Raymond K. Kostuk, Jose Castillo, Juan Manuel Russo, "Spectral-Shifting and Holographic Planar Concentrators for use with Photovoltaic Solar Cells", SPIE Optics and Photonics 2010.

A comparison of two types of solar concentrators for use with standard silicon photovoltaic cellsis provided. The first is spectral shifting luminescent concentrator that absorbs light in onespectral band and re-emits light at longer wavelengths where the absorption of standard silicon photovoltaic cells is more efficient. The second type is a holographic planar concentrator that selects the most useful bands of the solar spectrum and concentrates them onto the surface of photovoltaic cell. Both types of concentrators take advantage of total internal reflected light, do not require tracking, and can operate with both direct and diffuse sunlight. The holographic planar concentrator provides a simpler and more cost effective solution with existing materials and construction methods.

Niket Thakkar, Daniel Cormode, Vincent P.A. Lonij, Steve Pulver, Alexander D. Cronin, "A Simple Non-Linear Model for the Effect of Partial Shade on PV Systems", Photovoltaics Conference 2010.

The effect of shade from one PV module on another is incorporated into a model for the power generated by PV systems. The model is calibrated with data from the Tucson Electric Power solar test yard. Shade de-rating factors from the model are compared with data every minute of the day and every day of the year. The model is then used to predict final yields (kWh/kWDC) for different PV system deployments with various (non-tracking) module orientations and ground-cover ratios. Several heuristics are put forth to help understand how the observed non-linear response to shade can impact the yield from PV systems. In one example, we find that a PV system deployed in the Tucson Electric Power solar test yard could produce 22% more kWh for the month of December (and 3.8% more annually) if the modules were separated by twice as much distance. In another example, we predict that a system in Tucson with south-facing modules at 12-degrees from horizontal can generate 1.5 times as many kWh/yr per square-meter of land compared to a system with modules at 32-degrees (the latitude angle). These examples emphasize the non-linear impact of partial shade on PV system performance.

G. Shih*, C.G. Allen, and B.G. Potter, Jr., "RF-sputtered Ge:ITO nanocomposite thin films for photovoltaic applications." Solar Energy Materials and Solar Cells 94, 797 (2010).

Nanocomposite thin films, composed of a germanium nanocrystalline phase embedded within a tin-doped indium oxide (ITO) matrix, were produced using a multisource, sequential, RF-magnetron sputter deposition technique. The influence of nanocomposite structure on the resulting optical absorption and carrier transport properties was investigated in the context of the use of such materials as functional elements in thin film photovoltaic architectures. Deposition controls and post-deposition thermal anneals were successful in modifying the phase assembly of the nanocomposites, enabling the manipulation of Ge volume fraction, nanocrystallite size and morphology, and spatial distribution within the ITO embedding phase. Modifications in semiconductor nanostructure were correlated with changes in nanocomposite spectral absorption that were consistent with quantum-size-induced variation in Ge absorption onset energy, despite the close agreement in electron affinity between the Ge and ITO components. This suggests the formation of a high band-gap (low electron affinity) interfacial phase between the Ge and ITO components of the nanocomposite. Increased free-carrier (n-type) densities and spectrally resolved photoconductivity were also associated with the presence of the Ge phase. These results emphasize the impact of local and extended length scale structure on properties of importance to photovoltaic performance in semiconductor-based nanocomposites and the utility of the sequential sputter deposition method as a means to manipulate nanocomposite structure.

C.G. Allen, G. Shih, and B.G. Potter, Jr., "Microstructual and optical characterization of germanium:indium-tin-oxide (Ge:ITO) nanocomposite films," Mat. Sci. Eng. B, Vol. 175, pp. 150-158, (2010) .