A simple technique for molecular doping to polymer films, the maskless dye diffusion, is developed. In this method, prepatterned electrodes beneath precoated receiver film are utilized as heaters for activating dye molecules. Upon doping with three types of dye, 1, 1, 4, 4-tetraphenyl-1, 3-butadiene, coumarin 6 and Nile red into poly (N-vinylcarbazole) by the present diffusion method, blue, green and red emissions were obtained. By applying this technique three times on a glass substrate, RGB light-emitting devices were successfully integrated on the glass plate. It is found that the onset voltage of emission does not depend on the type of dye. It is also found that the condition for dye diffusion was independent of dye.