Inorganic copper-based hole transport materials for perovskite photovoltaics: Challenges in normally structured cells, advances in photovoltaic performance and device stability

Abstract

As one of the key components of a perovskite solar cell (PSC), the hole transport layer (HTL) plays a crucial role in achieving both device high efficiencies and long-term stability. High power conversion efficiencies (PCEs) have been reported for PSCs with HTLs made of organic hole transport materials (HTMs). However, some of these materials have been shown to induce device instability, while others are stable but highly expensive. In this regard, various inorganic HTMs, with relevant physical and chemical properties, have been explored and investigated in PSCs as they are more stable and economically affordable. In this review, we summarize the development of inorganic copper-based HTMs in both normal and inverted PSC architectures. We put a special emphasis on the challenges related to their processing in the normal PSC geometry and the current advances in the photoelectric performance of both device structures. Moreover, the long-term stability of PSCs with p-types Cu-based compounds is discussed in comparison with state-of-art PSCs using organic HTMs. We hope that this review, by highlighting the potential of Cu-based HTMs to overcome the issues related to the use of organic HTMs in PSCs, will arouse more interests in these materials for further improvements in the performance metrics of their PSC devices.