【作者】 王凯；

【导师】 王悦；

【作者基本信息】 吉林大学 ， 有机化学， 2014， 博士

【摘要】 近年来，随着在全色显示和固态白光照明领域展示出巨大的应用前景，有机电致发光技术在科研界以及产业界都得到了广泛的研究和关注。有机小分子光电材料因其结构明确、易于修饰、提纯加工简单等优点而被大量的用来开发作为高性能材料。目前来讲绿光和红光的器件水平已经基本满足实用化的需求，相比之下蓝光器件的水平有所滞后，尤其是高性能深蓝光材料依然比较稀缺。高效的深蓝光材料不仅可以明显降低显示器件的功耗，还可以用作其它低能发射材料的主体材料来使用，同时蓝光材料也是实现白光照明的不可或缺的组成部分。另一方面，磷光器件通常需要将发光材料以低浓度掺杂在主体材料中，所以磷光主体材料的性能与成本也明显地影响着磷光器件的效率和发展。因此，发展高效的蓝色荧光材料以及磷光主体材料，对于推进有机电致发光产业的发展并且进一步的实用化和工业化有着十分重要的意义。菲并咪唑类化合物具有刚性的平面骨架、良好的热稳定性，较为平衡的载流子注入/传输能力及高的蓝色荧光量子产率，而且合成步骤简单，产率高，提纯相对容易。针对以上几点，本论文主要以菲并咪唑为核（PPI），进一步拓展及开发优异蓝光材料及高性能磷光主体材料，系统地研究了这些菲并咪唑衍生物的结构与性质的关系，并以得到的这些多功能有机材料制备了高效率的有机电致发光器件。1、第二章中，我们通过简单的化学反应合成了苯环间位连接的菲并咪唑/邻菲啰啉并咪唑衍生物m-DPPI和m-PPPI。单晶结构显示化合物m-DPPI分子间不存在π···π等强相互作用，主要依靠C–H···π相互作用堆叠起来。化合物具有良好的热稳定性，从光物理性质测试上看，吸电子基团邻菲啰啉并咪唑基团的引入构成了一定的分子内电荷转移，但它们仍保留了PPI核较高的三线态能级。电化学和理论计算显示m-PPPI的能级较m-DPPI略有降低。通过对比非掺杂与掺杂客体分子的单载流子器件表明磷光客体的掺杂使得两者的空穴电流密度降低，电子电流密度提高。以它们作为主体材料制得了高效率的绿光及红光磷光发光器件，并且都展现出比较低的效率滚降。2、第三章中，我们将具有优异电子传输能力的二米基硼基团通过对位及间位的连接方式引入到菲并咪唑核上，得到了p-BPPI和m-BPPI。光物理性质测试显示间位取代方式有效抑制了分子内电荷转移，使得m-BPPI的三线态能级（2.60eV）与PPI核（2.61eV）几乎一样，而对位取代分子p-BPPI的三线态能级降低较多（2.39eV）。电化学测试表明m-BPPI的能级与PPI核相差不多，而p-BPPI的LUMO能级有一定程度的下降。通过单载流子器件的考察，与母体PPI相比，二米基硼的引入较大幅度提升了化合物的电子注入/传输能力，p-BPPI相比m-BPPI无论掺杂与非掺杂膜都具有更为平衡的空穴/电子电流密度。以p-BPPI为主体制得了高效的黄光和红光磷光发光器件；以m-BPPI为主体制得了高效的绿光，黄光和红光磷光发光器件，通过对比，基于p-BPPI的器件展现了更好的器件性能，表明在三线态能级满足磷光客体的前提下，载流子的注入/传输能力的大小和平衡程度对器件效率的影响会更大。3、第四章中，我们通过经典的反应将二苯氧磷基团（DPO）引入到菲并咪唑核上，合成了DPO-PPI和DPO-2PPI。光物理和电化学测试表明DPO基团的引入并没有扩展母核PPI的共轭程度，依然保留了母核PPI较高的三线态能级，与理论计算结果相符。分子间因强氢键受体P=O基团而往往存在比较强的P=O···H–C及C–H···π等相互作用，使得薄膜的发射由PPI的近紫外区红移到更有价值的深蓝光发射区，并且表现出较高的效率（0.57和0.55）。单载流子器件显示相较母核PPI，DPO基团的引入较大幅度提升了化合物的载流子注入/传输能力，两个化合物均具有双极传输性质。此外，DPO-2PPI相比DPO-PPI增加了一个PPI基团，使得基于DPO-2PPI的单载流子器件的电子电流密度略大于DPO-PPI。以它们作为蓝光发光层制备了具有一定潜力的深蓝光荧光器件，作为主体材料掺杂磷光客体制得了高效的绿光及红光磷光发光器件，其中绿光器件效率最高可达65.4cd A1,73.3lm W1,18.0%，红光器件效率最高可达19.0cdA1,21.3lm W1,13.5%。4、第五章中，我们设计合成了酚基-菲并咪唑配位的铍和锌配合物。铍配合物晶体显示分子有较大的空间扭曲，分子间存在着一定的π···π相互作用。两个化合物都具有高的熔点（387°C-409°C）和热分解温度（472°C-477°C）。分子的推拉电子结构使得两者的溶液和薄膜的发射红移到了深蓝光区，并且展现出较窄的半峰宽和较高的荧光量子效率。它们都具有比较小的单线态-三线态能极差（△EST），分别是0.35eV和0.21eV。理论计算和单载流子器件表明它们都具有双极传输性质，且铍化合物的空穴和电子的注入/传输能力相对锌化合物更加平衡。以其作为发光层的深蓝光荧光器件展现出优异的性能，最大效率为2.82%，2.41cdA1和2.52lm W1；作为磷光主体制得了效率较高的绿光（最大效率为15.3%，55.6cd A1和61.4lm W1）及红光（15.2%，15.9cd A1和21.7lm W1）磷光发光器件，并且基于铍化合物的器件展现出较低的效率滚降的性质。综上所述，我们设计合成了四个系列的基于菲并咪唑（PPI）的光电功能材料，对材料的光物理、热力学、电化学和载流子传输等性质进行了系统研究，探讨了其结构与性能的关系，并制备了一些具有一定应用潜力的有机电致发光器件，为进一步开发新型的菲并咪唑类功能材料提供了参考和依据。更多还原

【Abstract】 In recent years, along with the great potential in full-color displays and solid-statelighting sources, organic light-emitting devices (OLEDs) received much attention fromboth scientific and practical points. Organic small molecules are easily modified,well-organized, and of easy purification, therefore, they are widely used to develophigh-performance materials. To date, the20%theoretical external quantum efficiency hasalready been achieved in red and green PhOLEDs, however, highly efficient stabledeep-blue fluorescent emitter is still under developed. Excellent blue emitters can not onlyeffectively reduce the power consumption of a full-color OLED but also be utilized togenerate light of other colors by energy cascade to a lower-energy fluorescent orphosphorescent dopant. On the other hand, the phosphorescent emitter is usually embeddedin a