Electroluminescence from polymeric halides subjected to an AC voltage

Electroluminescence (EL) from polymeric halides and hydrocarbons has been investigated under voltages to clarify the effect of halogens in the polymers on the EL. We used polymer films with semi-transparent gold electrodes, namely, polytetrafluoroethylene (PTFE), polyvinylchloride (PVC), low-density polyethylene (LDPE), and polypropylene (PP). The light emission from PVC and PTFE started from lower fields and had a larger light intensity than that from LDPE and PP. However, the basic natures of the physical mechanisms of light emission involved seemed to be similar in all samples. The characteristics of light emission can be explained by considering the energy band structure of electron at the surface of polymer. The necessary condition of light emission will be the formation of long-term electron space-charges near the metal-polymer interface sufficiently enough to generate the reverse field for the hole injection. Halogens in the polymers act as strong trapping centers for injected electrons and enhance the formation of long-term electron space-charges. The light may be emitted dominantly by radiative recombination of electrons and holes.