Interlayer coupling driven by polarization and stacking: A mechanism for tailoring optoelectronic properties in CuInP2S6/AsSBr heterostructures

Two-dimensional (2D) van der Waals (vdW) ferroelectric heterostructures serve as an ideal platform for tunable optoelectronic devices, yet the precise regulation mechanism of interlayer coupling on their performance remains unclear. Here, a developed method to systematically investigate the interlayer coupling in CuInP2S6/AsSBr (CIPS/ASB) heterostructures based on first-principles calculations and theoretical calculations is proposed. The interlayer coupling constant K and interlayer coupling strength t are primarily driven by enhanced pz-orbital overlap, and the heterostructures with an S–S interface exhibit stronger coupling, K = ∼23 × 1019 N/m3 and t = ∼0.7 eV, than those with an S–Br interface, K = ∼15 × 1019 N/m3 and t = ∼0.5 eV. We find the tunable coupling by strain governs a spectrum of functional responses: it dictates band alignment transitions between type-I and type-II under strain at ∼4%, modulates interlayer vibrational modes at ultralow frequencies ∼28 cm−1, and switches semiconducting behavior between n-type and p-type to govern the electronic band structure and charge transfer dynamics of heterostructures. Crucially, optimized interlayer coupling in the CIPS(u)/ASB(d) configuration yields exceptional transport properties, achieving a hole mobility of 2990 cm2/V s. Consequently, power conversion efficiency is maximized at 9.25%, demonstrating that polarization- and stacking-engineered interlayer coupling provides a deterministic route to tailor optoelectronic performance. The calculations are consistent with the available evidence, implying that the proposed model could be a general approach to deal with interlayer coupling for designing high performance 2D vdW heterostructures.