Improved electroluminescent performances of europium-complex based devices by doping into electron-transporting/hole-blocking host

Abstract

High-efficiency, pure red organic light-emitting devices were fabricated by doping a europium-complex Eu(DBM)3pyzphen (DBM=dibenzoylmethane, pyzphen=pyrazino[2,3-f][1,10]phenanthroline) into 4,7-diphenyl-1,10-phenanthroline as emission layer. A maximum current efficiency of 5.1cd∕A at the current density of 1.2mA∕cm2 and a maximum luminance of 1400cd∕m2 were obtained from a 25wt% Eu(DBM)3pyzphen doped device. High efficiencies were maintained at high current densities and high luminance. For example, at the current density of 10mA∕cm2, the efficiency reached 3.8cd∕A. It means that the efficiency roll-off, a major obstacle to the development of Eu-complex ogranic light-emitting devices, was greatly alleviated. The mechanisms behind the improvement are discussed.