Effects of narrowband transport on near-field and far-field thermophotonic conversion
Effects of narrowband transport on near-field and far-field thermophotonic conversion
复制标题
DOI：
10.1117/1.jpe.9.032714
复制
发表时间：
2019-03
影响因子：
1.7
通讯作者：
Sean McSherry;T. Burger;A. Lenert
中科院分区：
文献类型：
--
作者：
Sean McSherry;T. Burger;A. Lenert
抽象的。理想的热光伏（TPV）转换器在单色辐射传输的极限下接近卡诺效率，从而激发了窄带热发射器和吸收器的设计。在这里，我们调查这种趋势是否持有转换器与现实的损失，通过研究传输带宽的影响，远场和近场TPV和热光子（TPX）转换器的性能。为了弥合近场和远场制度，分析依赖于一个近似，即近场谱能通量是远场通量的缩放版本，这是验证弱吸收材料使用严格的近场模拟。我们表明，最佳带宽取决于转换器的类型。对于具有实际热损失的远场TPV，窄带传输通常对效率有害，因为转换器变得更容易受到寄生损失的影响。然而，只要激发势垒与热能相当，窄带传输就能提高TPX转换器和近场TPV的效率。给定与TPV相同的激发能垒，TPX转换器由于施加的偏压而受益于更大的可用光子态密度。这项研究表明，近场TPX转换器与一个大的应用偏置有最大的有用的能量通量寄生损耗的比例。利用这种机制进行实际改进取决于大的近场增强，从而提高光子提取。
Abstract. Ideal thermophotovoltaic (TPV) converters approach Carnot efficiency in the limit of monochromatic radiative transfer, motivating the design of narrowband thermal emitters and absorbers. Here, we investigate whether this trend holds for converters with realistic losses by studying the effects of transmission bandwidth on the performance of far-field and near-field TPV and thermophotonic (TPX) converters. To bridge the near-field and far-field regimes, the analysis relies on an approximation that the near-field spectral energy flux is a scaled version of the far-field flux, which is validated for weakly absorbing materials using a rigorous near-field simulation. We show that the optimal bandwidth depends on the type of converter. For far-field TPVs with realistic heat losses, narrowband transport is typically detrimental to the efficiency because the converter becomes more susceptible to parasitic loss. However, narrowband transport boosts efficiencies in TPX converters and near-field TPVs as long as the excitation barrier is comparable with the thermal energy. Given the same excitation energy barrier as TPVs, TPX converters benefit from a larger available photon density of states due to the applied bias. This study suggests that near-field TPX converters with a large applied bias have the largest ratio of useful energy flux to parasitic loss. Leveraging this mechanism for actual improvement is contingent on large near-field enhancements improving photon extraction.