Investigation of Cu In,Ga Se2 thin film formation during the multi stage co evaporation process

Abstract

In order to transfer the potential for the high efficiencies seen for Cu In,Ga Se2 CIGSe thin films from co evaporation processes to cheaper large scale deposition techniques, a more intricate understanding of the CIGSe growth process for high quality material is required. Hence, the growth mechanism for chalcopyrite type thin films when varying the Cu content during a multi stage deposition process is studied. Break off experiments help to understand the intermediate growth stages of the thin film formation. The film structure and morphology are studied by X ray diffraction and scanning electron microscopy. The different phases at the film surface are identified by Raman spectroscopy. Depth resolved compositional analysis is carried out via glow discharge optical emission spectrometry. The experimental results imply an affinity of Na for material phases with a Cu poor composition, affirming a possible interaction of sodium with Cu vacancies mainly via In Ga Cu antisite defects. An efficiency of 12.7 for vacancy compound based devices is obtaine