染料敏化太陽能電池的材料與製程研究

The Materials and Process Study for Dye-sensitized Solar Cells.

王修璇(Hsiou-Hsuan Wang)

指導教授 ： 蘇昭瑾教授

國立臺北科技大學/工程學院/有機高分子研究所/博士(2013年)

https://doi.org/10.6841/NTUT.2013.00699

摘要

本論文主要是在探討硬式導電玻璃與軟性塑膠基材在染料敏化太陽能電池的製程，希望能簡化製備流程、降低成本，以應用至全軟式染料敏化太陽能電池。本研究分為二部分，第一部分為硬式染料敏化太陽能電池工作電極及對電極的開發：首先為了製作平坦無裂縫的二氧化鈦薄膜當作工作電極，以添加乙基纖維素含量提升二氧化鈦鍍膜液分散性，利用網版印刷方式將其均勻塗佈於FTO導電玻璃上，形成奈米多孔結構的二氧化鈦薄膜當做活化層。利用四丁基氧化鈦為前驅物，醋酸當催化劑，以水熱法在200 ℃成功製備銳鈦礦相二氧化鈦奈米顆粒，藉由添加不同重量乙基纖維素的條件，使其薄膜表面形態團聚現象與裂縫明顯減少，研究結果顯示當乙基纖維素含量佔鍍膜液總重5.82%時，所製備的工作電極活化層，浸漬在N719染料中，在光強度為100 mW/cm2的模擬太陽光源下，其Jsc = 15.07 mA/cm2, VOC = 0.75 V, and FF = 0.68，而光電轉換效率提升至7.64%。此外，利用具有次微米二氧化鈦顆粒塗佈在活化層上當作雙功能的散射層，確實可以增加光的捕獲率以應用在染料敏化太陽能電池，當活化層在11 ?m和散射層在3 ?m時得到最佳光電轉換效率為9.75%，與未添加散射層的電池相比較，其光電轉換效率提高19%。最後，本實驗在製備對電極時，以六氯鉑酸 ( H2PtCl6•(H2O)6) 為鉑前驅物，以熱還原法 (thermal decomposition) 在450 ℃中燒結，使其在陰極的表面形成鉑奈米顆粒藉以增加比表面積，提高碘離子對 (I－/I3－) 的氧化還原速度。同時為了降低鉑使用量，添加石墨烯高導電材料做對電極材料，除了增加鉑的分散性也增加鉑對電極催化能力。將活化層結構 (A-TiO2) 的工作電極以及石墨烯-鉑對電極 (sc-GPt) 封裝為染料敏化太陽能電池其光電轉換效率可達9.57%明顯高於濺鍍技術19.63%。
本論文第二部分為了拓展染料敏化太陽能電池相關應用性，開發全軟式染料敏化太陽能電池，製作出易於攜帶、更輕薄、更低價的太陽能電池，使染料敏化太陽能電池商業應用範圍更廣泛。開發全軟式染料敏化太陽能電池的製造技術有三個階段如下: (1) 以製備可低溫燒結的二氧化鈦鍍膜液，經由網版印刷方式塗佈在ITO-PET導電基材做為工作電極，並利用機械加壓法可以將工作電極上的二氧化鈦膜層龜裂部分填平之外，亦可增加薄膜與基材之間的附著力。此階段以ITO-PET基材製備TiO2工作電極將以FTO導電玻璃製備鉑對電極所封裝的半軟式染料敏化太陽能電池，最佳光電轉換效率為5.00%。 (2) 利用低溫化學還原法製備鉑對電極，以六氯鉑酸作為前驅物，旋轉方式塗佈在ITO-PET導電基材上，此階段將以ITO-PET基材製備鉑對電極與以FTO導電玻璃製備TiO2工作電極所封裝的半軟式染料敏化太陽能電池，其最佳光電轉換效率為6.91%。 (3) 修正全軟式基材的封裝程序，為了改善全軟式染料敏化太陽能電池電解質漏液的問題，採用由下往上注入電解質溶液，避免電解質溶液氣泡及洩漏現象產生，進而提升電池的填充因子與光電轉換效率。此階段以ITO-PET基材製備TiO2工作電極與鉑對電極，將其所封裝的全軟式染料敏化太陽能電池，得到最佳光電轉換效率為4.06%。

