Electronic energy trapping in a crystal with a dopant of higher singlet level than the host

Efficient electronic energy trapping occurs in 9-cyanoanthracene crystals doped with either 9-methoxyanthracene or 9,10-dimethylanthracene although in both cases the lowest guest excited singlet state lies much higher in energy than that of the host. Energy trapping is due to the formation of an exciplex between a host and a guest molecule. The exciplex is shown to be populated by energy transfer from the host excimer level. In 9-methoxyanthracene doped 9-cyanoanthracene crystals, the exciplex energy may be dissipated by heterophotodimerization.