Abstract
•A selenization free CIGS absorber layer is fabricated by thermal evaporation.•Heat treatment during and after deposition is used to develop a novel pristine chalcopyrite CuIn0.7Ga0.3Se2 structure at a low temperature (250 °C).•Raman signatures of phase pure chalcopyrite structure are displayed.•Near optimum band gap values of CuIn0.7Ga0.3Se2.
Copper Indium Gallium Selenide (CIGS) thin film solar cell absorber layers are fabricated by the conventional co-evaporation of metal stack precursors followed by a selenization process at a high-temperature range. The article deals with an alternative approach to fabricate the CIGS layer by sequential evaporation of metal selenides followed by a low-temperature treatment (250 °C) during pre-and post-deposition processes. Our post annealing treatment on substrate heat treated film reported a first-ever pristine CuIn0.7Ga0.3Se2 thin film structure without selenization was reported at a very low temperature. A better microstructure with an enhanced grain growth, preferential (112) plane orientation, and Raman signatures of pristine chalcopyrite without a secondary Cu2-xSe phase at the surface was observed. Electron microscopy studies affirm the polycrystalline nature of film structure. Optical analyses have shown near-optimum values as of standard absorber layers. Crucial optical parameters such as refractive index, static and high-frequency dielectric constants were estimated by different relations. The values are concurrent with the semiconductor scale. These features in a low-temperature range optimistically land them as promising candidates in flexible electronics.
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