Highly porous film of TiO 2 nanoparticles synthesized using carbon nanospheres for highly efficient dye-sensitized solar cells

Highly porous films of TiO2 nanoparticles were prepared by a doctor blade method using carbon nanospheres as a porosity enhancer. At first, carbon nanospheres with a diameter ranging from 100 to 600 nm were synthesized by a hydrothermal method; then, a paste of TiO2 nanoparticles was mixed with various amounts of carbon nanospheres. To obtain a porous TiO2 nanoparticles photoanode and removing carbon nanospheres, photoanode was sintered at a temperature of 500 °C. XRD patterns and Raman analysis revealed the anatase phase of TiO2 and show that the carbon spheres acted only as a porosity enhancer. Removing carbon nanospheres leads to the creation of cavities with various sizes in dye-sensitized solar cells (DSSCs). Under illumination, these random cavities increase porosity and light scattering of the photoanode which leads to a larger surface area for dye loading and improve light absorbance by dye N719 and consequently enhance the performance of DSSCs. For the optimum sample by mixing 3 wt% carbon nanospheres in the TiO2 pastes, the efficiency (η) and short-circuit current density (Jsc) were increased by 33% (from 5.72 to 7.59%) and 40% (from 12.59 to 17.73 mA cm−2), respectively.