Solar selective absorbers have significant applications in various photothermal conversion systems. In this work, a global optimization method based on genetic algorithm was developed by directly optimizing the solar photothermal conversion efficiency of a nano-chromium (Cr) film-based solar selective absorber aiming to work at the specified working temperature and solar concentration. In consideration of the semi-transparent metal absorption layer employed in multilayered solar selective absorbers, the optical constants of ultrathin Cr film were measured by spectroscopic ellipsometer and introduced into the optimization process. The ultrathin Cr film-based solar selective absorber was successfully designed and fabricated by the magnetron sputtering method for the working temperature at 600 K and a solar concentration of 1 Sun. The measured reflectance spectra of the sample show a good agreement with the numerical simulations based on measured optical constants of ultrathin Cr film. In comparison, the simulated results by using the optical constants of bulk Cr film or literature data exhibit a large discrepancy with the experimental results. It demonstrates the significance of considering the actual optical constants for the semi-transparent metal absorption layer in the design of nano-metal film-based solar selective absorber.

中文翻译：

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基于测得的纳米Cr薄膜光学常数的太阳能选择性吸收剂的精确设计

太阳能选择性吸收剂在各种光热转化系统中具有重要的应用。在这项工作中，通过直接优化基于纳米铬（Cr）薄膜的太阳能选择性吸收器的太阳能光热转换效率，开发了一种基于遗传算法的全局优化方法，旨在在指定的工作温度和太阳光浓度下工作。考虑到在多层太阳能选择性吸收器中使用的半透明金属吸收层，通过椭圆偏振光谱仪测量了超薄Cr膜的光学常数，并将其引入优化过程。通过磁控溅射法成功地设计和制造了超薄铬膜基太阳能选择性吸收剂，其工作温度为600 K，太阳浓度为1Sun。样品的反射光谱测量结果与基于超薄铬膜光学常数的数值模拟结果吻合良好。相比之下，使用块状Cr膜的光学常数或文献数据进行的模拟结果与实验结果存在较大差异。它证明了在设计基于纳米金属膜的太阳能选择性吸收体时考虑半透明金属吸收层的实际光学常数的重要性。