Design of star-shaped molecular architectures based on carbazole and phosphine oxide moieties: towards amorphous bipolar hosts with high triplet energy for efficient blue electrophosphorescent devices
作者:Junqiao Ding、Qi Wang、Lei Zhao、Dongge Ma、Lixiang Wang、Xiabin Jing、Fosong Wang
DOI:10.1039/c0jm00846j
日期:——
With a carbazole moiety as the electron donor and a phosphine-oxide moiety as the electron acceptor, two novel star-shaped bipolar hosts, 4,4′,4″-tri(N-carbazolyl)triphenylphosphine oxide (TCTP) and 3,6-bis(diphenylphosphoryl)-9-(4′-(diphenylphosphoryl)phenyl)carbazole (TPCz), have been designed and synthesized. Their topology structure differences are that the phosphine-oxide moiety is located in the molecular centre and the periphery for TCTP and TPCz, respectively. The star-shaped architecture imparts them with high decomposition temperatures (Td: 497 °C for TCTP and 506 °C for TPCz) and results in the formation of a stable amorphous glassy state (Tg: 163 °C for TCTP and 143 °C for TPCz), while the phosphine oxide linkage ensures the disrupted conjugation and the high triplet energy (>3.0 eV). In addition, both TCTP and TPCz possess a bipolar transporting capability. However, TCTP mostly transports holes and TPCz primarily conducts electrons. On the basis of appropriate device configurations, high performance blue electrophosphorescent devices with comparable efficiency (35.0–36.4 cd A−1, 15.9–16.7%) have been realized using TCTP and TPCz as the host for the blue phosphor, respectively. Compared with the unipolar host, 4,4′,4″-tri(N-carbazolyl)triphenylamine (TCTA, 15.9 cd A−1, 7.8%), the efficiency is improved by more than two-fold. As far as the obtained state-of-the-art performance is concerned, we think that these novel materials should provide an avenue for the design of amorphous bipolar hosts with high triplet energy used for blue PhOLEDs on a star-shaped scaffold.
以咔唑分子为电子供体,以氧化膦分子为电子受体,设计并合成了两种新型星形双极载体:4,4′,4″-三(N-咔唑基)三苯基氧化膦(TCTP)和 3,6-双(二苯基磷酰)-9-(4′-(二苯基磷酰)苯基)咔唑(TPCz)。它们的拓扑结构差异在于,TCTP 和 TPCz 的氧化膦分子分别位于分子中心和外围。星形结构使它们具有较高的分解温度(Td:TCTP 为 497 ℃,TPCz 为 506 ℃),并能形成稳定的无定形玻璃态(Tg:TCTP 为 163 ℃,TPCz 为 143 ℃),而氧化膦连接则确保了共轭中断和较高的三重能(大于 3.0 eV)。此外,TCTP 和 TPCz 都具有双极传输能力。不过,TCTP 主要传输空穴,而 TPCz 主要传导电子。在适当的器件配置基础上,以 TCTP 和 TPCz 分别作为蓝色荧光粉的宿主,实现了效率相当(35.0-36.4 cd A-1, 15.9-16.7%)的高性能蓝色电致磷光器件。与单极宿主 4,4′,4″-三(N-咔唑基)三苯胺(TCTA,15.9 cd A-1,7.8%)相比,效率提高了两倍多。就所获得的先进性能而言,我们认为这些新型材料应能为在星形支架上设计用于蓝色 PhOLED 的具有高三重能的非晶双极宿主提供一条途径。