成果報告書詳細
管理番号20140000000597
タイトル*平成25年度中間年報 新エネルギー技術研究開発 革新的太陽光発電技術研究開発 (革新型太陽電池国際研究拠点整備事業) 低倍率集光型薄膜フルスペクトル太陽電池の研究開発 (構造設計とカルコパイライト系トップセル)
公開日2015/2/19
報告書年度2013 - 2013
委託先名学校法人立命館
プロジェクト番号P07015
部署名新エネルギー部
和文要約
英文要約Lift-off technology to realize full spectrum solar cells has been developed. In this fiscal year, we worked on lift-off technology of chalcopyrite solar cells. High efficiency chalcopyrite solar cells typically employ substrate-type structure due to process temperature limitation. Buffer and window layers are generally deposited after chalcopyrite thin film growth. If chalcopyrite thin films are deposited on buffer and window layers at 550 degree Celsius which is typical temperature for high quality chalcopyrite growth, buffer and window layers deteriorate and thus output voltage of the device drastically decreases. Thus, in the current understanding, substrate-type structure is important to realize high efficiency chalcopyrite solar cells. In the lift-off technology, an alternative glass substrate is attached on the surface of high efficiency chalcopyrite solar cells and peeled off from chalcopyrite and back contact interface. Then, transparent electrode is deposited on the peeled-off surface of the chalcopyrite film to fabricate high efficiency superstrate-type chalcopyrite solar cells with transparency for sub-Eg light. Our final goal is to establish the lift-off technology for high efficiency Cu(In,Ga)Se2 (CIGS) and Ag(In,Ga)Se2 (AIGS) solar cells and to fabricate high efficiency full-spectrum solar cells. In this fiscal year, the basic process of the lift-off technology for CIGS solar cells was developed. First, substrate-type CIGS solar cells with Al-NiCr/ZnO:Al/ZnO/CdS/CIGS/Mo/Glass structure was fabricated. Then, alternative glass was attached on the cell surface with transparent glue. The glass/glue/Al-NiCr/ZnO:Al/ZnO/CdS/CIGS structure was peeled off at CIGS/Mo interface. Then, the back contact of MoO3 (20 nm in thickness)/ZnO:Al or MoO3 (20 nm in thickness)/Au stacked structure was directly deposited on the peeled off surface. In these cells, photocurrent could be obtained due to the large work function of MoO3. However, series resistances of these cells were very high owing to the high resistivity of MoO3. To solve this problem, thin MoO3 (~10 nm in thickness) was deposited between CIGS and Au back contact (~5 nm in thickness). In this case, short-circuit current of almost 70% for the reference cell was obtained and double-diode like current-voltage behavior was improved. However, series resistance was high compared to the reference substrate-type CIGS cells. Thus, thickness of MoO3 should be optimized to realize high efficiency lift-off solar cells. In addition, we tried to peel off AIGS and middle-gap CIGS absorber layers. Although middle-gap CIGS absorber layers could be peeled off, AIGS absorber layers could not be peeled off. Thus, the lift-off technique should be improved to peel off AIGS absorber layer.
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