螢光-磷光混成白光有機發光二極體奠基於鉑錯合物及多種主體材料之研究

Abstract

鉑錯合物應用於有機發光二極體的研究在近年受到矚目，因其有易形成激發聚物的特性、因而有更寬的發光頻譜，在製作高演色性白色有機發光二極體的方面具有優勢。 應用白色有機發光二極體於固態照明的領域時，常見的作法是用藍色螢光材料取代藍色磷光材料，以避免其壽命低的劣勢。在陳錦地博士實驗室前幾年的研究中，他們研發出多種鉑錯合物並使用兩種主體材料「4P-NPD(藍色螢光材料)、CBP」，成功製作出螢光-磷光混成白光有機發光二極體。然而元件的亮度和效率仍需改善。 本篇論文使用FPtmND作為磷光發光材料，在單體狀態時其能放出綠光、在激發二聚物的狀態時其能放出橘紅光。我們的研究目的是找出合適的材料和元件結構以得到高演色性、高亮度和高效率的混成白光有機發光二極體。 本篇研究分為三部分。第一部分我們將FPtmND以不同濃度分別摻雜在4P-NPD、CBP和TCTA中，探討濃度跟發光頻譜之間的關係，其中4P-NPD扮演主體材料和藍色螢光發光體的角色。第二部分則是研究FPtmND同時摻雜在兩種主體材料，或一個元件包含兩層單主體材料-單客體材料的發光層，並且分析不同摻雜濃度對於發光頻譜形狀的影響。 第三部分，我們將超薄發光層的概念應用在FPtmND上。我們找出最佳的CBP和FPtmND的厚度，並重複CBP(3.3nm)/FPtmND(0.15nm)的結構來改善有機發光二極體的亮度與效率，再加上沒有摻雜的4P-NPD層來調整發光顏色跟演色性。 本篇論文最好的實驗結果為 ITO / NPB(40nm) /【CBP (3.3nm) / FPtmND (0.15nm) 】* 9 / 4P-NPD (5 nm) / TPBi (40nm) / LiF(1nm) / Al (150nm) 最大亮度為8130 cd/m^2，演色性>85；在亮度為1000 cd/m^2 時，外部量子效率= 4.25%，電流效率為6.70 cd/A，功率效率為2.00 lm/W。

Platinum complexes have drawn increasing attention for the use in organic light-emitting diode(OLED) applications because they can easily form excimers and have broadened emission spectrums, which is an advantage for high color rendering index(CRI) white organic light-emitting diode (WOLED). For WOLED solid-state lighting, fluorescence-phosphorescence hybrid WOLED is a common method that researchers utilize the blue fluorescent material instead of the blue phosphorescent material to avoid the poor lifetime of blue phosphorescence. In the previous research of Chin-Ti Chen’s lab, hybrid WOLEDs with various platinum complexes, 4P-NPD(blue fluorescent material) as the host material and CBP as the host material have been studied. However, the devices still need further improvements in luminance and efficiency. In this whole thesis, we utilized FPtmND as the phosphorescent emitter, which can emit green photons as the monomer and orange photons as the excimers. Our goal is to find the appropriate materials and structures to get WOLED with high CRI, luminance and efficiency. Our studies can be categorized into 3 parts. In the first part, we figured out the relation between the doping concentration of FPtmND and the emissive spectrums in 3 different host materials: CBP, 4P-NPD and TCTA, while 4P-NPD is not only the host but also the blue fluorescent emitter. In the second part, we discussed 6 kinds of co-host EML and one kind of two EML in one OLED, and analyzed the influence of different mixing ratios to the shape of the emission spectrums. In the third part, we applied the idea of the ultra-thin emissive layer(UEML) on FPtmND. We optimized the OLED by tuning the appropriate thicknesses of FPtmND and CBP, repeating the CBP(3.3nm)/FPtmND(0.15nm) structures to get higher luminance and efficiency, and adding a non-doped 4P-NPD layer into the OLED to enhance the CRI and tune the color. Our best result in this thesis is: ITO / NPB(40nm) /【CBP (3.3nm) / FPtmND (0.15nm) 】* 9 / 4P-NPD (5 nm) / TPBi (40nm) / LiF(1nm) / Al (150nm), which is with Lmax = 8130 cd/m^2, CRI > 85, and EQE = 4.25%, current efficiency = 6.70 cd/A, power efficiency = 2.00 lm/W at 1000 cd/m^2.