Advances in thin layer deposition techniques in perovskite solar cells

Perovskite solar cells (PSCs) have shown excellent performance in the photovoltaic field, with the highest power conversion efficiency (η) reaching 27%. This significant achievement was possible due to the optimization of various active layers, such as the perovskite light absorber and charge transport layers. Various defects arise during the deposition of thin-film layers, such as defects in the bulk or surface and at the perovskite/electron transport layer (ETL) or perovskite/hole transport layer (HTL). These defects act as a catalyst and trigger the degradation of PSCs. The non-radiative recombination caused by these defects significantly lowers the open circuit voltage, fill factor and current density of the device. Various techniques have been established to develop pinhole-free and compact layers that could significantly improve the crystallinity of the perovskite and the ETL or HTL, thereby reducing the density of defects. In this review, we provide an overview of recent advances in the synthesis of perovskite materials using diverse techniques such as vapour deposition, spin coating (single and double steps), and hot casting. To our knowledge, the hot casting and spin coating approaches yield high photovoltaic parameters.