Investigation on the structural, morphological, electronic and photovoltaic properties of a perovskite thin film by introducing lithium halide.

The performance of perovskite solar cells (PSCs) including device efficiency and stability is mainly dependent on the perovskite film properties which are critically related to the organic cations used. Herein, we studied the role that the inorganic lithium (Li) cation played in perovskite thin films and its influence on crystal growth, film properties, and device performance. We found that within the threshold limit of a 1.0% molar ratio, the Li dopant had a positive effect on the film formation and properties. However, after replacing more MA with Li, the device performance was degraded significantly with reduced short-circuit current density ( ) and fill factor (FF) values. With a doping ratio of 10 mol%, the film morphology, crystallinity, photophysical, and electronic properties totally changed due to the unstable nature of the Li doped, distorted 3-D perovskite structure. The Li doping mechanism was discussed, and it was thought to contain two different doping mechanisms. One is interstitial doping at the much lower doping ratio, and the other is substitutional doping for the MA cation at the higher doping ratio.