Achievement of 16% milestone with 30cm×30cm-sized CIS-based thin-film submodules

The efficiency of 16.03% on a 30cm × 30cm-sized Cu(In, Ga)(Se, S)₂ (CIS)-based thin-film circuit was achieved by review of its design for absorber layer. Increase in a CIS-based absorber thickness confirms enhancement of short-circuit current density. In this study, we report that it is critical to understand the correlation between the film thickness of the absorber and sulfurization degree to improve the efficiency. It has been found that by optimizing the sulfurization degree as a function of the film thickness of a precursor layer, the carrier concentration and crystal growth are enhanced through an improved diffusion of gallium. From electron-back scattering diffraction maps and electron beam induced current profile analyses, it is confirmed that improvement in the crystallinity of the CIS-based absorber and extension of the space charge region by increased severity of sulfurization degree for thicker precursor layer. These results lead to the progress of improvement in the conversion efficiency.