Optical sensors based on the NiPc–CoPc composite films deposited by drop casting and under the action of centrifugal force

In this study, solution processed composite films of nickel phthalocyanine (NiPc) and cobalt phthalocyanine (CoPc) are deposited by drop casting and under centrifugal force. The films are deposited on surface-type inter-digitated silver electrodes on ceramic alumina substrates. The effects of illumination on the impedance and capacitance of the NiPc–CoPc composite samples are investigated. The samples deposited under centrifugal force show better conductivity than the samples deposited by drop casting technique. In terms of impedance and capacitance sensitivities the samples fabricated under centrifugal force are more sensitive than the drop casting samples. The values of impedance sensitivity ($S_z$) are equal to (−1.83) $M\Omega \cdot {cm}^2/mW$ and (−5.365)$M\Omega \cdot {cm}^2/mW$ for the samples fabricated using drop casting and under centrifugal force, respectively. Similarly, the values of capacitance sensitivity ($S_c)$ are equal to $0.083pF\cdot {cm}^2/mW$ and $0.185pF\cdot {cm}^2/mW$ for the samples fabricated by drop casting and under centrifugal force. The films deposited using the different procedures could potentially be viable for different operational modes (i.e., conductive or capacitive) of the optical sensors. Both experimental and simulated results are discussed. (paper)