INTERFACIAL EFFECTS IN POLYMER LEDS

A polymer LED in which the emitter layer was a blend of an alternating block copolymer and poly(N-vinyl carbazole) (PVK) was fabricated with intermediate hole transporting layers of polyphenylene vinylene (PPV) . It was found that this provided greatly enhanced quantum efficiency, as expected, but also that the photoluminescent and electroluminescen t spectral properties of the system were functions of the thickness of the PPV, which in certain cases contributed to the overall emission. From a detailed study of this effect it was concluded that radiative d ecay of surface or interfacially located excitons in PPV displayed a v ibronic structure which differed from that produced by decay of excito ns in the bulk. (C) 1998 Elsevier Science B.V.