Propriétés optiques des nanoparticules d'oxyde d'indium dopé à l'étain en vue d'applications électrochromes

Abstract

Indium tin oxide (ITO) is a transparent conducting oxide (TCO) whose conductivity comes mainly from tin doping. In the form of nanoparticles, the tin doping of this oxide places its plasmonic resonance frequency in the near infrared, which makes it an excellent candidate for the manufacturing of smart windows operating under the principle of electrochromism. In this work, we make a numerical study of the optical properties of ITO nanoparticles immersed in a liquid electrolyte solution and deposited on a fluorine tin oxide (FTO) glass substrate. The Maxwell-Garnett and Bruggeman effective media theories are used to evaluate the dielectric function of the composite medium consisting of the ITO nanoparticles and the liquid electrolyte. Our numerical studies are made considering only the case where the electrochromic device operates in open circuit voltage. The numerical methods of rigorous coupled wave analysis (RCWA) and transfer matrices (TMAT) allow us to obtain the transmission spectra of the light in the multilayer and we then compare the numerical results with the experimental results. In general, the numerical spectra obtained are in agreement with the experiment. However, when the thickness of the ITO layer increases, we observe the disagreement between the experiment and the numerical for high energies of the incident light. This disagreement is due to the fact that the dielectric function of the isolated ITO nanoparticles used in our numerical model does not take into account the absorption of light during the electronic transitions between the valence band and the and the conduction band. Moreover, the tin doping places the plasmonic resonance of ITO in the near infrared. the infrared. The maximum electron density is reached in ITO for a tin doping of 10%. In this case, the pic of the plasmonic resonance leads to a blue shift. The additional doping (15%) leads to the trapping of electrons around the tin atoms, which reduces the concentration of free charge carriers and a red shift of the plasma frequency take place.

Date of Award	22 Jun 2022
Original language	French
Awarding Institution	University of Namur
Supervisor	Luc Henrard (Supervisor) & Michael Lobet (Co-Supervisor)