以咔唑并噻吩熔合之七環分子為主體之非富勒烯受體之合成與鑑定及其於有機太陽能電池之應用

Synthesis and Characterization of Non-Fullerene Acceptors Based on Dithienocyclopentacarbazole Fused Heptacylic Unit and Their Application in Organic Photovoltaics

蕭育堂(Yu-Tang Hsiao)

指導教授 ： 許千樹

國立交通大學/理學院/應用化學系所/碩士(2018年)

摘要

本研究中以咔唑并噻吩熔合之七環分子 (dithienocyclopentacarbazole, DTC) 為主體，並在末端修飾上含有腈基之缺電子基團2-(3-oxo-2,3-dihydroinden-1-ylidene)malononitrile (IC)，設計出新的受體材料，另外在不同末端及側鏈上做不同的修飾，合成出四個新的非富勒烯受體。本研究第一部份討論不同側鏈的影響，設計並合成出首兩個非富勒烯受體：側鏈為烷苯基之 DTC(4Ph)-IC 及側鏈為烷基之 DTC(4R)-IC，第二部份則是在末端 IC 上接上氟原子，設計並合成出另外兩個非富勒烯受體：DTC(4Ph)-4FIC 及 DTC(4R)-4FIC。
我們分別鑑定及分析了四個材料之熱性質、光學性質及電化學性質，同時也利用理論計算來模擬出分子之最佳構型。四個非富勒烯受體皆擁有良好的熱穩定性，DTC(4Ph)-IC 為非晶性，DTC(4Ph)-4FIC、DTC(4R)-IC及DTC(4R)-4FIC則有較明顯的結晶性，在光學性質上，這些非富勒烯受體皆在 500-800 nm 有吸收帶且擁有高消光係數，另外藉由修飾上末端的 IC 基團來降低其 LUMO 能階，使其從予體性質轉換為受體性質。最後將此四個新的非富勒烯受體搭配適合的予體 J71 並做太陽能電池元件測試，得到最高的光電轉換效率 10.89%、開路電壓 0.82 V、短路電流 18.92 mA cm-2、填充因子 70.22%。

關鍵字

太陽能 ； 有機薄膜太陽能電池 ； 非富勒烯受體 ； 咔唑并噻吩 ； 混摻異質接面

並列摘要

In this study, a heptacyclic carbazoled-based dithienocyclopentacarbazole (DTC) structure was formylated to couple with two 2-(3-oxo-2,3-dihydroinden-1-ylidene)malononitrile (IC) moieties, forming a series of new non-fullerene acceptors. Four new non-fullerene acceptors (NFAs) were synthesized by utilizing different functional groups on either end groups or side chains. The side-chain engineering was used to design the first two NFAs, DTC(4Ph)-IC and DTC(4R)-IC which contain four alkylphenyl side chains and four alkyl side chains on the DTC unit respectively. The fluorination approach was used to design the other two NFAs, DTC(4Ph)-4FIC and DTC(4R)-4FIC which contain four fluorine atoms on the IC units.
The thermal, optical and electrochemical properties of four NFAs were characterized respectively. We also used DFT calculations to calculate the optimized geometries of molecular structure. These four NFAs are all thermally stable. Notably, DTC(4Ph)-IC shows amorphous character while DTC(4Ph)-4FIC, DTC(4R)-IC and DTC(4R)-4FIC have higher crystallinity. For optical properties, all NFAs exhibit broad absorption in the range from 500 to 800 nm with high extinction coefficients. Moreover, IC units can downshift the LUMO levels, which gives sutible energy levels to be acceptors. Furthermore, devices based on these acceptors were fabricated by employing narrow-bandgap polymer J71 as the donor because of its compatible energy alignments and complimentary absorption. Overall, the device gave the best performance of 10.89% with a Voc of 0.82 V, a Jsc of 18.92 mA cm-2, and an FF of 70.22%.

並列關鍵字

solar energy ； organic photovoltaics ； non-fullerene acceptors ； dithienocyclopentacarbazole ； bulk heterojunction

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