Patent ID: 8294341

Claim:
An organic electroluminescent device comprising: a transparent substrate; a first electrode disposed over the substrate for injecting charge of a first polarity; a second electrode disposed over the first electrode for injecting charge of a second polarity opposite to said first polarity; an organic light-emissive region disposed between the first and the second electrode for emitting light of a wavelength λ from a recombination zone within the light-emissive region; and a layer of charge injecting material disposed between the first electrode and the light-emissive region, wherein the second electrode is reflective, the first electrode is transparent or semi-transparent, the first electrode having a thickness in the range 35 nm to 90 nm, the sum of the thicknesses of the first electrode and the charge injecting layer is in the range 75 nm to 125 nm, and a microcavity is formed between the substrate and the second electrode, the distance between the transparent substrate and the second electrode being [(¼n i )λ+(½n j )aλ]±40 nm, where a is 0, 1 or 2, n i is an average refractive index of the material disposed between the recombination zone and the second electrode and n j is an average refractive index of the material disposed between the recombination zone and the substrate.