A comparative study of solution based CIGS thin film growth on different glass substrates

CuIn_xGa_1−xSe_yS_2−y (CIGS) thin films were synthesized on glass substrates by a paste coating of Cu, In, and Ga precursor solution with a three-step heat treatment process: oxidation, sulfurization, and selenization. In particular, morphological changes of CIGS films for each heat treatment step were investigated with respect to the kinds of glass substrates: bare, Mo-coated, and F-doped SnO₂ (FTO) soda-lime glasses. Very high quality CIGS film with large grains and low degree of porosity was obtained on the bare glass substrate. Similar morphology of CIGS film was also acquired on the Mo-coated glass except the formation of an undesired Mo oxide interfacial layer due to the partial oxidation of Mo layer during the first heat treatment under ambient conditions. On the other hand, CIGS film with much smaller grains and higher degree of porosity was gained when FTO glass was used as a substrate, resulting in slight solar to electricity conversion behavior (0.20%). Higher power conversion efficiency (1.32%) was attained by the device with the CIGS film grown on Mo-coated glass in spite of the presence of a Mo oxide impurity layer.