太陽電池材料與結構之開發

The Development of Material and Structure for Solar Cell

陳易良(Yi-liang Chen)

指導教授 ： 林烱暐

大同大學/電機資訊學院/光電工程研究所/博士(2012年)

摘要

摘要
為提昇太陽電池功率轉換效能，有兩大方向必須努力:首先，讓多數光子進入太陽電池內部。其次、盡可能將這些光子轉換成電子，並全數輸出電池外部。我們提出一簡單的表面粗糙化方法將反射光抑制於極低的準位；以非晶矽膜所含多數微晶粒邊界為遮罩，搭配濕式蝕刻將矽晶片表面型態予以複雜化。此法能使晶片在250~850 nm波長範圍裡達成1.6 %之低反射結果。關於太陽電池主動層品質之改善，我們利用自行發展之能量輔助媒介結晶技術將金屬材料易於吸收紅外線的特性，有效使紅外線轉換成熱能。此熱量藉由金屬板覆蓋在非晶矽膜上而傳遞至矽膜，進而讓非晶矽再結晶成多晶矽。結晶後之多晶矽膜並未檢出金屬殘留。同時所得之多晶矽膜晶粒大約0.4 μm；平坦的矽膜僅有0.34 nm之表面粗糙度。第五單元的內容為我們以矽基電漿改質製程解決了氧化鋅與矽材料接面的密合度問題。一種氧化鋅與矽異質太陽電池得以完成。它可讓更多光子直接被吸收而產生更多光電流。另外，高導電且黝黑之奈米碳管在論文的第六單元中用來還原太陽電池表面複合所損失的電流。我們使用自我組裝方式，在柵狀電極間均勻散佈碳管形成電流還原網。既增加電流輸出，也不會減少光子入射的數目。最後一部分，第七單元的內容為討論電漿處理對於p-i-n型太陽電池的元件電性的影響。為了充份減少其中本質矽膜的缺陷數目，我們提出氫氬混合電漿解離大量氫原子將矽膜內的缺陷鈍化。與一般氫處理之元件相比，氫氬混成電漿處理大幅改善光電流輸出。然而整個製程需要最佳化，否則過度處理將導致本質層受到轟擊。元件空乏層之並聯電阻因此降低，元件開路電壓也因此減少。

關鍵字

網絡 ； 奈米碳管 ； 太陽電池 ； 改質 ； 鈍化 ； 氧化鋅 ； 金屬板 ； 多晶矽 ； 能量輔助媒介 ； 微遮罩 ； 非晶矽 ； 粗糙化 ； 抗反射 ； 本質 ； 混合 ； 電漿

並列摘要

Abstract
Enhancing the conversion efficiency of solar cells requires two conditions: (1) the absorption of photons into the solar cell must be maximized, and (2) the external output of the solar cell through the conversion of photons into electrons must be increased. This study proposes a simple method of surface roughening to suppress the reflection of incident light. An amorphous fine-grained silicon film was used as a micro-mask. When the sample was subjected to wet etching, the fine grain boundaries resulted in selective etching on the silicon wafer surface. The completed sample showed a complex morphology. This method produced samples in the 250 to 850 nm wavelength range, with a low average reflectance of 1.6 %. To enhance the quality of the solar cell emitter, an energy–assisted agent was used to allow the metal material to absorb infrared frequencies, which was then converted into heat. This heat passes through the metal plate cover to the amorphous silicon film, thereby allowing the amorphous silicon to crystallize into polysilicon. The content of metal atoms within the crystallized film has been proven to be negligible. The average grain size obtained was 0.4 μm, and the surface roughness was only approximately 0.34 nm. Chapter 5 focuses on the silane plasma modification process for solving the mismatch problem of zinc oxide and the silicon junction. This process can mitigate ZnO/p-Si interface problems for the production of effective solar cells. It allows for higher photon absorption, thereby generating more photocurrent. Chapter 6 presents a discussion on the high-conductivity dark carbon nanotubes used to restore current losses resulting from solar cell surface recombination. The self-assembly method was used, to be spread evenly between the finger electrode by carbon nanotubes to create a current restore network. The increase in photocurrent output does not reduce the number of incident photons. Finally, Chapter 7 discusses plasma treatment on the electrical characteristics of p-i-n solar cells. To eliminate the defects in silicon film, hybrid hydrogenation plasma treatment was used, and the dissociation of the hydrogen atom passivated silicon film defects. Compared to the general device for hydrogen treatment, hybrid hydrogenation plasma treatment enhanced photocurrent output significantly. However, the whole process needs the optimized to avoid excessive handling, which can result in selective etching of the intrinsic layer by hydrogen. The device within the depletion layer of the shunt resistance is lowered, thus leading to a reduced open circuit voltage.

並列關鍵字

carbon nanotube ； solar cell ； modification ； passivation ； zine oxide ； metal plate ； polysilicon ； energy-assisted agent ； micro-mask ； porous ； anti-reflective ； mesh ； intrinsic ； hybrid ； plasma

參考文獻

Chapter 1

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[1.2] P. Rappaport,“The electron-voltaic effect in p-n junctions induced by beta-particle bombardment” Phys. Rev. Vol. 93, pp. 246-247, (1954).

[1.3] J. J. Loferski,“Theoretical considerations governing the choice of the optimum semiconductor for photovoltaic solar energy conversion”J. Appl. Phys., Vol. 27, pp. 777-784,(1956).

[1.4] D. E. Carlson and C. R. Wronski,“Amorphous silicon solar cell” Appl. Phys. Lett. Vol.28, pp.671-673, (1976).