Investigation On Noval Texturization Of Crystalline Silicon Solar Cells

Texturing is one of the key processes in high efficiency solar cell fabrication. Textured wafer surface can effectively improve short-circuit current and lead to an improvement of solar cell performance.Firstly, the reaction mechanism of silicon texturing in HF/HNO3/H2O system was carefully studied. By changing the ratio in etching solution, temperature and etching duration, reaction rate, wafer reflectance and electrical properties of solar cells were studied. With the increase of HF in HF/HNO3/H2O system, reaction rate increased first then decreased, and keep increasing as the rising of temperature. Wafers treated by HF: HNO3 =3: 1 solution had the lowest reflectance after texturization, but after the anti-reflectance coating process by PECVD, the advantage on reflectance was weakened. On the electrical properties, efficiency of wafers in HF: HNO3 = 3:1 group was low, while HF: HNO3 = 1: 5 group, with a relatively higher reflectance, had the highest cell efficiency.According to the study on reaction mechanism of silicon texturing in HF/HNO3/H2O system, this dissertation reported a novel approach on the surface treatment of multi-crystalline silicon using a HNO3-rich HF/HNO3 mixture, followed by a secondary texturing treatment using a HF-rich HF/HNO3 mixture, which resulted in lower reflectivity on silicon surface. After texturing treatment, scanning electron microscopy (SEM) and Carry 5000 spectrophotometer were utilized to determine optical properties of silicon surface. The reflectivity (without ARC) of wafers using secondary texturing treatment was markedly reduced to 20.34%, compared to conventional treatment of 22.70%. Besides, the novel approach of secondary texturing was used in solar cell fabrication, and electrical properties were measured for evaluation. The results showed that comparing with conventional treatment, secondary texturing resulted in an increase of short circuit current Jsc, open circuit voltage Voc, fill factor FF and efficiencyη. Tests have shown the highest efficiency of solar cells using optimized secondary texturing treatment at 15.45%.