Decreasing energy loss and optimizing band alignment for high performance CsPbI3 solar cells through guanidine hydrobromide post-treatment

On account of their superior thermal stability and applicable band gap (similar to 1.7 eV), the inorganic halide CsPbI3 perovskite solar cells (PSCs) have aroused intense interest in recent years. Nevertheless, the CsPbI3 PSCs still face a problem of high energy loss (E-loss) which leads to low open-circuit voltage (V-OC). Herein, we developed efficient CsPbI3 PSCs through guanidine hydrobromide (GABr) post-treatment on the surface of CsPbI3 films. After optimizing, a supreme power conversion-efficiency (PCE) of 18.02% was obtained, which was higher than the original one (16.58%). By further studying, the characterization of passivation was found, which led to a reduced nonradiative recombination rate. Besides, the band alignment between CsPbI3 and the interface layer was also optimized, leading to the decreased electron transport barrier for electron collection, and superb hole contact for furnishing a driving force in the hole transfer and preventing electrons from flowing in the opposite direction.