Mobility-dependent charge injection into an organic semiconductor

Measurements of charge injection from indium tin oxide (ITO) into the organ ic semiconductor, tetraphenyl diamine doped polycarbonate (PC:TPD), were ca rried out. The current injected at the contact was measured as a function o f the hole mobility in the organic semiconductor, which was varied from 10( -6) to 10(-3) cm(2)/V.s by adjusting the concentration of the hole transpor t agent, TPD, in the PC host. These experiments reveal that the current inj ected at the contact is proportional to the hole mobility in the bulk. As a result, the ITO/PC:TPD contact is found to limit current flow in all sampl es, regardless of the hole mobility in PC:TPD.