Carrier injection and transport characteristics of copper phthalocyanine thin films under low to extremely high current densities

We investigated current density-voltage (J-V) characteristics of copper phthalocyanine (CuPc) thin films depending on active device areas. We prepared CuPc thin-film devices with active areas smaller than S=625 mu m(2) using a photolithography technique. The maximum breakdown current density (J(MAX)) and voltage (V-MAX) of the devices markedly increased as the active area was decreased from S=625 to 7.9 mu m(2). In the smallest device, with S=7.9 mu m(2), we obtained not only an extremely high current density of J(MAX)=128 kA/cm(2) at V-MAX=9.2 V, but also unique J-V characteristics, indicating that the carrier conduction process shifted from the Fowler-Nordheim tunneling injection mechanism to shallow-trap and trap-free space-charge-limited current mechanisms.