Synergistic Effects of Multifunctional Lanthanides Doped CsPbBrCl2 Quantum Dots for Efficient and Stable MAPbI3 Perovskite Solar Cells

The passivation effect of inorganic perovskite quantum dots (PQDs) is a promising method to attain outstanding performance in perovskite solar cells (PSCs), which has ignited widespread interest recently. Lanthanides (Ln) doped PQDs demonstrate unique properties, but nevertheless, are not explored in PSCs. In this work, four kinds of Ln3+ doped CsPbBrCl2 PQDs (Ln3+ = Yb3+, Ce3+, Eu3+, Sm3+) are firstly introduced into PSCs, which displays the synergistic effect of composition engineering and defect engineering. The results indicate that the introduction of CsPbBrCl2: Ln3+ can not only improve the crystallinity and passivate the intrinsic and surface defects of the MAPbI3 layer through ion and ligand passivation, but also form a stronger LnI bond than PbI, adjust work function (WF), and optimize band alignments. CsPbBrCl2:Sm3+ PQDs possess the best performance and exhibit remarkable promotions of open‐circuit voltage (Voc) from 1.13 to 1.20 V and power conversion efficiency from 18.54% to 22.52%. The humid‐resist, thermal‐resist abilities, and the long‐term stability of PSCs are energetically improved due to enhanced structure stability by Sm3+ doping and the hydrophobic characteristic. The strategy of Ln3+ doped PQDs applied to PSCs provide an approach to achieve high‐performance PSCs. CsPbBrCl2: Ln3+ PQDs are employed in a perovskite solar cell to achieve a “lattice to lattice” doping effect and passivate the intrinsic defects in MAPbI3‐based PSCs. CsPbBrCl2: Ln3+ PQDs can adjust work function, optimize bandgap alignment, and form stronger Ln‐X bonds, and displays a power conversion efficiency of 22.52% and a high Voc of 1.20 V.