Highly Efficient Electron‐Selective Layer Free Perovskite Solar Cells by Constructing Effective p–n Heterojunction

A heterojunction concept with an n‐type self‐doped perovskite and a p‐type hole‐transport material was proposed for fabricating highly efficient electron‐selective layer (ESL)‐free perovskite solar cells (PSCs). The self‐doping property of the perovskite is controlled by defects engineering, which can change from p‐ to n‐type, and the n‐type self‐doping degree is tuned serially by precursor composition and process conditions. Meanwhile, the compact homogenous and large‐grain film morphology is achieved by introducing mixed nonpolar aprotic solvents to obtain optimal balancing between densification and grain size. Hence, the ESL‐free PSCs with n‐type self‐doped compact CH 3 NH 3 PbI 3 film exhibit state of the art performance with the highest efficiency of 15.69%. Besides, the as‐fabricated ESL‐free PSCs, which keep their initial efficiencies for a period of 21 days without degradation, demonstrate better long‐term stability compared to the conventional planar PSCs.