Capacitance measurement in organic thin-film device with internal charge separation zone

To verify the concept of electric-field-assisted bipolar charge spouting in organic thin films, model devices with an internal charge separation (ICS) zone were fabricated. A double-insulation-type organic thin-film device, indium-tin-oxide (ITO)/ poly-chloro-p-xylylene (PCPX)/tris(8-quinolinolato)aluminum(III) (Alq₃)/Mg-doped Alq ₃/V₂O ₅/N,N′-bis(3-methylphenyl)-1,1′-biphenyl-4, 4′-diamine (TPD)/PCPX/Al (device with an ICS zone), and four devices with similar structures without the ICS zone were fabricated. The capacitance of the devices under positive and negative applied biases was measured. The device with the ICS zone showed a clear capacitance increase when the bias condition met the electric-field-assisted bipolar charge separation.