suitable host to avoid self-quenching and triplet-triplet annihilation, so theperformance and cost of host materials significantly influences the efficiency anddevelopment of phosphorescent devices. Therefore, the development of efficient bluefluorescent and host materials are very important for the industrialization and practical useof OLEDs. Phenanthroimidazole derivatives have rigid planar skeleton, good thermalstability, balanced carrier injection/transport ability and high fluorescence quantum yield innear-ultraviolet region, and they are easily synthesized with simple purification and highyields. In this regard, we designed and synthesized four series of optoelectronic moleculesbased on phenanthroimidazole moiety, investigated their crystal structures, thermalproperties, photophysical properties, electrochemical properties and electroluminescent properties, and finally discussed the relationship between the structures and properties.1、 In chapter II, two phenanthroimidazole derivatives (m-DPPI and m-PPPI)connected at the para-position of the phenyl ring have been designed and synthesizedthrough simple synthetic procedure. There is no interfacial π···π interaction in the packingmode of the crystal of compound m-DPPI, it stacks mainly by C–H···π intermolecularinteractions. Both the compounds exhibit good thermal stability. The photophysicalmeasurement indicates that the introduction of1,10-phenanthroline leads to intramolecularcharge transfer within m-PPPI, but it still keeps the high triplet energy of PPI core.Compared with m-DPPI, m-PPPI possesses lower HOMO and LUMO energy levels. Thesingle-carrier devices of undoped films and guest molecules doped films for both of themindicate that the phosphorescent dyes decrease the hole current density owing to chargetrapping sites; in contrast, the electron currents are slightly increased, which should arisefrom that doped molecules creates an additional electron transporting channel.High-performance green and red phosphorescent devices using them as host materials werefabricated and they exhibited low efficiencies roll-off.2、In chapter III, the electron transfer group dimesitylboryl group was attached to thepara-postion or meta-postion of PPI core. Intramolecular charge transfer is suppressed bythe meta linkage, leading to a similar triplet energy level (2.60eV) of m-BPPI as the corePPI (2.61eV). The triplet energy of p-BPPI is2.39eV. They both undergo reversibleoxidation and reduction process to permit the formation of stable cation and anion radials.The single-carrier devices exhibite that the electron current densities for both of them aregreatly increased compared to PPI, indicating that the appending Mes2B moiety improvedthe electron injection/transport properties. Both the hole and electron current densities aregreatly decreased after doping the phosphorescent dyes, implying the doped iridiumcompound act as carrier trapping sites. The hole and electron current of p-BPPI baseddoping films are slightly higher than m-BPPI. High-performance yellow and redphosphorescent devices using p-BPPI as host material were fabricated andhigh-performance green, yellow and red phosphorescent devices using m-BPPI as host material were fabricated. The devices based on p-BPPI