在本論文中，我們將熱活化延遲螢光材料2BPy-mDTC及BPy-p3C以10-20 %的濃度摻雜於螢光元件的發光層，稱為輔助型客體(Assistant dopant)，並搭配低摻雜濃度(≤ 2 %)的一般螢光材料作為發光客體(Emitter dopant)，在此雙客體系統中，利用輔助型客體捕捉三重態激子經由逆向系統間跨越回到單重態的方式，增加可放光的單重態激發子之數量，再透過Förster resonance energy transfer (FRET)將能量傳遞至發光客體，藉此高效運用激子的機制達到提升元件效率之目的。文中設計的四組雙客體系統皆用mCBP作為分散濃度的主體(Host)，第一組2BPy-mDTC搭配C545T的綠色螢光元件與第二組BPy-p3C搭配TBPe的藍色螢光元件，其外部量子效率分別高達28.5 %及14.0 %，相較未引入輔助型客體的各項元件表現皆有翻倍的增長。第三組引入本實驗室吳奕靚開發之具有三重態-三重態自我焠熄(Triplet-triplet annihilation, TTA)的材料OCzSSO作為發光客體，並由元件非其放光推測未發生FRET歸因於輔助型客體之放光光譜與發光客體之吸收光譜的極低光譜重疊度，且即便提高濃度仍未發生Dexter energy transfer。第四組則利用與BPy-p3C相異光色的TTPA，結果顯示引入輔助型客體使元件各項表現皆有大幅增長，並提升元件光色之色純度，上述結果充分突顯熱活化延遲螢光材料應用於雙客體系統之必要性。

In this thesis, we demonstrate a route for triplet harvesting by utilizing thermally activated delayed fluorescence (TADF) molecules as assistant dopants that provide efficient transfer path for not only singlet but also triplet electrically generated excitons from them to the fluorescence emitters. In these four double-dopant systems, we use mCBP as a wide-energy gap host, 2BPy-mDTC and BPy-p3C as TADF-assistant dopants and C545T, TBPe, OCzSSO and TTPA as fluorescence emitter dopants. First, we report the green and blue fluorescence-based OLEDs that realized external quantum efficiency as high as 28.5 and 14.0 % by using C545T and TBPe as emitter dopants, respectively. Moreover, we use OCzSSO to testify the absence of Dexter energy transfer between the triplets of assistant dopants and emitter dopants, and to confirm that the poor performance of Förster resonance energy transfer (FRET) is attributed to the small spectral overlap between two dopants. In the last part, we replace TBPe with TTPA, which emission color is different from BPy-p3C for preliminary test, and the results also show an improvement in efficiency, color purity and emission intensity after introducing the assistant dopant. Therefore, we summarized that the cascade energy transfer scheme using TADF assistant dopants and fluorescent emitters will be the promising OLEDs devices architecture with outstanding performance.

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