Rubrene was doped into the hole transport layer of an organic thin film electroluminescent (OTFEL) device with a double-layered structure. It was found that the dopant has a profound influence on the EL characteristics-it changed the region of light emission, increased the luminescence efficiency by more than 50% and improved the device stability tenfold. The reasons for these effects are discussed based on injection theory and the energy level diagram of the device.

A description is given of a pressure driven shock tube and the techniques which have been developed to investigate the variation with gas temperature of the electron-. molecular ion dissociative recombination coefficient c!. Double probe detectors are used to measure, at times in the afterglow, electron densities of a plasma slice located between the shock front and contact surface of the nearly one-dimensional gas flow. The experimental parameters are discussed in relation to their influence on the recombination process. In krypton at 900 K: c! is found to have the value 4.2 x cm3 s -' and at 2700 K it has followed a T 3 " variation to the value 9.6 x cm3 s -' .