複合式發光層於有機發光元件之應用

Abstract

本論文以研究「複合式發光層系統」應用於有機發光元件(OLED)為主題，其概念是利用一具有載子傳輸能力的有機材料，摻雜於傳統的「主-客發光層系統」中，利用此載子傳輸材料促進載子注入於發光層中，提升載子的再結合率和降低操作電壓，達到提升OLED元件發光功率的目的。特別是應用在以寬能帶主發光體所組成的藍色磷光OLED元件上。此外，本論文也將「複合式發光層系統」應用於綠色磷光OLED元件、綠/紅色之黃色磷光OLED和堆疊式白光OLED元件上。

(1) 藍色磷光OLED元件 將「複合式發光層系統」應用於以FIrpic為藍色磷光客發光體之磷光OLED元件上。在以PPT為主發光體和TCTA為載子傳輸材料下，藍色磷光OLED元件在發光亮度1000 cd/m2下，電流效率可達26.5 cd/A、發光效率為19.9 lm/W、操作電壓為4.2V，色度座標CIEx,y為(0.17, 0.36)。相較於傳統的主客發光體系統，發光功率可提高2.1倍。

(2) 綠色磷光OLED元件 將「複合式發光層系統」應用於以Irppy為綠色磷光客發光體之磷光OLED元件上。在以CBP為主發光體和TCTA為載子傳輸材料下，綠色磷光OLED元件在發光亮度1000 cd/m2下，電流效率可達52.7 cd/A、發光效率為47.7 lm/W、操作電壓為3.4V，色度座標為CIEx,y(0.33, 0.61)。相較於傳統的主客發光體系統，發光功率可提高1.2倍。

(3) 綠/紅色之黃色磷光OLED元件 將「複合式發光層系統」應用於以Irppy為綠色磷光客發光體，並同時以Os(fptz)2(PPh2Me)2為紅色客發光體材料，組合成黃色磷光OLED元件。在以CBP為主發光體和TCTA為載子傳輸材料下，綠/紅色之黃色磷光OLED元件在發光亮度1000 cd/m2下，電流效率可達44.1 cd/A、發光效率為40.7 lm/W、操作電壓為3.4V，色度座標CIEx,y為(0.45, 0.52)。相較於傳統的主客發光體系統，發光功率可提高1.4倍

(4) 堆疊式白光OLED元件 最後，本論文將以「複合式發光層系統」所建立的藍色磷光OLED元件和綠/紅色黃色磷光OLED元件，透過n-doped/p-doped連接層製作堆疊式白光OLED元件。堆疊式白光OLED元件在發光亮度1000 cd/m2下，電流效率70.1 cd/A、發光效率為27.5 lm/W、操作電壓為8V，色度座標為CIEx,y(0.33, 0.48) 和演色性(color-rendering index, CRI)~72。為提高白光OLED元件的演色性達實用標準CRI>80，將藍色磷光OLED單元改以具有較飽和色度的藍色螢光OLED單元取代。堆疊式白光OLED元件在發光亮度1000 cd/m2下，電流效率44.2 cd/A、發光效率為18.8 lm/W、操作電壓為7.4V，色度座標為CIEx,y(0.39, 0.45)和演色性可達CRI~84。

In this thesis, we introduce a concept of “composite emitter” for applying on organic light-emitting devices (OLEDs). The composite emitter is doping a carrier-transporting material into conventional host-guest emitter for promoting the transport of carriers from carrier-transporting layer into emitter to increase the efficiency and decrease the driving voltage of OLED. Especially, the composite emitter can apply to blue phosphorescent OLED which need to use a wide-bandgap host material; in additional to we also apply this concept to the green phosphorescent OLED, Green/Red yellow phosphorescent OLED and tandem white OLED.

(1) Blue phosphorescent OLED A blue phosphorescent OLED with a current efficiency of 26.5 cd/A, a power efficiency of 19.9 lm/W, a driving voltage of 4.2V and CIEx,y of (0.17, 0.36) at a brightness of 1000 cd/m2 can be achieved by composite emitter which was composed a host material of PPT and a carrier-transporting material of TCTA. Under the composite emitter, the blue phosphorescent OLED was improved by a factor of 2.1 comparing to that of using conventional host-guest emitter.

(2) Green phosphorescent OLED A green phosphorescent OLED with a current efficiency of 52.7 cd/A, a power efficiency of 47.7 lm/W, a driving voltage of 3.4V and CIEx,y of (0.33, 0.61) at a brightness of 1000 cd/m2 can be achieved by composite emitter which was composed a host material of CBP and a carrier-transporting material of TCTA. Under the composite emitter, the green phosphorescent OLED was improved by a factor of 1.2 comparing to that of using conventional host-guest emitter.

(3) Green/Red yellow phosphorescent OLED A yellow phosphorescent OLED which was co-doping green and red phosphorescent dopant into composite emitter at the same time with a current efficiency of 44.1 cd/A, a power efficiency of 40.7 lm/W, a driving voltage of 3.4V and CIEx,y of (0.45, 0.52) at a brightness of 1000 cd/m2 can be achieved by composite emitter. Under the composite emitter, the yellow phosphorescent OLED was improved by a factor of 1.4 comparing to that of using conventional host-guest emitter.

(4) Tandem white OLED Finally, under the concept of composite emitter, applying a blue phosphorescent OLED and a green/red yellow phosphorescent OLED to fabricate a tandem white OLED through a connecting layer which was constructed by n-doped/p-doped layers. A tandem white OLED with a current efficiency of 70.1 cd/A, a power efficiency of 27.5 lm/W, a driving voltage of 8V, CIEx,y of (0.33, 0.48) and a color rendering index (CRI) of 72 can be achieved. In order to improve the CRI for attaining a practical value of 80, using a blue fluorescent OLED with saturated color to instead of blue phosphorescent OLED. The tandem white OLED with a current efficiency of 44.2 cd/A, a power efficiency of 18.8 lm/W, a driving voltage of 7.4V, CIEx,y of (0.39, 0.45) and a color rendering index (CRI) of 84 can be achieved.