Cross‐Correlation Between Crystallinity and Optoelectronic Properties of Mixed‐Perovskite Thin Films Through Multiple Time‐Resolved Spectroscopy

A power conversion efficiency (PCE) exceeding 25% is achievable using perovskite solar cells (PSCs), with compositional engineering as the most effective strategy for high‐efficiency PSCs. However, the understanding of structural properties, charge‐carrier dynamics, and photoelectric properties, crucial for solar cell performance, still remains insufficient to establish a correlation with device performance for improving the PCE and stability of PSCs. This study uncovers the crucial links between structural disorder, charge‐carrier dynamics, and photoelectric properties of mixed‐perovskite (FAPbI 3 ) 1‐x (MAPbBr 3 ) x thin films by investigating device performance for different mol%. Structural and morphological analyses reveal that the mixed perovskite‐thin‐film disorder exhibits composition dependence in the form of a checkmark trend, with a minimum near 0.8 mol%. Time‐resolved transient absorption spectroscopy demonstrates that charge‐carrier dynamics and optoelectronic properties exhibit a corresponding dependence on disorder. As the disorder of the perovskite thin film decreases, the trap density decreases, charge‐carrier loss decreases during the thermalization process, and the carrier lifetime is prolonged. Optical pump‐THz probe measurements show 20% effective mobility and a diffusion length of 34%. The device performance shows composition dependence and superior PCE is achieved at 0.8 mol%. This study highlights the significance of charge‐carrier dynamics in optimizing mixed perovskite composition for enhanced PCE and stability of PSCs.