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.