Efficiency assessment of perovskite solar cells: A focus on hole transporting layers

The rapid advancement of perovskite solar cells (PSCs) marks a significant breakthrough in affordable photovoltaic technology with simple fabrication process and excellent performance. The remarkable intrinsic properties of perovskite materials, coupled with continuous optimization of key functional layers such as the hole transporting layer (HTL), have resulted in achieving an impressive power conversion efficiency of around 26 %. This review article primarily focuses on the analysis of different hole transporting materials (HTMs) used in the HTL of PSCs. The review instigates by presenting an overview of the developments in PSCs, followed by highlighting the crucial roles played by HTL in enhancing the photovoltaic performance of PSCs. Subsequently, the HTLs are broadly classified into organic as well as inorganic categories, and their respective pros and cons are discussed. By evaluating the reported HTLs in recent years, this review aims to offer insights and inspiration for the design and application of novel HTLs that can further enhance the performance of PSCs.