Wu C.-H.Chen F.-S.Lin S.-H.Ou C.-Y.Lu C.-H.2019-05-132019-05-13201820531591https://scholars.lib.ntu.edu.tw/handle/123456789/407338Copper indium gallium diselenide (Cu(In,Ga)Se 2 ) films with different gallium-ion contents were prepared via a spin coating method followed by a selenization process. Increasing the gallium-ion contents of the prepared films decreased the lattice constants and increased the band gaps. Secondary ion mass spectroscopy analysis revealed that Cu(In,Ga)Se 2 films with different band gap grading types were successfully fabricated. Increasing the contents of gallium ions near the substrate resulted in an increase in the short-circuit current density. On the other hand, increasing in the contents of gallium ions near the surface of the Cu(In,Ga)Se 2 films significantly increased open-circuit voltage V oc . By combining a normal and a reverse grading of gallium-ion contents, Cu(In,Ga)Se 2 films with double grading types of gallium-ions contents exhibited superior electrical properties. The conversion efficiency and fill factor of solar cells with a double grading type of gallium-ion contents reached 6% and 58.7%, respectively. ? 2018 IOP Publishing Ltd.chalcopyriteCu(In,Ga)Se 2gallium gradingspin coatingjournal article10.1088/2053-1591/aaa4172-s2.0-85043507722https://www.scopus.com/inward/record.uri?eid=2-s2.0-85043507722&doi=10.1088%2f2053-1591%2faaa417&partnerID=40&md5=d80663ce3483daaaa28fee3c1e8ad28e