Efficient Inverted Cs₂AgBiBr₆Solar 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 V_oc of >1.0 V, which is much higher than that of the control device (0.459%).