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 CH3NH3PbI3 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.