalline films displaying crystal-like behaviour, as evidenced by the ultra-fast (sub-microsecond) and good detection performances under UV light. The effective detection of X-Rays (up to 150 kVp) is demonstrated with Sensitivity values up to 806 ?C Gy-1 cm-2 and a Limit of Detection (LoD) of 42 ± 4 nGy s-1, thus combining the excellent performance for two of the most relevant figures of merit for solid-state detectors. Additionally, the tested devices exhibit exceptionally stable response under constant irradiation and bias, assessing the material robustness and the intimate electrical contact with the bottom electrodes. PEA2PbBr4 micro-crystalline films directly grown on flexible pre-patterned substrate open the way for large-area solid-state detectors working at low radiation flux for ultra-fast X-Ray imaging and dosimetry.

Resume : The properties of a novel P3HT:PC71BM:SnO2-nanoparticles (NPs) composite, used as potential absorber for Organic Photovoltaic Cells (OPCs), were investigated. The structural, morphological and optical characterizations of this composite demonstrated an enhancement of the ITO/PEDOT:PSS/P3HT:PC71BM:SnO2-NPs/LiF/Al ternary structure when compared to the ITO/PEDOT:PSS/P3HT:PC71BM/LiF/Al binary one. This behavior is due, on one hand to the fact that SnO2-NPs behave as a secondary non-fullerene acceptor, and on the other hand to the superior electrical conductivity of the SnO2-NPs, very well dispersed in the polymeric blend as compared to other nanostructured inorganic materials. These properties led to a better photogeneration and transport of charge carriers, decreasing the series resistance, increasing the fill factor, and consequently the cell?s efficiency, too. The incorporation of nanoparticles into ternary OPCs could represent a way to enhance their performances by improving the photogeneration of charge carriers, as well as their transport and collection to the electrodes. Keywords: Conductive polymers; Fullerene derivatives; Tin dioxide nanoparticles (SnO2-NPs); Organic photovoltaic cells (OPCs). Acknowledgements: This research was supported by the "Executive Unit for Financing Higher Education, Research, Development and Innovation" ? UEFISCDI (Romania) through the grants: 115/2020 (PN-III-P1-1.1-TE-2019-0868), 25/2020 (PN-III-P1-1.1-TE-2019-0846), 195/2020 (PN-III-P1-1.1-PD-2019-0466), and 40PCCDI/2018.

Resume : High-performing organic materials are required for efficient opto-, bioelectronic and thermoelectric applications. Among these materials, (semi-)conducting polymers are particularly appealing for these technologies, as they benefit from unique optoelectronic properties, low-cost production and their solution processability make them fully compatible with large-scale deposition methods. The most common way to reach high electrical conductivities with this class of materials is to dope the polymers through the addition of a heterogeneous doping entities to the system. With the goal to produce highly-performing materials, huge efforts have been provided by the scientific community, notably through molecular design adjustments of these active materials. A current strategy towards this end is the planification and the rigidification of the polymer backbone, leading to a higher degree of order through a favorable molecular packing while decreasing the energetic disorder. This is the case, for example, for poly(p-phenylene vinylene) derivatives that benefit from both carbon-carbon double bonds between polymer units and intramolecular hydrogen bonds. Another way of enhancing the performances of (semi)conducting polymers is to increase the microscopic order and then the crystallinity of the polymeric assembly by adjusting the processing of deposition. One way to do so is to use Langmuir-Schaefer (LS) technique that relies on the assembly of the polymer chains at the air/water interface when compressed between two moving barriers. The assembled film composed by a monolayer of polymers with a low degree of defect is then transferred onto a substrate integrating electrodes to make a fully functional device. Here we report on LS films that are highly ordered and oriented at the monolayer limit. This describes a microscopic structure that is optimized for the transport of charges with strong anisotropic properties of electron conduction. Through a systematic analysis including scanning probe microscopy, optical spectroscopy, GIWAXS, NEXAFS and electrical measurements, we characterized the system in terms of structure, packing, energetics, and thermoelectric properties. We further optimized the electrical performances of the film when doping it with different molecular entities through secondary doping mechanisms, reaching n-type conductivities up to 4 S cm-1, and a power factor of 1.5 µW m-1 K-2. Finally, we integrated this system as active material in organic electrochemical transistors (OECT) to study the penetration of ions within this structured thin-film.

