For efficient charge injection and transportation, wide bandgap nanostructured metal oxide semiconductors with dye adsorption surface and higher electron mobility are essential properties for photoanode in dyesensitized solar cells (DSSCs). TiO 2-based DSSCs are well established and so far have demonstrated maximum power conversion efficiency when sensitized with ruthenium-based dyes. Quest for new materials and/or methods is continuous process in scientific investigation, for getting desired comparative results. The conduction band (CB) position of CeO 2 photoanode lies below lowest unoccupied molecular orbital level (LUMO) of rose bengal (RB) dye. Due to this, faster electron transfer from LUMO level of RB dye to CB of CeO 2 is facilitated. Recombination rate of electrons is less in CeO 2 photoanode than that of TiO 2 photoanode. Hence, the lifetime of electrons is more in CeO 2 photoanode. Therefore, we have replaced TiO 2 by ceria (CeO 2) and expensive ruthenium-based dye by a low cost RB dye. In this study, we have synthesized CeO 2 nanoparticles. X-ray diffraction (XRD) analysis confirms the formation of CeO 2 with particle size ∼7 nm by Scherrer formula. The bandgap of 2.93 eV is calculated using UV-visible absorption data. The scanning electron microscopy (SEM) images show formation of porous structure of photoanode, which is useful for dye adsorption. The energy dispersive spectroscopy is in confirmation with XRD results, confirming the presence of Ce and O in the ratio of 1:2. UV-visible absorption under diffused reflectance spectra of dye-loaded photoanode confirms the successful dye loading. UV-visible transmission spectrum of CeO 2 photoanode confirms the transparency of photoanode in visible region. The electrochemical impedance spectroscopy analysis confirms less recombination rate and more electron lifetime in RB-sensitized CeO 2 than TiO 2 photoanode. We found that CeO 2 also showed with considerable difference between dark and light DSSCs performance, when loaded with RB dye. The working mechanism of solar cells with fluorine-doped tin oxide (FTO)/CeO 2 /RB dye/carbon-coated FTO is discussed. These solar cells show V OC ∼360 mV, J SC ∼0.25 mA cm −2 and fill factor ∼63% with efficiency of 0.23%. These results are better as compared to costly ruthenium dye-sensitized CeO 2 photoanode. Keywords. Wide bandgap; dye-sensitized solar cells; CeO 2 ; rose bengal dye.

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The present work deals with the study of TiO 2-CeO 2 bilayered photoanode with low-cost Rose Bengal (RB) dye as sensitizer for dye-sensitized solar cell application. The recombination reactions are reduced in bilayered TiO 2-CeO 2 photoanode as compared to the singlelayered CeO 2 photoanode. Once the electrons get transferred from lowest unoccupied molecular orbital level of RB dye to the conduction band (CB) of TiO 2 , then the possibilities of recombination of electrons with oxidized dye molecules or oxidized redox couple are reduced. This is because the CB position of CeO 2 is higher than that of TiO 2 , which blocks the path of electrons. The electrochemical impedance spectroscopy (EIS) analysis shows negative shift in frequency for bilayered TiO 2-CeO 2 photoanode as compared to CeO 2 photoanode. Hence, in bilayered photoanode lifetime of electrons is more than in single-layered photoanode, confirming reduction in recombination reactions. The X-ray diffraction patterns confirm both anatase TiO 2 and CeO 2 with crystalline size using Scherrer formula as 24 and 10 nm, respectively. The scanning electron microscopy images of photoanode show the porous structure useful for dye adsorption. The presence of Ti and Ce is confirmed by electron diffraction studies. The band gap values for TiO 2 and CeO 2 were calculated as 3.20 and 3.11 eV, respectively, using diffused reflectance spectroscopy. The bilayered TiO 2-CeO 2 photoanode showed open-circuit voltage (V OC) *500 mV and short-circuit photocurrent density (J SC) *0.29 mA/cm 2 with fill factor (FF) *62.17 %. There is increase in V OC and J SC values by 66.67 and 38.10 %, respectively, compared to RB-sensitized CeO 2 photoanode. Keywords Dye-sensitized solar cell Á Photoanode Á Rose Bengal dye Á TiO 2-CeO 2 Electronic supplementary material The online version of this article (