Twist-Angle Engineering of Atomically Thin Halide Perovskite/WSe2 Van der Waals Heterojunctions for Enhanced Optoelectronic Performance

Abstract

The development of atomic-level heterojunctions between halide perovskites and 2D van der Waals semiconductors offers a promising route to boost optoelectronic performance by tailoring interfacial coupling, yet achieving deterministic control of interlayer alignment at the atomic scale remains challenging. Here, we report atomically thin (PEA)₂PbBr₄/WSe₂ van der Waals heterojunctions with precisely defined twist angles (0°, 5°, 7°, 10°, 12° and 15°), and systematically investigate their twist-angle-dependent and optoelectronic responses. Twist-dependent Raman, PL and density-functional-theory analyses consistently show that increasing twist strengthens interlayer coupling, leading to phonon hardening, PL redshift and quenching, and a pronounced narrowing of the effective type-II bandgaps via enhanced interlayer hybridization and band-edge density of states. In line with this microscopic picture, the 15° heterojunction delivers a high photoresponsivity of 2.8 A W⁻¹, an on/off ratio of 2.33 × 10⁵, and a mobility of 117.1 cm² V⁻¹ s⁻¹ under 405 nm. Our results establish twist angle as a programmable, atomic-scale knob for jointly tuning band structure and device performance in perovskite/2D heterostructures, providing a general strategy for high-performance optoelectronic devices.