A high triplet energy, high thermal stability oxadiazole derivative as the electron transporter for highly efficient red, green and blue phosphorescent OLEDs

Abstract

A high glass transition temperature (T_g = 220 °C), high triplet energy gap (E_T = 2.76 eV) and high electron mobility material bis(m-terphenyl)oxadiazole was readily synthesized. It can serve as a universal electron transporter for blue, green and red phosphorescent OLEDs with excellent efficiencies. The material shows high current density compared to other electron transport materials and exhibits reduced driving voltage for all color PhOLEDs irrespective of the energy level of the host materials, due to efficient electron injection from 2,5-di([1,1′:3′,1″-terphenyl]-5′-yl)-1,3,4-oxadiazole (TPOTP) to the host material. For the green PhOLED, maximum external quantum efficiency (EQE) over 25%, current efficiency of 97.6 cd A⁻¹ and power efficiency of 100.6 lm W⁻¹ were achieved. The red and blue devices using TPOTP as the electron transporter also show EQE higher than 23% with very low roll-off in efficiencies in practical brightness level.