硒吩與噻吩作為π-架橋於有機光伏打高分子之光電性質探討

Abstract

本篇論文提出兩種以二聚茚噻吩與氟化喹喔啉作為單體，並分別以噻吩(pIDTTFQ)與硒吩(pIDTSFQ)作為之π-架橋之共聚高分子，為達到更優良的光電轉換效率，選用不同的π-架橋是以往修飾共聚高分子的一個有效策略。理論計算的結果指出，pIDTSFQ因硒吩之芳香環較噻吩來得大，得以有效舒緩二聚茚噻吩與氟化喹喔啉之間，因為長碳鍊所導致的分子內斥力；數據顯示二聚茚噻吩與氟化喹喔啉之間有較小的二面角，代表pIDTSFQ具有更好的分子平面性。相較於pIDTTFQ，pIDTSFQ在固態的吸收極限由685奈米延展至742奈米，而最高佔有電子軌域之能階由-5.37電子伏特，上升至-5.31電子伏特。在所有變因的影響下，由pIDTTFQ製備的元件表現出2.0±0.1%的效率，而pIDTSFQ則是 2.6±0.5%。

In this study, we report two conjugated copolymers, combined with indacenodithiophene- (IDT) and fluorinated quinoxaline- (FQ) based monomers, while using thiophene and selenophene as π-bridge in both, yielding pIDTTFQ and pIDTSFQ, respectively. In an aim to apply them into polymer photovoltaics and achieve better power conversion efficiencies (PCEs), alternating variant π-space to harness the photochemical properties of conjugated copolymers has been one of the strategies in modifying present copolymer combinations. Theoretical calculations reveal that the usage of selenophene reliefs the intramolecular repulsion and the corresponding twist, with the decrease of dihedral angle. Compared with pIDTTFQ, the absorption edge of pIDTSFQ in solid state is extended from 685nm to 742nm, while the EHOMO was increased from -5.37eV to -5.31eV. Considering the decreased Voc and the enhanced Jsc, the optimized pIDTTFQ- and pIDTSFQ-based devices achieve PCE values of 2.0±0.1% and 2.6±0.5%, respectively. However, the two polymers exhibit similar devices performance but much different absorption ranges, which signifies the potential of choosing selenophene as π-bridge to achieve better device performance.