Investigation of Structural and Optical Properties of Copper Oxide Nanoparticles Applicable in Flexible and Transparent Windows

Abstract

In this work, glucose is used as the reducing agent and CuCl₂ as the precursor to create Cu, CuO and Cu₂O NPs by a chemical reduction method. By using X-ray diffraction (XRD), energy dispersive X-ray (EDX) and scanning electron microscopy (SEM), the Cu, CuO and Cu₂O NPs structure and morphology are studied. The generation of Cu, CuO and Cu₂O NPs is confirmed by the UV-Visible absorption spectra, which exhibit peaks at 559, 558 and 557 nm, respectively. The three samples are prepared at different growth temperatures i.e. 60⁰, 70⁰ and 80⁰, named as Cu-T₁, Cu-T₂ and Cu-T₃, respectively. Using Tauc plots and absorption data, the band gaps of the Cu-T₁, Cu-T₂ and Cu-T₃ NPs are found to be 2.04 eV, 2.15 eV and 2.21 eV, respectively. The XRD patterns demonstrates the crystalline and monoclinic nature of the Cu, CuO and Cu₂O NPs. The crystallinity of Cu, CuO and Cu₂O NPs is likewise shown to rise with an increase in annealing temperature and the diffraction peaks are made sharper. The structural analyses exhibit base-centered spherical nanocrystals with crystallite sizes of 12 nm, 23 nm and 18 nm for the said samples. The SEM images reveal the corresponding non-agglomerated particle diameters of about 310 nm, 200 nm and 100 nm, respectively. To obtain the optical responses from Cu₂O NPs, hydroxyl ethyl cellulose (HEC) as an adhesive agent mixed with the sample “Cu-T₃ NPs” is used as an ink and spread on a flexible substrate (Polyethylene-terephthalate/PET) with different dispersion volumes (0 mL, 0.04 mL, 0.08 mL, 0.12 mL, 0.16 mL and 0.2 mL). As prepared flexible substrate-based sample are tested for their transmittance measurements. The maximum transmittance obtained is 82.37% for 0.04 mL dispersion and the minimum value is 53.23% for 0.2 mL dispersion ink, suggesting the Cu₂O NPs desirable candidates for low cost flexible and transparent windows applicable in solar panels and other technologies.