The degradation of conjugated polymer poly(p-phenylene vinylene) (PPV) in the atmosphere upon exposure to ultraviolet light limits its applications as the emitting layer in organic light emitting diodes. In this paper we show that a thin layer of aluminum oxide around 10 nm in thickness prevents photoluminescence degradation of PPV during exposure to blue light in the atmosphere but not at lower excitation wavelengths. This oxide film is free of cracks and pinholes from transmission electron microscopy analysis. (C) 2010 Elsevier B.V. All rights reserved.