有機無機混合太陽電池製程之研究

The Study and Fabrication on Organic-Inorganic Hybrid Solar Cells

鄭弘彬(Hung-Pin Cheng)

指導教授 ： 洪勝富

國立清華大學/電機資訊學院/電子工程研究所/碩士(2006年)

摘要

以共軛高分子製作的有機太陽電池具有質輕、製程簡單且易於大面積製作的特點，由於共軛高分子材料具有較低的電子遷移率，尋找可用以傳輸電子的材料，可大幅提高共軛高分子太陽電池的效率。
本論文以硒化鎘(CdSe)膠體奈米晶體為電子傳輸材料，與共軛高分子P3HT(poly(3-hexylthiophene))混摻形成太陽電池元件的主動層。無機膠體奈米晶體具有可溶解於有機溶劑的特性，且可合成具有方向性的形狀，利於形成直接傳輸電子的路徑。利用旋轉塗佈的主動層具有塊材異質接面的特性，克服了共軛高分子中激子擴散長度過短的問題，且硒化鎘奈米晶體與P3HT界面所形成的異質接面，可有效分離光激發激子，與P3HT單層相比，P3HT混摻硒化鎘奈米晶體的光電流可提升100倍以上，。
本論文主要著重在有機無機混合太陽電池元件製程的建立與理解，探討可能影響元件表現的製程變數。在奈米晶體材料處理方面，多次表面改質可改良奈米晶體與共軛高分子的界面特性，以利電荷分離；使用不同比例的混合溶劑，可改善主動層中奈米晶體的分散性。在元件製程方面，利用不同溫度對主動層加熱退火，改善主動層結晶情況，可加強載子傳輸的效益；利用高沸點溶劑，在超低轉速下形成主動層，溶劑慢速的揮發可改善共軛高分子材料的排列，有利於載子傳輸。

關鍵字

有機無機混合太陽電池 ； 共軛高分子 ； 奈米晶體 ； 塊材異質接面

並列摘要

Organic Solar Cells fabricated by conjugated polymer using solution-based processes are light-weighted, cost-effective in manufacturing and scalable to large-area devices. Due to the low electron mobility of conjugated polymer, it is believed that using materials which can efficiently transport electron may enhance the performance of the solar cells.
We fabricate the active layer of solar cells by using blends of P3HT and colloidal CdSe nanorods. Colloidal nanorods are soluble in organic solvent and are able to provide a direct route for electron transport due to their anisotropic shape. Active layer spin coated by blend forms bulk heterojunction, which provide a large area of interface between P3HT and CdSe for charge separation. Efficient charge separation occurs at the interface of polymer and inorganic nanocrystals due to the heterojuntion structure, the short-circuit current of blend is 100 times larger than P3HT single layer.
We successfully fabricate basic solar cell devices, and study the effects of processing steps. We find that surfactant exchange of CdSe nanorods is critical for charge separation and using mixed solvent will prevent nanorods from aggregation. The use of heat treatment and high-boiling-point solvent for blend enhances the performance of solar cells, which is tentatively attributed to more orderly arrangement of the polymer under these processing steps.

並列關鍵字

Organic-Inorganic Hybrid Solar Cells ； Conjugated Polymers ； Nanocrystals ； Bulk Heterojunction

參考文獻

陳婉如, 光連雙月刊, 54期, 10~15 (2004)

R. McConnell, S. Kurtz, M. Symko-Davies, “Concentrator Photovoltaic Technologies”, Refocus. July/August (2005).

C. W. Tang, “Two-layer organic photovoltaic cell”, Appl. Phys. Lett. 48, 183 (1986).

P. Peuman, A. Yakimov, S. R. Forrest, “Small molecular weight organic thin-film photodetectors and solar cells”, J. Appl. Phys. 93, 3693 (2003).

J. Xue, S. Uchida, B. P. Rand, S. R. Forrest, “4.2% efficient organic photovoltaic cells with low series resistances”, Appl. Phys. Lett. 84, 3013 (2004).