Charge injection mechanisms in solid state organic light-emitting devices based on alizarin violet

Abstract

Light-emitting devices utilizing a dye-insulating matrix blend have been fabricated. The emitting dye material used was alizarin, while poly(methylmethacrylate) has been used as the insulating matrix material. Current-voltage and luminance-current characteristics have been studied for different molar concentrations of alizarin. Luminance has been observed in both bias directions in devices with lower alizarin concentration. Luminance under forward bias has been independent of alizarin molar concentration, while it decreased with molar concentration under reverse bias. Fowler-Nordheim tunnelling mechanism and Richardson-Schottky thermionic emission have been shown to be applicable in different ranges and directions of fields. Parameters of the device-like dielectric constant of the emitting layer, and barrier height for holes have been calculated from the models and compared in terms of different injection mechanisms operative in the devices.