Maolin Bo

Coordination-Resolved Electron Spectrometrics

Xinjuan Liu,† Xi Zhang,‡ Maolin Bo, Lei Li, Hongwei Tian, Yanguang Nie, Yi Sun, Shiqing Xu,*,† Yan Wang,* Weitao Zheng,* and Chang Q Sun* †Institute of Coordination Bond Metrology and Engineering, College of Materials Science and Engineering, China Jiliang University, Hangzhou 310018, China ‡Institute of Nanosurface Science and Engineering, Shenzhen University, Shenzhen 518060, China Key Laboratory of Low-Dimensional Materials and Application Technologies (Ministry of Education) and School of Materials Science and Engineering, Xiangtan University, Hunan 411105, China School of Materials Science, Jilin University, Changchun 130012, China School of Science, Jiangnan University, Wuxi 214122, China Harris School of Public Policy, University of Chicago, Chicago, Illinois 60637, United States School of Information Technology, Hunan University of Science and Technology, Xiangtan 411201, China NOVITAS, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798, Singapore

Ge-based bipolar small molecular host for highly efficient blue OLEDs: multiscale simulation of charge transport

Bipolar host materials can achieve excellent charge-transport balance and enhance device performance in phosphorescent organic light-emitting diodes (PhOLEDs). In this work, we designed three Ge-based bipolar host materials, (4-((4-(9H-carbazol-9-yl)phenyl)diphenylgermyl)phenyl)diphenylphosphine oxide (CzGeTpo), 2-(4-((4-(9H-carbazol-9-yl)phenyl)diphenylgermyl) phenyl)-5-(4-(tert-butyl)phenyl)-1,3,4-oxadiazole (CzGeOdz), and 9-(4-(diphenyl(4-(1-phenyl-1H-benzo[d]imidazol-2-yl)phenyl)germyl)phenyl)-9H-carbazole (CzGePbzd), for blue PhOLEDs. These Ge-based bipolar hosts incorporate both the electron-donating group and electron-withdrawing group into the Ge-based core moiety (tetraphenylgermane) at the same time. The frontier molecular orbital energy levels of these materials suggest that all these Ge-based hosts are not only facilitated to obtain holes but also electrons. A multiscale simulation of charge transport in the amorphous thin film was developed to investigate the charge-transport properties of these materials. The simulation was based on quantum chemical calculations, molecular dynamics simulations, and Monte Carlo calculations. The results showed that all these materials exhibited both good electron and hole transport properties. CzGeTpo showed balanced charge-transport properties with a hole/electron ratio of 8 (the electron and hole mobilities were 1.6 × 10−3 and 1.2 × 10−2 cm2 V−1 s−1, respectively). At the same time, the lowest triplet energy of CzGeTpo was 3.31 eV, which is higher than that of most blue phosphorescent materials. The findings suggest that CzGeTpo would be a promising candidate for Ge-based bipolar small molecular hosts for highly efficient blue PhOLEDs.