Resume : Control over the conformation of conjugated polymers using nucleic acids (NAs) as templates can be very advantageous in inducing unique and readily controllable properties. Complexation of NAs with conjugated polyelectrolytes such as cationic polythiophenes (CPT) is facilitated by the presence of charged side groups on the backbone.[1] Previous studies on the biosensing ability of a certain CPT has revealed a tremendous impact of the ssDNA sequence on the conformational and optical response of the polymer.[2] The complex formed of CPT and oligocytosine (dC20) strands is especially noteworthy due to the formation of highly ordered and extended chains due to ?-stacking between the cytosine bases and thiophene rings, further stabilized by ?-stacking with the imidazole side chain.[3,4] This stands in contrast to the complex with oligoadenosine (dA20), where ?-stacking between the bases limits any stacking interactions with the polymer resulting in a flexible and torsionally disordered conformation. Interestingly, though, our previous ultrafast transient absorption (TA) work showed that both complexes showed only excitonic behavior, with similar and much faster decay dynamics compared to the polymer alone, which forms interchain aggregates.[4] Therefore, we used TRIR to directly probe the role of NA templating in the excited state species formed in the two complexes responsible for the faster dynamics observed with vis-nIR probes, as well as compare the photophysics of loosely bound complexes with the more rigid and ordered systems. We find that with excitation of the polymer in the visible (532 nm) both complexes form the P0 intrachain polaron evidenced by a broad absorption background that decays faster than the delocalized polaron DP1 formed in the case of CPT alone. The lower intensity of the P0 absorption in the CPT/dA20 case is consistent with increased intrachain disorder, while higher interchain long range order leads to the higher DP1 absorption.[5] The rigid complex formed in the case of CPT/dC20 limits the geometric relaxation observed in the C=C stretch Fano antiresonance, in agreement with our previous work.[4] Excitation in the UV (266 nm) shows that a charge transfer complex is formed between CPT and dC20 with the observation of the cytosine anion and a broad absorption background, in contrast to CPT/dA20 case, where the TRIR spectra solely reflect the excited state behavior of the oligoadenosine. These results show that non-covalent interactions between NAs and CPTs can determine the excited state species formed, which has implications to the applicability of these complexes in molecular electronics. 1. Rubio-Magnieto, J. et al, Soft Matter 2015, 11, 6460?6471. 2. Duan, X. R. et al, Acc. Chem. Res. 2010, 43, 260?270. 3. Charlebois, I. et al, Macromol. Biosci. 2013, 13, 717?722. 4. Peterhans, L. et al, Chem. Mater. 2020, 32, 7347?7362. 5. Pochas, C. M.; Spano, F. C. J. Chem. Phys. 2014, 140, 244902.

Resume : Photoactive organic semiconductors are envisioned as a novel class of materials able to transduce light into stimulating signals inside biological cells or tissue [1]. The direct interface between the semiconductor and the electrolyte gives rise to different, competing electrochemical phenomena such as the photofaradaic or the photocapacitive processes, depending whether the photogenerated charges get involved in redox processes or accumulate at an interface. A detailed understanding of such chemical and photo-induced interactions is necessary to develop and optimize future devices. We addressed the problem in organic photoelectrodes considering both polymeric single-layer and organic molecular p/n junction thin-films [2]. Both are material systems that have been recently demonstrated to achieve the photomodulation of cardiac regeneration processes [3] or retinal neurons response [4]. By spectroscopic photovoltage and photocurrent measurements we gain insight into the energetics of the involved processes, while performing transient measurement we are able to identify the kinetics of light stimulated charge transfer processes. By combining these techniques with impedance spectroscopy, electric modelling and kinetic modelling, we identify the role of interfacial energy levels in the photoactivated processes and distinguish photocapacitive and photofaradaic contributions. The findings are further combined with nanoscale morphological investigations and Kelvin-Probe Force Microscopy leading to a quantitative interfacial energy diagram. We highlight how the energy diagram enables a comprehensive understanding of the photoelectrochemical reaction pathways and how the findings can be translated to predict the response of novel materials and devices, such as transducers based on floating semiconducting nanoparticles. [1] J. Hopkins, L. Travaglini, A. Lauto, T. Cramer, B. Fraboni, J. Seidel, and D. Mawad, ?Photoactive Organic Substrates for Cell Stimulation: Progress and Perspectives,? Adv. Mater. Technol., vol. 4, no. 5, pp. 1?10, 2019. [2] T. Paltrinieri, L. Bondi, V. ?erek, B. Fraboni, E. D. G?owacki, and T. Cramer, ?Understanding Photocapacitive and Photofaradaic Processes in Organic Semiconductor Photoelectrodes for Optobioelectronics,? Adv. Funct. Mater., vol. 2010116, 2021. [3] F. Lodola, V. Rosti, G. Tullii, A. Desii, L. Tapella, P. Catarsi, D. Lim, F. Moccia, and M. R. Antognazza, ?Conjugated polymers optically regulate the fate of endothelial colony-forming cells,? Sci. Adv., vol. 5, no. 9, 2019. [4] D. Rand, M. Jake?ová, G. Lubin, I. V?brait?, M. David-Pur, et al., ?Direct Electrical Neurostimulation with Organic Pigment Photocapacitors,? Adv. Mater., vol. 30, no. 25, pp. 1?11, 2018.

