发光材料的合成及其光致、电致发光性能

1、朱为宏论文题目：多发色团发光材料的合成及其光致、电致发光性能研究作者简介： 朱为宏，男，1970年05月生，1996年09月师从华东理工大学田禾教授，于 1999年06月获得博士学位。摘要有机电致发光器件（organic electroluminescent devices, OELD）由于具有全色、低压直流 驱动、视角广、高效率、发光颜色丰富等优点，在平板大面积显示领域具有广阔的应用前景， 已引起广泛的重视。至目前为止，各式各样多层结构的器件、新的荧光染料和电极材料都在 深入研究，各种发光颜色甚至全色器件都已经相继报道。考虑到发光材料的复杂性、多层器件层层界面和微腔效应（microcavit

2、y effect）的影响，我 们在1996年首次提出并采用了一个全新的分子设计思路，应用分子组装原理（molecular assembling principle），将载流子注入传输体与发光材料直接相连。在本论文中，我们重点 合成新型的多发色团有机小分子和聚合物，在这些化合物中，电子传输单元和空穴传输单元 通过共价键作为桥链直接与发色单元相连。这样从载流子的注入、复合到激子的产生都发生 在多色团分子内，这就为制备高效率的单层电致发光器件成为可能。这种创造性地应用分子 组装原理具有以下三个优越性：1）与掺杂发光单层器件相比，该类多发色团的单层电致发光 器件可以避免掺杂的复杂性（如由于不同有机小分

3、子的真空升华速率不一样而引起的掺杂不 均匀性、低的形态稳定性（low morphological stability）； 2）器件的单层化，避免层与层 界面的影响和简化器件的制作工艺。据目前研究认为，层与层界面的影响是决定电致发光器 件性能的重要因素之一，这是因为一方面载流子（电子和空穴）必须克服层与层能垒的障碍， 另一方面由于采用真空蒸镀法，特别是采用旋涂甩胶法，由于溶解而相互渗透，造成层与层 相互交错，严重影响了电子和空穴的复合及激子的产生；3）从载流子的注入、复合到激子的 产生都发生在多发色团分子内,整个有机层都能电致发光。为了简化器件的制作工艺，消除层与层界面激子的猝灭，根据分子组装原

4、理，设计并合成 了新型的双发色团或三发色团化合物，其结构中通过共价键将1,8-萘酰亚胺组份（发光功能 团）以及恶二唑组份（电子传输功能团）和三苯胺组份（空穴传输功能团）连接成为一个有机分 子。这五个新型的多发色团化合物和五个未见报道的中间体均通过紫外一可见光谱、核磁共 振光谱和质谱进行了结构表征。研究发现，这些多发色团化合物在基态发色团之间没有作用 或作用很小，而其中恶二唑和三苯基胺单元的荧光被严重的猝灭，这说明在激发态下，萘酰 亚胺发色团与恶二唑、三苯胺功能团之间发生了分子内单线态一单线态能 量转移（Intra-SSET）。这类多发色团化合物已成功地应用于电致发光器件研究，电致发光峰 的波长

5、约为540 nm，当电压达14 V时，电流密度可达到260 mA/cm2,发光亮度可达350 cd/m2，其发光效率为3.02 lm/W。研究证明这种分子组装设计思路是可行且有效的。为了发展电致发红光的材料，设计并合成了四个三发色团北酰亚胺衍生物，在其结构中 1,8-萘酰亚胺和1,3,4-恶二唑单元通过饱和共价键与北酰亚胺母体相连。7个未见报道的中 间体和四个新型目标化合物的化学结构均经紫外一可见光谱、核磁共振光谱和质谱表征，确 定了其结构。光致荧光光谱表明该化合物的荧光强度和化学结构有密切关系，在发色团之间 存在着光诱导电荷转移作用。考虑到有机小分子掺杂到聚合物膜中低的形态稳定性，我们在上面

6、多发色团有机小分子研 究的基础上，通过自由基引发共聚合成了六个新型的共聚物。在该类共聚物的侧链上含有三 个功能团：1,8-萘酰亚胺单元(发色功能团)、恶二唑单元(电子传输功能团)和N-乙烯基恶唑 单元(空穴传输功能团)。六个未见报道的双发色团单体结构分别经1H-NMR和MS谱图表征。 此外，还合成了三种不同发色团比例的主链共聚物。研究表明，在激发态下也存在类似的多 发色团有机小分子的分子内单线态能量转移。该类型的聚合物作为单层电致器件进行了研究， 其电致发光的峰形很宽(450-650 nm)，其颜色用CIE坐标表示为(0.32, 0.37)。合成并研究了巴比妥酸衍生物的电致发光特性。研究表明，

