标题: 聚亚醯胺发光二极体及奈米复合材料之合成与特性研究
Synthesis and Characterization of Polyimide Light-Emitting Diodes and Nanocomposites
作者: 徐守谦
Shou-Chian, Hsu
黄华宗
Wha-Tzong Whang
材料科学与工程学系
关键字: 聚亚醯胺;发光二极体;奈米复合材料;polyimides;light-emitting diodes;nanocomposites
公开日期: 2005
摘要: 显示和奈米科技是近年来不管在基础学科或高科技产业中相当热门的两个课题。本论文将分成两个部分,共七个章节,针对聚亚醯胺之发光二极体及奈米复合材料的特性 (2–5章),和一维奈米材料的制备两个主题做深入的研究(6,7章)。

首先在第二章为BAO系列聚亚醯胺发光二极体特性研究。所有合成的BAO系列聚亚醯胺玻璃转化温度皆大于250℃,5 wt.-% 热裂解温度也大于510℃,显示良好的热安定性及机械性质。这些聚亚醯胺也均有萤光特性,而且萤光强度跟分子链的排列有密切的关系。进一步将合成之聚亚醯胺制作成单层发光二极体元件,只有BAO-ODPA和BAO-6FDA两种聚亚醯胺观察到电致发光性质,BAO-PMDA 和BAO-BPADA两种聚亚醯胺可能因薄膜均匀性太差导致原件短路。另外,BAO-ODPA在双层发光二极体元件中(ITO/PPV-PVA/PI/Al)也具有良好的电子传输及电洞阻障的功能,可将PPV-PVA发光效率提高两个级数。

第三章为利用真空蒸镀聚合制备以BAO-6FDA和BAPF-6FDA两种聚亚醯胺为发光层之单层发光二极体。利用真空蒸镀聚合,聚亚醯胺薄膜的厚度可降低至150 Å,两种聚亚醯胺二极体元件也都表现出4.5V 和6.5V相当低的启动电压。经由原子力显微镜的分析,BAO-6FDA和BAPF-6FDA两种聚亚醯胺薄膜皆有良好的表面平整度,分别为8.8 Å和4.7 Å。BAO-6FDA发光二极体具有较宽的电致发光频谱,其范围从400 nm 到700 nm。而BAO-BAPF发光二极体则表现出较佳的发光效率,这可能是因为较平衡的电子/电洞注入及较强的分子间电荷转移作用。

第四章叙述聚亚醯胺/ZnO奈米混成膜的制备与特性。PMDA-ODA和BTDA-ODA两种不同柔软度的聚亚醯胺作为高分子基材进行研究。经由FTIR和XPS的分析,推断ZnO表面的OH基和聚亚醯胺的C=O官能基会形成交链,进而提升混成膜的热和机械性质。另外,穿透式电子显微照片说明,ZnO奈米粒子分散在较刚硬的PMDA-ODA聚亚醯胺,粒子尺寸会大于分散在较柔软的BTDA-ODA聚亚醯胺中。


第五章为利用蒸镀/氧化二段法大量制备ZnO奈米单晶粒子于石英及聚亚醯胺基材上。蒸镀后的Zn金属在350℃热风循环机进行氧化2小时,可完全转变成透明的ZnO。经由高解析度TEM观察,制备的ZnO奈米粒子为晶格规则排列的单晶结构,并无晶格缺陷,并显示出一395 nm 的紫外光发光特性。

第六章叙述oleic acid/1-decanol/ammonium hydroxide 三相系统的inverse hexagonal (HII) 液晶相的制备与特性。HII相位于此三相图的中央,由21/55/24, 28/27/45和62/5/33 (oleic acid/1-decanol/ammonium hydroxide) 三点组成的三角形区域。在此HII相区域中,随着1-decanol含量的减少液晶消失温度(isotropic temperature)变化从55℃到142℃。经由XRD分析,推断制备的HII相的圆柱直径为4−4.4 nm,内部水相直径为1−1.4 nm。在此三相系统中,ammonium hydroxide的含量提高至45 wt.-%,及掺入多种金属离子,如Ag+, Cu2+, Ni2+, Co2+, Zn2+, 和 Cd2+,皆不会破坏原本规则的HII相。

本论文第七章叙述利用先合成的管状银离子先驱物,在室温下即时还原制备银奈米电缆(nanocable)。经由FTIR分析,推论配位的银离子错合物形成交链,自身聚集,进而促成管状先驱物的形成。此银离子管状先驱物长度达数微米,外径为155−200 nm,径/长比,管壁厚度为60−70 nm。经甲醛还原后,原本管状先驱物的中空部份,均匀的被直径30−45 nm的银奈米线所填充,形成奈米电缆结构。还原条件,如还原剂浓度和还原方法,对于最后产物的型态有很大的影响。
Display and nano technologies are two hottest topics in recent years not only in academic research but in high-tech industry. This thesis is divided into two parts to investigate the characterization of polyimide (PI)-based light emitting diodes (LED) and nanocomposites (chapter 2−5), and the preparation of one-dimensional nanostructures (chapter 6, 7).

