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The Structure Optimization of Phenanthroimidazole Based Isomers with External Quantum Efficiency Approaching 7% in non-doped Blue OLEDs

Abstract

In this work, four phenantroimidazole (PI) based isomers TPA-PPI-PBI, TPA-PPI-NPBI, PBI-PPI-TPA and NPBI-PPI-TPA for high-efficiency blue organic light-emitting diodes (OLEDs) have been designed and synthesized. The structure-property relationship is systematically studied. Devices based on TPA-PPI-PBI, TPA-PPI-NPBI, PBI-PPI-TPA and NPBI-PPI-TPA achieved blue emissions with the Commission Internationale de L'Eclairage (CIE) coordinates of (0.15, 0.07), (0.15, 0.07), (0.15, 0.09) and (0.15, 0.05) and high external quantum efficiencies (EQE) of 4.12%, 4.66%, 6.88% and 5.59%, respectively. Especially the PBI-PPI-TPA based device exhibited negligible efficiency roll-off with EQE 6.48% at 1000 cd m-2. Moreover, the EQE is still above 5% even at a high brightness of 10,000 cd m-2. Comparing the four isomers, we found that substituent at the C2 position of PI core has a significant influence on the emission wavelength and CIE coordinates. This work provides a rational design strategy that modifying electron acceptor (A) at the C2 position and electron donor (D) at the N1 position of PI core will be an effective way to fabricate high-performance PI-based bipolar emitters.

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Supplementary files

Article information


Submitted
04 Dec 2019
Accepted
03 Feb 2020
First published
03 Feb 2020

J. Mater. Chem. C, 2020, Accepted Manuscript
Article type
Paper

The Structure Optimization of Phenanthroimidazole Based Isomers with External Quantum Efficiency Approaching 7% in non-doped Blue OLEDs

J. Zhu, Y. Chen, Y. Xiao, X. Lian, G. Yang, S. Tang, D. Ma, Y. Wang and Q. Tong, J. Mater. Chem. C, 2020, Accepted Manuscript , DOI: 10.1039/C9TC06658F

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