All-laser scribing for thin-film CuInGaSe2 solar cells

This paper describes the results from collaborative efforts in establishing an all-laser scribing technological capability for fabricating monolithically integrated CuInGaSe₂ (CIGS) mini-modules. The scribing parameters required for each of the three scribing steps (P1, P2, P3) were determined and optimized by using three specific samples fabricated at NREL. A fiber laser system using a single wavelength at 1064 nm was employed for the scribing, which allowed fine control of programmable pulse shape and pulse train. In general, the three scribe lines were clean and smooth. For the first time, two mini-modules, with an effective area of ~7-cm × 7-cm having 10 cell strips in series connection, were fabricated by the “all-laser-scribing” technology. Small-beam localized quantum efficiency (QE) analysis showed large non-uniformity across the cell arrays. Performance-degrading factors were investigated by photoluminescence (PL) and electroluminescence (EL) analysis. By increasing the ZnO:Al (AZO) thickness and re-scribing with P3, the two reworked mini-modules showed substantial improvements in efficiency (best at 8.3%) with a decrease in series resistance and an increase in shunt resistance and fill factor.