Urea treated WO3 and SnO2 as cost effective and efficient counter electrodes of dye sensitized solar cells

A novel method was developed to convert the electro-catalytically inactive commercial WO 3 and SnO 2 into high efficient WO 3−x and SnO 2−x counter electrodes for dye sensitized solar cells (DSSs) to replace Pt. Both WO 3 and SnO 2 was treated with Urea with different Urea mass ratio concentrations and annealed under N 2 environment at 500°C. The energy conversion efficiency (PEC) was significantly improved by urea treatment with 8.57% compared to 2.91 % for non-treated CE in case of WO 3 and increases from 2.76 % for non-treated CE to 8.7 % after urea treatment in case of SnO 2 . All other characterizations performed for urea treated WO 3 and SnO 2 support the hypothesis of creating oxygen vacancies inside the metal oxides by the treatment. These oxygen vacancies facilitate the redox process in iodide/trioxide electrolyte. The density of these oxygen vacancies could be controlled by controlling the urea concentration during the treatment.