Cation-Assisted Restraint of a Wide Quantum Well and Interfacial Charge Accumulation in Two-Dimensional Perovskites

Two-dimensional (2D) layered perovskite compounds hold promise to solve stability issues for photovoltaic devices. However, the naturally formed multiple quantum well structure contributes to a large distribution of optical band gaps in 2D perovskite materials. Therefore, intensive efforts have been devoted to control the quantum well width into an extremely small distribution and optimize the charge-transport characteristic. Herein, we report that a cation-induced recrystallization process (CIRP) can form well alignment orientation and increase the crystallinity of 2D perovskite (BA)2(CH3NH3)3Pb4I13 (where BA is butylammonium) via an intermediate catalytic effect. More importantly, CIRP treatment enables a homogeneous distribution of organic cations, narrows the distribution of the quantum well width, and reduces charge accumulation as well. The 2D perovskite devices with CIRP treatment using a metal oxide TiO2/Al2O3/NiO/C framework exhibited an impressive power conversion efficiency of 8.2%, which is the highest value among its counterpart category. The super stability has been verified in air (sustained origin efficiency until 4000 h).