Recent advances in defect passivation of perovskite active layer via additive engineering: a review

The performance and stability of Perovskite solar cells (PSCs) are mainly affected by various defects inside the perovskite active layer and the corresponding electron/hole transport layers interfaces. A lot of work has been done in progressing perovskite layer passivation strategies contributing to efficient performance PSCs with improved ambient environment stability. Here, the additive engineering techniques for the perovskite active layer passivation with the aim of improving perovskite crystallization, reducing carrier recombination and improving device stability are reviewed. Passivation, by different additives, of the active layer can improve the performance of PSCs by reducing trap states and enhance the moisture stability by reducing the grain boundaries. Optimizing the ratio of PbI2 in the perovskite precursor has been discovered to be effective in passivating trap states at the grain boundaries and on the surface of the film. Non-radiative recombination trap centers inside the active layer can be passivated through the incorporation of additives such as organic surfactants, elemental iodine, and metal compounds or nanoparticles. This technique has also taken part in improving energy band alignment between the perovskite layer and the respective electron/hole transport layers. The present work covers most of the published reports on the additive engineering approach, the precursor preparation, the effect on different properties of the perovskite layer, the effect on device efficiency, the effect on device hysteresis and finally, the effect on device stability are presented.