Integrating Sphere

The integrating sphere allows for angularly and wavelength resolved reflection and transmission measurements. Coupled to a Fianium white laser, reflection and transmission of light can be measured across the solar spectrum. Furthermore, motorized stages allow for angular variation across two axes in transmission mode and one axis in reflection mode. This characterization tool has been particularly useful for characterizing microwire arrays. Specifically, the two angular axes have allowed us to characterize the effect of different wire patterns, such as square, hexagonal and chirped. Furthermore, wavelength and angularly resolved reflection and transmission measurements allow us to find expected day integrated absorption for the wire arrays, which we find is more than 80%. The integrating sphere has also been key to the experimental collaboration between Illinois and Caltech on the microsphere solar cells. Reflection measurements in the integrating sphere allow for comparison with FDTD simulations of the microspheres. The integrating sphere is vital here because the sphere arrays are not necessarily specularly reflective, so it is necessary to capture diffuse reflectivity as well to fully understand reflections from these arrays.