Observation of Dual Room Temperature Fluorescence–Phosphorescence in Air, in the Crystal Form of a Thianthrene Derivative

Thianthrenes have been nearly forgotten as phosphors in recent years, but are now coming back, showing their strong potential in luminescent applications. Here, we present a comprehensive photophysical study of a carbazolyl derivative of thianthrene in different matrices and environments. The diffusion of oxygen is slowed down in the rigid environment of thianthrene organic crystals, suppressing their phosphorescence quenching-Triplet triplet annihilation is also not significantly active in these systems. Both conditions facilitate the observation of simultaneous fluorescence and phosphorescence emissions at room temperature, in air, giving origin to strong white luminescence. Moreover, the color coordinates of the dual fluorescence-phosphorescence white emission, which is observed only in rigid amorphous media and in crystals, can be tuned.