Achieving high-quality perovskite crystal films is a critical prerequisite in boosting solar cell efficiency and improving the device stability, but the delicate control of nucleation and growth of the perovskite film remains limited success. Herein, a facile but effective strategy has been developed to finely tailor the crystallization of thermally stable cesium/formamidinium (Cs/FA) based perovskite via partially replacing PbI₂ with PbCl₂ in the precursor solution. The incorporation of chlorine into the perovskite crystal lattice derived from PbCl₂ changes the crystallization process and improves the crystal quality, which further results in the formation of larger crystal grains compared to the control sample. The larger crystal grains with high crystallinity lead to reduced grain boundaries, suppressed non-radiative recombination, and enhanced photoluminescence lifetime. Under the optimized conditions, the methylammonium free perovskite solar cells (PSCs) delivers a champion power conversion efficiency (PCE) of 21.30% with an open-circuit voltage as high as 1.18 V, which is one of the highest efficiencies for Cs/FA based PSCs up to now. Importantly, the unencapsulated PSC devices retain more than 95% and 81% of their original PCEs even after long-term (over one year) storage under ambient conditions or 2000 h's thermal aging at 85 °C in a nitrogen atmosphere, respectively.

获得高质量的钙钛矿晶体膜是提高太阳能电池效率和改善器件稳定性的关键先决条件，但是对钙钛矿膜成核和生长的精细控制仍然有限。在本文中，已经开发了一种简便而有效的策略，以通过在前体溶液中用PbCl ₂代替PbI ₂来精细调整热稳定的铯/甲ami（Cs / FA）基钙钛矿的结晶。将氯结合到源自PbCl ₂的钙钛矿晶格中改变结晶过程并改善晶体质量，与对照样品相比，这进一步导致形成更大的晶粒。具有高结晶度的较大晶粒导致减小的晶界，抑制了非辐射复合以及延长的光致发光寿命。在优化的条件下，无甲铵钙钛矿太阳能电池（PSC）的功率转换效率（PCE）为21.30％，开路电压高达1.18 V，这是基于Cs / FA的最高效率之一到目前为止的PSC。重要的是，即使在环境条件下长期存储（一年以上）或在氮气氛下于85°C进行2000 h的热老化后，未封装的PSC器件仍保留其原始PCE的95％和81％以上。