Resume : Historically, acoustic waves were first generated by piezoelectric materials [1]. To increase the spatial resolution of these waves, it is necessary to increase their frequency. Whereas the frequency of the acoustic waves generated by piezoelectric transducers is still limited to a few hundreds of MHz [2], this frequency can extend up to several hundreds of GHz for acoustic waves generated by femtosecond lasers [3]. That means that the sample thickness can be typically evaluated from a few microns to several millimeters with high-frequency transducers and from a few nanometers to several microns with picosecond ultrasonics that is based on femtosecond lasers. In this presentation, we will see how the embedded technology in Neta?s system opens high resolution mapping or massive data acquisition. Indeed, as a measurement only needs less than one second, a mapping can be considered. This significantly improves the speed of acquisition and leads to much more data for control itself or potential online inspection. After illustrating how the thickness of a layer can be evaluated, this presentation will focus on another possibility offered by Neta?s system: to determine the acoustic velocity in the material. Two practical applications will then be detailed: a multilayer W-TiN-SiO2 typical from MOS devices and a multilayer SiOx-SiNx typical from display components. [1] J. Bok and C Kounelis: "Paul Langevin (1872-1946)" Europhysics News 38.1, pp. 19-21, 2007. [2] Chen, Dongdong, et al. "Recent Development and Perspectives of Optimization Design Methods for Piezoelectric Ultrasonic Transducers." Micromachines 12.7, p. 779, 2021. [3] Pupeikis, Justinas, et al. "Picosecond ultrasonics with a free-running dual-comb laser." Optics Express 29.22, p. 35735-35754, 2021.

Resume : The p-doping of organic semiconductors (OSC), that is conjugated organic molecules (COMs) and polymers (COPs), is generally done by using strong molecular acceptors as dopants. In principle, high doping efficiency is achieved with dopants of high electron affinity (EA) to promote electron transfer between COP/COM and the p-dopant. This leads to an increase in mobile charges (holes) in the COP/COM, which translates into an increase in conductivity. However, molecular p-doping of COMs/COPs with high ionization energy (IE) is a challenge as it requires p-dopants of similar EA. Common dopants of high EA (> 5 eV) are typically light-weight, unstable, show low solubility in common solvents with most COPs/COMs, and tend to diffuse through the semiconductor host. Furthermore, their planarity can lead to the formation of ground-state charge transfer complexes (CPXs) with the COPs/COMs, which is detrimental to the doping efficiency. Recently, a new generation of dopants has been introduced based on a cyclopropane core such as hexacyano-trimethylene-cyclopropane (CN6-CP) of high EA (5.87 eV) which is, however, highly unstable in air, and solvents and therefore largely unsuitable for practical applications. An analogue of CN6-CP, trimethyl 2,2?,2?-(cyclopropane-1,2,3-triylidene)-tris(cyanoacetate) (TMCN3-CP), has high EA (5.5 eV) and is suitable for solution processing techniques, but turned out to be unstable even under inert atmosphere. Here, we introduce a novel dopant 2,2',2''-(cyclopropane-1,2,3-triylidene)tris(2-(perfluorophenyl)acetonitrile) (3PFP3CN-CP) in which three of the nitrile groups of CN6-CP have been replaced by pentafluorophenyl groups. This dopant has an EA of 5.07 eV (determined by cyclic voltammetry) and a bulky, non-planar 3D structure which is poised to inhibit CPX formation with organic semiconductors. In aging experiments we have observed a remarkable stability of this dopant under inert atmosphere and first doping experiments juxtaposing the doping of poly- and oligothiophene evidence IPA for the former and the suppression of CPX formation for the latter, which occurs with planar dopants such as tetracyanoquinodimethane (TCNQ).

