Extremely-high-density carrier injection and transport over 12000A∕cm2 into organic thin films

Abstract

We achieved extremely-high-density steady state carrier injection and transport at over ∼ 10 000 A ∕ cm 2 into organic thin films using high thermally conductive substrates, which suppress the temperature rise inside the devices by transferring the joule heat into the substrates. Using a silicon substrate with a high thermal conductivity of 148 W ∕ m K and a small size cathode with a radius of r = 25 μ m , we achieved a maximum current density of J max = 12 222 A ∕ cm 2 and power density of P max ∼ 10 5 W ∕ cm 2 in an ITO ( 110 nm ) ∕ copper phthalocyanine (CuPc) ( 25 nm ) ∕ Mg Ag ( 100 nm ) ∕ Ag ( 10 nm ) device during a fraction of a second under direct current sweep. Further, we also achieved J max = 514 A ∕ cm 2 in a conventional organic light-emitting diode structure using the same techniques. In the CuPc based devices, we observed characteristiccurrent density ( J ) –voltage ( V ) behavior, indicating that the J – V characteristics are controlled by the trap-free space-charge-limited currents in the high current region, and by the trapped-charge-limited current in the low current region.