Study of the refractive index change in a-Si:H thin films patterned by 532 nm laser radiation for photovoltaic applications

Laser scribing of hydrogenated amorphous silicon (a-Si:H) is a crucial step in the fabrication of thin film photovoltaic modules. During such process, inherent thermo-mechanical effects associated to laser ablation mechanisms lead to thermal damages. In that sense, the state of the material remaining in the vicinity of the ablated area has a critical influence on the electrical properties of the final devices. In this work, a comprehensive analysis of refractive index variations for the material surrounding the ablated area by means of Infrared–Visible Fourier transform spectrometry is proposed. Besides, in order to evaluate the material microstructure, Raman spectroscopy is employed as a complimentary technique. It was seen that the refractive index variation decreased as the distance from the center of the ablated groove was increased. Likewise, a clear transition from highly crystalline to amorphous material could be also observed as a function of the distance from the groove.