Development of Selective Solar Absorber Coating by・ Stratified Integration of Mesoscopic Structures

现在是促进能源从化石燃料向天然替代能源转变的时候了。光热能量转换是解决方案之一。这种太阳能吸收涂层的表面需要高的太阳能吸收率（α）和伴随的低热发射率（ε），即，太阳能选择性为了提高光热能量转换效率（η），本论文重点研究了纳米颗粒和粗糙表面等介观结构。首先，评价了纳米结构Ag的光学性质和热稳定性。在此基础上，成功地实现了高性能的光热转换（在373 K时，AM1.5的光热转换效率η=0.72，极限温度为550 K）。这是用射频反应溅射法制备的Al-N薄膜。我们澄清了高a的原因之一是由表面粗糙度引起的梯度折射率。因此，在本研究中，我们制备了一种具有粗糙表面的太阳能选择性吸收涂层。首先，通过在两种不同的衬底温度下两步沉积Al层的方法制备具有适当表面粗糙度的Al膜作为红外反射器，这有助于降低e.然后在此铝反射镜上淀积铝氮薄膜作为吸收层。此外，一个透明的氮化铝薄膜被检查用作抗反射器的太阳能选择性吸收器与表面粗糙度。实验结果表明，在室温下，α=0.92（AM1.5），ε=0.06（373 K），η=0.86。通过在298 K下沉积ITO膜，然后在773 K下退火，可以成功地抑制发射率。

It is the time to promote the energy shift from fossil fuel to natural alternative energy resources. The photothermal energy conversion is one of the solutions. Surfaces of this kind of solar absorber coating require a high solar absorptance (α) and a concomitant low thermal emittance (ε), i.e., solar selectivity. In order to improve photothermal energy conversion efficiency (η), the mesoscopic structure such as nano-particles and rough surface are especially concerned in this study.First of all, optical properties and thermal stability of the nano-structured Ag are evaluated. Based on the result, the high performance of photothermal conversion (η=0.72 at 373K for AM1.5 and ultimate temperature of 550K) is successfully realized.We recently developed a solar absorber coating with high a induced by surface roughness. This is the Al-N film prepared by reactive rf sputtering. We clarified that one of the reasons for the high a is the gradient-refractive index caused by the surface roughness. Unfortunately, the t was rather high and this should be improved.Therefore, in this study, a solar selective absorber coating with surface roughness is fabricated. First, the Al film with proper surface roughness, the degree of which is prepared by a method of two-step deposition of an Al layer at two different substrate temperatures, is prepared as an infrared reflector, which contributes to the low e. Then the Al-N film as an absorber layer is deposited on this Al reflector. In addition, a transparent AlN film is examined for use as an anti-reflector in the solar selective absorber with surface roughness. As the result, high performance of α=0.92(AM1.5),ε=0.06(373K), and then η=0.86 have been realized.As the other method, the courting by the Sn doped indium oxide (ITO) film on the AI-N film was examined. By the deposition of ITO film at 298K followed by the annealing at 773K, the emittance could be successfully suppressed.