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  • 學位論文

透過氧化物中間層改質銅銦鎵硒太陽能電池之背電極介面

Rear Contact Interface Modification by Introducing Oxide Interfacial Layer in Cu(In, Ga)Se2 thin film solar cells

指導教授 : 賴志煌
本文將於2025/08/25開放下載。若您希望在開放下載時收到通知,可將文章加入收藏

摘要


根據IEA國際能源總署的統計結果,由於世界人口總數的不斷成長,石油燃料蘊藏不超過百年,因此開發再生能源燃料勢在必行。銅銦鎵硒薄膜太陽能電池具有較目前市佔率90%的矽晶太陽能電池較高的吸收係數,因此厚度可減薄至矽晶太陽能電池的百分之一倍,使應用可以更加廣泛,且成本與材料使用率的減少是非常可觀的;目前銅銦鎵硒薄膜太陽能電池的世界光電轉換效率達到23.35%,使得銅銦鎵硒太陽能電池逐漸受到學術界與產業界的重視,然而載子介面復合一直是限制銅銦鎵硒異質接面太陽能電池效率進一步增加的主要原因,相對於背電極與吸收層的接觸介面,有較多研究探討如何改善吸收層與緩衝層接觸介面的載子復合,因此本論文即著眼於如何改善背接觸介面的能帶結構,藉此提高元件光電轉換效率。 第一部分,我們提出透過將鉬背電極於氧氣氛下退火刻意在表面形成高功函數的氧化物達到降低背接觸介面能障的目的,進而使效率得到2%以上的提升,並以此來探討氧化物中間層對於元件表現的影響。 第二部分,接續第一部份的氧氣退火處理,我們從四大層面探討元件表現提升的原因,分別為(1)鹼金族元素擴散影響(2)MoSe2厚度影響(3)吸收層的品質(4)背接觸介面改善,最後利用變溫電性量測擬合得出背接觸介面能障與介面載子復合活化能確實可以透過氧化物中間層得到改善。 第三部份,我們引入氧化鎢中間層確保氧化鎢會於高溫硒化製程後存在於背接觸介面中,達到進一步降低背接觸介面能障效果,因此FF可以從無氧化處理的鉬背電極元件的65%提升至73%,並且有效達到效率的提升,最後我們推測出背接觸介面的能帶結構來解釋介面能障降低的原因。

並列摘要


According to the statistical results of the International Energy Agency, due to the limited resources that petroleum reserves do not exceed a hundred years and growing population of the world. The development of the renewable energy is imperative. Because of the higher absorption coefficient in Copper indium gallium selenide thin film solar cells than Silicon solar cells which holds over 90% market share, the thickness of the film could be reduced to one hundredth of the Silicon solar cells. Therefore, the application would be more extensive and the reduction in cost or materials utilization is extremely considerable. The highest conversion efficiency of CIGSe solar cells is 23.35% which attracts lots of attention of academia and industry, but the interface recombination has always been the critical reason to limit the further efficiency improvement in heterjunction CIGS solar cells. Compared with the rear contact interface, there are more studies about how to passivate the front interface recombination. As a result, we focus on how to modify the rear contact interface band structure to enhance the device conversion efficiency. In the first part, we propose intentionally to form a high work function oxide on the surface of molybdenum back electrode by annealing it in oxygen atmosphere. Therefore, the conversion efficiency could be enhanced more than 2% compared with as-deposited molybdenum back electrode. Afterwards, we discuss the influence of oxide interfacial layer on device performance base on this approach. In the second part, we discuss the performance improvement from four perspectives which are the effect of alkai elements diffusion, MoSe2 thickness, absorber quality and rear contact interface modification respectively. At last, we confirm the rear contact barrier height and interface recombination activation energy could be modify by fitting the results from low temperature measurement. In the third part, we introduce tungsten oxide as interfacial layer to make sure it will exist at the rear interface after selenization process that further reduces the back contact barrier height. Therefore, the fill factor will be improved from 65% to 73% and thereby enhance the device efficiency. Finally, we depict the rear contact interface band structure to explain the reason of reduced back barrier height.

參考文獻


[1] IEA. (2019). 國際能源總署(IEA)2018年能源效率市場報告解析. Available: https://km.twenergy.org.tw/DocumentFree/reference_more?id=208
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[5] 太陽能分類. Available: https://sites.google.com/site/ensatptd/tai-yang-guang-dian-fa-dian

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