Optimization of Sputtered CIGS Thin Films for Enhanced Optical Absorption
Abstract
The optical absorption improvement in CIGS absorber thin film is a critical phenomenon. In this study, the effect of the set film thickness and working gas pressure on the absorption properties of CIGS thin films was studied. CIGS films were RF sputtered at high (15 mTorr) and low (5 mTorr) pressure with different set thicknesses of 200 nm, 400 nm and 600 nm. It was demonstrated that, as expected, the absorption increases with film thickness. Meanwhile, the higher absorption is observed for the films grown at high pressure compared to low pressure grown counterparts at all film thickness which is believed due to the porous film nature of the former films. At high pressure sputter, the films with higher porosity and more rough film surfaces, which was determined by SEM and AFM roughness imaging, were obtained, which results in higher optical absorption. It was shown that by simply tuning the Ar gas pressure slightly during sputtering, the absorption can be improved at a reasonable rate.
Keywords
References
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