In a conventional flat plate solar cell under direct sunlight,light is received from the solar disk,but is re-emitted isotropically.This isotropic emission corresponds to a significant entropy increase in the solar ce...In a conventional flat plate solar cell under direct sunlight,light is received from the solar disk,but is re-emitted isotropically.This isotropic emission corresponds to a significant entropy increase in the solar cell,with a corresponding drop in efficiency.Here,using a detailed balance model,we show that limiting the emission angle of a high-quality GaAs solar cell is a feasible route to achieving power conversion efficiencies above 38%with a single junction.The highest efficiencies are predicted for a thin,light trapping cell with an ideal back reflector,though the scheme is robust to a non-ideal back reflector.Comparison with a conventional planar cell geometry illustrates that limiting emission angle in a light trapping geometry not only allows for much thinner cells,but also for significantly higher overall efficiencies with an excellent rear reflector.Finally,we present ray-tracing and detailed balance analysis of two angular coupler designs,show that significant efficiency improvements are possible with these couplers,and demonstrate initial fabrication of one coupler design.展开更多
The interplay between free electrons,light,and matter offers unique prospects for space,time,and energy resolved optical material characterization,structured light generation,and quantum information processing.Here,we...The interplay between free electrons,light,and matter offers unique prospects for space,time,and energy resolved optical material characterization,structured light generation,and quantum information processing.Here,we study the nanoscale features of spontaneous and stimulated electron–photon interactions mediated by localized surface plasmon resonances at the tips of a gold nanostar using electron energy-loss spectroscopy(EELS),cathodoluminescence spectroscopy(CL),and photon-induced near-field electron microscopy(PINEM).Supported by numerical electromagnetic boundary-element method(BEM)calculations,we show that the different coupling mechanisms probed by EELS,CL,and PINEM feature the same spatial dependence on the electric field distribution of the tip modes.However,the electron–photon interaction strength is found to vary with the incident electron velocity,as determined by the spatial Fourier transform of the electric near-field component parallel to the electron trajectory.For the tightly confined plasmonic tip resonances,our calculations suggest an optimum coupling velocity at electron energies as low as a few keV.Our results are discussed in the context of more complex geometries supporting multiple modes with spatial and spectral overlap.We provide fundamental insights into spontaneous and stimulated electron-light-matter interactions with key implications for research on(quantum)coherent optical phenomena at the nanoscale.展开更多
基金Thanks to D Callahan,M Sheldon and J van de Groep for insightful discussions and advice on the manuscript.The authors also found advice from O Miller on handling non-radiative recombination,R Briggs on mode structure calculations,J Zipkin on numerical methods and C Eisler on internal fluorescence yield derivations extremely helpful.The authors are grateful for technical assistance from G Vollenbroek.The Caltech researchers are supported by the‘Light-Material Interactions in Energy Conversion’Energy Frontier Research Center funded by the US Department of Energy,Office of Science,Office of Basic Energy Sciences under grant DE-SC0001293(EK and HA).EK also acknowledges the support of the Resnick Sustainability Institute.Researchers of the Center for Nanophotonics at AMOLF are supported by the research program of FOM which is financially supported by NWO and by the European Research Council.
文摘In a conventional flat plate solar cell under direct sunlight,light is received from the solar disk,but is re-emitted isotropically.This isotropic emission corresponds to a significant entropy increase in the solar cell,with a corresponding drop in efficiency.Here,using a detailed balance model,we show that limiting the emission angle of a high-quality GaAs solar cell is a feasible route to achieving power conversion efficiencies above 38%with a single junction.The highest efficiencies are predicted for a thin,light trapping cell with an ideal back reflector,though the scheme is robust to a non-ideal back reflector.Comparison with a conventional planar cell geometry illustrates that limiting emission angle in a light trapping geometry not only allows for much thinner cells,but also for significantly higher overall efficiencies with an excellent rear reflector.Finally,we present ray-tracing and detailed balance analysis of two angular coupler designs,show that significant efficiency improvements are possible with these couplers,and demonstrate initial fabrication of one coupler design.
基金This project has received funding from the European Research Council(ERC)under the European Union’s Horizon 2020 research and innovation programme(Grant Agreement No.695343 and Grant Agreement No.101017720(FET-Proactive EBEAM))The work at AMOLF was partly financed by the Dutch Research Council(NWO)+8 种基金The work at the University of Göttingen was funded by the Deutsche Forschungsgemeinschaft(DFG,German Research Foundation)(217133147/SFB 1073 project A05 and 255652344/SPP 1840 project‘Kohärente Wechselwirkungen starker optischer Nahfelder mit freien Elektronen’)and the Gottfried Wilhelm Leibniz programThe work at URV was financed by Spanish Ministerio de Economia y Competitividad(MINECO)(CTQ2017-88648R and RYC-2015-19107)the Generalitat de Cataluña(2017SGR883)the Universitat Rovira i Virgili(2018PFR-URV-B2-02)the Banco Santander(2017EXIT-08)J.G.A.received funding from the ERC(Advanced Grant No.789104-eNANO)Spanish MINECO(MAT2017-88492-R and SEV2015-0522)Catalan CERCA ProgramFundacióPrivada Cellex.
文摘The interplay between free electrons,light,and matter offers unique prospects for space,time,and energy resolved optical material characterization,structured light generation,and quantum information processing.Here,we study the nanoscale features of spontaneous and stimulated electron–photon interactions mediated by localized surface plasmon resonances at the tips of a gold nanostar using electron energy-loss spectroscopy(EELS),cathodoluminescence spectroscopy(CL),and photon-induced near-field electron microscopy(PINEM).Supported by numerical electromagnetic boundary-element method(BEM)calculations,we show that the different coupling mechanisms probed by EELS,CL,and PINEM feature the same spatial dependence on the electric field distribution of the tip modes.However,the electron–photon interaction strength is found to vary with the incident electron velocity,as determined by the spatial Fourier transform of the electric near-field component parallel to the electron trajectory.For the tightly confined plasmonic tip resonances,our calculations suggest an optimum coupling velocity at electron energies as low as a few keV.Our results are discussed in the context of more complex geometries supporting multiple modes with spatial and spectral overlap.We provide fundamental insights into spontaneous and stimulated electron-light-matter interactions with key implications for research on(quantum)coherent optical phenomena at the nanoscale.