二氧化鈦光電極、導電高分子對電極、膠態或含碳固態電解質之染料敏化太陽電池

Dye-sensitized Solar Cells based on TiO2 Photoanode, Conducting Polymer Cathode, and Gel-type or Solid-type Carbon-containing Electrolyte

陳建清(Jian-Ging Chen)

指導教授 ： 何國川

國立臺灣大學/工學院/化學工程學研究所/博士(2012年)

https://doi.org/10.6342/NTU.2012.10081

摘要

本論文主要探討染料敏化太陽能電池 (DSSC)中各極材料的性能改進，以及電池系統改變對電池元件光電轉換行為影響，同時也針對元件效率及穩定性進行探討。
本文的第一部份為針對染料敏化太陽電池TiO2光電極進行改質探討，此部分分三個研究主題。第一，本研究 (第4章)提供一種簡易、有效的技術，名為金屬有機沈積法 (metallorganic deposition method, MOD)，可在FTO導電玻璃上形成一層TiO2緻密層 (compact layer)。此有別於其它傳統方法，如將FTO導電玻璃含浸TiCl4水溶液內反應 (溫度70℃、時間30分鐘)，再將FTO導電玻璃取出烘乾，雖可在FTO導電玻璃上形成一層TiO2緻密層，然而此方法卻會因基材的不同，而無法有效控制緻密層厚度。此技術可精密控制緻密層膜厚，以有效改善染料敏化太陽能電池效率。第二，以不同金屬離子 (如鍶、釔與鋅等)來改質TiO2材料的表面，由結果得知，鍶離子與釔離子可以降低電子的再結合率 (TiO2與電解質液間) 並能增加電子密度 (donor density) (第5章)；第三，以陽極氧化法將鈦板直接蝕刻成陣列式TiO2奈米管，以不同的蝕刻時間 (15分鐘至12小時)，可製備出不同長度的TiO2奈米管 (0.5至16.6 μm)。將這些不同長度的TiO2奈米管當作光電極，組裝成染料敏化太陽能電池，測試其電池性能，效率可從0.95提升至3.46%。另外，本研究亦成功利用物理填充技術將14 nm TiO2顆粒直接填充至TiO2奈米管中，以增加染料的吸收，進而提升光電流 (第6章)。
本文的第二部分為針對染料敏化太陽電池電解質作一系列探討。本論文為第一次利用新穎的電解質triethylamine hydroiodide (THI) 混入液態電解質液，所得元件之最佳效率為8.45%，而以碘化鋰為電解質的系統，最佳效率僅為7.70%，可見THI可以取代常用的電解質碘化鋰 (LiI)，此研究成果與分析說明置於本文第7章。另外，本研究亦嘗試以同步聚合法製備DSSC用膠態電解質。利用雙馬來醯亞胺(bismaleimide)單體，在無添加起始劑且在溫度30 ℃下混入於液態電解質，可製備出膠態電解質，接著再添加0.3 wt%的剝層奈米雲母 (exfoliated alkyl-modified nano-mica, EAMNM)於系統中，可得最佳光電轉換性能 (短路電流達17.08 mA/cm2，效率可達7.05%)，此研究成果與分析說明置於第8章。本論文亦嘗試分別添加導電性碳材，如奈米碳管、次微米碳球以導電性石墨於全離子液體電解質液內，以得到類固態形式 (quasi-solid-type) 的電解質。其中，以次微米碳球所製備之離子液體電解質液 (染料為CYC-B6S) 的效率最高，可達6.16%。經過溫度55℃、1000小時長效測試之後，效率還有原來的93.6%，此研究成果與分析說明置於第9章。
本文的第三部分以導電高分子PEDOT:PSS (Poly(3,4-ethylenedioxythiophene):Poly(styrene sulfonate))薄膜當作對電極觸媒，進行一系列的性能探討，得到與用Pt對電極觸媒的效率相似，此研究成果置於第10章。由實驗得知，PEDOT:PSS薄膜的電子導電度大小與所使用的有機溶劑有及密切的關係，發現以dimethyl sulfoxide (DMSO)、N,N-dimethyl acetamide (DMAc), N,N-dimethyl formamide (DMF) 以及dichloromethane (DMC)加入PEDOT:PSS中，其所製成的膜之導電度分別為85 15, 45 10, 36 7與 20 6 S/cm，而未經有機溶劑處理的 (bare PEDOT:PSS)，其導電度僅為2 0.05 S/cm。以DMSO-PEDOT:PSS film為對電極的DSSC，在AM 1.5G下最高效率為5.81%。
本文的第四部分為各種釕金屬染料的光電性質分析與比較。各有10個染料，分別為CYC-B1, CYC-B3, SJW-E1, CYC-B6S, CYC-B6L, JF-1, JF-2, JF-5, JF-6與JF-7。前面五個染料為國立中央大學吳春桂教授所提供，而後五個染料為中央研究院化學所呂光烈教授提供。這些染料的性能分析，於第11、12與13章有詳細的性能探討與結果說明。

