Liquid Cleaning of Perovskite Single Crystal Surface for High Performance Semi‐Transparent Solar Cells

Wide‐bandgap perovskite single crystals with high optical transparency and outstanding electronic transport capacity are promising building blocks in semi‐transparent solar cells. However, surface defects and residual solvent contamination on single crystals severely compromise charge extraction and lead to non‐radiative recombination. Here, we address this challenge by a liquid cleaning approach that effectively removes residual precursors and eliminates surface defects of MAPbBr 3 thin single crystal. We integrate an indium tin oxide (ITO)/Ag/ITO composite electrode to balance high conductivity and excellent transmittance, which give rise to first reported semi‐transparent single crystal solar cells with a power conversion efficiency (PCE) of 4.92% and an average visible transmittance (AVT) of 59.1%. This synergistic strategy of interface optimization and electrode design broaden the application scope for perovskite single crystals into transparent electronics, and may offer critical wide‐gap units for advanced tandem photovoltaics.