Ilic Ognjen, Jablan Marinko, Joannopoulos John D, Celanovic Ivan, Soljacić Marin
Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139, USA.
Opt Express. 2012 May 7;20(10):A366-84. doi: 10.1364/oe.20.00a366.
Near-field thermophotovoltaic (TPV) systems with carefully tailored emitter-PV properties show large promise for a new temperature range (600 – 1200K) solid state energy conversion, where conventional thermoelectric (TE) devices cannot operate due to high temperatures and far-field TPV schemes suffer from low efficiency and power density. We present a detailed theoretical study of several different implementations of thermal emitters using plasmonic materials and graphene. We find that optimal improvements over the black body limit are achieved for low bandgap semiconductors and properly matched plasmonic frequencies. For a pure plasmonic emitter, theoretically predicted generated power density of 14 W/cm2 and efficiency of 36% can be achieved at 600K (hot-side), for 0.17eV bandgap (InSb). Developing insightful approximations, we argue that large plasmonic losses can, contrary to intuition, be helpful in enhancing the overall near-field transfer. We discuss and quantify the properties of an optimal near-field photovoltaic (PV) diode. In addition, we study plasmons in graphene and show that doping can be used to tune the plasmonic dispersion relation to match the PV cell bangap. In case of graphene, theoretically predicted generated power density of 6(120) W/cm2 and efficiency of 35(40)% can be achieved at 600(1200)K, for 0.17eV bandgap. With the ability to operate in intermediate temperature range, as well as high efficiency and power density, near-field TPV systems have the potential to complement conventional TE and TPV solid state heat-to-electricity conversion devices.
具有精心定制的发射极-光伏特性的近场热光伏（TPV）系统在新的温度范围（600 - 1200K）的固态能量转换方面显示出巨大潜力，在该温度范围内，传统热电（TE）器件因温度过高无法运行，而远场TPV方案则存在效率和功率密度低的问题。我们对使用等离子体材料和石墨烯的几种不同热发射体实现方式进行了详细的理论研究。我们发现，对于低带隙半导体和适当匹配的等离子体频率，相对于黑体极限可实现最佳改进。对于纯等离子体发射极，理论预测在600K（热端）时，对于0.17eV带隙（InSb），可实现14 W/cm²的发电功率密度和36%的效率。通过开发有洞察力的近似方法，我们认为与直觉相反，大的等离子体损耗有助于增强整体近场传输。我们讨论并量化了最优近场光伏（PV）二极管的特性。此外，我们研究了石墨烯中的等离子体，并表明可以使用掺杂来调整等离子体色散关系以匹配光伏电池的带隙。对于石墨烯，理论预测在600（1200）K时，对于0.17eV带隙，可实现6（120）W/cm²的发电功率密度和35（40）%的效率。由于能够在中间温度范围内运行，以及具有高效率和功率密度，近场TPV系统有潜力补充传统的TE和TPV固态热电转换装置。
