Comment on “Three-dimensional photonic-crystal emitter for thermal photovoltaic power generation” [Appl. Phys. Lett. 83, 380 (2003)]

In a recent article, Lin et al. [Appl. Phys. Lett. 83, 380 (2003)] reported on the light-emitting properties of three-dimensional tungsten photonic crystals and their potential applications as improved thermal emitters in thermophotovoltaic (TPV) systems. Their findings have attracted considerable interest throughout the media and the application of this type of materials has been praised as a potential superior future energy source; e.g., in waste heat-driven electrical generators (http://www.photonics.com). The results of the theoretical modeling in the work of Lin et al. suggest that a TPV system can achieve higher heat to electric energy conversion efficiencies in combination with a three-dimensional tungsten photonic crystal than with any conventional selective thermal emitter. These theoretical results are based on the experimental observation that the photonic crystal, when heated to a given temperature, emits more radiation in certain spectral regimes than a black body of the same temperature. This experimental observation shall briefly be discussed here.