Amidino-based Dion-Jacobson 2D perovskite for efficient and stable 2D/3D heterostructure perovskite solar cells

In metal halide perovskite solar cells the formation of a 2D/3D bulk heterostructure has a positive effect on device stability but can be detrimental to charge transport and power conversion efficiency (PCE). Herein, we report that amidino-based Dion-Jacobson 2D perovskite enables the creation of an efficient and stable FAPbI3-based 2D/3D heterostructure in perovskite solar cells. The 2D-perovskite-assisted nucleation/growth of 3D perovskites during film formation was found by using time-resolved optical diagnostics, which decrease concentrations of voids and bulk defects of perovskite films for efficient charge transport. The planar perovskite solar cells based on 2D/3D heterostructures achieved efficiencies of 24.9% and 22.3% on rigid and flexible substrates, respectively, which are the highest efficiencies among all 2D/3D composite solar cells. Improved stability was further demonstrated, with 97% of original efficiency retained for rigid solar cells without encapsulation after 1,000 h of storage under ambient conditions (RH 30%–40%) and 92% for flexible solar cells after 3,000 bending cycles.