Boosting the Performance of Carbon‐Based Hole‐Transport‐Layer‐Free CsPbI 2 Br Solar Cells by Adding Imidazole Small Molecules

ABSTRACT Carbon‐based hole‐transport‐layer (HTL)‐free CsPbI 2 Br solar cells have attracted considerable interest due to the improved stability, simple structure, rich application scenarios, and low cost, as compared with their organic–inorganic hybrid counterparts. However, the uncoordinated Pb 2+ and mobile I − ions impose challenges for fabricating a cell with good comprehensive performance. To address the related issues, herein, we introduce a facile additive strategy using an organic small molecule material, i.e., 1H‐imidazole‐4‐carboxylic acid (ICA), to improve the comprehensive performance of carbon‐based HTL‐free CsPbI 2 Br solar cells. Benefitting from the effective passivation of Pb 2+ and anchoring of I − , as well as the increased crystallinity and reduced surface roughness of the CsPbI 2 Br layers by ICA, the optimal cell delivers a power conversion efficiency (PCE) of 14.71%, ⁓24.7% increment relative to the PCE of 11.80% for the control device without ICA addition. Moreover, the ICA‐added device exhibits evidently reduced hysteresis of the current–voltage characteristics and notably enhanced stability, in contrast to the control device.