Phase-dependent materials design and characteristic properties of two-dimensional (2D) halide perovskite single crystals for optoelectronic applications

Two-dimensional organic-inorganic hybrid halide perovskites have garnered much attention owing to their outstanding stability alongside unique quantum-well structures and anisotropic properties, leading to improved charge dynamics. Two-dimensional perovskites can be divided into three phases including Ruddlesden-Popper, Dion-Jacobson, and Alternating cations in the interlayer space phase. Each phase of these perovskites shows distinguished phase-dependent structural and optoelectrical properties. Tuning their properties by designing the materials can be a key strategy to enhance the device performance in optoelectrical applications. Configuration of spacer cations and the control of octahedral layer numbers (n) can be important parameters in material design, enabling the tuning of dielectric properties, exciton binding energy, and bandgaps, as well as materials structures, thereby influencing stability and charge transport behaviors. In this point, two-dimensional perovskite single crystals can play essential roles in not only understanding phase-dependent intrinsic natures but also enhancing performance of optoelectronic applications, specifically owing to their long carrier diffusion length and enhanced stability with little grain boundaries and low trap density. This review will deliver the strategy of phase-dependent materials design with an understanding of their anisotropic properties and charge dynamics for optoelectronic applications, including photodetectors and X-ray detectors.