Plasmonic Properties of Doped Metal Oxides Investigated through the Kubelka–Munk Formalism

Materials with broadband tunable optical properties are looked for in smart windows applications. Doped metal oxides presenting dual-band visible (VIS)–near-infrared (NIR) electrochromic properties can be used for solving such a challenge, and their accurate optical characterization is therefore of prime importance. The Kubelka–Munk model is a state-of-the-art way to optically quantify the absorption properties of materials and is occasionally applied to plasmonic materials, even if great care should be taken to meet the formalism hypotheses. In the present work, Kubelka–Munk theory is discussed in the context of particles of indium–tin oxide and molybdenum–tungsten oxide formulations that are used as single-NIR and both-VIS/NIR active advanced electrochromic materials, respectively. An analytical model is derived for particles of much smaller dimensions than the incident wavelength and is experimentally verified. A dilution method is applied to verify the plasmonic characteristics of the particles. This study is key for the efficient characterization of the optical properties of metal oxides and plasmonic materials in general, from diffuse reflectance measurements.