Localized 2D/3D heterojunction enhances photovoltage for perovskite-organic tandem solar cells

Wide-bandgap perovskite solar cells are essential for constructing multi-junction solar cells; nevertheless, their achievable photovoltage is often limited by non-radiative recombination losses caused by defect states, mismatched energy levels, and poor contact at interfaces, resulting in a photovoltage plateau beyond 1.68 eV. Here, we explore intricate Lewis acid-base interactions between hole-selective self-assembled monolayer and ammonium ligands to engineer a localized 2D/3D perovskite heterojunction at the buried interface. This structure not only help reduce defect density but also facilitate charge extraction and templated perovskite crystallization without compromising the bulk optoelectrical properties of 3D perovskite. These resulted in 1.30, 1.38, and 1.42 V photovoltages for 1.68, 1.79, and 1.85 eV bandgap perovskite solar cells, respectively, all exceeding 90% of their thermodynamic limits. We also demonstrate high-efficiency monolithic tandem solar cells by integrating the optimized wide-bandgap perovskite solar cell with an organic subcell to achieve a PCE of 27.11% (certified 26.3%).