Improvement in Systematized Photo-thermoelectric Energy Conversion Film by Controlling Mesoscopic Film Structure

为了提高系统化光热电能量转换膜的性能，从控制光热转换膜和热电转换膜的介观结构的意义上研究了光热转换膜和热电转换膜的单个功能组件。作为光热转换膜，在MgO层之间形成了纳米结构的Ag层。银层的形貌经过中间纳米结构，即岛状膜或迷宫裂纹膜，从分散的纳米颗粒到连续的膜有系统的变化。研究发现，具有这些中间纳米结构的银膜具有应用于太阳能吸收器涂层的有效光学性能，即在可见光和近红外区域具有较大的吸光度和热稳定性。在纳米结构银层的基础上，成功制备了具有功能梯度结构的热稳定选择性太阳能吸收膜。在典型工作温度为373K下，空气质量1 （AM1）的光热转换效率为0.72,AM1.5的光热转换效率为0.66，AM2的光热转换效率为0.59。用氩气和氮气混合气溅射制备了Al-N薄膜。N_2分压浓度（C_<N2>）发生变化。当C_<N2>的n_2浓度为7.3%时，样品的太阳吸收率最高，为0.95。α值高的原因是由于薄膜生长过程中表面粗糙度的增加而引起的梯度折射率的抗反射效应。在一种很有前途的热电材料CoSb_3中，由于晶格的存在，其热导率的降低是一个问题。探讨了用Co-Sb-N三元体系形成多孔结构的可能性。由于N和/或Sb的升华，形成了高密度的纳米级空位。因此，形成Co-Sb-N三元薄膜并进行退火是控制薄膜多孔形貌的有效方法之一。为了评价薄膜的热扩散率，研究了用红外摄像机代替热电偶的交流量热法。将该方法应用于SUS304的热扩散系数的测量。验证了非接触式测温方法的实用性。少

In order to improve the performance of systematized photo-thermoelectric energy conversion film, individual functional components, i.e., photo-thermal conversion film and thermoelectric conversion film, are studied in the sense of controlling their mesoscopic structure.As a photo-thermal energy conversion film, nano-structured Ag layers sandwiched between MgO layers are formed. The morphology of Ag layer changes systematically from the dispersed nano-particles to the continuous film via the intermediate nano-structures, i.e., the insular film or the maze-cracked film. It is found that the Ag films with these intermediate nano-structures have the effective optical properties applying to the solar absorber coating, i.e., the large absorptance at both visible and near infrared regions and the thermal stability. Based on the results obtained about the nano-structured Ag layers, a thermally stable selective solar absorber coating with the functional graded structure is successfully fabricat … More ed. Then the photo-thermal energy conversion efficiency of 0.72 for air mass one (AM1), 0.66 for AM1.5, and 0.59 for AM2 are realized at a typical operating temperature of 373K. Al-N films are also formed by rf sputtering using Ar and N_2 gas mixture. The concentration of partial N_2 gas pressure (C_<N2>) is changed. The specimen with 7.3%N_2 of C_<N2> shows the highest solar energy absorptance (α) of 0.95 for the air mass one. The reason for the high value of α is the antireflection effect due to the gradient-refractive index caused by the enhanced surface roughness during film growth.In a promising thermoelectric material of CoSb_3, the problem is to reduce the thermal conductivity due to lattice. A possibility to form the porous morphology by using Co-Sb-N ternary system is examined. High density of vacancy with a scale of nanometer due to sublimation of N and/or Sb is successively formed. As a result, it may be mentioned that the formation of Co-Sb-N ternary film and following annealing is one of the noble methods to control the porous morphology of the film.In order to evaluate thermal diffusivity of the film, the AC calorimetric method by using infrared camera instead of thermocouple is examined. This method is applied to the measurement of thermal diffusivuty of SUS304. Then the usefulness of the noncontact temperature measurement method is confirmed. Less