Synergistic Effects of Interfacial Energy Level Regulation and Stress Relaxation via a Buried Interface for Highly Efficient Perovskite Solar Cells.

An electron-transport layer with appropriate energy alignment and enhanced charge transfer is critical for perovskite solar cells (PSCs). In addition, interface stress and lattice distortion are inevitable during the crystallization process of perovskite. Herein, IT-4F is introduced into PSCs at the buried SnO 2 and perovskite interface, which assists in releasing the residual stress in the perovskite layer. Meanwhile, the work function of SnO 2 /IT-4F is lower than that of SnO 2 , which facilitates charge transfer from perovskite to ETL and consequently leads to a significant improvement in the power conversion efficiency (PCE) to 23.73%. The V OC obtained is as high as 1.17 V, corresponding to a low voltage deficit of 0.38 V for a 1.55 eV bandgap. Consequently, the device based on IT-4F maintains 94% of the initial PCE over 2700 h when stored in N 2 and retains 87% of the initial PCE after operation for 1000 h.