show better performance,indicating that on the premise of the triplet energy is large enough, the ability and balanceof carrier injection/transport play a greater role on the devices performance.3、In chapter IV, two novel electron-accepting phosphine oxide moiety attachingphenanthroimidazole hybrids have been designed and synthesized, namely DPO-PPI andDPO-2PPI. The P=O group is used as a point of saturation between PPI moiety and theouter phenyl groups, so the high triplet energy of PPI is almost preserved. The strongintermolecular interactions owing to P–O···H–C and C–H···π bonds red shift thefluorescence of films to deep-blue emission with high quantum yields (0.57for DPO-PPIand0.55for DPO-2PPI). The thermal stability and carrier injection/transport ability havebeen greatly improved after appending the DPO moiety. Moreover, they exhibit balancedcarrier injection/transport ability in non-doped films and phosphorescent emitters-dopedfilms. Compared to DPO-PPI, an additional PPI moiety in DPO-2PPI increases its electrontransporting ability. The multifunction enables adaptation of several simplified deviceconfigurations. The non-doped deep-blue fluorescent device exhibits external quantumefficiency of2.24%with CIE of (0.16,0.08), very close to NTSC blue standard CIE (0.14,0.08). High-performance green (65.4cd A-1,73.3lm W-1and18.0%) and red (19.0cd A-1,21.3lm W-1and13.5%) phosphorescent devices using them as hosts have been achieved.The relationship between molecular structures and optoelectronic properties are discussedexperimentally and theoretically.4、In chapter V, two coordination complex emitters as well as host materials Be(PPI)2and Zn(PPI)2are designed, synthesized and characterized. The incorporation of the metalatom leads to a twisted conformation and rigid molecular structure, which improve thethermal stability of Be(PPI)2and Zn(PPI)2with high decomposition and glass transitiontemperature at around475°C and217°C. The introduction of the electron-donating phenolgroup results in the emission color shifting to the deep-blue region and the emissionmaximum appears at around429nm with narrow full-width at half maximum (FWHM).Thus, then have small singlet-treplet splitting of0.35eV for Be(PPI)2and0.21eV for Zn(PPI)2. The theoretical calculations and single-carrier devices indicate that bothcompounds have ambipolar transport property and pure Be(PPI)2and Be(PPI)2doped withphosphorescent dyes possess a more balanced charge transport ability then Zn(PPI)2. Anundoped deep-blue fluorescent device using Be(PPI)2as emitter exhibits maximum powerefficiency of2.5lm W-1with CIE coordinates of (0.15,0.09). Green and redphosphorescent OLEDs using them as host materials show high performance. The highestpower efficiencies of67.5lm W-1for green PhOLEDs and21.7lm W-1for red PhOLEDsare achieved. In addition, the Be(PPI)2-based devices show low efficiency roll-off behavior,which is attributed to the more balanced carrier injection/transport property of Be(PPI)2.In summary, we have designed and synthesized four series of organic optoelectronicmolecules based on PPI core. The relationship between structures and properties have beencarefully investigated. At the same time, we got some materials with excellentperformance.更多还原