Accelerating perovskites: towards stable composites and solar cell devices

Christoph J. Brabec, Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany

Perovskite based on metal halide perovskites is a most promising material system for photovoltaics as well as for photodetectors. However, further advance demands improved device stability. Here we show the distinctly different impact of perovskite composition and interface engineering for demonstrating long-term stable perovskite composites and devices. Most interestingly, the perovskite composite appears to be significantly more stable than the corresponding device, which is a strong argument that a major part of the instabilities are introduced from the interface.

A high-throughput robotic approach is used to screen 160 mixed-cation mixed-halide perovskites based on several optical characterizations, such as UV-vis absorption and photoluminescence spectra. Such automated big data approaches allow to uniquely identify the most photo-thermal-stable perovskites under elevated temperature and illumination. Most interestingly, while several perovskite compositions are found to be stable against high temperatures of up to 85 C, the situation is more complex in working devices, as a stable device requires both – a stable semiconductor layer and stable interfaces. A p-type interface consisting of polymeric multilayers with variable doping isintroduced as a most robust anode interface at elevated temperatures of 65 degrees Celsius, but still shows degradation at temperatures beyond 85 C. This work further introduces into the fundamentals how to accelerate the screening for stable perovskites layer and devices for long term operation.