Ti3C2 MXene Nanosheets–Modified TiO2 Electron‐Transport Layers Enables Efficient Solar Cells with Outstanding Device Consistency

The electron‐transport layer (ETL) of n–i–p‐structured perovskite solar cells (PSCs) plays vital important roles determining their photovoltaic performance. It is known that the ETL lying underneath can affect the crystallization process of the upper perovskite layer. Furthermore, the buried interface between ETL and perovskite is usually the place where severe non‐radiative recombination happens. Herein, MXene (Ti3C2)‐modified TiO2 (TiO2:MXene) is demonstrated as an excellent ETL for high‐performance PSCs. The FAPbI3‐based and MAPbI3‐based cells with TiO2:MXene achieved a power conversion efficiency (PCE) of up to 24.63% and 20.1%, respectively. Importantly, the target cell shows superior stability and device consistency. The target devices keep ≈98% of their initial PCE after 7 weeks stored in an ambient environment with 40%–60% relative humidity at 25 °C, whereas the PCE of the reference cell declined to ≈90% of its initial value under the same test conditions. It is found that the perovskite film on TiO2:MXene ETL has excellent crystallinity and structural uniformity. For the first time, grazing‐incidence small‐angle X‐ray scattering technique is employed to probe the structural information of complete PSC devices on a large scale, providing new possibilities of characterizing large‐size PSC modules.