高效磷光OLED材料的设计、合成与性能研究

【作者】 陈华；

【导师】 纪顺俊；

【作者基本信息】 苏州大学 ， 有机化学， 2014， 博士

【摘要】 有机电致发光器件（OLED）诞生20多年来已经有了长足的发展，在信息显示领域已经有了一定规模的应用，在固态照明领域也已步入了实用化的进程中。目前OLED仍旧是有机电子领域的研究热点。无论是OLED的新材料开发还是器件过程的机理研究都吸引着众多研究力量。本论文着重于OLED新材料的设计合成，并对材料的各项物理性能和器件性能进行了系统的表征。目前OLED材料中最为重要的是发光层材料，而目前效率最高的器件发光层都采用的是参杂结构。本论文的研究重点就是作为发光层主要构成部分的主体材料，尤其是具有高三线态能级的主体材料。而在众多的主体材料结构类型中，本论文主要就三苯胺螺芴类材料和四苯基硅类材料进行了研究，设计合成了一批功能材料，并对它们的器件性能进行了表征。在表征它们作为主体材料的能力的同时，还探索了部分材料作为阻挡层材料和空穴传输层材料的应用。以下是对各章节主要内容的简介：（1）在第一章和第二章中，主要对OLED的研究历史和发展现状进行了简介。并从器件的理论基础，器件的基本结构以及各项性能参数的物理意义对OLED器件技术进行了剖析。在OLED材料方面，对各个不同的功能层材料都进行了简要的介绍，对本论文的研究重点主体材料则进行了全面的综述，从化学结构和物理载流子传输能力两个方面，分类对各类主体材料进行了分析和总结。（2）第三章和第四章，我们以三苯胺螺芴为基本单元，分别在芴环的2位和2、7位进行衍生，采用非共轭的三苯基硅和二苯基膦氧作为功能单元合成了四个新型主体材料，并对他们进行了系统的表征。通过引入非共轭的功能单元，成功的保持了三苯胺螺芴基团的三线态能级。通过调整引入功能单元的数量，对分子的各项性能进行了调节。采用膦氧基团的两个材料表现出了双极传输的性能，于设计完全相符。所合成的四个材料均进行了蓝光磷光器件表征，其中单取代的化合物表现出较双取代的更好地器件性能。对性能更好地两个材料，我们进一步制备了白光器件，取得了很好地器件效率。（3）在第五章中，我们继续研究了三苯基硅和二苯基膦氧衍生的三苯胺螺芴材料。为了进一步提高材料的三线态能级，我们通过将取代基的位置调整到芴环的3位，成功的合成了两个高三线态能级主体材料，三线态较2位取代的材料提高了0.1eV。经过对化合物系统的表征后，我们分别采用两种蓝光客体制备了蓝光器件，这两个材料都表现出非常优良的器件性能。（4）第六章和第七章，为了发挥3位取代的三苯胺螺芴的潜力，我们在3位分别引入了二苯胺，咔唑和苯基咔唑合成了3个空穴传输型主体材料。虽然功能基团和三苯胺螺芴之间是共轭连接，但这三个材料仍然保持了较高的三线态能级。苯基咔唑取代的三苯胺螺芴的设计借鉴了联咔唑的设计思路，通过咔唑3位和芴环3位连接使材料既具有较高的三线态，又具有较高的空穴迁移率。蓝光器件的结果表明该材料的器件性能优良。咔唑和二苯胺衍生的化合物则采用了N原子和3位直接连接的方式。得到的材料不仅具有较高的三线态，同时也具有较高的LUMO能级，在器件表征中，这两个材料不仅能作为高效的主体材料，同时也能够胜任电子/激子阻挡层材料，取得了非常好的器件性能。（5）第八章中，我们延续第七章的结构，但将三苯胺螺芴里的三苯胺换成咔唑，合成了二苯胺和咔唑衍生的螺芴咔唑主体材料。材料都进行了系统的表征。由于采用了更为刚性的咔唑构建螺环结构，材料表现出更高的玻璃化转变温度。同时因为继续采用了3位取代的结构，两个材料的三线态得到了保持。最后通过制备蓝光器件对材料的器件性能进行了评价，其中咔唑取代的材料表现出更好的器件性能。（6）由于三苯胺螺芴单元具有非常好的空穴传输能力，同时螺环的结构也具有很好的热稳定性，在第九章中，我们合成了一系列基于三苯胺螺芴的空穴传输材料。通过在芴环的2位或2，7位引入苯基萘胺或甲氧基二苯胺单元，进一步增强了化合物的空穴传输能力，同时提高了材料的HOMO能级以利于空穴的注入。这一系列材料表现出了非常好的热稳定性和很高的空穴迁移率，其中在2，7位进行苯基萘胺衍生的化合物在器件性能的表征中表现出了比传统空穴传输材料NPB更好的器件性能。（7）在第十章，我们针对四苯基硅类材料进行了研究，设计合成了一系列二苯并噻吩/二苯并呋喃-吡啶衍生的四苯基硅类主体材料，并对这系列材料进行了系统的表征。考虑到材料的三线态能级并不高，我们制备了绿光林光器件对材料进行表征。结果表明，作为绿光主体，这系列材料表现出了非常高的器件效率。更多还原