關鍵字

全硬式染料敏化太陽能電池 ； 全軟式染料敏化太陽能電池 ； 奈米多孔二氧化鈦薄膜 ； 活化層 ； 散射層 ； 網版印刷 ； 半軟式染料敏化太陽能電池

並列摘要

The purpose of this thesis is to investigate the optimum process condition for the fabrication of working electrode using hard transparent conductive glass and flexible plastic substrate for dye sensitized solar cells (DSSCs). In the first part of this thesis, ethyl cellulose (EC)-based TiO2 pastes were prepared in order to fabricate flat and crack-free TiO2 films employing screen-printing technique. Pure anatase TiO2 was synthesized via hydrothermal process using titanium (IV) n-butoxide as Ti-precursor and peptized by acetic acid. The as-prepared TiO2 sol was employed for making a series of pastes with various weight ratios of ethyl cellulose which was used to prepare the TiO2 electrode using screen-printing technique. The printed TiO2 electrode was observed under the micro-scale condition which exhibited a porous and crack-free structure. The DSSCs fabricated using the paste with 5.82 wt % of EC demonstrated a high energy conversion efficiency of 7. 64% with Jsc = 15.07 mA/cm2, VOC = 0.75 V, and FF = 0.68 under the AM 1.5 with an illumination of 100 mW/cm2. In addition, the dual-function scattering layer made of submicron anatase TiO2 was applied on top of the active layer to increase light harvesting efficiency in DSSCs. The optimized photoconversion efficiency obtained using 11 ?m thick TiO2 active layer and 3 ?m thick TiO2 scattering layer was 9.75%, which was 19% enhancement compared to the DSSCs efficiency without scattering layer. Finally, the counter electrode was made by thermal decomposition of screen-printed dihydrogen hexachloroplatinate (IV) hexahydrate (H2PtCl6, a Pt precursor) on FTO glass. The formation of Pt nanoparticles on FTO showed the enhancement of DSSCs efficiency. The homogeneous dispersion of Pt particles on FTO can be achieved by incorporation of graphene into the Pt precursor solution. The graphene-Pt electrode showed the excellent DSSCs photoconversion efficiency up to 9.56%.
The second part of this thesis was mainly focused on the flexible plastic based DSSCs. ITO-PET was chosen as the flexible plastic substrate for working electrode and Pt as counter electrode. Three steps towards the full flexible DSSCs assembling were performed as follows: (1) The preparation of less-crack flexible TiO2 electrode using low temperature sintering TiO2 paste on ITO-PET followed by mechanical compression in order to increase the adhesion between TiO2 and ITO-PET. In this stage, the semi-flexible DSSCs device was made from ITO-PET based TiO2 electrode and FTO based Pt counter electrode. The best efficiency obtained was 5.00%. (2) The demonstration of low temperature process for counter electrode fabrication by spin-coating H2PtCl6 solution on ITO-PET. In this stage, the semi-flexible DSSCs device was made from FTO based TiO2 electrode and ITO-PET based Pt counter electrode. The best efficiency obtained under this condition was 6.91%. (3) To modify the sealing process, including the electrolyte injecting procedure in order to improve the leakage problem of flexible DSSCs as well as the device fill factor and photoconversion efficiency. In this stage, the full flexible device was made from ITO-PET based TiO2 electrode and ITO-PET based Pt counter electrode. The best efficiency of 4.06% can be achieved in this work.

並列關鍵字

Dye-sensitized solar cell ； Nnano-porous titanium dioxide films ； Active layer ； Dual-function scattering layer

參考文獻

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