Chapter 2 describes the characteristics of a single layer and a double layer 2,5-Bis(4-aminophenyl)-1,3,4-oxadiazole (BAO)-based PI LED. All the resultant PIs possess high glass transition temperatures ( >250℃) and high decomposition temperatures of 5 wt.-% weight loss (Td, >510℃). They also show obviously fluorescent characteristic, and the intensity is related to the arrangement of the molecular chains. Electroluminescent (EL) spectra were detected when BAO-ODPA and BAO-4,4’-(hexafluoroisopropylidene)diphthalic anhydrid (6FDA) acted as an emitting layer in a single LED device. In addition, in the double layer LED device, ITO/PPV-PVA/BAO-ODPA/Al, BAO-ODPA can be used as an excellent electron transport and electron/hole blocking layer, a significant improvement in the EL efficiency by two order of magnitude.

In chapter 3 presents that BAO and 4,4’-(9-Fluorenylidene)dianiline ( BAPF ) reacting with 6FDA were carried out by using vapor deposition polymerization (VDP) for single layer LED devices. The thickness of the PI thin film can be reduced to 150Å, and both PI-LEDs show low threshold voltages, 4.5V and 6.5V for BAO-6FDA and BAPF-6FDA LEDs, respectively. The root mean square of the surface roughnesses of the BAO-6FDA and BAPF-6FDA PI thin films are 8.8Å and 4.7Å, respectively, which are far smaller than that of wet coating process. The BAO-6FDA LED film emits a broader EL band, covering the full range of visible light (400 nm to 700 nm), than the BAPF-6FDA LED. However, the electroluminescent efficiency of BAPF-6FDA LED is higher than BAO-6FDA LED. It may suggest the better balance on holes and electrons injection in the former and better intermolecular charge transfer.

Chapter 4 reports the study of a series of PI/ZnO nanohybrid films with different ZnO content, which prepared from a rigid pyromellitic dianhydride (PMDA)-4,4’-diaminodiphenylether (ODA) and a flexible 3,3’,4,4’-benzophenonetetracarboxylic acid dianhydride (BTDA)-ODA PI matrixes. Analyses of Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy depict that the ZnO nanoparticles function as a physical crosslinking agent with PI through hydrogen bonding between the OH on the ZnO surfaces and the C=O of the imide groups. This crosslink causes the enhancement of thermal and mechanical properties of the hybrid films. Transmission electron microscopy (TEM) images reveal that the rigid matrix induces larger ZnO particle size (30−40 nm) compared the flexible matrix (10−15 nm).

In chapter 5 describes the study of the evaporation/oxidation two-step approach to massive prepare ZnO nanocrystals on a quartz and a PI film by using a thermal coater and an air-circulating. ZnO crystals were formed via low temperature oxidization at 350℃ for 2h. TEM images show the singular ZnO nanocrystals have regular lattice order without stacking faults. Deposited ZnO on PI film substrates can obtain individual and well distribution nanocrystals with average crystal size is 20-30 nm after dispersing by an ultrasonic bath. In photoluminescence, the produced ZnO nanocrystals exhibit strong UV emission at 395 nm, and no visible emission was detected.

Chapter 6 presents the ternary system oleic acid/1-decanol/ammonium hydroxide exhibiting an inverse hexagonal (HII) liquid crystalline phase, which exists between the compositions 21/55/24, 28/27/45, and 62/5/33 (oleic acid/1-decanol/ammonium hydroxide). The isotropic temperature increases from 55 °C to 142 °C with decreasing 1-decanol content. X-ray diffraction reveals interdigitated columns of 4−4.4 nm diameter with an internal water channel of 1−1.4 nm diameter. The system can tolerate up to 45 wt-% of ammonium hydroxide before the hexagonal phase collapses and can be doped with up to 0.1 mM concentrations of metals such as Ag+, Cu2+, Ni2+, Co2+, Zn2+, and Cd2+.

Chapter 7 describes a simple and efficient method to in situ fabricate silver nanocables at room temperature from a self-assembling silver precursor. Properly control of the reaction condition, such as reagent concentration and method of reduction, is important to obtain well-defined nanocables. In addition, FTIR spectroscopy revealed the organic sheath to be crosslinked via bridging-type coordination to the silver ions, which helps in the formation of the tubular aggregation.
URI: http://140.113.39.130/cdrfb3/record/nctu/#GT008818552
http://hdl.handle.net/11536/61890
显示于类别:Thesis


文件中的档案:

  1. 855201.pdf

If it is a zip file, please download the file and unzip it, then open index.html in a browser to view the full text content.