Validation of monolithic interconnection conductivity in laser scribed CIGS thin-film solar cells

Abstract

Over the last few years, thin-film based CIGS solar cell technology became even more attractive for producers and end-users. Implementation of laser based tools for module scribing still face serious challenges in terms of the laser damage to the CIGS active layer. Shunt formation near the scribing zone can lead to module efficiency losses, therefore optimization of laser based processes according to the cell electrical behavior is needed. We investigate two methods for cell parallel resistance measurement, including the linear laser scribing technique (LLST) and the nested circular laser scribing technique (NCLST). Also, we introduce simple cell conductance simulation. We found that for high conducting samples the series resistance of the top-contact layer plays significant role in the measurement of the structure parallel conductance, therefore careful measurement interpretation is needed. We also found, that he LLST technique provided more reliable measurement in these conditions. It was possible to optimize the scribing geometry and minimize measurement errors caused by the AZO film series resistance. The in-process laser-induced shunt evaluation is a useful method for scribing process optimization in the same material, although using both LLST and NCLST techniques, the fitting results are more reliable for low conducting samples.