Singlet excitation energy transfer in tetracene doped p-terphenyl single crystals

Abstract

Fluorescence quantum yields of host and guest molecules in tetracene doped p-terphenyl crystals were measured for different guest concentrations c G between 1.2 × 10 −6 and 1.3 × 10 −4 mol/mol at temperatures ranging from 2 to 300 K. In the low-temperature region (2–60 K) the ratio of the quantum yields from guest to host molecules decreases with rising temperature, where the slope of the decrease depends significantly on c G. On the other hand, for temperatures higher than 60 K the ratio of quantum yields increases with rising temperature and this temperature behaviour is independent of c G. These different temperature characteristics of the quantum yield ratio in relation to the guest concentration are interpreted in terms of singlet excitation energy migration processes on the host molecules. The discussion is based on a rationalization which postulates a temperature inhibited exciton motion at temperatures below 60 K and dopant concentrations below 10 −4 mol/mol.