Analysis And Optimization Of P-N Junction Manufacturing Process Metallurgical Silicon Solar Cells

This paper aims at studying the purification of metallurgical physical polycrystalline silicon solar cells, using the conventional screen printing technology. To improve the life time of minority carriers, a process of short-time phosphorus gettering was utilized. The minority carrier lifetime was increased from0.8-0.9μs to1.26-1.44μs. The p-n junction was formed by using the liquid source single diffusion of phosphorus doping. Through the control experiment, optimized parameters can be obtained as following:the diffusion temperature was806℃, nitrogen gas flow rate with the source was1100ml/min, the oxygen flux was1100ml/min,the protective nitrogen gas flow rate was25000ml/min, the inputting source time was23min. The average square resistance after diffusion was67.3Ω/□, increased by16.2Ω/□than non-optimal ones, so as to improve the p-n junction characteristics of metallurgical silicon cells. Using optimized diffusion process for small batch production of the cells, the on-line test of cells showed that the average conversion efficiency of metallurgical silicon cells after optimizing diffusion conditions increased from16.43%to16.60%. The open-circuit voltage average value was0.6334V, the short-circuit current average value was8.10A, the fill factor average value was76.48%. The test showed that there were still about20%cells with12V reverse leakage more than conventional standard, mainly coming from the nonuniformity of resistivity and impurities of original metallurgical silicon.