Células solares bifaciais finas com campo retrodifusor localizado de alumínio e seletivo de boro e alumínio

• Ano de defesa: 2012
• Autor(a) principal: Osório, Vanessa da Conceição
• Orientador(a): Moehlecke, Adriano
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Pontifícia Universidade Católica do Rio Grande do Sul; Porto Alegre
• Palavras-chave em Português: ENGENHARIA DE MATERIAIS; CÉLULAS SOLARES
• Link de acesso: http://hdl.handle.net/10923/3321

The aim of this work is to develop and optimize processes for manufacturing of bifacial silicon solar cells with n+pp+ structure and by using 150 μm thick p-type Cz-Si and FZ-Si wafers. Local BSF was implemented by Al deposited by screen-printing and diffused in a belt furnace and surfaces were passivated by SiO2. Initially, the process for thinning the wafers was optimized and the average value of (146 ± 4) μm was obtained after texturing, obtaining an average reflectance of 11. 2 %. The Al and Ag/Al pastes diffusion/firing was optimized as well as analyzed different approaches to passivate the surfaces with SiO2. It was observed that the best temperature for diffusion/firing was 840 °C for cells without passivation oxide and 850 °C for those with a SiO2 layer with a thickness of approximately 10 nm. The analysis of the minority-carrier lifetime showed that phosphorus diffusion produced gettering, but due to contamination in belt surface, minority-carrier lifetime decreased, reaching values similar to the initial. In order to improve the cell efficiency when it is illuminated by p face with local Al-BSF, boron (PBF20) was deposited on the rear face and two different orders of boron diffusion in the process were checked. For the process called α, in which the boron was diffused after phosphorus, the best efficiency obtained was 11. 2% when the n+ face was illuminated and it was 8. 3% when the cell was illuminated by the p+ side. For the process called β, with boron diffusion performed before the phosphorus diffusion (producing a n+ region with sheet resistance of 43 Ω/□) and with antireflective coating (AR) on both sides, the efficiency achieved was 14% when the solar cell was illuminated by n+ face and it was of 10. 4% when illuminated by p+ face. With the comparison of experimental results of the Cz-Si and FZ-Si cells, it was possible to conclude that, there is no advantage in using substrates higher life time of minority carriers considering the developed processes.