Type-II Lateral Heterostructures of Monolayer Halide Double Perovskites for Optoelectronic Applications

Recently, layered halide double perovskites (A₄M^IM^IIIX₈) have attracted growing interest and provided a wide range of basic building blocks for fabricating vertical and lateral heterostructures (LHs). Here, we take Cs₄AgInI₈ and Cs₄CuBiI₈ as the representative compounds of monolayer double perovskites to design suitable LHs for optoelectronic applications using first-principles calculations. Our results reveal that the constructed (Cs₄CuBiI₈)₃/(Cs₄AgInI₈)₃ LH could possess the desired direct band gap and type-II band alignment. The electronic properties such as band gap and effective mass can be further tuned by applying strain or adjusting components. More importantly, we find that the transition dipole moments between the band edges can be modulated effectively by tensile strain and components, providing new insights for the rational utilization of double perovskites that possess partially forbidden transitions for optoelectronic devices. Our studies propose stable atomic structures for optoelectronic devices based on double perovskite LHs with desired electronic and optical properties.