Enhancing Optical, Electronic, Crystalline, and Morphological Properties of Cesium Lead Halide by Mn Substitution for High-Stability All-Inorganic Perovskite Solar Cells with Carbon Electrodes

In this work all-inorganic perovskite CsPbIBr₂ are doped with Mn to compensate their shortcomings in band structure for the application of perovskite solar cells (PSCs). The novel Mn-doped all-inorganic perovskites, CsPb_{1− x}Mn_xI_{1+2 x}Br_{2−2 x}, are prepared in ambient atmosphere. As the concentration of Mn²⁺ ions increases, the bandgaps of CsPb_{1− x}Mn_xI_{1+2 x}Br_{2−2 x} decrease from 1.89 to 1.75 eV. Additionally, when the concentration of Mn dopants is appropriate, this novel Mn-doped all-inorganic perovskite film shows better crystallinity and morphology than its undoped counterpart. These advantages alleviate the energy loss in hole transfer and facilitate the charge-transfer in perovskites, therefore, PSCs based on these novel CsPb_{1− x}Mn_xI_{1+2 x}Br_{2−2 x} perovskite films display better photovoltaic performance than the undoped CsPbIBr₂ perovskite films. The reference CsPbIBr₂ cell reaches a power conversion efficiency (PCE) of 6.14%, comparable with the previous reports. The CsPb_{1− x}Mn_xI_{1+2 x}Br_{2−2 x} cells reach the highest PCE of 7.36% (when x = 0.005), an increase of 19.9% in PCE. Furthermore, the encapsulated CsPb_0.995Mn_0.005I_1.01Br_1.99 cells exhibit good stability in ambient atmosphere. The storage stability measurements on the encapsulated PSCs reveal that PCE is dropped by only 8% of the initial value after >300 h in ambient. Such improved efficiency and stability are achieved using low-cost carbon electrodes (without expensive hole transport materials and Au electrodes).