Quantum-dot concentrator and thermodynamic model for the global redshift

Abstract

The use of quantum dots can turn the old concept of a luminescent solar collector into a practical concentrator. The quantum efficiency, tunability of absorption threshold, and size of the redshift make quantum dots an ideal replacement for the organic dyes whose performance limited this inexpensive technology. Progress in photovoltaic cells, in particular, the ability of quantum-well cells to tune the band gap, also suggests high efficiency is possible in solar and thermophotovoltaic applications. A thermodynamic model is used to show quantitatively how the separation of absorption and luminescent peaks under global illumination is related to the spread of quantum-dot sizes. Hence, the redshift can be determined during the growth process. The model can be used to optimize concentrator performance and to study the effect of reabsorption, which is important for high concentration even if the quantum efficiency is unity. This model provides a quantitative explanation for the contribution of the spread of sizes to the redshift, which should help in the extraction of the much smaller, single-dot effects.

Quantum dot containing nanocomposite thin films for photoluminescent solar concentrators

“…By choosing dyes with suitable absorption and emission properties, stacks of fluorescent collectors can be designed, with absorption edges chosen in a manner similar to multi-junction photovoltaic cells. The same geometry has been used in quantum dot solar concentrators (Barnham et al, 2000;Gallagher et al, 2004), where photoluminescent semiconductor nanocrystals replace the fluorescent dyes. Instead of immersing quantum dots in transparent resins, we deposit CdS quantum dot containing silicon dioxide films (SiO 2 :CdS) on highly transparent low iron glass substrates by sol-gel dip-coating.…”

“…One of the most promising applications might be planar photoluminescent concentrators for photovoltaics where high concentration factors on the solar cells can be achieved even for diffuse solar radiation. Such devices have originally been designed on the basis of organic dyes (Goetzberger and Greubel, 1977), and might benefit from a considerably improved lifetime when replacing the organic fluorescent substances by inorganic quantum dots (Barnham et al, 2000;Gallagher et al, 2004). Additionally, the tunability of the optical properties by the size of the nanocrystals provide a large amount freedom for the design and optimization of such devices.…”

Flexible concentrator photovoltaics based on microscale silicon solar cells embedded in luminescent waveguides

“…The first effect results from partial overlap of the absorption and emission spectra of the luminophore. This overlap can be reduced with materials (for example, semiconductor quantum dots) 14,15 that have large Stokes shifts, or with alternative conversion processes based on near-field energy transfer 16 or phosphorescence 17 . The waveguide losses can be decreased by increasing the difference between the index of refraction of the LSC material and its surroundings, and by engineering the structures to avoid scattering.…”

Modelling the Effect of Device Geometry on Concentration Ratios of Quantum Dot Solar Concentrators

“…Mirrors can be placed adjacent and parallel to the rear surface and sides 1, 2 and 3 to reflect light that may be outside the angular range for TIR. A quantum dot solar concentrator (QDSC) [3] operates in the same way as an LSC, but employs quantum dots rather than a luminescent dye. Current QDSCs [4] are fabricated using square plates of uniform thickness.…”