Influence of oxygen doping on the electrical and photovoltaic properties of Schottky type solar cells based on α-nickel phthalocyanine

Single layer thin film cells were fabricated by successive thermal sublimation of gold, nickel phthalocyanine and lead under high vacuum conditions (10^-4 Pa). Structural properties of NiPc film were studied using X-ray diffraction measurements. Charge carrier transport mechanisms were identified from the dark current density-voltage (J-V) characteristics. A rectifying junction was found to exist at the NiPc/Pb interface. The potential barrier height was evaluated under high vacuum and upon exposure of the cells to dry air for different periods of time. Density of acceptors was calculated for O₂ doped cells utilising the small a.c. signal capacitance-voltage technique. A photovoltaic effect was observed upon illumination of the sample with white light. Various photovoltaic parameters were determined from the J-V characteristics of the cells as a function of incident light intensity and exposure time to dry air. Although the initial power conversion efficiency (under vacuum) was low the cells show promising photovoltaic characteristics upon doping with O₂.