Analysis of CuPc-based organic solar cell with high photovoltage

Photovoltaic devices of the configuration ITO-PEDOT:PSS/CuPc/PTCBI/AI were investigated. A high open circuit voltage (V/sub OC/) of 1.125 V was obtained when the PTCBI layer was 7 nm thick. Value of V/sub OC/ was lower when silver, copper or gold electrode was used instead of aluminum. However, short-circuit current density (J/sub SC/) with these electrodes was much higher (4 mA/cm/sup 2/) than in the case of aluminum (0.12 mA/cm/sup 2/). These results could be understood in terms of a modified CuPc/AI Schottky diode model for the thin PTCBI case and a CuPc/PTCBI heterojunction model for the thick PTCBI case. Also, the formation of a thin, protective aluminum oxide layer under the aluminum electrode was postulated. For devices with silver, copper and gold electrodes, absence of this protective layer was thought to be the cause of the relatively lower V/sub CO/ and higher J/sub SC/.