Impact of Synthesis Technique on Lanthanum Doped Copper Oxide Nanocrystals, an Alternative Counter Electrode for Pt-Free Dye-Sensitized Solar Cells

The ascendancy of a counter electrode (C.E) in a dye-sensitized solar cell (DSSC) has an unrivaled impact on the performance of the dye-sensitized solar cell, where the Pt-based C.E has set up a phenomenal benchmark against its counterparts. Due to the high cost of such noble metals, an operative and a much cost effective replacement were greatly in demand to gratify this need. To address this issue, monoclinic lanthanum doped copper oxide (CuO) nanoparticles were prepared by solution combustion and co-precipitation techniques respectively as they possess highly superior optoelectronic, catalytic and charge transfer properties. The effect of incorporating lanthanum (La) ions and the variation of synthesis technique on their structural, optical, photo-thermal and morphological properties are empirically investigated by XRD, FTIR, TEM, UV-Vis, Raman and Photoacoustic Spectroscopy (PAS). The X-ray diffraction pattern revealed the formation of La-doped CuO nanoparticles. The finger-print vibrational modes of the as-synthesized samples are confirmed by the FTIR spectra. The required optical properties of the as-synthesized nanocrystals were confirmed using UV-Vis absorption spectra, from which the bandgap was determined by Kubelka-Munk plot. The Raman modes were determined using Raman spectra, further a multi-phonon band was revealed, which was formed due to the plasmon-phonon coupling. The photothermal phenomenon was revealed using the photoacoustic spectra. The morphological investigation by TEM found the change in the morphology of the material as the synthesis route is varied. The power conversion efficiency results unveiled that the combustion-derived C.E posted a promising efficiency (η) of 0.20% and the co-precipitation derived C.E posted an efficiency of 0.02%. Overall results suggest that the combustion derived La doped CuO nanostructures exhibited substantive properties with deeper implication and also stood out to be a viable, cost-effective and self-exemplifying replacement for Pt as C.E in DSSC’s.