Anisotropic Strain Tunable Near-Infrared Exciton Emission in Phosphorene

• • Tensile strain along the zigzag direction increases the phosphorene bandgap, as governed by the negative hopping parameter t1 = -1.220 eV; this contrasts with MoS2, where tensile strain reduces the bandgap due to positive hopping parameters (t11, t22, t12 > 0), enabling opposite strain-tuning strategies for NIR versus visible emitters. • • The bandgap of phosphorene is dominated by the nearest-neighbor hopping terms: E_g^BP ≈ 4t1 + 2t2, with t1 = -1.220 eV and t2 = 3.665 eV; this simplification allows rapid prediction of strain effects, critical for designing NIR photodetectors and lasers with tailored emission wavelengths. • • For monolayer MoS2, the bandgap at K is given by E_g^MoS2 = ε1 - ε2 - 3t0 + (3/2)(t11 + t22) + 3√3 t12, where t0 is negative and t11, t22, t12 are positive; tensile strain reduces the bandgap, underscoring the material-specific strain response that must be accounted for in heterostructure integration. • • The anisotropic strain response in phosphorene enables selective tuning of NIR exciton emission, with potential for strain-tunable emitters operating in the 0.3–0.8 eV range (corresponding to 1.5–4 µm), essential for telecommunications and infrared sensing; this contrasts with TMDs, which typically operate in the visible range.