Improvement of Performance of Amorphous Silicon-Germanium Thin-Film Solar Modules With Large Width P2 Process Technology

In this paper, the laser power density is varied to increase the P2 laser spot size to investigate its effects on the performance of hydrogenated amorphous silicon-germanium (a-SiGe:H) thin-film solar modules. A larger P2 line spot size is expected to lower the series resistance of the modules, due to the increased contact area between the front and rear electrodes. However, increasing the laser power density faces several problems, which are: 1) damage of the SnO2 front electrode if the used power density exceeds the ablation threshold; 2) reduced quality of a-SiGe: H films; and 3) low spot size increasing rate at high power densities. The first can further lead to the presence of silicon oxide formation at the bottom of the P2 scribes. This paper demonstrates another method to obtain a larger spot size. A multiple P2 line scribing process has been performed to increase the spot size without deteriorating the film's quality and the module performance. Finally, a 6-P2 linewidth of about 160 mu m leads to a balance between the gain in fill factor and the loss in photocurrent. The optimal module conversion efficiency of 8.82%, which is 8.7% higher than that using a single P2 line process, can be obtained.