Resume : Understanding the impacts of weak electronic interaction on the electron delocalization is required to discuss the rich functionalities of organic molecular materials. Moreover, effects of the strong coupling of phonon (collective lattice vibration) and/or local molecular vibration to the electron must be unveiled. Angle-resolved UPS (ARUPS) is known to be a powerful technique to study the electronic structure. The HOMO-band features can offer a wide variety of key information, that is essential to comprehend charge-hopping transport (small-polaron related transport) [1] as well as to coherent band transport in the molecular single crystal [2,3]. However, the experimental study of fine features in the HOMO state has not been progressed till recently due to difficulty in the sample preparation, damages upon irradiation, and so on [4,5]. We present recent findings regarding on the precise measurements of the electronic structure of rubrene (C42H28) single crystals by using synchrotron-light based, high-resolution ARUPS. We describe the characteristic electronic structure of rubrene that 1) the UPS HOMO bands show a clear linear dichroism for bonding and anti-bonding HOMO, 2) a band-unfolding behavior as for intrinsic spectral function of HOMO, and 3) polaron-like quasiparticle effects on the electronic structure. The precise experiments of the 2D momentum scan in the ARUPS would provide a perspective of designing the organic semiconductor devices in non-trivial way. References [1] S. Kera, H. Yamane. N. Ueno, Prog. Surf. Sci. 84 (2009) 135-154. [2] N. Ueno and S. Kera, Prog. Surf. Sci. 83 (2009) 490-557. [3] Y. Nakayama, S. Kera, and N. Ueno, J. Mater. Chem. C 8 (2020) 9090-9132. [4] S. Machida, et al. Phys Rev. Lett. 104 (2010) 156401. [5] F. Bussolotti, et al., Nat. Comm. 8 (2017) 173.

Resume : Abstract Title : Operando XPS Investigation of Chemical State and Electronic Structure of MoTe2 Field-effect-transistor Depending on Channel Charge Accumulation Transition metal dichalcogenide field-effect transistors (TMD-FETs) could be one of next-generation transistors because they have novel material properties including high on-off ratio above 106, subthreshold swing of 140 mV/dec, Hall mobility around 10 cm2/Vs,1 and tunable bandgap depending on the number of layers. Among TMDs, MoTe2 is mainly studied to application for FETs and photodetectors because the minimal difference between band gaps of bulk and monolayer MoTe22, which is suitable for the FETs having high current on/off ratio3. Operando analysis enables to investigate the operation mechanism of devices from a material point of view under operating condition. In general, doping level and electronic structure of FET channel have been known to critically depend on the position of Fermi energy level (EF). In this presentation, we will introduce operando X-ray photoelectron spectroscopy (XPS) system including transistor probe stage and special sample holder built in ULVAC-PHI XPS system. Using the operando XPS, the chemical information and the electronic structure at the surface/interface of MoTe2-FET under device operation will be discussed. 1. N. R. Pradhan, D. Rhodes, S. Feng, Y. Xin, S. Memaran, B.-H. Moon, H. Terrones, M. Terrones and L. Balicas, ACS nano, 2014, 8, 5911-5920. 2. I. G. Lezama, A. Arora, A. Ubaldini, C. Barreteau, E. Giannini, M. Potemski and A. F. Morpurgo, Nano Lett., 2015, 15, 2336-2342. 3. H. Huang, J. Wang, W. Hu, L. Liao, P. Wang, X. Wang, F. Gong, Y. Chen, G. Wu and W. Luo, Nanotechnology, 2016, 27, 445201.

