Tuning the emission color of organic semiconductor films with cholesteric liquid crystals

This paper reports on the color-tunable emission from organic semiconductor films composed of Alq₃ doped with DCM. The composite system was excited using an ultraviolet laser to enable the emission of light from green to red regions of the visible spectra based on the nonradiative Förster transfer mechanism. A cholesteric liquid crystal film was used as a blue emitter, while simultaneously serving as a temperature-controlled optical filter based on Bragg reflection to tune the emission color of the organic semiconductor films. The corresponding color points on the CIE chromaticity diagram located near the black-body locus exhibited a wide color-tuning range within a narrow temperature range.