Polarized superradiant emission and exciton delocalization in tetracene single crystals are reported. Polarization-, time-, and temperature-resolved spectroscopies evidence the complete polarization of the zero-phonon line of the intrinsic tetracene emission from both the lower ($F$ state) and the upper (thermally activated) Davydov excitons. The superradiance of the $F$ emission is substantiated by a nearly linear decrease in the radiative lifetime with temperature, being 15 times shorter at 30 K compared to the isolated molecule, with an exciton delocalization of about 40 molecules.

• Received 23 December 2009

DOI:https://doi.org/10.1103/PhysRevB.81.033306