含噻吩并噻吩有機小分子材料之設計、合成與太陽能電池的應用

Abstract

有機太陽能電池因具有低成本、化合物結構可設計性、材質輕和可撓曲等特性，而吸引許多研究致力開發出新的有機材料來提升有機太陽能電池效率及壽命。在本論文中，使用噻吩并[3,2-b]噻吩為分子核心，並引入具強拉電子性的氰基團 (CN) ，合成出一系列D-A-A及A-D-A分子做為太陽能電池的電子予體及電子受體材料及D-A-D分子做為OLED發光層材料。 第一部分，在D-A-A架構中引入具醌 (quinoid) 性質的噻吩并[3,2-b]噻吩，並引入強拉電子性的氰基團，調控予體材料的能階，開發出DTCPTT、DTCPTT-2CN、DTDCPTT、DTDCPTT-2CN四個小分子材料。分析結果顯示，引入氰基團，確實使最高佔有軌域 (HOMO) 和最低未佔有軌域 (LUMO) 能階都下降，且LUMO能階下降幅度較大，達到調整能階、能隙縮小及提升熱穩定性的效果，但也改變分子排列的型態。應用於蒸鍍製程的元件，其中以DTDCPTT的表現最佳，元件最佳化結果在AM1.5G下得到0.85 V之開路電壓，13.56 mA/cm2之短路電流，67.81%之填充因子，以及7.81%之光電轉換效率；在500lux下，光電轉換效率超過16%。第二部分，在A-D-A架構中，在分子核心引入不同取代基團，一是引入氰基來調控能階，使LUMO能階下降，做為電子受體；另一則是引入烷氧基來增加分子偶極矩，使吸光紅移拓展吸光範圍，開發出TTCN-DC、TTCN-RH、TTOHex-DC及TTOHex-RH四個小分子材料。從物理性質來看，引入氰基使得LUMO能階下降至-3.68 eV；引入烷氧基使得吸光紅移約100 nm，達到拓展吸光範圍的效果。預期四個分子與常見的電子予體搭配下，能階的匹配度及吸光的互補度，都能比使用富勒烯做為電子受體，獲得更好的Voc以及Jsc，達到良好的光電轉換效率；第三部分，探討引入不同氰基數目對於D-A-D架構有機電致發光材料的影響。其中，以引入單個氰基的DDTCNTT，分子在exciplex-host的情況下，擁有最好的元件外部量子效應3.52%。

Organic photovoltaics (OPVs) have advantages of low cost, structure designability, light weight and flexibilility. Therefore, many studies have focused on the development of new materials to enhance the power conversion efficiency and stability. In this thesis, we introduced electron-withdrawing cyano groups onto thieno[3,2-b]thiophene (TT) and synthesized three series of molecules as donor, acceptor and emitter material. In the first part, we used TT and TTCN as acceptor unit in a configuration of D-A-A type molecule and synthesized four molecules: DTCPTT, DTCPTT-2CN, DTDCPTT and DTDCPTT-2CN. The results showed the strategy can dramatically lower LUMO while slightly lowering HOMO, thus decreasing the energy gap. Overall, the device of DTDCPTT not only exhibited high PCE (up to 7.81%) under AM 1.5 G irradiation with Jsc of 13.56 mA/cm2, Voc of 0.86 V and FF of 67.81%, but also performed PCE over 16% under TLD-840 lamp, indicating its promising prospect for photovoltaic application. In the secondary part, we used different substituents onto A-D-A type molecules. One was introduced cyano groups to tune energy level, and the other was introduced alkoxy groups to redshift the absorption due to increased dipolar moment. The results showed that TTCN-DC and TTCN-RH, introducing cyano groups could lower LUMO to -3.68 eV to as acceptor, and TTOHex-DC and TTOHex-DC introducing alkoxy groups could redshift the absorption of 100 nm. Because of the matching energy level and complementary absorption, they were expected to achieve better PCE. In the third part, we introduced different numbers of cyano groups onto D-A-D type molecules, which influenced those material’s properties. Among those molecules, DDTCNTT with a cyano group has the best external quantum effect 3.52% in the case of dopant in exciplex-host.