Luminescence properties of Ga-graded Cu(In,Ga)Se2 thin films

► The influence of Ga-grading on the luminescence of Cu(In,Ga)Se2 (CIGS) films is investigated. ► The emission energies from Ga-graded CIGS films correspond to the local band-gaps. ► The band-gap grading is measured using monochromatic cathodoluminescence cross section imaging. ► Charge carrier drift to the band-gap minimum is observed and described in a model. ► Ignoring grading related effects leads to misinterpretation of luminescence data.