Thickness modulated optical and bandgap properties at visible frequencies of GeSe thin films

Abstract

GeSe holds significant potential for solar cell and spectral absorber applications due to its excellent absorption characteristics. However, the influence of thin film thickness on GeSe optical properties remains underexplored. In this study, we achieve the modulation of GeSe thin films’ optical and bandgap properties by varying their thicknesses. Non-destructive and highly accurate spectroscopic ellipsometry is employed to determine the complex optical constants, reflectivity, and bandgaps of GeSe thin films with different thicknesses. The multicolor phenomenon of GeSe adjusted by its thickness, is interpreted by the complementary color that the wavelength absorbed by the material. A negative correlation between the bandgaps and thin film thicknesses is extracted by calculating the Tauc-plot (αhν)^1/2. This phenomenon is verified by the first-principles calculations by applying the compressive strain along the zigzag direction. Our findings provide a solid foundation for further research and practical applications for GeSe depending on thickness.