| The Solar Optical Properties
Laboratory contains a complete set of instruments for analysis of the
radiometric properties and optical constants of all types of solar
energy materials including monolithic, nanolayer coated, laminated and
geometrically complex products Spectroradiometers: Measurements of solar spectral transmittance and reflectance are made with highly automated instruments. Our most modern UV-VIS-NIR spectroradiometer is the Perkin-Elmer Lambda 950. Two earlier instruments in that series, a Lambda 19 and a Lambda 9, are also still in use in our lab dedicated to special purposes.
Spectroradiometer attachments: In addition to the base instruments, we also have a number of attachment modules each of which performs a specialized type of measurement. Each of the base spectrometers is equipped with a direct detection module as well as an integrating sphere detection module. Other accessories can perform specular transmittance and specular reflectance at variable angles of incidence.
Variable-angle spectroscopic ellipsometer: Ellipsometry is a powerful tool for determining the optical indices and thicknesses of the layers in a thin-film coating especially when combined with radiometric data from our other instruments. This information is used both for analysis of our coating structures and to develop models for optical properties of various solar energy materials. The ellipsometer shown below by the J.A. Woollam Co. covers the ultraviolet, visible and near infrared range from 250-1700 nm.
Figure 1 Scatterometry: When sample and detector are mounted on goniometers so that the angles of incidence and the angles of detection can be varied, the full bidirectional radiometric properties can be gathered. This collection of transmission and reflection values is sometimes called the bidirectional scattering distribution function (BSDF). The figure below shows the complex sample holder and stepper motors. The solar spectral range and resolution is similar to the spectroradiometers described above but the possible motion of the sample and detector is much wider. The ellipsometer described above is also capable of operating in scatterometry mode but only in the horizontal plane.
Figure 3 Electrochromic monitoring: A multichannel optical test station for electrochromics (figure 4) allows continuous monitoring of optical and electrochemical cycling during electrochemical testing . Both devices and electrodes in solution can be tested either inside or outside of a dry box. Remote access has been built into this system because experiments of this type tend to run unattended for days or weeks. We intend to test off-site access in the near future.
Figure 4 Emittance: An FTIR with and extended-range beamsplitter and a variable-angle reflectance attachment is used for measurements of emittance from specular glazing materials. We also have an emissometer for measurements of total emittance on either specular and diffuse materials. In a nearby lab there is a dispersive infrared spectrometer which is superior for this purpose to FTIRs which are now manufactured exclusively. |
