Columnar liquid crystal as alignable host for perylene-based emitters

Abstract

Organic light emitting diodes (OLEDs) can currently achieve 100% internal quantum efficiency. However, the external quantum efficiency of the device is limited by the poor extraction of photons. Molecular alignment with the emitter dipole moment parallel to the surface has been demonstrated to improve light outcoupling. We investigated the role of a triazine columnar liquid crystal as self-assembling anisotropic host compared to non-liquid crystalline hosts DPEPO and PMMA. Two perylene derivatives were studied as guests, one of them itself a columnar liquid crystal at room temperature. Their spectral overlap with the liquid-crystalline host favoured Förster Resonance Energy Transfer (FRET). The columnar host improved FRET with photoluminescence quantum yields (PLQY) of the guest emitters up to 84% due to host excitation, which is higher than the PLQY with direct guest excitation. The results highlight the potential and peculiar characteristics of liquid-crystalline hosts for OLEDs.