Unraveling urea pre-treatment correlated to activate Er2(WO4)3 as an efficient and stable counter electrode for dye-sensitized solar cells

The interest has been rapidly increased in oxygen vacancies and defects of metal oxides in view of their intimate connection with the key electrocatalytic performance of these materials, especially in photovoltaic applications. In this work, Erbium tungstate, Er2(WO4)3, has been synthesized and used as a novel counter electrode for the DSSCs. A facile method has been utilized to introduction oxygen vacancies in Er2(WO4)3 via doping different weight percentages (0–15 wt%) of urea-pretreatment under air or N2 gas atmosphere. The structural investigation of pristine and urea-treated Er2(WO4)3 films using different techniques. The SEM micrograph images revealed the creation of pores and voids are introduced in the morphology surface of Er2(WO4)3 films after urea pretreatment which confirms the creation of oxygen vacancies. This may facilitate the charge transfer at Er2(WO4)3 counter electrode/electrolyte interface. The optical band gap of the Er2(WO4)3 film reduced from 2.05 to 1.57 eV attributed to the creation of vacancies. Different electrical aspects were used to evaluate the electrocatalytic performance of Er2(WO4)3 as a counter electrode. The addition of urea (5 wt%) to Er2(WO4)3 as counter electrode in presence N2 environment jumped the power conversion efficiency of dye-sensitized solar cell (DSSC) from ∼ 0.12% to 4.18% revealed an efficient catalytic performance of urea-treated Er2(WO4)3 as counter electrode for the present DSSCs.