Different configurations of multiwall carbon nanotube sheet as counter electrode of DSSCs

Dye-Sensitized Solar Cells (DSSCs) are capable of revolutionizing the energy production industry by producing the optimum amount of energy from affordable materials and its capability to be a cheaper substitute for one layered solar cells. The DSSC is an innovative approach to solving the energy crisis by taking advantage of available cheap materials to collect the energy of sun. This research analyzes how the components of DSSCs affect its effectiveness with the goal of maximizing the photo-electric conversion efficiency. Electrodes were fabricated from plates of plain soda lime glass commercially provided FTO coated glass and microscope glass.  Conventional platinum CEs were prepared by spreading 30 nm film of commercially available platinum paste on FTO glass plates and heat treating at 400 °C for 25 min in air. The working electrode for each DSC was prepared by first depositing a compact TiO₂ thin film on an FTO glass plate substrate by soaking in an aqueous solution of TiCl₄ at 70^oC for 30 minutes, rinsing with deionised water and air drying. A layer of transparent TiO₂ paste  followed by a layer of reflector TiO₂paste  were spread by doctor blade onto the substrate and sintered from room temperature to 500 °C for 45 min.  After cooling to 110 °C, sintered electrodes were immersed in a 0.3 mM solution of cis-bis-bis-ruthenium(II) bis dye in acetonitrile for 24 h. Platinized counter electrode is common in most of the DSSC researches because of its high catalytic activity and corrosion stability against iodine in the electrolyte.  Pt film coating on FTO glass surface by using alcoholic solution of hexachloroplatinic acid , paste containing Pt precursors or sputtering are widely used techniques. Pt is very expensive material, so it is reasonable to find more affordable materials with good catalytic activities and lower price. The goal was to use different type of carbon materials to replace platinum, and they also may be applicable for DSSC on flexible substrates. This work presents an application of multi-walled carbon nanotubes with different materials with good catalytic activities as AgNW and graphene flakes. Under 1 sun illumination , the open-circuit voltage (V_OC), short-circuit current density (J_SC), and fill factor (FF) of MWCNT doped with AgNW counter-electrode DSSC were 680 mV, 6.6 mA/cm², and 0.57, respectively, yielding an energy conversion efficiency (η) of 2.57%. The same parameters for graphene/MWNT counter-electrode DSSCs were 690 mV, 11.97 mA/cm², and 0.68, respectively, yielding energy conversion efficiency (η) of 5.64%. The corresponding values (V_OC, J_SC, FF, and η) of the platinum counter-electrode device were 770 mV, 11.54 mA/cm², 0.72, and 6.38% respectively. Counter electrodes based on Graphene Oxide/MWCNT network films show promising results for replacing Pt in low cost DSSCs , Catalytic activity and sheet conductance needs to be improved to achieve the better efficiency in full sunlight conditions, MWCNT sheets can be used on the flexible solar devices because of their high flexibility.