Toward Long-Term Stability: Single-Crystal Alloys of Cesium-Containing Mixed Cation and Mixed Halide Perovskite

Perovskite
solar cells are strong competitors for silicon-based
ones, but suffer from poor long-term stability, for which the intrinsic
stability of perovskite materials is of primary concern. Herein, we
prepared a series of well-defined cesium-containing mixed cation and
mixed halide perovskite single-crystal alloys, which enabled systematic
investigations on their structural stabilities against light, heat,
water, and oxygen. Two potential phase separation processes are evidenced
for the alloys as the cesium content increases to 10% and/or bromide
to 15%. Eventually, a highly stable new composition, (FAPbI3)0.9(MAPbBr3)0.05­(CsPbBr3)0.05, emerges with a carrier lifetime of 16 μs.
It remains stable during at least 10 000 h water–oxygen
and 1000 h light stability tests, which is very promising for long-term
stable devices with high efficiency. The mechanism for the enhanced
stability is elucidated through detailed single-crystal structure
analysis. Our work provides a single-crystal-based paradigm for stability
investigation, leading to the discovery of stable new perovskite materials.

钙钛矿(Perovskite)太阳能电池是硅基太阳能电池的强劲竞争对手，但长期稳定性欠佳，其中钙钛矿材料的本征稳定性是核心关注点。本研究中，我们制备了一系列结构明确的含铯混合阳离子混合卤化物钙钛矿单晶合金，借此系统探究其在光照、热、水及氧气条件下的结构稳定性。当铯含量提升至10%、溴化物含量提升至15%时，该合金体系出现两种潜在的相分离过程。最终我们得到一种稳定性优异的全新组分：(FAPbI3)0.9(MAPbBr3)0.05(CsPbBr3)0.05，其载流子寿命达16 μs。该组分在至少10000小时水氧稳定性测试与1000小时光照稳定性测试中均保持稳定，对于制备高效且长期稳定的器件极具应用前景。我们通过精细的单晶结构分析，阐明了该组分稳定性提升的内在机制。本研究为稳定性探究提供了基于单晶的研究范式，助力新型稳定钙钛矿材料的发现。