NN-LABS, LLC

This Small Business Innovation Research Phase 1 project intends to demonstrate a spectral down-converter based on metal ion-doped nanocrystalline quantum dots to increase the efficiency of polycrystalline silicon solar cells. Attempts to add a luminescent spectral downconversion layer to semiconductor solar cells to shift inefficiently-utilized light below 500 nm in the solar spectrum to longer wavelength have been made over several decades because of predicted relative efficiency gains of 10-20%, a very significant improvement. No practical device has resulted because of the very high performance requirements for the emissive overlayer. Manganese-doped zinc selenide nanoparticles exhibit little absorption longer than 500 nm, yet luminescence with high efficiency in a single band near 600 nm, thus eliminating both optical filtering and luminescence reabsorption. The objective of this research is to evaluate this material?s potential to be a practical spectral downconverter. This involves modeling calculations using solution data as input, measurement of actual performance gains using liquid-reservoir downconverter plus solar cell, and preparation of concentrated thin solid films and their photophysical evaluation. It will then be possible to determine the efficiency gains that can be expected from an integrated thin-film downconverter/solar cell module. This, in turn, will drive a decision on commercialization development. Broader Impacts/Commercial Potential: Polycrystalline silicon solar cells represent a mature technology, and even small improvements in their efficiency are very difficult and costly to realize. Yet the advantages of improving their performance is potentially enormous, both commercial and societal, given their current and anticipated increased utilization. Therefore a gain in efficiency on the order of 10% (relative) would have a large commercial impact, especially if it can be obtained from a fairly simple and inexpensive add-on layer. Spectral downconversion has been recognized for many years as having the potential to deliver this performance gain. But materials that meet the long list of requirements for such a practical device have been lacking. This includes cadmium selenide quantum dots, which have been proposed and tested in the last several years without success. The new manganese-doped zinc selenide quantum dots, which lack cadmium?s toxicity, have not been evaluated for this application and appear to possess the needed properties to deliver the performance. By conducting the research outlined, it will be possible to determine if this is so, and also to provide technological understanding as to why or why not that is the case, which is valuable for future efforts and improvements.

Clarification of Codes