Effect of surface passivation by two-step low pressure and temperature environment-grown thermal oxide layer for multi-crystalline silicon solar cells

• Main Authors: Liao, Shun-Sing, 廖順興
• Other Authors: Chang, Edward-Yi
• Format: Others
• Language: en_US
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/d8nte7

博士 === 國立交通大學 === 材料科學與工程學系所 === 107 === In this study, the efficiency of the multi-crystalline was improved by inserting a two-step growth thermal oxide layer as the surface passivation layer. First, we studying lower temperature (750 °C – 780 °C) two-step grown SiOx film as passivation layers between SiNx and N type emitter layer under atmosphere pressure. Compared to the conventional MC-SiSC, conversion efficiency was significantly increased by 0.37% with the surface passivation layer grown by low temperature two-step TO process. Second, we show that the efficiency and carrier life time of multi-crystalline silicon solar cells were significantly improved by using a low pressure (20000 Pa) and temperature (650 °C – 750 °C) environment grown thermal oxide (TO) as the surface passivation layer. In this experiment, during the first stage, the oxidation process was done at 650 °C and a lower pressure of 20000 Pa for 2 mins under the flow a gas mixture of N2/O2 in ratio of 2:1. In the second stage, a temperature of 750 °C was used at the same pressure for the post-growth annealing process under a pure N2 ambient for 25 mins. Consequently, conversion efficiency was significantly increased by 0.55% with the surface passivation layer grown by low pressure and temperature TO process. The sheet resistance, carrier lifetime, internal quantum efficiency (IQE), increased by 6.32 Ω/sq, 22.18 μs, 4.33%, respectively, and the average reflection was reduced of 0.62%. Finally, compared to the conversion efficiency of and lower temperature (650 °C – 750 °C) plus a low pressure (20000 Pa) TO layer was increased 0.18% than lower temperature (750 °C – 780 °C) two-step under atmosphere pressure TO layer. Thus, the low pressure and temperature thermal oxidation process was an efficient way to increase the efficiency of the multi-crystalline silicon solar cells.