Micro-homogeneity of lateral energy landscapes governs the performance in perovskite solar cells

Suppression of energy disorders in the vertical direction of a photovoltaic device, along which charge carriers are forced to travel, has been extensively studied to reduce unproductive charge recombination and thus achieve high-efficiency perovskite solar cells. In contrast, energy disorders in the lateral direction of the junction for large-area modules are largely overlooked. Herein, we show that the micro-inhomogeneity characteristics in the surface lateral energetics of formamidinium (FA)-based perovskite films also significantly influence the device performance, particularly with accounting for the stability and scale-up aspects of the devices. By using organic amidinium passivators, instead of the most commonly used organic ammonium ones, the micro-inhomogeneity in the lateral energy landscapes can be suppressed, greatly improving device stability and efficiency of FA-based single-junction perovskite solar cells.