Modification of TiO2 Photoanode and Its Improvement in Efficiency for Dye-sensitized Solar cells
陳俊宏、姚品全
E-mail: [email protected]
ABSTRACT
In this study, Sol-Gel TiO2 were used as the working electrode (pHoto-anode) of the dye-sensitized solar cells(DSSC). The key process parameters in fabricating high efficiency of DSSC including the deposition of wide band gap semiconductor thin films, the sensitized dye(chromopHore), the mediator(redox couples, electrolyte), cell assembly, etc. It has been investigated by the preliminary tests for further detailed study later. The porous TiO2 thin films were indeed formed by the sintered Sol-Gel TiO2, which resulting in being essential to deposited porous TiO2 thin film with controlled morphology both with large surface area as well as optimal porosity. Unfortunately,due to these two factors of contradiction each other: if the porosity becomes too large, the surface area of the films will decrease.;on the other hand, if the pore size of the porous films becomes smaller, the overall surface of TiO2 films will increase rapidly while the smaller the pore radius will hinder the diffusion of redox couple which can in turn decrease the
photocurrent from the TiO2 photoanode. As for the most optimal cell performance, it is laborious to find the suitable parameters in DSSC fabrication.
In this study, the process parameters in fabricating high efficient TiO2 working electrodes for the photo-injected electron transport had been investigated.
Finely ground Sol-Gel TiO2 was evenly deposited on ITO by spin coating. Different ratio additives, such as PEG were tested. The as-deposited films were further annealed at different temperature with different thickness of the TiO2 films. Two Iodide/Iodine electrolytes was used to compare the influence of redox mediator in regenerative photo-electrochemical reaction in this system.
The addition of PEG was capable of manipulating the pore size of porous photo-anode by which the ions transferring rate at the counter-electrode interface was improved. Under higher annealing temperature, the sintering of TiO2 microstructures were more prominent while the crystalline phase might have transformed to the thermodynamically stable phase. The photocurrent conversion efficiency was closely related to the sintering crystalline phase of TiO2.
The result of the preliminary results in this study shows that the best cell performance was under theses given conditions:VOC=0.7 V，JSC=10 mA/cm2，FF=63%，η ?l 4.05%. In addition to the process parameters, the choice of chromopHore is still another vital factor for high efficient DSSC. Owing to the unstable character and relatively low spectrum response, the sensitized dye used here suffered from low photocurrent and FF which need endeavor to recognize more efficient ones.
Keywords : Dye-sensitized solar cells、Sol-Gel、TiO2、SnO2
Table of Contents
封面內頁 簽名頁
授權書...iii
中文摘要...iv
ABSTRACT...vi
誌謝...viii
目錄...ix
圖目錄...xiii
表目錄...xvii
第一章 緒論...1
1.1 前言...1
1.2 太陽能電池簡介...4
1.2.1無機太陽能電池簡介...7
1.2.2 有機太陽能電池...11
1.3 研究背景與目的...13
1.4 本文架構...14
第二章 色素增感型太陽能電池原理及文獻...15
2.1 色素增感型太陽能電池之結構與簡介說明...15
2.2 TiO2工作電極...19
2.3 染料...21
2.4 電解質...22
2.5 對電極...24
2.6 色素增感型太陽能電池之工作原理...25
2.6.1太陽光譜簡介...25
2.6.2 工作原理的起源:光合作用機制...27
2.6.3色素增感光技術之演化與應用...28
2.6.4光電化學太陽電池的氧化還原機制...31
2.6.5色素增感型太陽電池之供電原理...35
2.7 色素增感型太陽能電池之等效電路...38
2.8 色素增感型太陽能電池之光電轉換特性...40
2.8.1 短路電流( Isc，short circuit current )...40
2.8.2 開路電壓 ( Voc，open circuit voltage )...41
2.8.3 填充因子 ( FF，fill factor )...41
2.8.4 能量轉換效率 ( η，power conversion efficiency )...42
2.9 色素增感型太陽能電池之串聯電阻...44
第三章 實驗設備與方法...47
3.1實驗流程...47
3.2 實驗設備...48
3.3 藥品耗材...49
3.3.1 燒結系統...50
3.3.2 天秤...51
3.3.3 磁石共震機...52
3.3.4 烤箱...52
3.3.5 超音波震盪器...53
3.3.6 塗佈機(Spin-Coater)...53
3.3.7 濺鍍機(Sputter)...54
3.3.8濃縮系統(Enrichment system)...54
3.4 量測設備...55
3.4.1 掃描式電子顯微鏡(Scanning Electron Microscopy; SEM)...55
3.4.2 太陽光模擬器與IV量測儀器...56
3.4.3 紫外/可見光分光光譜儀(UV-VIS)...57
3.5 實驗內容...58
3.5.1氧化銦錫玻璃(ITO)基板之清洗...58
3.5.2 染料調製...59
3.5.3 工作電極製作...59
3.5.4 對電極製作...64
3.5.5 電解液調製...64
3.5.6 組裝及電解液注入...64
第四章 結果與討論...67
4.1 旋塗轉速比較...67
4.2 添加PEG於TiO2之影響...73
4.3 熱處理溫度...78
4.3.1 熱處理溫度IV量測...78
4.3.2 熱處理溫度XRD分析...82
4.4 修飾結構分析...83
4.4.1 修飾結構IV量測...84
4.4.2 修飾結構FE-SEM圖...87
4.4.3 修飾結構XRD圖...89
4.4.4 修飾結構之吸附染料反萃取探討...90
4.4.5 異質結構之原子?顯微鏡觀察...94
4.5 以PEG調整工作電極孔隙結構...98
第五章 結論與建議...102
5.1 結論...102
5.2 建議...103
參考文獻...105 REFERENCES
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