title: Novel Bipolar Indole-Based Solution-Processed Host Material for Efficient Green and Red Phosphorescent OLEDs.
abstract: A new bipolar host material 2-(2'-(5-(dibenzo[b,d]furan-4-yl)-1H-indol-1-yl)-1,1'-biphenyl]-4-yl)-1-phenyl-1H-benzo[d]imidazole (INDY) has been designed and synthesized for solution-processed PHOLEDs. A hole-transporting indole conjugated dibenzofuran scaffold and an electron-transporting benzimidazole unit were orthogonally connected with incorporation of a 2,4'-biphenyl bridge, which endows a balanced bipolar charge transfer distribution and appropriate triplet energy level (>2.6 eV). The twisted conformation of INDY also ensures good thermal/morphological stability with high Tg(148 °C). The solution-processed green PHOLEDs achieved great device efficiencies with 27.33 cd/A and 12.26 lm/W at 7 V. Meanwhile, the red solution-processed PHOLEDs gained excellent performance with the maximum efficiencies of 17.20 cd/A, 9.82 lm/W, and 12.61%. In addition, all of the red devices presented excellent color stability with the same CIE coordinate as (0.65, 0.35) under varying dopant contents and operating voltages.
authors.affiliation: Key Laboratory for Advanced Materials and Institute of Fine Chemicals, School of Chemistry and Molecular Engineering, East China University of Science and Technology , 130 Meilong Road, Shanghai 200237, China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Key Laboratory of Advanced Display and System Applications, Ministry of Education, Shanghai University , 149 Yanchang Road, Shanghai 200072, China.
authors.forename: Xiang
authors.initials: X
authors.lastname: Wei
authors.affiliation: Key Laboratory of Advanced Display and System Applications, Ministry of Education, Shanghai University , 149 Yanchang Road, Shanghai 200072, China.
authors.forename: Jin
authors.initials: J
authors.lastname: Cao
authors.affiliation: Shanghai Taoe Chemical Technology Company, Ltd. , Shanghai 200030, China.
authors.forename: Jinhai
authors.initials: J
authors.lastname: Huang
authors.affiliation: School of Chemistry and Chemical Engineering, Queen's University , Belfast BT7 1NN, Northern Ireland, United Kingdom.
authors.forename: Lei
authors.identifier: http://orcid.org/0000-0002-7215-7870
authors.initials: L
authors.lastname: Gao
authors.affiliation: Key Laboratory of Advanced Display and System Applications, Ministry of Education, Shanghai University , 149 Yanchang Road, Shanghai 200072, China.
authors.forename: Jianhua
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Key Laboratory for Advanced Materials and Institute of Fine Chemicals, School of Chemistry and Molecular Engineering, East China University of Science and Technology , 130 Meilong Road, Shanghai 200237, China.
authors.forename: Jianhua
authors.identifier: http://orcid.org/0000-0002-4746-6022
authors.initials: J
authors.lastname: Su
authors.affiliation: Key Laboratory for Advanced Materials and Institute of Fine Chemicals, School of Chemistry and Molecular Engineering, East China University of Science and Technology , 130 Meilong Road, Shanghai 200237, China.
authors.forename: He
authors.identifier: http://orcid.org/0000-0003-3547-7485
authors.initials: H
authors.lastname: Tian
keywords: bipolar host material; high thermal stability; highly efficient; indole derivatives; phosphorescent OLEDs