Color-tuning of polymer light-emitting devices through maskless dye diffusion technique

The maskless dye diffusion technique is a method to dope dye molecules into polymer films by thermal activation. Since the patterned indium tin oxide (ITO) electrodes for the future devices are used as heat source so that the dye doping area mimics the shape of the ITO pattern heated, this method can remove the precise positioning between the ITO electrode and dye doping area which is usually required in other techniques. This paper reports some results on the polymer light-emitting devices made through the maskless dye diffusion technique. When poly(9,9-dioctylfluorene) (PDOF) was used as host material, diffusion of Coumarin 6 and a phosphorescent dye BtpIr yields green and red emission, respectively. In the case of BtpIr-diffused device, the quantum efficiency of the device was found to be about 2.5 times of the device with non-treated PDOF film. It is also found that the poly(N-vinylcarbazole) can be a host material for both green and red phosphorescent dyes.