含苯并噻吩有機小分子材料 之設計、合成與高效太陽能電池的應用

Design, Synthesis, and Characterization of Benzo[c]thiophene- based Small Molecules for High Efficiency Organic Solar Cells

10.6342/NTU201701894

黃懿萱

含苯并噻吩 ； 有機小分子 ； 材料 ； 設計 ； 合成 ； 太陽能電池 ； Design ； Synthesis ； Benzo[c]thiophene- baed ； Small Molecules ； Organic Solar Cells

國立臺灣大學化學系學位論文

2017年

碩士

汪根欉

繁體中文

本論文，我們延續D-A-A架構，修正實驗室先前研發出的DTTTP、DTPTP兩個材料之光與熱性質不穩定，而無法應用於蒸鍍型的小分子光伏元件製程。因此，新分子將中間拉電子基團噻吩并吡啶 (thienopyrazine, TP) 置換成苯并噻吩 (benzo[c]thiophene, BTh) ，開發出四個小分子材料分別為DTDCTBTh、DTDCPBTh、DTCTBTh與DTCPBTh。分析結果顯示熱穩定性確實有提升，並能應用於蒸鍍型的小分子光伏元件製程，其中以DTDCPBTh作為電子予體搭配C70為電子受體，利用BHJ結構進行蒸鍍型的元件製作，其光電轉換效率 (power conversion efficiency, PCE) 可以達8.0%，短路電流 (short circuit current, Jsc) 為14.1 mA/cm2、開路電壓 (open circuit voltage, Voc) 為0.86 V、填充因子 (fill factor, FF) 為0.63。 　　為了進一步捕獲更多近紅外光區 (near-IR) 的光子，我們設計出DTDCDBTh與DTDCBThB兩個分子，透過增強BTh的醌 (quinoid) 性質，使HOMO能階提升以利於縮小能隙，達到吸光波長紅移的效果。另外，我們在BTh結構上修飾兩個氰基團 (CN)，設計出DTDCTBTh-2CN與DTDCPBTh-2CN兩個分子，降低其HOMO與LUMO能階，並且同時提升分子內的電荷轉移能力，使吸光波長紅移。藉由以上合成策略調控分子材料的光物理電化學性質，建立一個分子結構與物理性質的關聯性，希望有助於提升元件中的Voc、Jsc，使其在太陽能電池當中有更好的元件表現。

In this research, the poor light and thermal stability of DTTTP、DTPTP which were synthesized before, suppress the application onto vacuum-deposited organic solar cells. To solve the stability problem, four molecules (DTDCTBTh, DTDCPBTh, DTDTBTh, and DTCPBTh) were synthesized by replacing thienopyrazine with benzothiophene. The results showed that our strategy indeed efficiently solve thermal stability problem. Worth mentioningly, the device of DTDCPBTh exhibited high PCE up to 8% for vacuum-deposited BHJ solar cells by using C70 as acceptor with Jsc of 14.1 mA/cm2, Voc of 0.86 V ,and FF of 0.63. 　　In addition, we have synthesized two materials (DTDCDBTh and DTDCBThB), which show that strong quinoid characteristic would result in higher HOMO level and narrower bandgap, leading to red-shifted absorption wavelength. Meanwhile, we introduced an electron-withdrawing cyano groups onto BTh, which two materials (DTDCTBTh-2CN and DTDCPBTh-2CN) have been synthesized. From optoelectronic investigation, these materials reduced HOMO and LUMO energy levels, while having red-shifted absorption because of strong intermolecular charge transfer. Taking advantages of synthetic strategies mentioned above to manipulate electrochemical properties, we hope those molecules will exhibit better PCEs with improved Jsc and Voc.

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