In solar cells, the mismatch between the Sun's emission spectrum and the cells' absorption profile limits the efficiency of such devices, while in incandescent light bulbs, most of the energy is lost as heat. One way to avoid the waste of a large fraction of the radiation emitted from hot objects is to tailor the thermal emission spectrum according to the desired application. This strategy has been successfully applied to photonic-crystal emitters at moderate temperatures, but is exceedingly difficult for hot emitters (>1,000 K). Here, we show that a plain incandescent tungsten filament (3,000 K) surrounded by a cold-side nanophotonic interference system optimized to reflect infrared light and transmit visible light for a wide range of angles could become a light source that reaches luminous efficiencies (∼40%) surpassing existing lighting technologies, and nearing a limit for lighting applications. We experimentally demonstrate a proof-of-principle incandescent emitter with efficiency approaching that of commercial fluorescent or light-emitting diode bulbs, but with exceptional reproduction of colours and scalable power. The ability to tailor the emission spectrum of high-temperature sources may find applications in thermophotovoltaic energy conversion and lighting.
Bibliographical noteFunding Information:
The authors thank P. Rebusco for critical reading and editing of the manuscript, and J.J. Senkevich, W. Chan, S. Kooi, I. Wang, A. Cukierman, M. Harradon, A. Musabeyoglu, S. Johnson and Y. Xiang Yeng for valuable input. This work was partially supported by the Army Research Office through the ISN (contract no.W911NF-13-D0001). The fabrication part of the effort was supported by S3TEC, an Energy Frontier Research Center funded by the US Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES) (award no. DE-SC0001299/DE-FG02-09ER46577).
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