Influence of laser scribing in the electrical properties of a-Si:H thin film photovoltaic modules

The third (P3) laser patterning step of thin film photovoltaic devices is studied experimentally using a diode pumped solid state laser with 532 nm wavelength and a delay generator. The effect on the electrical characteristics of the devices due to the patterning process is investigated by performing scribes on single, thin-film solar cells. As it is shown, in this type of experiments the inertia in the motion systems or in the scanner controlling the direction of the laser beam plays a critical role in the results. By controlling externally the output of the laser beam it is possible to overcome the inertia and investigate the real effect of the P3 laser scribing on the device electrical characteristics. When the laser scribing conditions are optimized and the inertia in the system is taken care of, the P3 process has very little effect on the device electrical characteristics. Translated to modules this means that by optimizing the P3 process, the decrease in the efficiency found when up-scaling from single cells to modules can be minimized (as far as the P3 process is concerned) to that coming from the removed area.