In order to realize the modulation of band-gap profile in low-cost and printable CuInxGa1-xS2 thin-film solar cells, a simple chemical route, namely a multi-stage paste coating method, was developed. In particular, with this method, multiple coatings with two precursor solution pastes with different compositions were applied. Elemental analysis techniques confirmed the formation of three different graded Ga distributions (front, back, and front-and-back gradient) throughout the absorber films depending on the coating sequence with two different pastes. The back gradient cell showed the largest power conversion efficiency of 7.29%, which was almost two times larger than those of the non-graded cells.
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