有機染料分子設計與高效能染料敏化太陽能電池

Abstract

本論文主要研究方向是設計與發展不同類型有機染料，進而應用於染料敏化太陽能電池。同時，我們進一步使用共吸附、染料共敏化以及改變光電極材料的方式去提升與改善光電轉換效率。並且利用各種物理分析方法去解釋實驗的結果，以了解染料分子結構與元件效率之關聯性。 以二氫菲上9,10 位置為主的小分子染料建構染料敏化太陽能電池，其光電轉換效率介於5.21％至5.95％。我們選擇當中效率最高者(BP-2)與可吸收紅外光之染料方酸染料（SQ2），進行不同混摻比例(體積比)之共敏化太陽能電池。其光電轉換效率隨著BP-2混摻比例增加而上升﹔其中，當BP-2與SQ2體積比為8比2時，效率可以提升至8.14%。最後，我們利用歐傑電子顯微鏡探測所述染料分佈於二氧化鈦薄膜之情形。 接下來，我們合成含缺電子材料苯並噻二唑（BT）之染料。此系列染料設計，是將苯並噻二唑直接與2 -氰基丙烯酸做連結，並且搭配使用氧化鋅光電極材料，以期氧化鋅光電極的電子傳遞可加速電荷的分離。我們也開發新穎的氧化鋅奈米粒子當作散射層之應用。藉由搭配此新穎的氧化鋅材料，其光電轉換效率可更進一步提升。 我們合成了一系列以蔥之2,6位置為主體之光敏化染料分子，此係列染料分子皆具有高莫耳消光係數及寬廣的吸收波長(~600 nm)，其薄膜吸收光譜更可延伸至700 nm。此系列染料於太陽能電池表現中皆達良好的光電轉換效率(4.69−7.52%)。我們進一步使用去氧鵝膽酸及SQ2染料與Ant3分子進行共敏化染料太陽能電池，使光電轉換效率可分別提升至9.11%與8.08%。於弱光下，光電轉換效率更可突破10%。 我們以2,3,5-取代位置的噻吩建構含有兩個錨基團的染料分子，D-π-(A)2。此系列染料表現出高莫耳消光係數和良好的光電轉換效率。進一步使用CDCA進行共吸附，此系列染料之光電轉換效率能提升1.03到2倍。其中，最佳效率表現（8.28％）可達到標準元件之95％。

New organic dyes were developed and used as the sensitizers for the dye-sensitized solar cells (DSSCs). Different approaches (co-sensitized, co-adsorbent, zinc oxide photoanode) were used to improve the cell performance. Various physical measurements, including UV–vis absorption spectroscopy, electrochemical impedance spectroscopy (EIS), and incident photo–to–current conversion efficiency (IPCE) spectra, charge extraction method (CEM) and intensity-modulated photovoltage spectroscopy (IMVS) were used to obtain important parameters relevant to the cell performance for correlation between the molecular structure and the cell performance. Bipolar organic dyes containing a 9,10-dihydrophenanthrene entity in the conjugated bridge were synthesized as the sensitizers for DSSCs. The DSSC exhibits good cell efficiencies ranging from 5.21% to 5.95% under 1 sun condition. When combining the best performed dye (BP-2) with a squaraine dye (SQ2), the efficiency increment of the co-sensitized DSSCs is in compliance with the increased ratio of BP-2/SQ2. The co-sensitized DSSC in which the ratio of BP-2 and SQ2 was 8:2 (v/v) exhibited a high efficiency of 8.14%. The TiO2 film adsorbed with co-sensitizers was subjected to Auger electron spectroscopy (AES) for probing the dye distribution across the TiO2 film depth. We synthesized benzothiadiazole (BT)-containing sensitizers with BT entity directly connected to 2-cyanoacrylic acid for DSSCs using ZnO as the photoanode aiming at better charge separation because of better electron transport. The cells performed better than those using TiO2 as the photoanode. The cell efficiency can be further improved when a newly developed brush hierarchical ZnO nanoplates were used as the light back scattering layer (SL) of the cell. Dyes consisting of 2,6-conjugated anthracene segment as the conjugated spacer, 9,10-bishexyloxyanthracen-phenylamino as the electron donor, and cyanoacrylic acid as the acceptor and anchor as well were synthesized. DSSCs using these sensitizers exhibited efficiencies 4.69−7.52% under AM 1.5 illumination, and an impressively high efficiency (9.11%) surpassing the N719-based standard cell has also been achieved with the use of CDCA co-adsorbent. In order to enhance electron injection and dark current suppression, the dyes with two anchoring groups, D-π-(A)2, were synthesized from a 2,3,5-substituted thiophene motif. These dyes exhibit high molar extinction coefficient and good power conversion efficiency of the cells. With addition of co-adsorbent, CDCA, the device performance of all the DA-based DSSCs were improved by 1.03 to 2-fold, with the best efficiency reaching 95% of the N719-based standard cell (8.28%).