Polarization-dependent angular-optical properties of spectrally selective reflector surfaces of fluorine-doped tin oxide (SnO<sub><i>x</i></sub>:F) deposited pyrolytically on anodized aluminum are reported. The angular-reflectance measurements, for which both <i>s</i>- and <i>p</i>-polarized light are used in the solar wavelength range 0.3–2.5 μm, reveal strong spectral selectivity, and the angular behavior is highly dependent on the polarizing component of the incident beam, the total film thickness, and the individual thickness of the Al<sub>2</sub>O<sub>3</sub> and the SnO<sub><i>x</i></sub>:F layers. The anodic Al<sub>2</sub>O<sub>3</sub> layers were produced electrochemically and varied between 100 and 205 nm in thickness. The SnO<sub><i>x</i></sub>:F films were grown pyrolytically at a temperature of 400 °C with film thicknesses varying in the range 180–320 nm. The reflectors were aimed at silicon solar cells, and good spectrally selective reflector characteristics were achieved with these thinly preanodized, SnO<sub><i>x</i></sub>:F/Al samples; that is, high cell reflectance was obtained for wavelengths below 1.1 μm and low thermal reflectance for wavelengths above 1.1 μm, with the best samples having values of 0.80 and 0.42, respectively, at near-normal angles of incidence. This corresponds to an anodic layer thickness of 155 nm. Both the angular calculations and the experimental measurements show that the cell reflectance is relatively insensitive to the incidence angle, and a low thermal reflectance is maintained up to an angle of ~60°.
© 2002 Optical Society of America
(120.5700) Instrumentation, measurement, and metrology : Reflection
(160.4760) Materials : Optical properties
(230.4170) Optical devices : Multilayers
(310.6860) Thin films : Thin films, optical properties
(350.6050) Other areas of optics : Solar energy
Mghendi Mwamburi, Ewa Wackelgard, Arne Roos, and Rogath Kivaisi, "Polarization-Dependent Angular-Optical Reflectance in Solar-Selective SnOx:F/Al2O3/Al Reflector Surfaces," Appl. Opt. 41, 2428-2434 (2002)