Role of rare-earth oxides, conjugated with TiO2, in the enhancement of power conversion efficiency of dye sensitized solar cells (DSSCs)

Different rare-earth (RE) metal-oxides nano-particles (NPs) viz. Samarium (III) oxide (Sm 2 O 3 ), Neodymium (III) oxide (Nd 2 O 3 ), and Gadolinium (III) oxide (Gd 2 O 3 ) were synthesized using co-precipitation route, and investigated by structural, optical, and morphological studies. Findings and supporting studies were presented to understand the role of RE-metal-oxides NPs as photo-anode material for dye sensitized solar cells (DSSCs) applications. Structural analysis of prepared RE-metaloxides, by X-ray diffraction (XRD), reveals the crystalline nature of the particles ranging from 24 to 37 nm. Morphological study by field emission scanning electron microscopy (FESEM) supports the crystalline nature in the nano range of the prepared RE-metal oxides particles. The observed d values of each sample support the growth of Gd 2 O 3 , Nd 2 O 3 , and Sm 2 O 3 material. The band-gap of prepared material was estimated from the UV–VIS absorption data and Tauc relation. The observed band gap values are 3.55 eV, 3.31 eV, and 3.52 eV for Gd 2 O 3 , Nd 2 O 3 , and Sm 2 O 3 respectively. These values are reasonably high compare to the bulk values, indicates the nanostructure formation. Optimized RE-metal oxides NPs employed in the form of TiO 2 photo anode for the fabrication of DSSCs. FESEM confirms that the Gd 2 O 3 -based photo-anode shows more uniform and decent coverage with more porosity on the TiO 2. The EIS measurements of prepared DSSCs also supported the improvement in the photovoltaic output for the modified photo-anode devices as cells with modified photo-anode exhibited less charge recombination at the photo-anode/dye/electrolyte interface with increased electron lifetime leading to improved device performance as compared to the unmodified-based DSSCs. The highest efficiency 5.51% was demonstrated by Gd 2 O 3 / TiO 2 photo-anode-based DSSCs compare to Sm 2 O 3 , and Nd 2 O 3 activated photo-anode.