Excitation mechanism in polymer layers doped with tetra-methylester of perylene tetracarboxylicacid: influences of doping concentration and external bias

Abstract

A spin-coated layer of poly(N-vinylcarbazole) (PVK) doped with tetra-methyl ester of perylene-3,4,9,10-tetracarboxylicacid (TMEP) is prepared, and the effects of dopant concentration and bias voltages on excitation mechanisms are studied through analyzing its emission characteristics. The investigation indicates that in photoluminescence (PL) cases energy and charge transfers between PVK and TMEP are cooperated for low dopant concentration, whereas the electroluminescence (EL) spectra imply that energy transfer is more important than charge trapping and transfer in these devices. For high dopant concentration, charge transfer is dominated in PL spectra but has a minor effect on EL spectra, and the external bias has less influence on the EL characteristics. A kinetic analysis is given to rationalize the experiment results.