高效率異靛藍素基高分子太陽能電池

高分子太陽能電池(PSC)由於具有低成本、可撓曲且易於以溶液方式製備等特性，因此近年來在替代性能源中被受到高度的重視。異靛藍素是一種天然色素，它可以從植物中萃取提煉而得，故為一種可再生的材料。此外，由於異靛藍素具有很強拉電子能力，因此可用於合成低能隙施體-予體交替型高分子。在本研究中，我們所使用的四種異靛藍素基低能隙導電高分子是由不同數目的噻吩作為電子予體並和電子受體異靛藍素共聚而成。依照噻吩在單體中的數目分別命名為:P3TI, P4TI, P5TI, P6TI。我們將此四種高分子分別和PC71BM進行混摻以製作元件，並利用一系列的方式以最佳化元件效率。我們採用的元件結構為:ITO/PEDOT:PSS/PnTI:PC71BM/Ca/Al。為了最佳化元件效率表現，在製程中分別依序以不同的混摻比例、不同的混摻濃度、使用不同的溶劑及添加物以逐步達成效率最佳化。由於單體中不同數目的噻吩具有不同的結構對稱性，造成此四種高分子具有不同的結晶性及溶解性。從掠角入射廣角X光散射射分析(GIWAXS)的結果可知，P4TI和P6TI具有高結晶性，而P3TI和P5TI的結晶性則較差。因此，此四種高分子在不同的溶劑組合下具有不同的溶解度。此外，PnTI的結晶性和溶解度的不同對於主動層的型態以及元件的表現有很大的影響，因此我們使用AFM和GIWAXS來分析PnTI:PC71BM主動層的型態以及結晶性和效率之間的關係。最後，得到P3TI:PC71BM最佳效率為6.52%, P4TI:PC71BM為6.04%， P5TI:PC71BM為3.87%，而P6TI:PC71BM為7.25%。我們預期藉由使用其他能夠讓主動層有最佳型態的溶劑組合，並在主動層和電極之間加入具有良好歐姆接觸的電荷傳導層，能夠使此系列太陽能電池的效率再進一步提升。

關鍵字

異靛藍素；溶劑添加劑；結構對稱性；結晶性；溶解性

並列摘要

Polymer solar cells (PSC) features low cost, flexibility, and can be manufacture by solution process. Therefore, PSC has drawn high attention among the alternative energy in recent year. Isoindigo has strong electron-pull property which is ideal to synthesize alternating donor-acceptor low bandgap copolymers. Here, we try to optimize the performance of solar cells which are made with four kinds of isoindigo based low bandgap conducting polymers: P3TI, P4TI, P5TI, P6TI blended with PC71BM as active layer. The repeating units of these polymers are constructed from alternative electron-push unit thiophene and electron-pull unit isoindigo, the different among them are the number of thiophene in the repeating unit. Our solar cells are fabricated with the forward structure of ITO/PEDOT:PSS/ PnTI:PC71BM/ Ca/Al. In order to optimize the device performance, we change the processing conditions by mixing polymer with PC71BM in different ratios, using different process solvents, and adding different additives. Due to the difference of structure symmetry and the number of thiophene in the repeating unit, PnTI has different crystallinity and solubility in different solvent. The grazing-incidence wide angle X-ray scattering (GIWAXS) results show that both P4TI and P6TI have the characteristic of high crystallinity. On the other hand, the crystallinity of P3TI and P5TI are relatively low. The crystallinity and solubility of PnTI affect the film morphology of the active layer dramatically and further impact the device performance. We used AFM and GIWAXS to analyze the film morphology and crystallinity in each solvent combination and investigate how they relate to the property of each PnTI:PC71BM in solar cell. Finally, the optimized power conversion efficiency of the devices made with different PnTI:PC71BM are: 6.52% in P3TI:PC71BM, 6.04% in P4TI:PC71BM, 3.87% in P5TI:PC71BM and 7.25% in P6TI:PC71BM. The efficiency of this type solar cell is expected to be further increased by using other combination of solvent system for favorable active layer morphology and by using ohmic contact interlayer between active layer and electrode.

並列關鍵字

Isoindigo ； solvent additives ； structure symmetry ； crystallinity ； solubility

參考文獻

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[3]Y.-W. Su, S.-C. Lan, and K.-H. Wei, "Organic photovoltaics," Materials Today, vol. 15, pp. 554-562, 2012.

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[7]P. Peumans, A. Yakimov, and S. R. Forrest, "Small molecular weight organic thin-film photodetectors and solar cells," Journal of Applied Physics, vol. 93, p. 3693, 2003.

[8]M. C. Scharber, D. Mühlbacher, M. Koppe, P. Denk, C. Waldauf, A. J. Heeger, and C. J. Brabec, "Design Rules for Donors in Bulk-Heterojunction Solar Cells—Towards 10 % Energy-Conversion Efficiency," Advanced Materials, vol. 18, pp. 789-794, 2006.

國際替代計量

高效率異靛藍素基高分子太陽能電池

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