ИСТИНА

A process employing laser technique to texture the front surface of multicrystalline silicon (mc-Si) wafer followed by chemical etching has been applied to mc-Si solar cells. Pulsed laser irradiation with energy density of 3.5 J/cm2 enables formation of the typical pillar array structures with aspect ratio of ≥3 (depth to width). Weighted reflectance values below 3 % were achieved immediately after texturing which increased up to 5.5 % after acidic etch and up to 13.4% after alkaline etch. The removal of the defect layer induced by laser texturing reduces the thickness of the wafers from 200 μm down to ~140 μm. The application of laser texturing process to mc-Si solar cells results in an increase of short circuit current density by 5.2 mA/cm2 (+18%) compared to the planar reference cells. This benefit is provided by superior reflectance suppression and shallower refraction angles. Some fill factor and open-circuit voltage losses are attributed to non optimized phosphorus diffusion that resulted in a much higher sheet resistance of n+ emitter (~200 Ω/sq) compared to untextured planar wafers (40 Ω/sq). With a further adaptation of the diffusion process, significant improvements of the cell efficiency could be achieved in the future.