화학공학소재연구정보센터
Korean Journal of Materials Research, Vol.21, No.5, 243-249, May, 2011
후면 형상에 따른 결정질 실리콘 태양전지의 후면전계 형성 및 특성
Back Surface Field Properties with Different Surface Conditions for Crystalline Silicon Solar Cells
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To reduce manufacturing costs of crystalline silicon solar cells, silicon wafers have become thinner. In relation to this, the properties of the aluminium-back surface field (Al-BSF) are considered an important factor in solar cell performance. Generally, screen-printing and a rapid thermal process (RTP) are utilized together to form the Al-BSF. This study evaluates Al- BSF formation on a (111) textured back surface compared with a (100) flat back surface with variation of ramp up rates from 18 to 89oC/s for the RTP annealing conditions. To make different back surface morphologies, one side texturing using a silicon nitride film and double side texturing were carried out. After aluminium screen-printing, Al-BSF formed according to the RTP annealing conditions. A metal etching process in hydrochloric acid solution was carried out to assess the quality of Al-BSF. Saturation currents were calculated by using quasi-steady-state photoconductance. The surface morphologies observed by scanning electron microscopy and a non-contacting optical profiler. Also, sheet resistances and bulk carrier concentration were measured by a 4-point probe and hall measurement system. From the results, a faster ramp up during Al-BSF formation yielded better quality than a slower ramp up process due to temperature uniformity of silicon and the aluminium surface. Also, in the Al- BSF formation process, the (111) textured back surface is significantly affected by the ramp up rates compared with the (100) flat back surface.
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