參雜碳材於染料敏化太陽能電池之電解質影響其離子導電度及擴散行為之分析

Analysis of impact on ionic conductivity and diffusion ability of the electrolyte in dye-sensitized solar cells with doping carbon materials

蔡宗翰

指導教授 ： 陳福榮 ； 蔡春鴻

國立清華大學/原子科學院/工程與系統科學系/碩士(2014年)

摘要

在染料敏化太陽能電池(Dye-sensitized solar cells)的研究中，對於其特點因其在太陽能電池領域中，相較以往的太陽能電池，染敏電池擁有較低成本、製程相對簡單、且其選用材料對於環境的影響較小的優勢，對於日後再生能源的發展，是一具有潛力的選擇。而在染敏電池的發展中，雖然液態電解質的型式有較佳的光電轉換效率，但是其之漏液問題一直是眾多科學家欲解決之問題，故此發展出膠態與固態電解質來改善，因其具有揮發性較低的特性。但是因為其黏滯性較高，導致電解質中的離子傳遞速度降低，增加了電子傳導得難度，故其在光電量測中會得到較低的轉換效率，故在本實驗中，應用具有導電特性的碳材添加進入膠態電解質中，改善了膠態電解質效率低落的狀況。
在此實驗中，將碳材添加進入不同有機溶劑製成的液態電解質中，利用交流阻抗儀(AC impedance)觀察碳材對於電解質的離子導電度的影響，以及循環伏安法測定電解質中的碘離子擴散能力因為添加碳材改變的分析，並且將之製成元件，做光電轉換效率量測，得到其之電流-電壓的特性量測分析(J-V curve)。研究結果顯示，在導入碳材後其電解質內部的阻抗降低、碘離子擴散有被其提升之效果，這也使得在效率量測中，其內部阻抗下降而得到較高之短路電流(Jsc)，電池效率也升高，其是因為碘離子的擴散路徑藉由碳材添加而降低的緣故。在此之後將碳材導入膠態電解質中，同樣做離子導電度、離子擴散能力分析、以及電池的元件效率量測，並在實驗結果中得知，碳材能夠在膠態黏稠度較高的環境中導通電子進入電解質，離子導電度相對未添加碳材之電解質系統有增加之趨勢，另外這也讓相對未添加碳材的系統碘根離子與碘三根離子之間的交換速率得以提升，故量得碘離子擴散系數提高。封裝成電池元件的效率更得到趨近液態電解質的好表現，由此證明，本實驗對於提升染料敏化太陽能電池中膠態電解質的效率有所貢獻，提高其之實用性及未來發展性。

關鍵字

染料敏化太陽能電池 ； 膠態電解質 ； 奈米碳材 ； 高分子

並列摘要

Since the dye-sensitized solar cell (DSSC) was reported in 1991 by M. Gratzel ,it has aroused intense interest owing to its low cost, simple preparation procedure, and more environment-friendly compared with traditional photovoltaic devices. Therefore, DSSCs have been considered one of the promising alternatives to conventional solar cells. But the leakage of the liquid electrolyte is the major problem which blocks the application of the flexible device. To solve this problem, the quasi-solid and solid type electrolyte is discovered to replace the liquid one. However, their ion conductivity and ion diffusion ability are limited by the higher viscosity so the cell performance of this type is lower than liquid type.

In this experiment, we added different ratio carbon materials (CM) into the organic solvent (MPN,NMP) as liquid type electrolyte by ultrasonic the CM in the electrolyte solution several hours. At first, we measured its ion conductivity by the AC impedance and then we use Cyclic voltammeter (CV) measurement to survey the influence of the diffusion ability changed by the CM added. The charge transfer resistance of Pt/electrolyte and Nernst diffusion in the electrolyte presents the catalytic ability of CE and diffusion ability of redox couple, and diffusion limited current is confirmed the triiode in electrolyte diffusion ability in different carbon materials ratio. We discovered that added CM can improve the ion conductivity and diffusion ability. Next, to identify the performance of cell, we measured the cell efficiency under illumination of AM1.5 (100mW/cm2). The conversion efficiency is also raised when we added the CM into the electrolyte. Because of that we infer adding carbon materials providing an extended electron transfer material facilitates electron transfer from counter electrode to tri-iodide ions to increase the exchange reaction of redox couple in the viscous electrolyte so that the performance of the cell also be improved.

At last we induce the polymer material into the system to form quasi-solid type electrolyte. We added 10wt% Polyvinyl butyral (PVB) into the NMP system, and 20 wt % Polyethylene Glycol into the MPN system. The ionic conductivity and the diffusion ability are measured after the different CM ratio added. We discovered that the resistance of the quasi-solid electrolyte is lowered and the diffusion ability is also raised due to CM added. In the efficiency rest, the performance of the quasi-solid electrolyte with CM is about 88% of the liquid type one. It can approve the fact that the quasi-solid type solar cells can achieve the high efficiency by CM added into the system which supplies DSSC a opportunity to apply in the flexible device.

參考文獻

[73]曾友利, 「奈米複合電極觸媒材料的製備與鑑定」, 國立清華大學化學系碩士論文, 2009.

[77]施仁親, 「太陽光模擬器要求與新型LED太陽光模擬器簡介」, 光連雙月刊, vol. 92, 2011.

[2]K. E. Martin A. Green, Y. H. , and W. W. a. E. D. D. , "Solar cell efficiency tables (version 43)," PROGRESS IN PHOTOVOLTAICS: RESEARCH AND APPLICATIONS, vol. 22, pp. 1-9, 2014.

[3]G. A. V. Sivakov, A. Gawlik, A. Berger, J. Plentz, F. Falk, and a. S. H. Christiansen, "Silicon Nanowire-Based Solar Cells on Glass: Synthesis, Optical Properties,

[4]R. B. Bergmann, "Crystalline Si thin-film solar cells: a review," Applied Physics A