The Influence of Spontaneous Oxidative Conversion on the Characteristics of Lead‐Free Halide Perovskite CsSn(IxBr1−x)3 and on the Performance of Perovskite Light‐Emitting Diodes

Abstract In this study, lead‐free perovskite CsSn(I x Br 1− x ) 3 films with photoluminescence emission wavelengths from 677 to 887 nm are prepared. The influence of air exposure on their characteristics is also investigated. It is found that CsSnI 3 can be transformed to Cs 2 SnI 6 upon increasing the air exposure time. The decomposition and oxidation mechanisms are confirmed by the X‐ray diffraction pattern due to the presence of CsI peak. It is observed that devices based on the CsSn(I x Br 1− x ) 3 film with increased Br − ratio and the CsSnI 3 film with prolonged air exposure time show inferior performance. These results are mainly attributed to the highest occupied molecular orbital levels of CsSn(I x Br 1− x ) 3 and Cs 2 SnI 6 . Defect density of state and binding energy of these materials are also investigated and reported in this study.