An Effective Modulation of Bulk Perovskite by V ₂T _xC Nanosheet for Efficient Planar Perovskite Solar Cells

Crystallization modulation and defect passivation are key for high performance perovskite solar cells (PSCs) through suppressing defects in the surface and/or near the grain boundaries (GBs) of solution-processed perovskite films. In this work, we report simultaneous modulation of crystallization and passivation of defects for perovskite through a new vanadium carbide (V2TxC) MXene that is employed in anti-solvent. The final modified perovskite film showed an improved crystallization, better energy level alignment and higher hole injection with hole-transporting layer, leading to an increased power conversion efficiency from 20.1% up to 23.47% for planar PSC, with enhanced device stability keeping over 90% of initial PCE after 1000-hour exposure under 40-60% relative humidity at 25 °C. We have further implemented synchrotron radiation in-situ GIWAXS equipment to monitor the kinetic process of crystallization during spin-coating, it is notable that a lower dimensional perovskite structure (n < 3) was observed in the modified perovskite film during the process of dropping antisolvent CB with V2TxC, which helps explain the enhanced device stability.