埋入式仿生奈米結構用以提升薄膜太陽能電池光學吸收效率

Embedded Biomimetic Nnanostructures for Enhanced Optical Absorption in Thin-film Solar Cells

蔡閔安 ； 韓皓惟 ； 蔡育霖 ； 曾斌誠 ； 余沛慈 ； 郭浩中 ； 沈昌宏 ； 謝嘉民

《國家奈米元件實驗室奈米通訊》 18卷3期 (2011/09) Pp. 10-15

https://doi.org/10.29913/NDLC.201109.0002

摘要

由於薄膜太陽能電池的主動吸收層太薄使得光學吸收受到限制，因此光線管理技術變得格外重要。傳統上使用的抗反射以及光捕捉結構是獨立分開的技術，我們在此希望利用一個埋入式仿生奈米結構(Embedded Biomimetic Nanostructure, EBN)來製作非晶矽薄膜太陽能電池而同時達成抗反射及光捕捉效果。將氮化矽薄膜沉積在透明玻璃之上，接著利用聚苯乙烯奈米球微影術再搭配反應式離子蝕刻在氮化矽薄膜上製作EBN結構，而此EBN結構的輪廓會隨著沉積非晶矽材料時一層一層的轉移。藉此所製作的太陽能電池可同時具備抗反射與光捕捉效應而在外部量子效率上有寬頻譜的提升，我們與使用Asahi U玻璃基板所製作的元件做比較，此Asahi U玻璃基板為業界普遍使用的具優良光捕捉效應之基板。整體來說，EBN基板太陽能電池可以達到17.74mA/平方公分的較大短路電流密度，相對於沒有結構的平的元件有37.63%的增加，而光電轉換效率可由5.36%提升至8.32%。此外，此EBN元件即使在光線以60°大角度入射時依然能維持非常好的效率，這有助於使用在真實環境之中。此新式的結構亦可用於其他薄膜太陽能電池而並不侷限在非晶矽薄膜太陽能電池之上。

關鍵字

光捕捉效應 ； 抗反射 ； 奈米結構 ； 非晶矽薄膜太陽能電池

並列摘要

Light-management is critical to thin .lm solar cells due to their usually limited optical absorption in the active layer. Conventional approaches involve employing separate techniques for antireflection and light trapping. Here, we demonstrate an embedded biomimetic nanostructure (EBN) that achieves both effects for hydrogenated amorphous silicon (a-Si:H) solar cells. The fabrication of EBNs is accomplished by patterning an index-matching silicon-nitride layer deposited on a glass substrate using polystyrene nanospheres lithography, followed by reactive ion etching. The profile of EBN is then reproduced layer by layer during the deposition of a-Si:H cells. We show that a solar cell with an optimized EBN exhibits a broadband enhanced external quantum efficiency due to both anti-reflection and light-trapping, with respect to an industrial standard cell using an Asahi U glass substrate which is mostly optimized for light trapping. Overall, the cell with an optimized EBN achieves a large short-circuit current density of 17.74 mA/cm^2, corresponding to a 37.63% enhancement over a flat control cell. The power conversion efficiency is also increased from 5.36% to 8.32%. Moreover, the light management enabled by the EBN remains efficient over a wide range of incident angles up to 60°, which is particularly desirable for real environments with diffused sun light. The novel patterning method is not restricted to a-Si:H solar cells, but is also widely applicable to other thin film materials.

並列關鍵字

Light Trapping ； Anti-reflection ； Nano-structure ； Amorphous Silicon Solar Cell