Halide Perovskites for photonic applications: stability and durability issues

Halide perovskites is a novel class of semiconducting materials with unique optoelectronic properties, such as a steep absorption coefficient, high defect tolerance and a tunable bandgap. Thanks to these properties halide perovskites gathered significant attention both from an academic and industrial perspective for several device applications, such as solar cells, light emitting devices, lasers, visible-to-X-Ray photodetectors.

Scope:

A roadblock towards the commercialization of halide perovskite is represented by the intrinsic lack of stability of the device’s performance, either for the electricity generation or for the light emission. Over the last years, several efforts from academic institutions and industrial partnerships took place to address this issue, which is threatening the forthcoming commercialization of perovskite optoelectronics. In this symposium, we revise the root causes that are supposed to be at the origin of the unstable character of the perovskites: the defects, the migration of ions, the halogen segregation for mixed halide perovskites, the environmental degradation for devices exposed to outdoor conditions, the light-induced and temperature-induced degradation, and more. Next, we present the last approaches to understand the mechanisms and the phenomena that leads to the instability, with multidisciplinary approaches based on chemistry, physics, material science and device engineering. In particular, we focus on new spectroscopic techniques and novel characterization protocols that address either a tailored problem or a degradation mechanism in the whole. Then, we overview on the more recent strategies that are currently employed to mitigate the instability of the perovskite, at the fundamentals or at the device level. Therefore, we discuss about defect passivation (both in the bulk and at the surface); the implementation of low-dimensional perovskites (2D or quasi-2D) either as a surface modification or as a bulk material; and finally, the incipient developments in tin halide (3D, 2D) and other lead-free perovskites for optoelectronic devices.

Towards the end, we revise the improvement in the device architectures, including new charge extraction layers, buffer layers, encapsulant layers, the current standard procedures for the evaluation of stable perovskite-based devices, and drawing a comparison with other optoelectronic technologies. We give attention particularly to the characterization standards for solar cells, whose performances are nowadays required to last for decades to preserve a competitive position in the photovoltaic and photonic markets.

Hot topics to be covered by the symposium:

• Stability of formamidinium-based perovskite both in standard and inverted configuration
• The potential of stable inorganic perovskites
• The challenges of Sn-based perovskites and their interaction with oxygen
• The impact of low-dimensional perovskites, the effect of the dimensionality (n)
• Stability of perovskite solar cells, both in single junction and in tandem configuration (all-perovskite, perovskite-silicon tandems, perovskite-CIGS tandems, and perovskite-OPV tandems.
• Stability of perovskite LEDs, with emission in the red, green, and blue.
• Stability in perovskite photonics and photodetectors