NdCl₃ Dose as a Universal Approach for High-Efficiency Perovskite Solar Cells Based on Low-Temperature-Processed SnO

The defects on the surface of low-temperature-processed electronic transport layers hindered the development of efficient flexible perovskite solar cells. Herein, we develop a universal NdCl₃ dosing strategy to circumvent the residual Sn(II)-OH defects from the incomplete wet-chemical reaction. The introduction of NdCl₃ does not lead to the doping of Nd³⁺ ions but rather the formation of a composite film of NdCl₃ with SnO. The dose of NdCl₃ effectively reduces surface trap states at low-temperature-processed SnO films, leading to increased carrier extraction and reduced carrier accumulation/recombination at the ETL/perovskite interface. These improvements result in perovskite solar cells (PvSCs) with significantly enhanced power conversion efficiency (PCE) and eliminated hysteresis. Finally, efficiencies of 18.62% and 21.49% for PvSCs based on MAPbI₃ and FA_1-MAPbI₃ perovskites, respectively, were achieved on rigid substrates. The test on a flexible device based on Cs_0.05(FA_0.83MA_0.17)_0.95(I_0.83Br_0.17)₃ perovskite realized a PCE of 16.14% and an incredible V_OC of 1.158 V. This study indicated the potential of NdCl₃ dose as a universal approach to enhance the performance of PvSCs with low-temperature-processed SnO ETL.