Exciton fission and annihilation in crystalline tetracene

Abstract

The time-resolved fluorescence of tetracene crystals excited by a single 7-ps pulse of 530-nm light has been measured with a streak camera/OMA system. The singlet exciton lifetime was found to be 300±30 ps at 293 K. Singlet-singlet exciton annihilation was observed, and the rate constant found to be 5 x 10^-9 cm³ s^-1. In order to fit the observed decay curves, an upper limit of c. 1 x 10^-9 cm³ s^-1 must be set on the singlet-triplet exciton annihilation rate. The measured singlet-singlet exciton annihilation rate is consistent with a hopping model for singlet exciton motion at room temperature.