Ultrashort pulsed laser induced material lift-off processing of CZTSe thin-film solar cells

摘要

The thin-film Cu-chalcopyrite-based solar cell technologies are becoming more attractive due to their lower cost and optimal performance. High efficiency of small cells might be maintained with the transition to larger areas if small segments are interconnected in series in order to reduce photocurrent in thin films and resistance losses. Interconnect formation is based on three step scribing processes and use of laser is thus crucial for performance of the device. For the first time we demonstrate the possibility to scribe the CZTSe thin-film solar cell structures with picosecond lasers. Investigations on the material lift-off effect in the CZTSe thin film were performed and the method was approved for the damage-free front-side scribing processes. Single pulse ablation and scribing experiments in the thin-film solar cell structures together with theoretical modeling of laser energy coupling in the complex CZTSe structure are presented. We found that the absorber layer removal process was triggered by a micro-explosive effect induced by high pressure of sublimated material due to temperature increase in molybdenum-CZTSe interface. This facilitated to minimize the remaining thermal effects since the laser-affected material was removed by thermo-mechanical process.