Enhancement of monolayer SnSe light absorption by strain engineering: A DFT calculation

Strain effects on the electronic and optical properties of monolayer SnSe is studied by APW + lo method in DFT framework. The applied strains cause direct-indirect transition of SnSe band gap which is mainly constructed by s/p hybridization. The armchair εac and zigzag εzz reduce the unstrained band gap of 1.05 eV down to 0 eV at 12% compression, but at 12% tension, the band gap decreases to 0.726–0.804 eV. The band gap always increases under biaxial strain εb at 12% compression to 12% tension. We observe an enhancement of real ε1(ω) and imaginary ε2(ω) parts of dielectric function by 14%–30% of magnitude, wider peak distribution to infrared and ultra-violet regions, and appearance of new peaks in the ε1(ω) and ε2(ω) spectrums. As a consequence, the light absorption α(ω) is significantly enhanced in the ultra-violet region and the absorption even starts at lower energy at infrared region. © 2019 Elsevier B.V.