High-Efficiency Carbon-based CsPbI 2 Br Perovskite Solar Cells from Dual Direction Thermal Diffusion Treatment with Cadmium Halides

In recent years, carbon-based CsPbI Br perovskite solar cells (PSCs) have attracted more attention due to their low cost and good stability. However, the power conversion efficiency (PCE) of carbon-based CsPbI Br PSCs is still no more than 16%, because of the defects in CsPbI Br or at the interface with the electron transport layer (ETL), as well as the energy level mismatch, which lead to the loss of energy, thus limiting PCE values. Herein, a series of cadmium halides are introduced, including CdCl , CdBr and CdI for dual direction thermal diffusion treatment. Some Cd ions thermally diffuse downward to passivate the defects inside or on the surface of SnO ETL. Meanwhile, the energy level structure of SnO ETL is adjusted, which is in favor of the transfer of electron carriers and blocking holes. On the other hand, part of Cd and Cl ions thermally diffuse upward into the CsPbI Br lattice to passivate crystal defects. Through dual direction thermal diffusion treatment by CdCl , CdI and CdBr , the performance of devices has been significantly improved, and their PCE has been increased from 13.01% of the original device to 14.47%, 14.31%, and 13.46%, respectively. According to existing reports, 14.47% is one of the highest PCE of carbon-based CsPbI Br PSCs with SnO ETLs.