CuPc film nitrogen dioxide gas sensor based on hole injection

In this paper a novel type of copper phthalocyanine (CuPc) film nitrogen dioxide (NO₂) gas sensor based on hole injection was discussed. The sensor structure is Al₂O₃/ITO/CuPc/Al: ITO (indium-tin-oxide) film prepared by DC magnetron reactive sputtering was used as underside electrode, while CuPc film prepared by vacuum evaporation was used as the sensitive functional layer. The work function of ITO is high and close to the HOMO (highest occupied molecular orbital) energy level of CuPc. When there is an offset voltage between ITO and Al, holes were injected from ITO into CuPc and the holes accumulated at the surface of the CuPc, thus the surface resistivity of CuPc and the resistance of the gas sensor decreases greatly. The preparation method, sensitive mechanism and sensitivity properties were discussed. Compared to the traditional CuPc film NO₂ gas sensor (Al₂O₃/Al/CuPc) this kind of sensor has better sensitivity, shorter response and recovery time, better humidity resistivity, and its resistance decreases by 3∼4 order of magnitude.