Resume : In the last decade organic semiconductors have demonstrated to be excellent candidates for the development of a new class of X-Ray detectors able to fulfill important emerging requirements such as the mechanical flexibility, the possibility to cover large and curved surfaces, low-cost, and the possibility to operate at low-bias. Moreover, they are the only material platform that can offer human tissue equivalence, i.e. due to their chemical composition (i.e. low-Z elements) organic materials have radiation absorption comparable to that of human organs and tissues. This is a highly desirable property for a dosimeter to be employed in the medical field because it eliminates complex calibration procedures and the perturbation of the radiation beam when the detector is placed between the radiation source and the patient. On the other hand, the low-Z elements provide a poor absorption of high energy photons, limiting the efficiency of these detectors. To tackle this issue, one of the most effective strategies is based on the deep comprehension and enhancement of their detection mechanism based on a photoconductive gain effect (PG) [1], [2]. This effect is mediated by electrically active trap states which induce an inner amplification of the photocurrent generated by the absorption of high energy photons. Thus, a deep study of the trap states, both for minority and majority carriers in the organic thin film-based devices, permits tuning the PG and boosting the sensitivity of the detectors. The presence of traps in organic semiconductors has a profound impact on the performance of electronic devices. Their characterization, however, is still not trivial [3]. Here we present a new technique called Photocurrent Spectroscopy Optical Quenching to investigate the electrically active traps in organic-based devices for the detection of ionizing radiation. For this purpose, we employed flexible organic field effect transistors based on TIPS-Pn and TIPGe-Pn thin films. We deposited the organic semiconductors from solution by Pneumatic Nozzle Printing, [4] which allowed us to deposit organic thin films in a fully controlled way and to obtain very uniform and well-packed and aligned microcrystalline structures. Exploiting these devices, we investigated the origin of the active trap states ruling the photoconductive gain mechanism in tissue-equivalent, printed organic X-Ray detectors by Photocurrent Spectroscopy Optical Quenching experiments shining the devices with visible light at specific wavelengths during the X-Ray irradiation tests. Due to the interference of two distinct photoconductive gain mechanisms (i.e. one induced by visible photons, and the other by high energy photons) these measurements allow us to identify the excitonic states responsible for the activation of the X-Ray induced PG and to justify the different detecting performances achieved with different organic molecules. References [1] L. Basiricò, et al., Nat. Commun., vol. 7, no. 1, p. 13063, Dec. 2016, doi: 10.1038/ncomms13063. [2] I. Temiño et al., Nat. Commun., vol. 11, no. 1, pp. 1?10, 2020, doi: 10.1038/s41467-020-15974-7. [3] H. F. Haneef, et al., J. Mater. Chem. C, vol. 8, p. 759, 2020, doi: 0.1039/c9tc05695e. [4] S. Yang, et al., Adv. Electron. Mater., vol. 4, no. 6, pp. 4?9, 2018, doi: 0.1002/aelm.201700534.

Resume : Authoring tools based on data-driven sciences is a hot research topic for researchers of big chemical data. However, several challenges prevent advancement in data-driven materials science, such as data integrity, experimental and computational data integration, data standardization, and the gap between academic efforts and industrial interests. In material science, materials data is derived from big data sources that are too complicated for common human reasoning and materials applications. Hence, there is a vital need to develop simulation and authoring tools to meet the challenges of raw big chemical data. This paper proposes a material relationship analysis-based authoring system for high-performance properties material discovery. The relationship analysis system recommends high-performance index material data based on correlation analysis. Correlation analysis is used to find the relationship between material data features of components, processes conditions, and performance index properties. A web-based relationship analysis authoring tool was developed to evaluate the proposed relationship analysis mechanism for material discovery. Data visualization mechanisms of the developed authoring and analysis system are used to visualize the output of relationship analysis using data tables and heatmaps-based correlation analysis. Furthermore, the data table-based relationship analysis results are used to recommend high-performance properties-based material discovery. The material discovery results depict that the proposed relationship analysis system will fill the research gaps of screening and accelerating new stable materials.

Resume : Doping of polymer semiconductors is a central topic in plastic electronics and especially in the design of new better performing thermoelectric materials. Sequential doping of highly ordered polymer semiconductors is widely used to tune the charge carrier density that determines the thermoelectric properties. Various studies have demonstrated that dopant molecules intercalate into the layers of side chains in the crystals of polymer semiconductors.(1-3) It is therefore essential to clarify the way dopants are incorporated into the crystal lattice of the pristine polymer and how this is related to the dopant size and electron affinity. A combination of electron diffraction and polarized UV-vis-NIR spectroscopy on highly oriented P3HT and PBTTT thin films allows to quantify the amount of intercalated dopant molecules as well as the molecular orientation of dopants such as F4TCNQ, F6TCNNQ with respect to the polymer chains. A mapping of the orientational distribution of dopant molecules in the polymer crystal can thus be obtained. In the case of P3HT/F6TCNNQ, modeling of the diffraction patterns of doped crystals identifies the stoichiometry of the doped polymer phase and confirms the dopant orientation obtained from spectroscopy measurements as well as the lattice parameter variation induced by intercalation. In the case of Magic blue, Rutherford Backscattering is used to quantify the dopant amount in the films, Polarized UV-vis-NIR helps determine the diffusion coefficients of the dopant into the P3HT matrix whereas TEM demonstrates preferential location of MB in the amorphous phase of P3HT. It is demonstrated that the highest charge conductivities (up to 3000 S/cm) are observed in oriented P3HT films when the amorphous phase of P3HT is selectively doped with MB. References. (1) Untilova, V.; Biskup, T.; Biniek, L.; Vijayakumar, V.; Brinkmann, M. Control of Chain Alignment and Crystallization Helps Enhance Charge Conductivities and Thermoelectric Power Factors in Sequentially Doped P3HT:F4TCNQ Films. Macromolecules 2020, 53 (7), 2441?2453. (2) V. Untilova, H. Zeng, P. Durand, P. Allgayer, L. Herrmann, N. Leclerc and M.Brinkmann. Intercalation and ordering of F6TCNNQ and F4TCNQ dopants in regioregular poly(3-hexylthiophene) crystals: impact on anisotropic thermoelectric properties of oriented thin films Macromolecules 2021, 54, 13, 6073-6084. (3) Vijayakumar, V.; Zhong, Y.; Untilova, V.; Bahri, M.; Herrmann, L.; Biniek, L.; Leclerc, N.; Brinkmann, M. Bringing Conducting Polymers to High Order: Toward Conductivities

