Review of Novel Passivation Techniques for Efficient and Stable Perovskite Solar Cells

Perovskite solar cells contain various defects within the perovskite absorber and the corresponding interfaces, affecting device performance and stability. Fortunately, there have been tremendous efforts in advancing passivation techniques contributing to high-efficiency perovskite solar cell with improved stability. Here, the state-of-the-art passivation approaches for each layer of the perovskite cell with the aim of improving carrier extraction, reducing carrier recombination, and/or improving cell stability are reviewed. Passivation of the electron transport layer can improve the stability of perovskite solar cells by reducing trap states or by physically separating the transport layer from contacting perovskite. Controlling the amount of PbI2 in the perovskite precursor has been found to be effective in passivating defect states at the grain boundaries and on the surface. Additives such as elemental iodine, organic surfactants, and Group 1 metal compounds incorporated in perovskite precursors have been reported to passivate recombination trap centers. These approaches have also contributed to improved energy band alignment between carrier transport layers and perovskite absorber improving device performance. An effective strategy to improve moisture stability is the use of 2D perovskites or hydrophobic large cation molecules forming 2D or quasi-2D phases at grain boundaries or film surfaces providing passivation and preventing moisture ingress.