成果報告書詳細
管理番号20120000000564
タイトル*平成23年度中間年報 太陽エネルギー技術研究開発 太陽光発電システム次世代高性能技術の開発 極限シリコン結晶太陽電池の研究開発(次世代超薄型結晶シリコン太陽電池の低コスト・高効率化プロセス開発)
公開日2012/12/21
報告書年度2011-2011
委託先名シャープ株式会社
プロジェクト番号P07015
部署名新エネルギー部
和文要約和文要約等以下本編抜粋:[研究開発目標]
平成24 年度中間目標:
セル変換効率20%( 単結晶シリコン基板:厚さ100μm以下、サイズ150mm 角)、モジュールでの変換効率18%を達成する。
英文要約Title: Development of Photovoltaic Power Generation Technology, High Performance PV Generation System for the Future. R and D on Ultimate Wafer-based Si Solar Cells. (Development of low cost and high efficiency manufacturing process for next generation ultra thin crystalline silicon solar cell) (FY2010-FY2012) FY2011 Annual Report
Results:Development of next generation ultra thin high efficiency mono-crystalline silicon solar cell: 1. Development of Interdigitated Back Contact (IBC) solar cell structure. One of the most promising approaches to improve silicon solar cell performance is to eliminate the shadowing loss caused by the front electrode. Therefore we decided to develop this type of solar cell, namely IBC solar cell. We have already achieved 22.1 % conversion efficiency (A.M. 1.5G, 100 mW/cm2, 25 oC, in-house measurement) in 90 mm square cell (81 cm2).Furthermore, we have been investigating for further improvement of cell performance. In our present IBC cell, no diffusion region is formed between p+ and n+ region at the rear surface. However, the carrier recombination loss in this region can't be ignored. It will be possible to form any diffusion region there, increase BSF effect and reduce the recombination loss at the rear surface. The two-dimensional simulation clearly show that the doping concentration in this region affects cell efficiency and the light doped n- region is effective to improve the cell performance. Next, we verified this idea by actual cell sample fabrication. As a result, we confirmed that the cell efficiency is improved by forming n- region between p+ and n+ region. This suggests that the improvement of BSF effect reduces the recombination loss at the rear surface. 2. Development of high quality pn junction formation technology To achieve the high efficiency, it is necessary to suppress the reverse saturation current density at the pn junction to the utmost limit. The Hetero-Junction (HJ) technology that consists of the crystalline silicon and hydrogenated amorphous silicon (a-Si:H) thin layer is the one of the most promising approaches to upgrade the pn junction quality and to suppress the surface recombination loss. We thought that we should be able to strike a balance between high Voc and high short circuit current density (Jsc) by the combination of HJ and IBC solar cell structure. Thus we tried to fabricate Hetero-Junction Back Contact (HJBC) solar cell samples experimentally and we have already achieved 14.5 % conversion efficiency. However Voc was 665 mV and Jsc was 35.0 mA/cm2, those values were still low. We are continuing the investigation to analyze the cause of these low performances and to improve the HJBC solar cell. The key issue to improve the performance of HJ solar cell is the improvement of quality of a-Si:H thin layer deposition. We have confirmed that the effective minority carrier lifetime of the mono-crystalline Si wafer passivated with a-Si:H thin layer is very high, that is over 1 m second. Furthermore, we fabricated HJ solar cell using this layer and obtained very high Voc, that is 718 mV.
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