Low-Temperature Processed Carbon Electrode-Based Inorganic Perovskite Solar Cells with Enhanced Photovoltaic Performance and Stability

All-inorganic perovskite solar cells(PVSCs) have drawn widespread attention for its superior thermal stability. Carbon-based devices are promising to demonstrate excellent long-term operational stability due to the hydrophobicity of carbon materials and the abandon of organic holetransporting materials(HTMs). However, the difficulty to control the crystallinity process and the poor morphology leads to serious non-radiative recombination, resulting in low VOCand power conversion efficiency(PCE).In this article, the crystal formation process of all-inorganic perovskites is controlled with a facile composition engineering strategy. By bromide incorporation, high-quality perovskite films with large grain and fewer grain boundaries are achieved. As-prepared perovskite films demonstrate longer carrier lifetime, contributing to lower energy loss and better device performance. Fabricated carbon-based HTM-free PVSCs with CsPbI2.33Br0.67perovskite realized champion PCE of 12.40%, superior to 8.80% of CsPbI3-based devices, which is one of the highest efficiencies reported for the carbon-based all-inorganic PVSCs to date. The high VOCof 1.01 V and FF of 70.98% indicate the significance of this composition engineering method.Moreover, fabricated carbon-based devices exhibit excellent stability, and unencapsulated device retains over 90% of its initial efficiency under continuous one sun illumination for 250 h in N2atmosphere and keeps～84% of its original value after stored in ambient environment with RH 15–20% for 200 h. This work provides a facile way to fabricate high-performance and stable carbon-based all-inorganic PVSCs.