7、该类化合物在固体状态下能发 出桔红至红光，光致荧光效率非常高，采用真空蒸镀法能形成质量很好的薄膜，其表现出类 似与Alq3的电流一电压特性曲线，其开启电压(5 V)甚至比目前研究最有希望的有机小分子 Alq3的开启电压(6 V)都要低。Synthesis and Photo- / Electro-luminescent Properties ofMulti-chromophoric MaterialsAbstractOrganic electroluminescent (EL) devices have attracted much attention due to their potenti

8、al for full colors, low operating voltage, wide angles and producing high conversion efficiency and high brightness materials for display application. Various multi-layer structure devices, fluorescent dyes and electrode materials have been studied to improve the efficiency and stability of devices,

9、 and various emitting colors, even white light, have been obtained.Considering the complication of doping in the emitting layer, multi-layer influence and microcavity effect, we firstly proposed a novel creative way to design luminescent materials for EL devices in 1996. According to the molecular s

10、elf-assembling principle, carrier-transporting units are incorporated into luminescent molecule via saturated covalent bonds. In this thesis we therefore focused on developing novel multi-chromophoric compounds and polymers, in which both electron and hole transporting units were connected directly

11、with the emitting unit via covalent bonds. Thus this makes it possible to develop high efficient single layer EL devices. Using such molecular design method, there are three advantages:1) Comparing with the single layer dye-doping EL devices, single layer EL devices with such multi-chromophoric mate

12、rials can dramatically eliminate the complication of doping, such as low morphological stability and low well-distribution; 2) Single layer EL devices can not only simplify the device fabrication, but also reduce the multi-layer interface, which is one of the most important factors determined the ef

13、ficiencyof EL devices; 3) The injection and recombination of carriers and the formation of excitons take place in the multi-chromophoric molecules, therefore the whole organic layer can luminescent light. This is a novel creative way to design luminescent materials for EL devices. The main contents

14、and results are generalized as follows:In order to simplify the fabrication process of EL devices and eliminate exciton quenching, according to the molecular self-assembling principle, five novel dyad or triad 1,8-naphthalimide compounds were designed and synthesized, in which both electron and hole

15、 transporting moieties were connected directly with the emitter via saturated covalent bonds. The chemical structures of the five novel multi-chromophoric compounds and five new intermediates were characterized by UV-Vis, 1H-NMR and Mass Spectra. Absorption spectra indicate that there is little or n

16、o interaction between chromphores in the ground state. However, the fluorescence emission of oxadiazole and triphenylamine moieties are almost quenched, which shows that in the excited ground state there exists very effective intermolecular singlet-singlet energy transfer (Intra-SSET). The EL wavele

17、ngth is near at 540nm, with a maximum of 350 cd/m2 and luminous efficiency of 3.02 lm/W at 14 V. It demonstrates that such molecular design is reasonable and very effective.In order to develop red luminescent materials for EL devices, four novel triad perylenetetracarboxydiimide derivatives were des

18、igned and synthesized, in which 1,8-naphthalimide and 1,3,4-oxadiazole moieties were linked with saturated covalent bonds. Seven new intermediates and four target compounds were characterized by UV-Vis, 1H-NMR and Mass Spectra. Fluorescence emission spectra show that the PL intensity of perylenetetr

19、acarboxydiimide derivatives is dependent on the chemical structure and there exits photo-induced electron transfer between chromophores.Considering the low morphological stability of dye-doped polymer thin film and based on the above multi-chromophoric organic small molecules, six novel copolymers h

20、ave been synthesized by the co-polymerization, in which there are three functions: 1,8-naphthalimide as emitting moiety, oxidiazole as electron transporting moiety, and N-vinyl carbazole as hole transporting moiety. Six dyad monomers were characterized by 1H-NMR and Mass Spectra. In addition, three kinds of condensation polymers with different moiety ratio have also been synthesized. In the excited state there also exists very effective Intra-SSET. It was demonstrated that single layer EL device with