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, CsPb1−xMnxI1+2xBr2−2x, are prepared in ambient atmosphere. As the concentration of Mn2+ ions increases, the bandgaps of CsPb1−xMnxI1+2xBr2−2x 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 CsPb1−xMnxI1+2xBr2−2x 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 CsPb1−xMnxI1+2xBr2−2x cells reach the highest PCE of 7.36% (when x = 0.005), an increase of 19.9% in PCE. Furthermore, the encapsulated CsPb0.995Mn0.005I1.01Br1.99 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). All‐inorganic perovskite materials have great potential in realizing long term stability in perovskite solar cells (PSCs). In this work a method to dope all‐inorganic perovskite CsPbIBr2 with Mn is developed. PSCs fabricated based on the Mn‐doped CsPbIBr2 using low‐cost carbon electrodes show substantially improved efficiency and stability.