氟取代苯並噻二唑型小分子於有機太陽能電池之合成、性質與應用

Abstract

小分子太陽能電池因具有分子結構明確、每批品質較一致之優勢，故近年吸引相當多領域投入研究。 先前的文獻指出，在電子予體中引入氟原子，可以同時降低分子的最高占有分子軌域與最低未占有分子軌域之能階。而降低之能階有助於太陽能電池獲得較高之開路電壓。故在本篇論文中，我們設計並合成了具予體-受體-受體 (D-A-A) 架構之含氟電子予體。其分別以噻吩與苯環為架橋，並在苯並噻二唑上引入朝內或朝外之氟原子，可得DTCTiFBT，DTCToFBT，DTCPiFBT及 DTCPoFBT。四個分子的最大吸收波長在500-600 nm，且有良好的吸收效率。相較於其對照組，四個分子皆表現些微紅移之吸收光譜，以及較低之能階。將其與電子受體材料C60共蒸鍍，並調變適當的膜厚及混合比例製作太陽能電池元件。四個分子之表現皆較未引入氟的對照電子予體優異。在與C60共蒸鍍的元件中，以噻吩為架橋的DTCToFBT/C60 最佳化元件結構可得到0.83 V 之開路電壓，6.85 mA/cm2之短路電流，以及3.28% 之光電轉換效率。而以苯環為架橋的DTCPoFBT最佳化元件結構可得到0.88 V 之開路電壓，6.50 mA/cm2 之短路電流，以及3.62% 之光電轉換效率。本論文展示了D-A-A架構之含氟電子予體之結構與性質對應。

In recent years, small-molecule organic solar cells (SMOSCs), because of their well-defined structure and batch-to-batch reproducibility, are under intense investigations. We anticipate that the introduction of fluorine atom onto a donor molecule can lower the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of the donor, giving the SMOSC device a larger open circuit voltage (Voc). In this thesis, four molecules configured as donor-acceptor-acceptor (D-A-A) were synthesized and characterized. Two electron donating moieties, namely ditolyaminothiophene or ditolyaminophenylene were respectively connected to an electron deficient cyano group, via F-substituted [2,1,3]benzothiadiazole (FBT) to give DTCTiFBT, DTCToFBT, DTCPiFBT, and DTCPoFBT. Four molecules showed slightly red-shifted absorption and lowered HOMO and LUMO level as compared to those of the non-fluorinated counterparts. After fabrication with fullerene C60 as the active layers in SMOSCs, all molecules showed better performance compared to the non-fluorinated counterparts. Among all, thiophene-bridged DTCToFBT/C60 device exhibited a Voc of 0.83 V, a short circuit current density (Jsc) of 6.85 mA/cm2, and a fill factor (FF) of 0.58, achieving a power conversion efficiency (PCE) of 3.28%. Pheneylene-bridged DTCPoFBT/C60 device exhibited a Voc of 0.88 V, a Jsc of 6.50 mA/cm2, and a FF of 0.63, achieving a PCE of 3.62%. A clear structure-property relationship has been established.