寡聚苯基乙烯及多苯代苯高分子於有機發光二極體之應用

Abstract

在此論文主要探討有機發光二極體才料及元件之製造。在第一及第二章中分別介紹OLED原理及本論文所需之儀器。在第三章中使用不同urethane做鏈結以聚合發光二級體之單體。為了提高元件的效率，我們使用BCP作一電洞阻擋層，Alq3作一電子傳輸層和新的高分子材料(OPV-IPDI)作一電洞傳輸層，這樣的結構與只有PEDOT：PSS的元件相比可以提高六倍的電流效率。更進一步的，我們將PEDOT：PSS作一電洞注入層，OPV-IPDI和它的衍生高分子(OPV-OXD，OXD-IPDI和OPV-Si)作電洞傳輸層應用在小分子電激發光元件上。與使用傳統電洞傳輸材料NPB的元件相比，使用新的高分子材料(OPV-IPDI和OPV-OXD)製作的元件可以降低約兩伏的驅動電壓並且改善元件的電流效率達至兩倍以上。在第四章及第五章中藉由不同的合成策略開發並製造出整套PPV系列的共聚高分子。並探討其在熱穩定性質、電化學性質、光學性質、以及元件製備上對於不同結構所影響的因素與變化。首先，我們合成出一系列之PPV-Fluorene共聚高分子，並將不同的結構分成三個系統來加以探討 (1)不同分子量對於PLED性質之影響與探討 (2) 不同末端基對於PLED性質之影響與探討 (3) 共聚高分子與三聚高分子改變上之影響與探討 並藉此三系統的討論對PPV-Fluorene系列之光電高分子應用於有機發光二極體有更深入的了解。而不同末端對於元件之光電性質也有相當大的影響，其中又以導入三苯基胺之末端基其對於元件光電性質的提升有最大的助益。並藉由簡單的旋塗製程與光轉換原理，成功的製作發出黃白光CIE 1931 (0.31,0.32)的元件。其最大亮度為400 cd/m2，效率高達3 cd/A。另外，在導入dibromobenzo thiadiazole單體成為三聚高分子之後，我們成功製作出高亮度綠光元件，在發光的強度上也提升至4250cd/m2，效率為2.3cd/A。在第七章中以9-(五苯代苯)卡唑為核心，利用簡易的Suzuki Coupling及Horner-Wadsworth-Emmons反應與不同單體聚合形成高分子P1~P6，並在高分子主鏈中分別

The essay were discussed the organic light emitting diodes. In the chapter 2 and chapter were discussed the theories and equipments of PLED. The chapter 3 and chapter 4 were discussed the polyurethane effect in the PLED devices. A novel family of hole-transport polyurethanes (PUs) has been developed. The PUs were prepared from the condensation polymerization of isophorone diisocyanate (IPDI) with (E,E)-1,4-bis(2-hydroxystyryl)benzene, an oligo p-phenylene-(E)-vinylene (OPV) unit, and various amounts of 2,5-bis(4-hydroxyphenyl)-1,3,4-oxadiazole (OXD), as well as with 4-tert-butyl phenol as the terminal group. The PUs demonstrates superior properties that were concluded on the basis of the improved current injection in the corresponding hole-only device. When compared to the control device, the current efficiency was improved 2.37 times. The maximum brightness increased to 14900 cd/m2 in comparison to that of 5780 cd/m2 for the control device. The performance of the OLED devices was fine-tuned by adjusting the combination of the OPV and OXD units to reach electron-hole balanced conditions. The maximum current efficiency increased to 4.12 cd/A at 5.5 V when the PU layer of OPV:OXD ) 67:33 was used. In the chapter 5 and chapter 6, a series of PPV system polymers was synthesized and the relationships between chemical structure design and thermal stability、optical properties、electro-chemical properties or device performance are discussed. At first, a series of PPV-Fluorene system copolymers was synthesized and discussed into three aspects (1) Molecular Weight Effect in PLED. (2) End Group Effect in PLED. (3) Copolymer and tricopolymer comparability in PLED. By doing research in these three systems, we interiorize the application of PPV-Fluorene system luminescent polymers in Polymer light emitting diode (PLED). It is found that the molecular weight mainly affects the film quality in device manufacturing when molecular weight increasing to a certain degree.End group is also an important improvement factor for luminescent properties of device, especially for applying triphenylamine group. On the other hand, based on luminescence conversion mechanism, a high efficiency PLED based on yellowish-white light CIE 1931 (0.423, 0.429) is successfully fabricated by simple spin-coating process. The device has external quantum efficiency of 3% and brightness of 400cd/m2. By combining dibromobenzo thiadiazole group into PPV-Fluorene system copolymers as tricopolymers, a high brightness green light PLED device is also successfully fabricated. The device has external quantum efficiency of 2.3% and brightness of 4250cd/m2. In the chapter 7, series of the co-polymers with huge hinder 4-pentaphenylphenyl-phenyl group as side chain were been synthesized by Suzuki coupling process. The co-polymers are introducing four different kinds of repeat unit when polymerized including carbazole, fluorene, benzothiadiazole and oligophenylenevinylene (OPV) with their own optical properties, respectively. Therefore, these co-polymers are not only to be the emitting layer by themselves but also be the host role in phosphorescence material when doping Ir(ppy)3 as guest and PBD in the PLED device. The optical performance of the co-polymers and device are measured, PL spectra, electroluminescence, UV-vis, turn-on voltage, efficiency are included in our research.