Thin polymeric CuO film from EPD designed for low temperature photothermal absorbers

The creation of a tandem solar absorber based on highly UV-Vis-NIR absorbing nanofilm deposited onto a highly IR reflecting platinized silicon wafer is processed through electrophoretic deposition (EPD). The stabilization of a CuO colloidal aqueous suspension is first studied by adding polyethyleneimine (PEI) as cationic polymer acting both as charging agent and as electro-steric stabilizer. The colloidal stability as a function of the suspension pH is investigated prior to EPD, by Laser Doppler velocimetry and atomic force microscopy. Tandem absorbers are obtained by varying different EPD parameters to control the thickness and the morphology of the film, in order to tune and optimize the final optical properties. The deposition thickness is then compared relative to the applied potential difference and the deposition time range. The morphology of the deposits and the thickness of the coatings are analysed by scanning electron microscopy (SEM). The density is obtained from energy-dispersive X-ray spectroscopy (EDX) using X-film software, total organic carbon (TOC) and Hamaker equation. CuO tandem absorbers are found to possess a high density with homogeneous and crack-free surfaces. Finally, absorptance (α) and emittance (ε) are calculated from the reflectance spectra of the UV-Vis-NIR and the Fourier Transform Infra-Red (FTIR) spectroscopy respectively. These latter values are combined to determine the efficiency (eta) of the tandem material. (authors)