Inorganic hole transport materials in perovskite solar cells are catching up

More research is required to further optimize device efficiency, stability, and reduce the materials cost as perovskite solar cells (PSCs) approach to industrialization. Modulating the optoelectronic features and chemical coupling of the hole transport materials (HTMs) remains a prominent field of study in PSCs due to the significant impact these materials have on the device performance and stability. In order to speed up the commercialization of these cells, it is also important to use cost-effective HTMs in PSCs. Inorganic-HTMs are superior to other types of HTMs in terms of their advantages in boosting device performance and producing PSCs at a reasonable cost, in addition to their superior charge transport capabilities, desired energy levels, and intrinsic thermal and chemical stability. A detailed overview of inorganic-HTMs, including metal oxides, cyanates, phthalocyanines, chalcogenides, nitrides, and carbides, is presented in this review. After briefly discussing the primary physical and optoelectronic characteristics of inorganic-HTMs, the critical functions of the above-mentioned materials as HTMs in PSCs are addressed. This review concludes by offering suggestions for future research that could considerably boost the performance of the PSCs with cost-effective inorganic-HTMs.