Optical and morphological properties of Ge-incorporated polycrystalline Sb₂Se₃ thin-film for photovoltaic applications

Crystalline Ge-incorporated Sb₂Se₃ thin-films are the promising absorber material for third-generation solar cells due to its optical, electrical, and material properties with earth-abundant materials. In this contribution, we have grown polycrystalline Ge-incorporated Sb₂Se₃ thin-film absorbers and conducted morphological and optical analysis by Scanning Electron Microscopy and UV–Vis spectroscopy along with the chemical structure analysis with Raman Spectroscopy for photovoltaic absorber applications. Ge-incorporated Sb₂Se₃ thin-films were deposited with Vapor Transport Deposition techniques, using thermally evaporated Sb₂Se₃ and Ge from each Sb₂Se₃ and Ge nanopowder source as precursors. Evaporation temperatures of Sb₂Se₃ and Ge nanopowder sources were independently controlled in the different heating zones of the furnace. At the deposition temperature of 300 °C, grains of Ge-incorporated Sb₂Se₃ thin-film begin to grow due to the increased crystallization temperature by Ge incorporation. With temperature-dependent absorption spectrum and the indirect optical transition natures, the optical bandgap of Ge-incorporated Sb₂Se₃ absorbers is extracted as 1.15 eV and 1.23 eV for samples grown at 500 °C and 520 °C.