一般的太陽能選擇性吸收膜(Solar Selective Absorber, SSA)是在基板表面直接塗上吸熱塗料或氣相沉積的方式製作，因此多為平面的構造，大部分的設計會隨著入射光角度增加轉換效率下降幅度甚多，而許多研究指出微奈米的表面結構對於大角度入射光有很好的抗反射效果，因此本研究嘗試製作次微米結構的太陽能選擇性吸收膜，增加大角度入射光的轉換效率。 實驗先以旋轉塗佈的方式再玻璃基板上製作出聚苯乙烯微奈米球自組裝單層鋪排，再搭配二氧化鈦溶膠凝膠的塗佈，製作出平均直徑387 nm、高度117.8 nm的二氧化鈦碗形孔洞陣列微結構。 太陽能選擇性吸收膜的部分則利用銀作為熱輻射高反射層降低紅外光熱輻射放射率，鈦和二氧化鈦作為拓寬吸收波段的金屬-介電質互層堆疊(D-M-D)，而最表面鍍上一層二氧化矽利用其相對的低折射率、高表面硬度達到抗反射及抗刮蝕的效果，以真空蒸鍍的方式將此Ag/ TiO2/ Ti/ TiO2/ SiO2多層型選擇性吸收膜覆蓋在二氧化鈦碗形孔洞陣列微結構上。 相較於相同堆疊的平面太陽能選擇性吸收膜，增加了此微結構的太陽能選擇性吸收膜在8~75度角、波長400~1000奈米的入射光照射下，吸收率皆有程度不等的提升，提升幅度呈現隨角度加大的趨勢，在75度入射光下吸收率提升了6.5%，而在8~75度入射角下整體平均效能(α/ε)微幅提升了0.37%。 ;Solar selective absorber (SSA) is a solar energy conversion device normally fabricated using painting or vapor-deposition methods on a flat substrate. The energy conversion efficiency of the flat surface can be reduced as the incident angle increased. To solve this problem, microstructures are claimed including wide-angle antireflection. Thus, the energy conversion efficiency of the SSA with micro-structures was studied for wide-angle incident lights. Based on the self-assembly of Polystyrene(PS) spheres and the sol-gel coating of TiO2, the TiO2 microstructure array of hexagonal close packing(HCP) and bowl-like holes were achieved. The hole size was 387 nm in diameter and 117.8 nm in height on the surface of BK-7 substrate. Then a multi-layered SSA was deposited on the microstructure by E-gun evaporator. The SSA consist of metals and dielectrics as follows: a thin Ag layer was applied as IR reflector to reduce the thermal emission of substrate; Ti and TiO2 composed a Dielectric-Metal-Dielectric (D-M-D) stack to broaden the anti-reflection band of visible spectrum; and SiO2 was coated at last as an anti-reflection and anti-scratch layer. The SSA came to be a stack of Ag/ TiO2/ Ti/ TiO2/ SiO2 on the surface of microstructure. The average absorptance(α) between 400nm ~ 1000nm of the micro-structured SSA is successfully improved for the incident angle between 8°~75° comparing to that of flat ones. The average absorptance increases 6.5% for the 75° incident angle and the average conversion efficiency (α/ε) increases 0.37% for the incident angle between 8°~75°.
