Selective ablation of thin films in latest generation CIGS solar cells with picosecond pulses

Abstract

Recent developments in Cu(In,Ga)Se₂ (CIGS) thin film photovoltaics enabled the manufacturers to produce highly efficient solar modules. Nevertheless, the production process still lacks a competitive process for module patterning. Today, the industry standard for the serial interconnection of cells is still based on mechanical scribing for the P2 and P3 process. A reduction of the non-productive "dead zone" between the P1 and P3 scribes is crucial for further increasing module efficiency. Compact and affordable picosecond pulsed laser sources are promising tools towards all-laser scribing of CIGS solar modules. We conducted an extensive parameter study comprising picosecond laser sources from 355 to 1064 nm wavelength and 10 to 50 ps pulse duration. Scribing results were analyzed by laser scanning microscope, scanning electron microscope and energy dispersive X-ray spectroscopy. We developed stable and reliable processes for the P1, P2 and P3 scribe. The best parameter sets were then used for the production of functional mini-modules. For comparison, the same was done for a selection of nanosecond pulsed lasers. Standardized analysis of the modules has shown superior electrical performance of the interconnections and confirmed the feasibility of a dead zone width of less than 200 μm on an entire mini module.