An Innovative Light Trapping Structure Fabrication Method on Diamond-Wire-Sawing Multi-Crystalline Silicon Wafers

An innovative fabrication method of light trapping structures on the surface of diamond-wire-sawing multi-crystalline silicon (DWS mc-Si) is proposed, which may trigger new progress in photovoltaic (PV) industry. A simple pre-etching step with HNO3/HF solution is used to remove the saw marks of the wafers as well as amorphous silicon layers, and form vermicular micro-hollows. Then, the HNO3/HF fog formed by ultrasonic vibration etches the silicon surface to fabricate nano-scale porous structures on the above microstructures. This micro-nano composite structure (MNCS) surface shows low average light reflectivity (similar to 5.5%) and relatively higher effective minority carrier lifetime (similar to 5.2 mu s). The innovative method is applied to fabricate the 156 mm x 156 mm DWS me-Si solar cells and the conversion efficiency of 18.01% has been obtained, which is 0.93% higher than the cells without MNCS. This method matches well with current PV industrial processes, which shows a promising prospect.