Selective Optical Surfaces for Solar Energy Converters

Improving optical properties of diffusion-based absorber coatings for CSP tower systems

“…Improved solar absorptance of the bilayer concept compared to Cr-Mn-coating in the initial stateImprovement PlanHowever, the assessment of optical properties depends on both solar absorptance α s as well as thermal emittance ε th . The two values can be combined into a single performance criterion[7,8], thermal efficiency η coating , defined in Eq. (1).…”

Almost zero reflectance of a silicon oxynitride/porous silicon double layer antireflection coating for silicon photovoltaic cells

“…The task of reducing the reflectance coefficient is close to the blooming task in optical systems [13]. However, the blooming in optical systems is restricted mainly to the visible range of the spectrum and, therefore, to the application of thin dielectric films having interference thickness.…”

“…Because of the high refractive index of bulk silicon (n ≈ 3.5), a considerable part of solar irradiation is reflected, which leads to a worsening of the solar cell performance. Therefore, to reduce the reflectance losses, it is necessary to design antireflection coatings having appropriate parameters with the refractive indices and thickness satisfying the well-known relationship between transmission and reflection coefficients and layer thickness [7,13]. In our previous study [7], we have investigated a double layer DLC/PS thin film antireflective and protective coating using the optical matrix approach method [7,15], which allows a rapid and accurate determination of the reflectance spectrum for different types of ARCs.…”

Hybrid collectors using thin-film technology

“…Surface texturing further reduces the emissivity in the far-IR due to so-called wavefront discrimination [13] which explains the large difference between the flat ZnO and the highly textured SnO 2 . This low emissivity for far-IR, together with high transparency in the range of the visible light, makes TCOs well-suited as a heat-mirror in a tandem absorber surface where the upper layer (TCO) is transparent for the sunlight and has a low emissivity coefficient and the lower layer absorbs the sunlight efficiently [11]. In our case, the TCO (ZnO) additionally is tuned to absorb that part of the sunlight which cannot be absorbed in the amorphous cell.…”

“…Highly doped semiconductors show a high reflectivity in the far-IR region [11,12]. Surface texturing further reduces the emissivity in the far-IR due to so-called wavefront discrimination [13] which explains the large difference between the flat ZnO and the highly textured SnO 2 .…”