Bipolar behavior in a near UV electroluminescent silicon polymer

To better understand the transport behavior of carriers in polymer LEDs, a near-ultraviolet electroluminescent polymer, poly[bis(p-butylphenyl)silane] was investigated by means of time-of-flight method. The signal of carrier migration was detected when pulsed coherent light at 387 nm was illuminated on the high electric field charged polymer thin film. It shows a hole drift mobility of 1×10^-4 cm²/Vs, a typical phenomenon often observed in polysilanes. For an oppositely charged polymer film, an intense signal appeared although there was no indication of electron migration. It strongly suggests that electrons are readily injected into the polymer film. Thus, the bipolar nature of the described polymer facilitates the injection of electrons and holes into the polymer matrix and leads to the occurrence of an efficient electroluminescence in spite of a single-layer diode structure