Effect of Laser Patterning on Properties of Crystalline Si Photovoltaic Cells and Substrates

Silicon used as active medium in solar cell production reflects a considerable part of solar light due to its high refraction index, especially when the light incidents not perpendicularly to its surface. Texturing of the surface can increase the solar energy coupling within an active medium. We present results of laser texturing of poly-Si solar cells surface by direct laser writing and novel Laser Beam Interference Ablation techniques. Solar cells with laser-modified surface were characterized by optical and Raman spectroscopy as well as photo-electrically. After laser texturing of polycrystalline silicon solar cells, reflection from their surface was reduced by up to 14%. Structural defects induced by laser irradiation and ablation decreased the lifetime of photo-generated charge carriers and they could not reach the p-n junction. Laser texturing of silicon substrate can be done using direct ablation by interfering laser beams. A reduction in the structure period was demonstrated by up to 3 times by sub-period shift of the workpiece between exposures.