ABSTRACT Molybdenum disulfide (MoS 2 )/lead sulfide (PbS) heterostructures exhibit exceptional potential because of their strong light‐matter interactions and high carrier mobility. Critically, bandgap engineering can further optimize the light‐absorption range for next‐generation phototransistors. However, the bandgap engineering capability for MoS 2 /PbS heterojunctions formed by conventional transfer‐after‐chemical vapor deposition (CVD) fabrication is typically inherently restricted due to solely vertical interlayer coupling. Here, to realize wafer‐scale bandgap‐tunable MoS 2 /PbS phototransistors, we investigate the band structure of vertical and lateral MoS 2 /PbS heterojunctions via ab initio calculations and find that lateral heterojunctions in heterostructures dominate the bandgap tunability via tuning of the Type‐II band alignment. To achieve wafer‐scale uniformity, we investigated how plasma treatment modulates the thin‐film surface energy, and the results substantially improved fabrication scaling of MoS 2 /PbS heterojunctions from traditional micro‐scale level to an incredible 4‐inch wafer‐scale with near‐ideal yields (97%) and enabled bandgap tunability (from 1.24 to 0.61 eV). The resulting phototransistors exhibit a maximum responsivity of 88 A/W, specific detectivity of 4.77 × 10 12 Jones, and a typical on/off ratio of 3.16 × 10 7 . This work establishes a pathway for developing wafer‐scale bandgap‐tunable optoelectronics.
Tang et al. (2026) studied this question.