Color Tuning of Poly(N-vinylcarbazole)-Based Light-Emitting Devices through Maskless Dye-Diffusion Technique Using Phosphorescent Dyes

Abstract

The maskless dye-diffusion technique, a method for the local color tuning of polymer light-emitting devices employing thermal dye transfer, is applied to introduce a phosphorescent dye into poly(N-vinylcarbazole) (PVK). It is mentioned that the maskless diffusion of various phosphorescent dyes, such as iridium(III)-bis[2-(2'-benzothienyl)-pyridinato-N,C3'](acetylacetonate) (BtpIr), iridium(III)-tris[2-(4-tolyl)pyridinato-N,C2] [Ir(tpy)3], and iridium(III)-bis[2-(4,6-difluoropheny)pyridinato-N,C2'] picolinate (FIrpic), into PVK results in red-, green-, and sky-blue-emitting devices. The quantum efficiency of the devices fabricated using dye diffusion was much higher than that of the device fabricated using pristine PVK; however, the emission onset voltages were almost the same for all the devices. It was also found that there was a red-shift in the emission spectrum due to prolonged FIrpic diffusion.