藍色複合激發體觸發三重態-三重態湮滅及不同熱活化延遲螢光發光體有機發光二極體之效率提升研究

Efficiency Enhancement of Organic Light-emitting Diodes by Exciplex Sensitized Triplet-triplet Annihilation for Blue Emission and Different Thermally Activated Delayed Fluorescence Emitters

曾柏宸(Po-Chen Tseng)

指導教授 ： 李君浩

國立臺灣大學/電機資訊學院/光電工程學研究所/碩士(2017年)

https://doi.org/10.6342/NTU201701087

摘要

本篇論文有兩個研究主題。其一為複合激發體觸發三重態-三重態湮滅藍色有機發光二極體之效率提升研究。其二為利用咔唑基團與咪唑基團合成之衍生物作為不同熱活化延遲螢光發光體之通用主體材料之研究。
我們利用具有推電子及拉電子特性的有機材料形成複合激發體，再藉由能量傳遞將能量傳給藍色螢光材料進行三重態-三重態湮滅上轉換得到藍光，我們稱為複合激發體觸發三重態-三重態湮滅過程。藉由嵌入一層三重態傳遞和單重態阻隔層以及加入螢光客體材料，可以達到最高外部量子效率5.1%，其中包含藍色部分3.8%。最後以電激發元件觀察激子的暫態行為，暫態放光中並沒有瞬時螢光的產生，而只有經由能量轉移形成的延遲螢光，表示此架構的藍光都是來自於複合激發體觸發三重態-三重態湮滅的過程。
利用咔唑基團與咪唑基團合成之衍生物作為藍色、綠色及紅色熱活化延遲螢光發光體之通用主體材料，期望簡化製程步驟及降低生產成本。經過元件結構的調整與優化，藍色、綠色與紅色熱活化延遲螢光之高效率有機發光二極體的最大電流效率、功率效率及外部量子效率分別為11.3 cd/A、91.8 cd/A及31.4 cd/A、11.9 lm/W、91.9 lm/W及28.2 lm/W與9.0%、26.2%及11.5%。也成功展現此主體材料作為熱活化延遲螢光發光體之通用主體材料的可行性。

關鍵字

有機發光二極體 ； 複合激發體 ； 觸發 ； 三重態-三重態湮滅 ； 暫態電致發光 ； 熱活化延遲螢光 ； 通用主體材料

並列摘要

There are two topics in this thesis. The first one is efficiency enhancement of exciplex sensitized triplet-triplet annihilation (ESTTA) blue organic light emitting diodes (OLEDs). The second one is red, green, blue OLEDs with 9,9'-(2-(1-Phenyl-1H-benzo[d]imidazol-2-yl)-1,3-phenylene)bis(9H-carbazole) (o-DiCbzBz) as the universal host material for thermally activated delayed fluorescence (TADF) emitters.
The exciplex was formed at interface of electron donor and acceptor organic materials, then triplet energy transfer (TET) to TTA blue emitter to generate upconversion blue emission, which was called exciplex sensitized triplet-triplet annihilation (ESTTA) process. With insertion of triplet assisting and singlet blocking (TASB) layer and incorporation of fluorescent dopant, the blue ESTTA-OLED exhibited maximum external quantum efficiency (EQE) of 5.1% including blue emission EQE of 3.8%. In addition, transient electroluminescence (TrEL) was used to examine the origin of blue emission. In turn-off luminance response, only slow decay was observed implying blue emission all came from exciplex energy transfer to emitter to facilitate TTA upconversion emission, called ESTTA process.
o-DiCbzBz was used as host material, doped with metal-free red, green, and blue TADF dopants to achieve high efficiency OLEDs in order to simplify manufacturing process and reduce production cost. After the optimization of the device structure, maximum current efficiency of 11.3 cd/A, 91.8 cd/A, and 31.4 cd/A, maximum power efficiency of 11.9 lm/W, 91.9 lm/W, and 28.2 lm/W, and maximum EQE of 9.0%, 26.2%, and 11.5% were obtained for blue, green, and red TADF-OLEDs, respectively, showing the feasibility of o-DiCbzBz as the universal host for RGB high efficiency TADF-OLEDs.

並列關鍵字

Organic light-emitting diode ； exciplex ； sensitized ； triplet-triplet annihilation ； transient electroluminescence ； thermally activated delayed fluorescence ； universal host

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