Unraveling the Role of 2D Ti3C2Tx MXene Nanosheets in Cu‐Based Double Perovskite Active Layer for Enhanced Photovoltaic Performance

Abstract Although the atmospheric stability of lead‐free inorganic double perovskite (DP) solar cells (PSCs) looks promising, their further development is hampered by inadequate film quality and non‐radiative carrier recombination at the interfaces. Herein, the incorporation of a newly developed intriguing class of 2D material Ti 3 C 2 T x MXene nanosheets with the photo‐absorbing Cu 2 AgBiI 6 (CABI) active layer of a fully inorganic solar cell is reported. The highly conductive Ti 3 C 2 T x nanosheets work as a multi‐functional additive by tuning the band gap, reducing the non‐radiative carrier recombination, and inhibiting carrier accumulation. In addition, the presence of Ti 3 C 2 T x MXene increases the surface free energy of the perovskite film, which elevates the energy barrier for nucleation and realizes a highly crystalline CABI perovskite film. Primarily, the MXene modification accelerates the charge extraction and transport at the interfaces of the active layer, utilizing energy level alignment with the charge transport layers. Consequently, the photo‐conversion efficiency (PCE) of the device with MXene is substantially enhanced to 1.50%. Moreover, the 2D Ti 3 C 2 T x nanosheets increased the long‐term stability of the devices by retaining 70% of the initial PCE after 1680 h. With regard to relieving the severe carrier recombination at the interfaces, this work sets a new paradigm toward imminent solar energy conversion.