Design of two-dimensional halide perovskite composites for optoelectronic applications and beyond

Two-dimensional (2D) halide perovskites have attracted increasing attention because of their unique optical and electronic properties, resulting in versatile applications in the fields of energy, information, display and lighting, etc. However, due to some unfavorable characteristics of 2D halide perovskites, such as their low carrier mobility and low radiation recombination efficiency, researchers have combined them with other functional materials to form composites with enhanced features not observed in their individual components, manifesting the positive "1 + 1 > 2" effect. In this review, we summarize the latest progress and future perspectives of 2D halide perovskite composites, focusing on their structures, fundamental optoelectronic properties, characterization techniques and typical use. 2D halide perovskite composites have become the most recently discovered goldmine to be exploited for endless possibilities beyond optoelectronic applications and require joint endeavors of researchers from interdisciplinary fields.