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 SnO2 and perovskite interface, which assists in releasing the residual stress in the perovskite layer. Meanwhile, the work function of SnO2/ IT-4F is lower than that of SnO2, 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 VOC 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 N2 and retains 87% of the initial PCE after operation for 1000 h.

Automated summary

An appropriate energy alignment and enhanced charge transfer electron-transport layer is crucial for perovskite solar cells (PSCs). Additionally, interface stress and lattice distortion occur during perovskite crystallization. By introducing IT-4F at the buried SnO2 and perovskite interface, residual stress in the perovskite layer is released. Furthermore, the lower work function of SnO2/IT-4F compared to SnO2 facilitates charge transfer and significantly improves the power conversion efficiency (PCE) to 23.73%.