Nickel phthalocyanine photovoltaic devices

Metal substituted phthalocyanines are a class of organic dye material that are weakly semiconducting. Many of these materials incorporating different metals have been investigated for molecular switching, gas sensing and photovoltaic properties. In this work we report the use of nickel phthalocyanine (NiPc) as the semiconductor in Schottky barrier photovoltaic devices. Sandwich structures of aluminium-NiPc-silver have been fabricated by vacuum deposition and investigated for both dark conductivity and photovoltaic response using a solar simulator. Previous workers have shown that this type of device is highly sensitive to different gasses, consequently a deposition process was used that did not break the vacuum from phthalocyanine deposition to characterisation. This process clearly shows that the presence of oxygen is essential to observe a photovoltaic response (i.e. short circuit current and open circuit voltage) in this type of device. The effect of incorporating tetracyanoquinodimethane (TCNQ), a strong electron acceptor, in the nickel phthalocyanine structure to enhance the conductivity is also reported.