Light-activated tautomeric transition enhanced buried heterointerface for highly efficient and ultraviolet robust perovskite solar cells

The buried heterointerface of perovskite solar cells (PSCs) suffers from serious nonradiative recombination and ultraviolet (UV) light stress, relentlessly limiting further increase in their power conversion efficiency and operational stability. Herein, we develop an emerging strategy of incorporating a thin UV-activated tautomeric transition layer onto underlying charge transport layer and then depositing perovskite layer to construct an efficient hole-selective buried heterojunction. It is revealed that the UV-activated tautomeric transition interlayer not only improves upper perovskite crystallinity, diminishes thermionic loss for collecting hole and passivates defect site at such buried contact that significantly promote charge transport and suppress nonradiative recombination, but also effectively protects adjacent perovskite from UV degradation through “UV sunscreen” effect. As a result, we report a remarkably enhanced efficiency of 24.76% compared to 22.02% of the control device. More importantly, the achieved high-efficiency PSC features excellent resistance against UV radiation at 365 nm of 100 and 850 mW cm⁻², which are approximately 21 and 184 times of UV flux (4.6 mW cm⁻²) under AM 1.5G solar illumination. This work provides a promising approach of strengthening buried heterointerface for simultaneous realization of highly efficient and UV robust PSCs.