LIGHTING DEVICE
A lighting device comprises an emission layer, and first and second electrodes between which a voltage can be applied to generate an electric field in at least part of the emission layer. The emission layer comprises a luminescent film composed of at least one crystal comprising repeating structural units of a crystalline framework material. The crystal has at least one crystallographic axis that is aligned substantially parallel to a planar surface of the luminescent film with a maximum deviation of up to +/−35° from this parallel orientation. Luminescent emitters are arranged in at least 30% of the repeating structural units of the crystalline framework material such that the transition dipole moments of the luminescent emitters are configured in a substantially parallel orientation relative to the crystallographic axis with a maximum deviation of up to +/−350 from this parallel orientation.
1 . A lighting device comprising:
a) an emission layer comprising a luminescent film; and
b) first and second electrodes between which a voltage can be applied to generate an electric field in at least part of the emission layer, wherein the film is composed of at least one crystal comprising repeating structural units of a crystalline framework material, the crystal has at least one crystallographic axis that is aligned substantially parallel to a planar surface of the luminescent film with a maximum deviation of up to +/−35° from this parallel orientation, and luminescent emitters having transition dipole moments are arranged in at least 30% of the repeating structural units of the crystalline framework material such that the transition dipole moments of the luminescent emitters are configured in a substantially parallel orientation relative to the crystallographic axis with a maximum deviation of up to +/−350 from this parallel orientation.
2 . The device of claim 1 , wherein the luminescent emitters are configured to emit light from the planar surface of the film at an average angle of emission of 450 or less from a surface normal to the planar surface.
3 . The device of claim 1 , wherein the luminescent emitters are configured to be substantially uniformly oriented relative to the planar surface such that their transition dipole moments have an orientation anisotropy factor ( 0 ) of less than 0.33.
4 . The device of claim 1 , wherein at least 50% of the repeating structural units comprise a luminescent emitter having a transition dipole moment configured to be substantially parallel to the planar surface of the film.
5 . The device of claim 1 , wherein at least 66% of the transition dipole moments of the luminescent emitters are oriented substantially parallel to the planar surface of the film with a maximum deviation of about +/−45°.
6 . The device of claim 1 , further comprising a controller or voltage source for applying the voltage (potential difference) between the first and second electrodes.
7 . The device of claim 6 , wherein the controller is arranged to apply an AC voltage having a waveform that is a square wave, a triangle wave, or a pulsed wave.
8 . The device of claim 1 , wherein the crystalline framework material comprises at least one metal-organic framework, covalent organic framework, porous coordination framework or porous coordination polymer.