Preparation of fuorine-doped tin oxide (FTO) template for coated platinum (Pt) layer counter electrode by electrochemical method for dye-sensitized solar cell application

In this work, we focus on increasing surface area of Pt layer used as a counter electrode in dye-sensitized solar cells (DSSC). The increasing surface area of Pt layer was prepared by coating Pt layer on FTO template. The FTO template was fabricated by dipping FTO glass in hydrochloric (HCl) acid with concentration of 0.016, 0.324 and 1.62 M and immersion time of 5, 15, 30, 45 and 60 s, respectively. The Pt layer counter electrode was coated on FTO template by electrochemical technique with Pt(NH₃)₄Cl₂ powder dissolved in HCl solution. The coating current was fixed at 25 mA and deposition times were varied from 10, 30 to 60 min. The sheet resistance, surface roughness and structural property of FTO substrate were examined by Van der pauw technique, atomic force microscopy (AFM) and X-ray diffraction, respectively. The AFM image shows that surface roughness of FTO template increases with increasing immersion time but sheet resistance decreases. The high surface area of FTO template can decrease sheet resistance because of increasing conducting Pt surface area. Based on AFM results, the surface area of Pt layer is highest with HCl concentration of 0.016 M and immersion time of 60 s. The DSSC were consisted of working electrode (FTO, TiO₂ blocking layer and TiO₂ porous layer) sandwich with the Pt counter electrode and iodide liquid electrolyte, respectively. The cell efficiency was measured by solar simulator operation at 1000 mW/cm^-2. The maximum cell efficiency of 2.78% was achieved from Pt deposition time of 60 min. Our results show that this simple preparation of Pt layer can be applied as a counter electrode for dye-sensitized solar cell.