Band edge emission enhanced organic light emitting diode with a localized emitter
A light emitting photonic crystal having an organic light emitting diode and methods of making the same are disclosed. An organic light emitting diode disposed within a photonic structure having a band-gap, or stop-band, allows the photonic structure to emit light at wavelengths occurring at the edges of the band-gap. Photonic crystal structures that provide this function may include materials having a refractive index that varies.
1. A single light emitting photonic crystal having an organic electroluminescent emitter material disposed within the single photonic crystal, wherein
the organic electroluminescent emitter material comprises an organic light emitting material localized in a zone having less than 10% of an optical thickness of the photonic crystal, wherein
the organic electroluminescent emitter material has a free space emission spectrum that at least in part overlaps a stop-band of the photonic crystal, wherein
the photonic crystal emits light at a wavelength corresponding to an edge of the stop- band that the organic electroluminescent emitter material overlaps, wherein
the photonic crystal further comprises a stack of layers of varying refractive index, wherein
a layer of lower index of refraction materials comprises the organic electroluminescent emitter material.
2. The single light emitting photonic crystal of claim 1 wherein the stack of layers has a periodic modulation, measured in optical thickness, of refractive index with a period of modulation of λ/2 wherein λ equals a central wavelength of the photonic crystal stop-band.
3. The single light emitting photonic crystal of claim 1 wherein the stack of layers of varying refractive index comprised by the single light emitting photonic crystal comprises at least one pair of layers of materials with different refractive indices that, in turn, comprises a first layer of material with a higher refractive index and a second layer of a material with a lower refractive index, wherein a total optical thicknesses of the pair of layers combined equals λ/2, wherein λ equals a central wavelength of the photonic crystal stop-band.
4. The single light emitting photonic crystal of claim 2 wherein the period of the refractive index modulation through the stack of layers is disrupted by insertion of a layer of constant refractive index having an optical thickness equal to 3λ/2 wherein λ is the central wavelength of the photonic crystal stop-band.
5. The single photonic crystal of claim 1 , wherein the edge of the stop-band occurs at a wavelength at which measured radiance of free space luminescent light emission by the organic electroluminescent emitter material is greater than one-quarter of a peak radiance of a free space luminescent emission spectrum of the emitter material.