Buried Interface Modulation via Preferential Crystallization in All‐Inorganic Perovskite Solar Cells: The Case of Multifunctional Ti 3 C 2 T x

Despite inorganic CsPbI 3− x Br x perovskite solar cells (PSCs) being promising in thermal stability, the perovskite degradation and severe nonradiative recombination at the interface hamper their further development. Herein, the typical MXene material, that is, Ti 3 C 2 T x , is employed to be the buried interface prior to the perovskite absorber layer in the device, which multi‐functionalizes the as‐prepared electron‐transfer layers by means of both fascinating preferential crystallization of perovskite and/or accelerating the charge extraction with respect to an ideal energy‐level alignment and suppressed trap states. Accordingly, the power conversion efficiency of the modified PSC device is substantially enhanced by as high as 19.56% in comparison to their counterparts with only the pristine CsPbI 3− x Br x active layer. More importantly, MXene modification is favorable to improve the wettability of perovskite precursor solution with enhanced grain size and crystallinity, thereby increasing the UV long‐term stability of solar cells. This work provides a new paradigm toward alleviating the severe nonradiative recombination at the interface in the device whilst enhancing the long‐term stability via the preferential crystallization process.