Solid state cathodoluminescence of poly (2-methoxy-5-(2-ethyl-hexyloxy)-1，4-phenylene vinylene in devices with Si3N4 as the electronic accelerating layer

Abstract

A solid state cathodoluminescence (SSCL) device in which Si3N4 acts as the electronic accelerating layer and poly (2-methoxy-5-(2-ethyl-hexyloxy)-1， 4-phenylene vinylene (MEH-PPV) as the luminescent layer is first designed. Under alternating current bias， SSCL of MEH-PPV is realized. The luminescence peak is located at 600 and 417nm， respectively, corresponding to the exciton emission and the recombination luminescence of lowest unoccupied molecular orbital (LUMO) to highest occupied molecular orbital (HOMO). The intensity of the twopeaks changes with the increasing of the driving voltage nonlinearly. Compared with the device with SiO2 as the accelerating layer， the short wavelength emissions are found to be the same and located at 417nm for both devices, although their accelerating layers are different. It confirms the SSCL theory and the short wavelength is caused by the direct recombination of electrons in LUMO and holes in HOMO. Finally， the accelerating abilities of Si3N4 and SiO2 are compared at high driving voltage, which showed that the accelerating ability of SiO2 is superior to that of Si3N4 at the driving voltage involved.