關鍵字

導電高分子 ； 對電極 ； 染料敏化太陽電池 ； 膠態電解質 ； 類固態電解質 ； 釕金屬染料 ； 二氧化鈦電極

並列摘要

The main objective of this dissertation is to investigate the behaviors of new approaches in electrodes (working and counter), sensitizers and gel-type electrolytes for dye-sensitized solar cells (DSSCs) and discuss the influences on the cell performance and stability of DSSCs.
In the first part of this dissertation, the optimization of solar energy conversion efficiency of DSSCs was investigated by the tuning of TiO2 photoelectrode’s characteristics. Firstly, we provide the simpler and more effective way of forming a compact TiO2 blocking layer, which is different from the way of the direct immersion of the FTO glass in the TiCl4 aqueous solution at temperature of 30 oC for 30 mins. The TiO2 precursor, Titanium isopropoxide (TTIP), was employed to acquire the thin uniform TiO2 film as a blocking layer by the metallorganic deposition method (MOD). TTIP and 2-methoxylethanol (ME) were employed as the source metallorganic solution and solvent, respectively. This study overcome successfully leads to the uniform TiO2 blocking layer onto a FTO glass by MOD and enhances the cell performance efficiently (shown in Chapter 4). Secondly, the fabrication of nanoporous metal ion (Zn2+, Sr2+ or Y3+)-surface modified TiO2 electrodes and the investigation of their photo-electrochemical properties. It is demonstrated that small amounts of Sr2+ and Y3+ ions surface modified TiO2 particles can facilitate the charge transfer in the TiO2 network due to the higher donor density. In addition, the doping of Sr2+ and Y3+ ions can restrain the charge recombination between the TiO2 working electrode and I-/I3- redox couple. On the other hand, the doping of Zn2+ ion in TiO2 particles does not enhance the efficiency of DSSCs(Chapter 5). Thirdly, we prepared titanium nanotubes (TNT) of different lengths and same crystallite size, by anodizing a Ti sheet for different periods. With the increase of anodization period from 0.25 h to 12 h, the length of the nanotubes increases from 0.5 μm to 16.6 μm, while the crystal size of the corresponding TiO2 remains the same. The solar-to-electricity conversion efficiency (η) of the corresponding DSSC also increases from 0.95% to 3.46%. Increase in surface area of TNT with increased tube length is perceived as the reason for corresponding increase in Jsc and decrease in Voc of the DSSC. TNT were successfully filled with TiO2 nanoparticels (14 nm) by vacuum system leads to the enhancement of photocurrent of DSSCs (in Chapter 6).
In the second part of this dissertation, the electrolytes of DSSCs are investigated in Chapter 7-9. For the first time, we explored that the photovoltaic application of a novel electrolyte, triethylamine hydroiodide, an efficient and alternative candidate to LiI, on the photovoltaic performance of the DSSC. The better conversion efficiency (η= 8.45%) was obtained for the DSSC containing THI when compared to LiI (η = 7.70 %) and this shows that the THI indeed may be used as an efficient and alternative candidate to the LiI in the current research of DSSC (this part are shown in Chapter 7). In addition, the fabrication of gel-type dye-sensitized solar cells (DSSCs) by in-situ low temperature polymerization of 1,1'-(methylenedi-4,1-phenylene)bismaleimide polymerized in liquid electrolyte without an initiator at low temperature of 30 oC, and shown in Chapter 8. The incorporation of 0.3 wt% of the exfoliated alkyl-modified nano-mica (EAMNM) in the gel electrolytes leads to increase in the short-circuit current density (from 15.34 to 17.08 mA/cm2) and efficiency (from 6.24 to 7.05%). Furthermore, three carbon materials, graphite, carbon nanotubes, and carbon spheres were incorporated in the ionic liquid electrolytes to fabricate the good performance quasi-solid-type DSSCs, were explored in this part (Chapter 9). These newly-developed electrolytes, the CYC-B6S sensitized cells with carbon spheres provided highest efficiency of 6.16%. Moreover, such good performance cell remarkably retained 93.6% of its initial efficiency after 1000 hours full light-soaking at 55 °C. have not only rendered higher solar-to-electricity conversion efficiencies to the cells but also improved the cell durability.
In the third part of this dissertation, a PEDOT:PSS film (Poly(3,4-ethylenedioxythiophene):Poly(styrene sulfonate)) coated FTO glass as counter electrode was investigated. The conductivity of a bare PEDOT:PSS film was only 2 0.05 S/cm. However, the conductivities of PEDOT:PSS films treated with dimethyl sulfoxide (DMSO), N,N-dimethyl acetamide (DMAc), N,N-dimethyl formamide (DMF) and dichloromethane (DMC) reached 85 15, 45 10, 36 7 and 20 6 S/cm, respectively. The DSSC using DMSO-PEDOT:PSS conductive coating as a counter electrode reached a cell efficiency of 5.81% under 100 mW/cm2 (AM 1.5G).
In the fourth part of this dissertation, the photo-characteristics of ruthenium dyes were explored. The ruthenium dyes (CYC-B1, CYC-B3, SJW-E1, CYC-B6S, CYC-B6L) were provided by Professor Chun-Guey Wu (Department of Chemistry, National Central University) and the ruthenium dyes (JF-1, JF-2, JF-5, JF-6 and JF-7) were provided by Professor Kuang-Lieh Lu (Institute of Chemistry, Academia Sinica), shown in Chapter 11-13.

並列關鍵字

Conducting polymer ； Counter electrode ； Dye-sensitized solar cells ； Gel-type electrolyte ； Quasi-solid-type electrolyte ； Ruthenium dye ； TiO2 electrode

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