Carbohydrazide-Assisted Morphology and Structure Controlling for Lead-Free Cs₂AgBiBr₆ Double Perovskite Solar Cells

Thestability and toxicity problems have haunted the developmentand applications of metal halide perovskite materials, for which thelead-free inorganic double perovskite Cs2AgBiBr6 has emerged as a promising substitute in recent years. However,poor film quality has severely limited its photovoltaic performancethat could have been induced by some key factors such as high annealingtemperature. Herein, we present a facile strategy to fabricate high-qualitypinhole-free Cs2AgBiBr6 films with large grainsizes by introducing carbohydrazide (CBH) into the precursor. Detailedcharacterizations have shown that the carbonyl group (C UO)in CBH plays the critical role in coordinating with Ag+ and Bi3+ cations during the film formation process. Asanother consequence, the as-fabricated devices have exhibited significantlyhigher reproducibility for fabrication. By optimizing the amount ofCBH, the power conversion efficiency (PCE) relatively increased 37to 1.57%, which remained 95.0% in an ambient environment for a 1000-htest. Hopefully, this work could facilitate the current technologiesin the exploration of high-performance lead-free perovskites suchas Cs2AgBiBr6 and better understanding of themechanism in the additive engineering as well.