Improved Perovskite CH₃NH₃PbI₃ Thin Films by ZIF‐67 Additive Assisted Co Ion Doping toward High‐Performance and Stable Photodetectors

Abstract Lead halide perovskites are considered important materials for the fabrication of high‐performance optoelectronic devices. However, the poor quality of thin films with abundant grain boundaries and defect states greatly lower the performance and stability of as‐fabricated devices. In the present work, the growth of improved perovskite CH₃NH₃PbI₃ thin films through Co‐based zeolite imidazole framework (ZIF‐67) additive assisted Co ion doping is reported. Investigation of the morphological, structural, optical, and electrical properties shows that the Co ion doped CH₃NH₃PbI₃ (CH₃NH₃Pb_0.98Co_0.02I₃) thin films exhibit low grain boundaries, low defect states, and improved structural stabilities. The positive roles of suppression of defect states are further demonstrated by improved performance and stability of photodetectors based on CH₃NH₃Pb_0.98Co_0.02I₃ thin films. Finally, density functional theory calculations are performed to reveal the mechanisms of passivation of undercoordinate Pb²⁺ vacancy defect states by Co ion doping. The results provided in this work will pave the way toward the fabrication of high performance and stable perovskite photodetectors in the future.