Efficient Inverted Cs ₂ AgBiBr ₆ Solar Cells through Crystallization Control

Cs2AgBiBr6 holds great potential as an alternative to lead-based perovskites due to its nontoxicity and relatively high stability. However, the rapid crystallization of Cs2AgBiBr6 usually induces a high defect density, leading to poor photovoltaic performance. Here we introduce thiourea (TU) and Methylammonium bromide (MABr) into the precursor solution to control the crystallization process of Cs2AgBiBr6. TU anchors Ag+ and Bi3+ to regulate the crystallization process and passivate potential defects. MABr works as a “solid solvent” to preoccupy the lattice sites for Cs+ insertion and will volatize without residuals after film annealing, inducing uniform growth of Cs2AgBiBr6. As a result, inverted Cs2AgBiBr6 solar cells show an efficiency of 0.955% with a high Voc of >1.0 V, which is much higher than that of the control device (0.459%).