Resume : Hybrid organic-inorganic halide perovskites (OIHPs) are a class of direct band gap semiconductors with attractive optoelectronic and material processing characteristics for use as an absorber material in next-generation photovoltaics. OIHP based solar cells already exhibit power conversion efficiencies comparable to crystalline silicon cells and potential for high performance tandem devices through band-gap tuneability and solution-based processing. Thus far, a major limiting factor for the widespread commercial breakthrough of this technology has been the limited operational stability. A contributing factor to performance losses during photovoltaic operation is charge redistribution effects, such as the migration of mobile ions, which can facilitate local phase changes in the OIHP active layer. These charge redistribution effects can be further promoted by the film microstructure, which in case of the typical polycrystalline film morphology of OIHP films is dominated by defect-rich grain boundaries. The resulting interplay between the film morphology and charge redistribution effects occurs over typical length scales of tens of nanometres, thus demanding advanced characterization techniques to study the connection between local charge imbalance and subsequent material instability under operational conditions. Herein, we employed advanced (time-resolved) electrical modes of scanning probe microscopy (SPM) to probe early-stage degradation in triple-cation mixed-halide OIHPs. Using the SPM platform under controlled inert environment, we were able to induce localised electrical bias stresses simulating photovoltaic operation and subsequently probe the system response with high spatial resolution. We observed the formation of nanometric sized grain structures at the film surface, which displayed a variety of coverage densities and spatial distributions depending on the bias and photoexcitation conditions employed. We link the emergence of such nanograin structures to a localised charge build-up at the film grain boundaries, which in turn facilitates the local perovskite phase decomposition, leaving behind lead halide nanostructures. These findings establish a direct link between charge redistribution effects (contributed by ion migration) and local phase decomposition. We propose the use of novel strategies for inhibiting charge accumulation effects at grain boundaries in order to prevent the initiation of these operational degradation pathways.

Resume : Advanced microscopy characterization methods have been widely utilized to characterize inorganic materials such as semiconductors. However, it is important to adapt these tools for soft materials to gain structural information required for novel cutting-edge technologies. We report on advanced microscopic techniques such as atomic force microscopy (AFM), He-Ion microscopy (HIM), scanning electron microscopy (SEM) and focused ion beam (FIB) 3D reconstructions methods for optimum characterization of soft materials. In particular, we adapted electron microscopy techniques at low operating voltages to avoid structural degradation. HIM was optimised for operation with charge compensation. AFM techniques were adapted to probe topographical features of very smooth and highly rough surfaces of soft materials (rough-mean-square values up to 0.5 µm). Furthermore, we demonstrate how FIB can be used to model structural density of fibrous materials and derive quantifiable data such as pore density and tortuosity (or the expected flow path through the pores) using simple methodologies using open-source software. Sample preparation for these microscopic techniques is also detailed. We focus on polymeric materials such as polymethyl methacrylate (PMMA), biopolymer materials such as lignin and chitosan and natural materials such as wood (pine, beach, oak, walnut, eucalyptus). The development of the advanced microscopic techniques for soft materials will open up new avenues for research possibilities and novel applications [1]. [1] I. E. McCarroll, P. A. J. Bagot, A. Devaraj, D. E. Perea, and J. M. Cairney, ?New frontiers in atom probe tomography: a review of research enabled by cryo and/or vacuum transfer systems,? Mater. Today Adv., vol. 7, p. 100090, Sep. 2020, doi: 10.1016/J.MTADV.2020.100090.