【Abstract】 Over two decades’ development, OLED technology has gradually perfected itself.Smart gadgets featuring OLED display have already made to market. In solid lightingindustry, OLED lighting panels are in the dawn of mass production. Although OLEDtechnology has already been successfully commercialized, there are still many challengesto tackle, such as materials development, device design and electronic process. OLED isstill one of the hottest research areas in organic electronics. In this thesis, we mainly focuson the design of novel host materials for blue phosphorescent OLED (PHOLED). Andtriphenylamine annulated fluorene and aryl silane were selected from numerousstructures for host materials as the basic backbone in our research. Several series novelmaterials were designed and synthesized using different functional groups and anchoringpositions. All these materials were fully characterized. PHOLED were fabricated usingthese materials as host materials. In addition, some materials were also explored asblocking layer or hole transport layer. Detailed research contents are listed as follow.(1) In chapter1and2, a brief history and current research status of OLED wereintroduced. Then, OLED technology was fully covered from the aspects of basic theory,device structure, physical parameters and materials. And host materials were fullyreviewed by chemical structures and charge transport properties.(2) Inchapter3and4,fournovelhostmaterialsweredesignedandsynthesizedusingtriphenylamine annulated fluorene as the basic structure. Unconjugated triphenyl silaneand diphenyl phosphine oxide were introduced to the C2or C2, C7position as functionalgroups. The triplet energy of the backbone was successfully preserved usingunconjugated functional groups. And, the charge transport property was tuned by thenumberoffunctional groups.Thesematerials were fullycharacterizedandbluePHOLEDdevices were fabricated using them as host materials. Mono-substituted materials showedbetter devices performance. To further exploit the potential of the mono-substituted materials, white PHOLEDs were made and excellent results were obtained.(3) In chapter5, we continued the study of triphenyl silane and diphenylphosphinoxide functionalized materials. In order to further increase the triplet energy ofthe material, the anchoring point was moved to C3on fluorene ring. As a result, twomaterialswithhightripletenergyweresuccessfullyobtained.ComparedtoC2substitutedones in the last two chapters, the triplet energy of these C3substituted materials are0.1eV higher. After the fully characterization of their chemical and physical properties,highly efficient blue PHOLEDs featuring two different dopants were fabricated usingthem as host materials.(4) In chapter6and7, three more C3substituted materials were synthesized withdiphenylamine, cabarzole and phenyl cabarzole as functional groups. These materials arehole transport host materials. And despite the functional were connected to the triphenylannulated fluorene via conjugated bond, these molecules still exhibit high triplet energylevels, sufficient enough to be used as blue host materials. The phenyl cabarzolesubstituted molecule, bearing similar configuration as the3,3’-bicabazole, showed bothhigh triplet energy and high hole mobility, which result in its excellent deviceperformance. On the other hand, diphenyl and cabarzole substituted materials show hightriplet energy and relatively high LUMO level, which make them possible candidates notonly for host materials, but also electron/exciton blocking materials. And in devicefabrication, they were used as host and as blocking layer, resulting in very goodperformance.(5) In chapter8, the molecule structures in chapter7were modified by replacing thetriphenylamineinthespirostructurewithphenylcabarzole.Duetothemorerigidstructureof cabarbole, the glass transition temperatures of these materials were higher. The tripletenergy of these materials are still very high. Blue PHOLED results suggest that they aregood candidates of host materials.(6) Since the triphenylamine annulated fluorene has very good hole transport abilityand high thermal stability, a series of hole transport materials were synthesized in chapter9.N-phenyl-1-naphthylamineand methoxyldiphenylaminewereintroducedonC2orC2, C7position to enhance the hole transport of the material. And in the meantime, theHOMO levels were raised, facilitating holeinjection.As expected, these materials exhibitvery good hole mobility and high Tg. The2,7-N-phenyl-1-naphthylamine substitutedmaterial showed better device performance than NPB as hole transport material.(7) In chapter10, tetraaryl silane was selected as the main structure. A series silanebased host materials were synthesized, incorporating dibenzothiophene, dibenzofuranand pyridine. All the materials were fully characterized. Due the relatively lower tripletenergy, these materials were evaluated as green phosphorescent hosts and excellentresults were obtained.更多还原