Layer-dependent electronic and optical properties of tin monoxide: a potential candidate in photovoltaic applications

Tunable band gaps make two-dimensional (2D) SnO a promising candidate for a wide variety of applications in optoelectronic devices. In this work, we calculated the structural, electronic, and optical properties of monolayer and mutilayer SnO up to seven layers based on density functional theory. We found that the band gaps of SnO can vary from 0.61 eV to 4.05 eV as the layer number of SnO decreases from seven to one, which is mainly because of the interlayer coupling effect. The interlayer coupling ensures improved carrier transport properties between neighbouring layers, which can benefit the performance of 2D SnO in photovoltaic applications. In particular, a suitable band gap of 1.20 eV for solar cell applications is obtained in trilayer SnO, and the predicted theoretical efficiency of solar cells with trilayer SnO as the active material achieves a high value exceeding 16%, which is relatively high for 2D materials.