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

现在是推动能源从化石燃料向自然替代能源转变的时候了。光热转换是解决这一问题的方法之一。这种太阳能吸收涂层的表面需要高的太阳吸收比(α)和伴随而来的低的热发射率(ε)，即太阳的选择性。为了提高光热转换效率(η)，本研究特别关注纳米粒子和粗糙表面等介观结构。首先，对纳米结构银的光学性质和热稳定性进行了评价。在此基础上，成功地实现了高性能的光热转换(373K时η=0.72，极限温度为550K)。我们最近开发了一种由表面粗糙度引起的高a太阳能吸收涂层。这是用反应射频溅射法制备的Al-N薄膜。我们阐明了a偏高的原因之一是表面粗糙度引起的梯度折射率。为此，本研究制备了一种表面粗糙度较高的太阳能选择性吸收涂层。首先，在两种不同的衬底温度下，通过两步沉积Al层的方法，制备出具有适当表面粗糙度的Al膜作为红外反射器，以获得较低的e，然后在该Al反射器上沉积Al-N膜作为吸收器层。此外，还研究了一种透明的氮化铝薄膜作为表面粗糙度太阳选择性吸收材料的减反射器。结果表明，α=0.92(AM1.5K)，ε=0.06(373K)，η=0.86。作为另一种方法，研究了掺锡氧化铟薄膜对Al-N薄膜的追求。通过在298K下沉积ITO薄膜，然后在773K下进行热处理，可以成功地抑制发射度。

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.