Review of current progress in inorganic hole-transport materials for perovskite solar cells

Abstract Plenty of options for inorganic electron transport materials (ETMs) for perovskite solar cells (PSCs) are available. However, most hole transport materials (HTMs) is of organic nature. Organic materials are less stable as they are easily degraded by water and oxygen. Developing more variants of inorganic HTM is a major challenge. Till date, many materials have been reported, but their performance has not superseded that of their organic counterparts. In this review article, we look into the various inorganic HTMs that are available and analyze their performance. Apart from stability, their performance is also a concern for reproducible parameters of device performance. CuSCN, NiOx and MoS2 based PSCs are highly stable devices, maintaining power conversion efficiency (PCEs) over 20% whereas, number of devices made from CuI, CuOx, CuS, CuGaO2 and MoOx but shows low PCEs below 20%. Recently, HTM-free carbon/CNTs/rGO based PSCs shows promises for commercialization. Inorganic HTMs is overcoming the stability and cost issue over organic HTMs, various techniques, their novelty is shown in this work which will contribute in paving a path for synthesizing the ideal inorganic HTM for PSCs.