Effect of substrate temperatures on evaporated In_2S_3 thin film buffer layers for Cu(In,Ga)Se_2 solar cells

摘要

For the realization of vacuum in-line process in the fabrication of Cu(In,Ga)Se_2 (CIGS) solar cells, In_2S_3 thin film buffer layers for CIGS have been deposited on glasses and CIGS layers with a thickness of about 650 A by thermal evaporation process. During the thermal evaporation, the temperature of the substrate was varied from room temperature to 500 ℃ by heating and the grown In_2S_3 films were investigated and analyzed in terms of the optimized buffer layer for CIGS solar cells. From the results of scanning electron microscope and X-ray diffraction, the In_2S_3 thin film deposited at a higher substrate temperature showed the larger grain size and the films have amorphous structural characteristics. Although the structural characteristics such as the atomic ratio of In to S and transmittance of the In_2S_3 thin films were not proportional to temperature, it was possible to obtain the large optical band gap of In_2S_3 films of about 3.8-3.9 eV enough to be used as the buffer layer of CIGS.