成果報告書詳細
管理番号20110000000836
タイトル*平成22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2011/7/28
報告書年度2010 - 2010
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:[研究開発の内容]
次世代超薄型高効率単結晶シリコン太陽電池の開発
(1)バックコンタクト(裏面電極型)セル構造開発
高効率セルを実現する為には受光面側に電極のないバックコンタクトセルが適している。
また、極薄ウエハを用いたモジュール製造にも適したセル構造としてバックコンタクトセルの開発を行う。本年度の検討において、バックコンタクト太陽電池セルを試作し、156.5mm 角/Φ199mm サイズ(240cm2)で19.8%(自社測定)の変換効率が得られた。また、薄型バックコンタクトセルに適したモジュール構造として、配線基板上に表面実装し、セル電極を配線に直接接続する表面実装方式を検討した。
(2)高品位pn接合形成技術開発
高効率実現の為には、pn 接合における逆方向飽和電流を極限まで抑制し、700mV を大きく越える高い開放電圧を得る必要がある。そのためにヘテロ接合などにより、高品位のpn接合を形成する技術を確立する。本年度は、バックコンタクト太陽電池の更なる高効率化のために、a-Si:H 層とのヘテロ接合を検討した。また、2 次元デバイス・シミュレーションによるヘテロ接合バックコンタクトセルの理論検討では、効率24.1%が得られ、この構造のポテンシャルが示された。さらに、ヘテロ接合バックコンタクトセルを試作し、Voc:635mVを得た。
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)
Results: 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 19.8 % conversion efficiency (A.M. 1.5G, 100 mW/cm2, 25 oC, in-house measurement) in 156.5 mm quasi-square cell (240 cm2). We also studied what module structure is suitable for thinner cells. IBC cells are usually connected among themselves by means of interconnector. However, in the case of thinner cell, the module fabrication becomes increasingly harder because the thinner cell is so fragile that the stress between the cell and the interconnector often causes cracks and chips in the cell. Thus we developed the module structure suitable for the thinner cell. In this structure, IBC cells are mounted on printed wiring board (PWB) or flexible printed circuit (FPC). IBC cell is directly mounted on PWB or FPC and the cell electrodes are connected to the wiring lines directly. We called this method surface-mount technology (SMT) concept. We fabricated the SMT concept module that consists of 24 pieces of 126 mm quasi-square IBC cell. The F.F. of this module is 0.781. On the other hand, the average F.F. of IBC cells used for this module is 0.789. The decrease of F.F. due to module process is only 1%. These are good evidences to show that SMT concept is one of most promising methods to fabricate IBC module. 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, and to obtain quite high open circuit voltage (Voc) far exceeding 700 mV. 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 develop the Hetero-Junction Back Contact (HJBC) solar cell. At first, we investigated the theoretical potential of HJBC solar cell using the 2-dimensional device simulation and obtained 24.1 % conversion efficiency as a result of the simulation. Thus we could theoretically confirm the potential of the HJBC solar cell. Secondly, we tried to fabricate HJBC solar cell samples experimentally. As a result, we were able to obtain normal IV characteristics and confirm the performance as the solar cell. However Voc was 635 mV and F.F. was 0.593, those values were still low. We will continue the investigation to analyze the cause of these low performances and to improve the HJBC solar cell hereafter.
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