NOVELTY - A solar module (100) comprises a set of photovoltaic cells (106); and a spectral concentrator (110) optically coupled to the cells. The spectral concentrator is configured to collect incident solar radiation; convert the incident solar radiation into substantially monochromatic, emitted radiation; and convey the substantially monochromatic, emitted radiation to the set of photovoltaic cells.    USE - As a solar module to convert energy from solar radiation into electricity, which is delivered to external load to perform useful work.    ADVANTAGE - The solar modules have enhanced efficiencies with respect to conversion of incident solar radiation to useful electrical energy. By converting a wide range of energies of the incident solar radiation to a narrow band of energies matched to the bandgap energy of the photovoltaic (PV) cells, significant improvements in efficiency can be achieved. In addition, the design of the PV cells can be optimized or otherwise tailored based on this narrow band of energies. The collection efficiency is typically improved by suitable optical coupling of incident solar radiation to the luminescent material, such as via an anti-reflection coating to reduce reflection of incident solar radiation. By performing the collection operation in place of the PV cell, the spectral concentrator allows a significant reduction in silicon consumption, which, in turn, allows a significant reduction in manufacturing costs. The amount of silicon consumption can be reduced by a factor of 10-1000. Also, the spectral concentrator enhances solar energy conversion efficiency based on at least two effects concentration effect; and monochromatic effect.    DETAILED DESCRIPTION - A solar module (100) comprises a set of photovoltaic cells (106); and a spectral concentrator (110) optically coupled to the cells. The spectral concentrator is configured to collect incident solar radiation; convert the incident solar radiation into substantially monochromatic, emitted radiation; and convey the substantially monochromatic, emitted radiation to the set of photovoltaic cells. The concentrator includes a luminescent stack containing a luminescent layer having a first surface and a second surface; a first reflector adjacent to the first surface; and a second reflector adjacent to the second surface. The luminescent layer includes a luminescent material that exhibits photoluminescence having an internal quantum efficiency of at least 50%; a spectral width not greater than 100 nm at Full Width at Half Maximum; and a peak emission wavelength in the near infrared range. The first reflector and the second reflector includes a dielectric stack. The concentrator defines multiple grooves, and multiple ones of the set of photovoltaic cells are positioned in respective ones of the grooves. The spectral concentrator includes a resonant cavity structure.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of the solar modules.    Solar modules (100, 102, 104)    Photovoltaic cell (106)    Side surface of photovoltaic cell (108)    Spectral concentrator (110)    Side surface of slab (112)