ABSTRACT
Perovskite solar cells (PSCs) have recently received much attention in photovoltaics research due to their excellent performance. The PSCs have attained 25.2% power conversion efficiency (PCE) and more developments have been carried out to improve their PCE and functional stability. The PCE and stability of PSCs are controlled by each functional layer including the active layer, electron transporting layer (ETL), and hole transporting layer ( HTL). The ETL and HTL are important components in PSCs owing to their nature of effective charge collection. The hole-transporting materials (HTMs) in PSCs are categorized as organic, inorganic, and polymer-based hole transporting layers. Mainly, we are going to discuss numerous inorganic HTMs which possess high chemical stability as well as cost-effective material. Our aim is to provide detailed information of the design and fabrication details of novel HTMs to improve the PSC’s performance based on the recently reported HTMs. PSCs rely heavily on HTMs to improve the PCE and stability of the device. The number of HTMs such as organic, polymer, carbon, and inorganic materials has increased significantly in recent years. Among them, the all-inorganic HTMs are receiving great attention as they have a higher PCE and are more stable.
