Superior photovoltaics/optoelectronics of two-dimensional halide perovskites

Taking advantage of the excellent stability and photoelectric properties, two-dimensional (2D) organic-inorganic halide perovskites have been widely researched and applied in optoelectronic and photovoltaic devices. The remarkable properties are attributed to the unique quantum well structures by intercalating large organic ammonium space layers. In this review, we first summarize the crystal structures and growth methods of 2D halide perovskite crystals. Then, the distinctive optical characteristics and enhanced stability under high humidity, phase stability, suppressed ion migration, and high formation energy, are discussed in detail. Furthermore, we discuss orientation control in 2D perovskite films. The applications of 2D perovskites in solar cells, photo detectors and X-ray detectors are discussed in detail. Finally, we propose an outlook and perspectives to overcome the present challenges and broaden this new class of perovskite materials with other 2D nanomaterials.