The International Research Fellowship Program enables U.S. scientists and engineers to conduct nine to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad.
This award will support a twenty-four-month research fellowship by Dr. Michael Y. Levy to work with Dr. Antonio Marti at Universidad Politecnica de Madrid in Spain.
This research addresses the central impediment towards realizing an intermediate band solar cell (IBSC), namely fabricating an intermediate band (IB) absorbing medium. The context of this work is the conversion of solar energy to electrical energy with efficiencies beyond that of the Shockley-Queisser limit (40%) and towards the Landsberg-Tonge limit (93%). The IBSC has a limiting efficiency (63%), nearly reaching the limit of three-junction tandems (64%). Theoretical calculations show that GaP:Ti alloys may form as IB materials. This, in conjunction with an array of experimental studies on these alloys, leads to the following hypothesis: ion-implanting a large concentration of Ti into GaP substrates is an excellent method and material system with which to demonstrate the salient features of IB materials and fabricate an IBSC. The solar cells are characterized to determine their performance. The expected result is an absorbing medium, with carrier lifetime sufficient for solar energy applications, that not only allows standard photo-induced electronic transitions between states in the valence band continuum and conduction band continuum, but also photo-induced electronic transitions between deep states and states in the two continua, respectively. The novelty of this approach towards implementing an IB material is that a very large density of deep-level states is present. The scientific merit of this research is demonstrating this approach for obtaining high-efficiency solar energy conversion.
The research activity's obvious impact on society may be a higher efficiency solar cell. The activity may have broader impact within the opto-electronics communities, and the U.S. solar energy program. The approach may find use in fabricating up- or down-converters, either of which may be used in conjunction with standard solar cells to boost their efficiencies, multi-color light emitting diodes, and multi-wavelength photodetectors. Finally, exposure to a large set of European researchers collaborating with the host institution may impact the U.S. solar program. The knowledge gained and networks formalized increase the potential for future collaboration with European counterparts and thus the scope of the US effort in high efficiency solar research.
