Charge-carrier injection and transport

Charge-carrier injection and transport have been studied in relation to light-emitting diodes based on poly-p-phenylene-vinylene (PPV). It was found that thermal conversion of the prepolymer on indium-tin-oxide (ITO) substrates leads to a p-type doping of PPV. It leads also to formation of an ohmic hole-injecting contact at the ITO/PPV interface. This is not like conversion on Au and other high-work-function metals. Devices made with low-work-function metals as the electron injecting contact display Schottky behavior, act as Schottky diodes, distinguished by a high rectification ratio and display electrolumiescence at bias voltages as low as 1.5 V for ITO/PPV/Ca light-emitting diodes.