Stable and scalable 3D-2D planar heterojunction perovskite solar cells via vapor deposition

The device stability and toxic-solvent-free processing are indispensable development to industrialize organometal halide perovskite solar cells. In this work, the conventional top surface of vapor prepared 3D-MAPbI3 was replaced by 2D-(BA)2(MA)n‐1PbnI3n+1 perovskite platelet via molecular substitution from MA (CH3NH) to BA (C4H9NH2). Our fully vapor process fabricated a 3D-2D perovskite heterojunction for solar cell application, realizing the power conversion efficiency as high as 16.50% and the average one as 15.40%. Furthermore, unencapsulated devices can sustain their 81% efficiency after 30 days under 55% RH, and also 74% efficiency after 30 days under 80 °C heat stress. Stability of humidity resistance arises from the reduced n value of 2D perovskite caused by the surface reaction of moisture, and the improvement of thermal stability comes from the buffering of MA molecules release. Meanwhile, the fabrication of large scale device with high efficiency is also demonstrated in our experiment.