Two-dimensional type-II vdW heterostructure MASnBr₃/MoS₂ for photovoltaic applications

Herein, we comprehensively investigated the structural, electronic, optical, and photocatalytic properties of van der Waals heterostructure (vdWHs) MASnBr₃/MoS₂ (MA: CH₃NH₃). Monolayer MASnBr₃ exhibits dynamical stability, as confirmed by phonon spectrum analysis, but suffers from a wide direct bandgap (2.72 eV at the HSE06-SOC (Heyd-Scuseria-Ernzerhof 2006 – Spin Orbit Coupling) level), limiting its photovoltaic efficiency. The formation of heterostructure with MoS₂ results in type-II band alignment that facilitates efficient carrier separation, with HSE06-SOC band gaps of 1.89 eV (for AA-configuration) and 1.36 eV (for AB-configuration), aligning optimally with the solar spectrum, while strain engineering further tunes the band gap, extending light absorption into the near-infrared region. The heterostructure exhibits remarkable optoelectronic performance, including a high optical absorption coefficient (8 × 10⁵ cm⁻¹) and a Spectroscopic Limited Maximum Efficiency (SLME) of up to 30 %, exceeding that of conventional lead-based perovskites and monolayer MASnBr₃. Favorable valence and conduction band offsets (VBO = 0.48 eV, CBO = 1.6 eV) ensure rapid electron-hole separation, while robust mechanical stability (Young's modulus ≈ 80 N·m⁻¹) underscores practical viability. These attributes, combined with its potential for photocatalytic hydrogen evolution, position the vdWHs MASnBr₃/MoS₂ as a promising candidate for sustainable photovoltaics and photocatalysis, offering tunable optoelectronic properties with robust structural stability.