Mobility-dependent charge injection into an organic semiconductor

Measurements of charge injection from indium tin oxide (ITO) into the organic semiconductor, tetraphenyl diamine doped polycarbonate (PC:TPD), were carried out. The current injected at the contact was measured as a function of 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 transport agent, TPD, in the PC host. These experiments reveal that the current injected 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 samples, regardless of the hole mobility in PC:TPD.