Inorganic Materials as Hole Selective Contacts and Intermediate Tunnel Junction Layer for Monolithic Perovskite‐CIGSe Tandem Solar Cells.

In order to surpass the theoretical limitation defined by the Shockley–Queisser equation for photovoltaic solar cells, multijunction devices are needed. Monolithic perovskite‐Cu(In, Ga)(Se, S)2 (CIGSe) tandem solar cells have recently become a hot research topic in photovoltaics because of the emergence of perovskite solar cells with high power conversion efficiency and the development of thin film chalcopyrite CIGSe solar cells with tunable bandgap and low cost manufacturing processes. In this review, some p‐type wide bandgap semiconductors are investigated as intermediate inorganic hole transport materials (IIHTM) and components of a tunnel junction in monolithic perovskite‐CIGSe tandem solar cells, which meet the requirements of band alignment and low‐temperature deposition process. The authors focus on designing a tandem configuration including band alignment, current matching, and optical management, describing some potential candidates of IIHTM owing to their successful implementation in single junction perovskite solar cells and the possibility of application in intermediate layers for tandem devices. Recent progress in the development of inorganic hole conductors is highlighted, and also some of the authors' work on IIHTM and their applications are presented. Finally, future research directions for IIHTM layers and monolithic perovskite‐CIGSe tandem solar cells are presented, with an aim to achieve higher photovoltaic performance than current devices. Potential candidates for inorganic intermediate layers with wide bandgaps as hole transport materials and one component of tunnel junction for the monolithic perovskite‐CIGSe tandem solar cells are reviewed. Several requirements for the fabrication of monolithic tandem devices are discussed in order to facilitate higher photovoltaic performance than in current devices. [ABSTRACT FROM AUTHOR]