High-speed and high-current density C60 diodes

A high-performance organic diode is demonstrated by using C-60 sandwiched between a cathode and an anode using metals with different diffusivity and donor ability. In this letter, copper (Cu) and aluminum (Al) are selected as the cathode and anode, respectively. C-60 is used as the organic electron-acceptor for its high stability and high carrier mobility. The as-prepared diode shows poor performance. However, after heat treatment, the Cu/C-60 interface becomes an Ohmic contact through Cu diffusion and charge-transfer processes, allowing highly efficient electron injection from the Cu electrode. On the other hand, a rectified C-60/Al contact is formed, prohibiting efficient electron injection from the Al electrode into C-60. Hence, a high-performance organic diode is formed through a heat treatment process, not by the selection of metals with different work functions. Due to the high mobility of C-60, the device shows megahertz frequency response, and it can also handle rather high current density (363 A/cm(2) at 2.4 V). This opens the way for the formation of high-performance organic electronic devices. (C) 2004 American Institute of Physics.