High triplet energy exciton blocking materials based on triphenylamine core for organic light-emitting diodes

A series of novel high triplet energy materials have been designed and synthesized from the simple starting compounds through a simple one-step Friedel-Crafts reaction by using triphenylamine and methoxy, fluoro substituted diphenylmethanoles and triphenylmethanol as the starting materials. The synthesized compounds exhibit the ionization potentials in an interval of 5.4-5.7 eV in the solid state, the wide bang-gaps of 3.6 eV and the high triplet energies of about 3.0 eV. The photophysical properties have been confirmed by DFT. The introduction of a material with the lowest ionization potential as the high triplet energy exciton blocking thin layer of the green organic light-emitting diode doubled the quantum efficiency of the device. The best fabricated green device exhibited the maximum current, power, and external quantum efficiencies of 80.1 Cd A(-1) and 31.4 Lm W-1, 23.2%, respectively. The triplet-triplet annihilation and triplet-polaron quenching effects for the devices without and with exciton blocking layer have been analyzed. (C) 2016 Elsevier B.V. All rights reserved.