Crystallization and Defect Chemistry Dual Engineering for MAPbI3 Perovskite Solar Cells with Efficiency Approaching 22%

Methylammonium lead triiodide (MAPI) has been the most commonly used light absorber layer for perovskite solar cells and also shows potentially high theoretical efficiency. However, the achievable efficiencies so far still lag behind those of their formamidinium- or mixed cation-based counterparts. In this work, the dual additives 2-mercaptopyridine (2-MP) and 1,2-dichlorobenzene (DCB) are applied to regulate the crystal orientation, yielding a high-crystal quality MAPI film and passivating the trap states of the film. Encouragingly, we are able to distinguish the efficacy of the two additives. DCB effectively reduced the size of colloidal clusters in the perovskite precursor, thus helping the wet film reach the critical concentration to initialize rapid nucleation. The resulting MAPI film exhibited extended grain size with a stronger grain orientation and smoother surface. With the subsequent introduction of 2-MP, the high crystal quality was maintained, and 2-MP interacted with uncoordinated Pb defects and passivated the related traps. The dual additive-processed devices exhibited the champion efficiency of 21.83% with a simultaneously high Jsc of 24.01 mA/cm2 and Voc of 1.15 V. This work provides a means to engineer the crystallization quality and defect chemistry toward efficient MAPbI3 perovskite solar cells.