Construction of 2D/3D/2D‐Structured Perovskite for High‐Performance and Stable Solar Cells

Abstract 2D/3D‐structured perovskites are promising for high‐performance and stable solar cells due to the passivation ability and hydrophobic character of the large organic cations. However, most of the 2D/3D‐structured perovskites prepared by adding ammonium halides into the precursors or depositing ammonium halides on top of a 3D perovskite film ignore the buried interface which is crucial for the device efficiency and stability. Here, 2D/3D/2D‐structured perovskite films with optimized buried interface are constructed by depositing phenethylammonium bromide (PEABr) on top and 2D perovskite PEA₂FA₂Pb₃Br₁₀ at the bottom of 3D Cs_0.07FA_0.85MA_0.08Pb(I_0.95Br_0.05)₃ perovskite. Thus, a power conversion efficiency (PCE) of 24.2% is achieved due to the minimal nonradiative recombination. The encapsulated device also shows an improved stability, maintaining 93.5% of the initial value after 1000 h under 1 sun equivalent illumination at the maximum power point. This strategy may provide important insights into designing perovskite film structures to achieve high‐performance solar cells with high stability.