Two-dimensional Dion-Jacobson halide perovskites as new-generation light absorbers for perovskite solar cells

Three-dimensional (3D) organic-inorganic halide perovskites have been regarded as promising sunlight harvesters for perovskite solar cells (PSCs). However, the intrinsic instability of 3D perovskites strongly limits their large-scale commercialization. Thus, the development of two-dimensional (2D) halide perovskites as light absorbers in PSCs has recently become a research hotspot, showing better stability than their 3D counterparts due to the introduction of bulky organic spacers. Among various 2D halide perovskites, Dion-Jacobson (DJ) phases exhibit a tighter connection between inorganic slabs than their Ruddlesden-Popper (RP) counterparts, leading to superior structural stability and charge transfer capability. Nevertheless, the power conversion efficiencies (PCEs) of DJ-PSCs are still inferior to their 3D counterparts. An in-time and comprehensive review of DJ perovskites as new-generation light absorbers for PSCs is presented by comparing of DJ perovskites and RP counterparts in terms of optical properties, crystal structure, charge transporting capability and energy level alignment. Furthermore, based on the summarized design criteria of halide perovskites for PSCs, several strategies are presented to improve the PCE and/or stability of DJ-PSCs. Finally, the remaining challenges and future directions for DJ-PSCs are presented and discussed. This review will provide guidelines for the fundamental understanding, design and fabrication of high-performance DJ-PSCs.