Multicolor Single-Layer Electroluminescence Device Using Poly(L-glutamate) for Hole Transport

Helical poly(L-glutamate) with carbazole (Cz) side chains (PCELG) was synthesized as a hole-transport host material for a dye-doped polymer electroluminescence (EL) device. The main- and side-chain conformations were investigated by a combination of polarized infrared spectroscopy and semi-empirical quantum chemical calculation. In an electrically poled PCELG crystalline film, the main chain was found to assume a right-handed a-helical conformation with an order parameter of similar to 0.8. The Cz plane at the terminal side chain is inclined by about 44 degrees toward the helical axis, creating a regular stacked structure conforming to the rigid a-helical backbone. The principal EL characteristics of these devices were determined and compared with those of devices made with poly(N-vinyl carbazole) (PVCz). For green and blue light, EL devices using PCELG exhibited luminance efficiencies comparable to those using PVCz. To the best of our knowledge, this was the first demonstration of primary colors emitted by an organic EL device with a polypeptide hole-transport host material. The experimental results suggested that the total concentration and spatial arrangement of the Cz groups play an important role in determining the EL characteristics of dye-doped polymer EL devices. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 496-502, 2010