In doped organic electroluminescent devices (OLEDs), the changes of the fluorescence spectra occurred due to the energy and charge transfer from guest to host. A quantitative relation between the energy and charge transfer for doping OLEDs was studied by means of a Hamiltonian model. It was found that there is a corresponding relation between the EL intensity of doped PVK and the amount of the transferred charge and the change of the energy derived from charge transfer with dopant concentration, and the more the amount of the transferred charge and the decreasing of the energy from charge transfer, the higher the EL intensity in doped OLEDs. We can deduce that the efficient energy transfer results from the transferred charge between PVK and perylene. Based on the transport mechanism of carriers in conjugated polymer, an expression of conductivity was presented. Calculated results indicated that there is also a corresponding relation between the EL intensity of doped PVK and conductivities with dopant concentration. The larger the conductivities, the higher the EL intensity in doped OLEDs.
