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Australian Journal of Chemistry Australian Journal of Chemistry Society
An international journal for chemical science
RESEARCH ARTICLE

Organic Light-Emitting Diodes Based on a Solution-Processable Benzimidazole-Functionalised Cationic Iridium Complex

Xiujuan Zhi A , Bin Du A B and Sichun Yuan A B
+ Author Affiliations
- Author Affiliations

A Beijing Key Laboratory of Agricultural Product Detection and Control of Spoilage Organisms and Pesticide Residue, Beijing Laboratory of Food Quality and Safety, Faculty of Food Science and Engineering, Beijing University of Agriculture, Beijing 102206, China.

B Corresponding authors. Email: Bindu80@bua.edu.cn; ysc@bua.edu.cn

Australian Journal of Chemistry 69(8) 890-895 https://doi.org/10.1071/CH16051
Submitted: 17 September 2015  Accepted: 23 February 2016   Published: 4 April 2016

Abstract

A cationic iridium(iii) complex with formula [Ir(ppy)2(pybmz)]+(PF6) (ppy = 2-phenylpyridine; pybmz = 2-(pyridin-2-yl)-N-hexylbenzimidazole) was synthesised. The photoluminescence spectrum of the complex showed an orange–red emission peak at 590 nm with a quantum efficiency of 18 % and a luminescence lifetime of 1.2 µs in solid state. The complex was used as a phosphorescent dopant in light-emitting diodes with the configuration ITO/PEDOT : PSS(50 nm)/PVK (70) : PBD (30) : complex (x wt-%, x = 5, 20, 50, 100)(75nm)/TPBI(50nm)/Ba(4 nm)/Al(150 nm) [ITO = indium tin oxide; PEDOT = poly(ethylenedioxythiophene); PSS = poly(styrene sulfonic acid); PVK = polyvinylcarbazole; PBD = 5-(4-tert-butylphenyl)-2-(bi-phenyl-4-yl)-1,3,4-oxadiazole; TPBI = 1,3,5-tris-(2-N-phenylbenzimidazolyl) benzene]. The best device performances were obtained for the non-doped (100 wt-%) material, with an external quantum efficiency of 5.6 %, a luminous efficiency of 9.3 cd A–1, and a power efficiency of 3 lm W–1. High brightness of 8700 cd m–2 and luminous efficiency of 8 cd A–1 were realised at a current density of 110 mA cm–2.


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