Improving the electrical conductivity and photo-conductivity of the photo-active layer P3HT:PCBM doped by Schiffbase for organic photo-sensor applications

A Schiff-base material was synthesized and characterized by the 1H- and 13C-NMR, FTIR, Mass, and UV-visible spectroscopy. A thin layer of pure P3HT:PCBM and P3HT:PCBM:Schiffbase with two concentrations 2 mM and 4 mM are prepared using spin coating method. At room temperature, doping of P3HT:PCBM active-layer by Schiff-base material at concentration of 4 mM led to enhance the electrical current and conductivity by a factor of 24x under dark conditions and by a factor of 27x under white-light illumination (I o = 50 mW cm −2 ). The electrical current, conductivity, and resistivity are measured as a function of time under illumination for three different wavelengths, white, green, and red, proving that the photo-sensors based on P3HT:PCBM:schiffbase thin films exhibit a good reproducibility, fast-response time, and high optical-sensitivity. It was also found that the photo-electrical characterization of the photo-sensors are wavelength dependent, where, under red-light, the samples exhibit the lowest optical-response while the highest value was obtained under white-light. The study revealed that the photo-responsivity and quantum efficiency of the P3HT:PCBM:Schiffbase(4 mM) based photo-sensors exposed by white light are higher than those the corresponding values of the photo-sensors based on P3HT:PCBM by a factor of ∼31x. Moreover, the performance of the photo-sensors were improved due to depositing an ultra-thin film of carbon on top of the active-layer, exhibiting a significant enhancement in the electrical and photo-electrical properties. The photo-sensors based on P3HT:PCBM:Schiffbase/carbon-nano-sheet show a superior quantum efficiency (∼6%) with photo-responsivity of ∼24 mA W −1 , confirming that the doped P3HT:PCBM active-layer are very interesting for organic optical sensors and photovoltaic devices.