Delayed fluorescence in α-quaterthiophene single crystal

The photoluminescence spectra were recorded, in α-quaterthiophene (α-4T) single crystal, for visible and UV excitation light. The latter exhibits a blueshift of about 5 meV with respect to the former. This value is comparable to the Van Der Waals energy. Delayed Fluorescence (DF), in α-quaterthiophene (α-4T) single crystal, was observed at room temperature. The delayed fluorescence emitted is explained in terms of a triplet exciton fusion model or the so called triplet-triplet excitons annihilation. Triplet excitons were created using direct excitation in their absorption band (1.91 eV). From the involved spectrum of delayed fluorescence the Davydov Splitting was experimentally evaluated.