White electroluminescent diodes from polymer blend

Abstract

Summary form only given. We report white light-emitting diodes (LEDs) made from polymer blends composed of poly(2,5-bis(cholestanoxy)-1,4-phenylene vinylene) (BCHA-PPV) in a hole transporting polymer, poly(9-vinylcarbazole) (PVK). The soluble BCHA-PPV and PVK allow fabrication of the LEDs by spin casting the electroluminescent polymer blend from solution at room temperature without subsequent processing or heat treatment. The initial devices utilized calcium as the electron injecting (rectifying) contact on the front surface of a BCHA-PPV/PVK film which has been spin cast onto a glass substrate partially coated with a layer of indium/tin-oxide (ITO) as the hole injecting contact. The LEDs turn on at ~ 30V and emit white light with three emission peaks at wavelengths in the blue at 440 nm, in the green at 535 nm and in the red at 600 mm (at room temperature). The quantum efficiency was measured as a function of the BCHA-PPV content in the blend; the maximum efficiency was approximately 0.06% photons/electron at a concent-ation of only 3% BCHA-PPV in PVK.