OPTICAL SPECTROSCOPY OF SINGLE PENTACENE MOLECULES IN AN ORDERED AND A DISORDERED P-TERPHENYL CRYSTAL

We investigated pentacene-doped p-terphenyl crystals with different degrees of disorder as evidenced by the inhomogeneous broadening of the O1-site distribution. Single pentacene molecules were detected in the wings of O1 by fluorescence excitation spectroscopy. The ISC rates for a number of single molecules were determined by measuring the intensity correlation function of the fluorescence photons. We found a dramatic dependence of the distribution of ISC rates on the crystal disorder. The fully saturated fluorescence emission rates as calculated using the ISC rates were found to be consistent with the experimentally measured photocount rates.