A molecularly doping method for polymer devices: maskless dye diffusion technique

The molecularly doping is known as an efficient way to improve various prop erties of polymers. For example, the conversion performance of polymer phot ocells can be drastically enhanced by incorporation of appropriate molecule s. In polymer light-emitting device, the emission color is tunable by dopin g appropriate dyes into emission layer. However, the molecularly doping by conventional method based on mixing the solutions of polymer and dopant sho uld not be compatible to the patterning of the emission color, which is req uisite for full-color display. Here, we show a novel molecularly doping met hod for polymer devices, the maskless dye diffusion technique. In this meth od, the highly doped and non-doped polymer films are brought into contact, and the electrode beneath the non-doped polymer film is heated by means of Joule heating. Then, the thermally activated dopant molecules diffuse into the non-doped polymer films. The most important feature of the present meth od is that the doping region can be limited near the electrode. That is, th e doped region directly reflects the shape of electrode. With this techniqu e, three-color (RGB) polymer light-emitting devices have been successfully integrated on a glass substrate. The application of this technique to a col or-sensing device is also proposed. (C) 2001 Elsevier Science B.V. All righ ts reserved.