Stefano Rampino

Single element spectral splitting solar concentrator for multiple cells CPV system

Shockley Read Hall equation poses a limit to the maximum conversion efficiency of broadband solar radiation attainable by means of a single bandgap converter. A possible approach to overcome such a limit is to convert different parts of the broadband spectrum using different single junction converters. We consider here a different modus operandi where a single low-cost optimized plastic prismatic structure performs simultaneously the tasks of concentrating the solar light and, based on the dispersive behavior of the employed material, spatially splitting it into its spectral component. We discuss its approach, optical simulations, fabrication issues and preliminary experimental results demonstrating its feasibility for cost effective high efficiency Concentrated Photovoltaic Systems (CPV) systems.

Single element point focus spectral splitting concentrator with CIGS multiple bandgap solar cells

The combination of optical concentration, spatial spectral splitting and the use of multiple cells of suitable bandgap, could provide a path for high PV conversion efficiency without requiring the use of monolithically integrated multi junction solar cells. We propose a dispersive point focus single element concentrator and spectral splitting optics coupled with multiple cells employing Cu(InxGa1-x)Se2 cells for the mid wavelengths region. The optical element is designed, taking advantage of the dispersion characteristics of the employed material, to concentrate and provide spatial spectral splitting. The component can be realized injection molding and be mass produced at low cost.

Efficiency enhancement in two-cell CIGS photovoltaic system with low-cost optical spectral splitter.

Spectrum splitting represents a valid alternative to multi-junction solar cells for broadband light-to-electricity conversion. While this concept has existed for decades, its adoption at the industrial scale is still stifled by high manufacturing costs and inability to scale to large areas. Here we report the experimental validation of a novel design that could allow the widespread adoption of spectrum splitting as a low-cost approach to high efficiency photovoltaic conversion. Our system consists of a prismatic lens that can be manufactured using the same methods employed for conventional CPV optic production, and two inexpensive CuInGaSe(2) (CIGS) solar cells having different composition and, thus, band gaps. We demonstrate a large improvement in cell efficiency under the splitter and show how this can lead to substantial increases in system output at competitive cost using existing technologies.