Two-dimensional Janus Sn₂SSe and SnGeS₂ semiconductors as strong absorber candidates for photovoltaic solar cells

Abstract

Two-dimensional materials provide new opportunities for the next generation of effective and ultrathin photovoltaic solar cells. Herein, we propose Janus monolayers of Tin monochalcogenides, especially Janus Sn₂SSe (type TA) and SnGeS₂ (type TB) nanosheets, as strong absorber candidates for solar energy conversion, referring to their excellent electronic and optical properties. Interestingly, based on the first-principles computations, both Janus Sn₂SSe and SnGeS₂ monolayers possess semiconductor character with indirect and moderate band gaps of 1.60 and 1.61eV, respectively. Accordingly, the considered systems, Sn₂SSe and SnGeS₂ single-layers, have high absorption coefficient, reaching up to 49.7 and 62.5μm⁻¹, high optical conductivity of about 4513 and 3559Ω⁻¹cm⁻¹, as well as low reflectivity never exceed 34.6 and 38.5% in visible region, respectively. Additionally, the maximum photovoltaic efficiency of single-junction solar cells based on SnGeS₂ and Sn₂SSe nanosheets can reach as high as 27.47% and 28.12%, respectively. The present outstanding results would motivate both theoretical and experimental researchers to deepen the study of the potential applications of two-dimensional Janus materials based on Tin monochalcogenides in solar cell technology.