Quantum-dot concentrator and thermodynamic model for the global redshift

The use of quantum dots can turn the old concept of a luminescent solar col lector 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 p ossible in solar and thermophotovoltaic applications. A thermodynamic model is used to show quantitatively how the separation of absorption and lumine scent peaks under global illumination is related to the spread of quantum-d ot 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 explana tion for the contribution of the spread of sizes to the redshift, which sho uld help in the extraction of the much smaller, single-dot effects. (C) 200 0 American Institute of Physics. [S0003-6951(00)03809-2].