In situ characterization of the oxidative degradation of a polymeric light emitting device

• Published in: Journal of applied physics 1997-04, Vol.81 (8), p.3716-3720
• Main Authors: Cumpston, B. H., Parker, I. D., Jensen, K. F.
• Format: Article
• Language: English
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.365493

Light-emitting devices with polymeric emissive layers have great promise for the production of large-area, lightweight, flexible color displays, but short lifetimes currently limit applications. We address mechanisms of bulk polymer degradation in these devices and show through in situ Fourier transform infrared characterization of working light-emitting devices with active layers of poly[2-methoxy,5-(2′-ethyl-hexoxy)-1,4-phenylene vinylene] that oxygen is responsible for the degradation of the polymer film. A mechanism is given based on the formation of singlet oxygen from oxygen impurities in the film via energy transfer from a nonradiative exciton. Fourier transform infrared and x-ray photoelectron spectroscopy results are consistent with the mechanism, involving singlet oxygen attack followed by free radical processes. We further show that oxygen readily diffuses into the active polymer layer, changing the electrical characteristics of the film even at low concentrations. Thus, polyphenylene-vinylene-based light-emitting devices will self-destruct during operation if fabricated without special attention to eliminating oxygen contamination during fabrication and device operation.