Highly efficient PERC cells fabricated using the low cost laser ablation process

Highly efficient passivated emitter and rear cells (PERC cells) were fabricated using low cost laser ablation (LA) for pilot production. The laser source for the LA system had a wavelength of 532 nm and pulse width of 20 ns. To minimize the damage created during the LA process, the laser power density was optimized at 2.8 J/cm2. Nevertheless, some damage occurred, such as dislocation and the formation of amorphous silicon, and was analyzed using energy-dispersive X-ray spectroscopy (EDS), Raman spectroscopy, and Sinton's quasi-steady-state photo-conductance (QSSPC). The measured laser damage depth was approximately 2.5 μm. Since the local contact depth (eutectic alloy+back surface field (BSF)) was over 10 μm when the cell fabrication was completed, this laser damage depth of 2.5 μm was not problematic. After optimizing the geometry of the local contacts, the measured efficiency of the laser-ablated PERC solar cell was 19.78%.