论文标题
能量收集的热增强光致发光:从基本面到工程优化
Thermally enhanced photoluminescence for energy harvesting: from fundamentals to engineering optimization
论文作者
论文摘要
如普朗克定律所述,热发射的辐射仅取决于人体的发射率和温度,并且随着任何发射波长的温度升高而单调地增加。非热辐射(例如光致发光)是一种基本的光物质相互作用,通常涉及吸收能量光子,热化和红移光子的发射。这样的量子过程受速率保护的约束,这取决于量子效率。过去,尚未研究速率保存对明显热激发的作用。最近,我们介绍了与热发射相反的理论和实验证明,即在温度升高时,在每种光子均升高时,PL速率是保守的。温度进一步升高导致突然过渡到热发射,其中光子速率急剧增加。我们还证明了这种热增强的PL如何在相似温度下产生比热发射的数量级更富的光子。这些发现表明,TEPL是一个理想的光泵,可以在最大理论效率为70%的光伏中收获热损失,实用概念可能达到45%的效率。在这里,我们将TEPL概念移至工程水平上,并将CR:ND:YAG作为设备级PL材料,吸收高达1微米波长的太阳辐射,并通过能量光子的热化加热。它的蓝升发射可以匹配GAAS细胞,是吸收功率的20%。基于详细的平衡模拟,这种材料与适当的光子管理结合可以达到34%的功率转换效率。这些结果提高了对TEPL成为光伏技术的潜力的信心。
The radiance of thermal emission, as described by Planck law, depends only on the emissivity and temperature of a body, and increases monotonically with the temperature rise at any emitted wavelength. Nonthermal radiation, such as photoluminescence, is a fundamental light matter interaction that conventionally involves the absorption of an energetic photon, thermalization, and the emission of a redshifted photon. Such a quantum process is governed by rate conservation, which is contingent on the quantum efficiency. In the past, the role of rate conservation for significant thermal excitation had not been studied. Recently, we presented the theory and an experimental demonstration that showed, in contrast to thermal emission, that the PL rate is conserved when the temperature increases while each photon is blueshifted. A further rise in temperature leads to an abrupt transition to thermal emission where the photon rate increases sharply. We also demonstrated how such thermally enhanced PL, TEPL, generates orders of magnitude more energetic photons than thermal emission at similar temperatures. These findings show that TEPL is an ideal optical heat pump that can harvest thermal losses in photovoltaics with a maximal theoretical efficiency of 70%, and practical concepts potentially reaching 45% efficiency. Here we move the TEPL concept onto the engineering level and present Cr:Nd:YAG as device grade PL material, absorbing solar radiation up to 1 micrometer wavelength and heated by thermalization of energetic photons. Its blueshifted emission, which can match GaAs cells, is 20% of the absorbed power. Based on a detailed balance simulation, such a material coupled with proper photonic management can reach 34% power conversion efficiency. These results raise confidence in the potential of TEPL becoming a disruptive technology in photovoltaics.