以化學濕式蝕刻形成表面倒金字塔之單晶矽太陽能電池研究

太陽能電池的研究除了致力於效率的提升以外，製程成本的降低也是格外的重要。本論文主要探討的是一種不同於業界的化學濕式蝕刻對單晶太陽能電池的表面進行製絨，形成倒金字塔結構以進一步降低反射率。現今一般使用的MCCE製絨技術因為有金屬輔助的關係造成成本相對高昂，而本論文探討的化學溶液不需使用任何金屬就能達到理想尺寸的倒金字塔結構，接著使用POCl3擴散形成n+後以PECVD機台鍍上SiNx作為抗反射層，最後網印正面銀漿與背面鋁漿後進行共燒，然後量測轉換效率以佐證本製絨技術是否達到業界製程的效率。除了效率探討以外，本論文也呈現了大量表面結構的SEM量測，不同的溶液或是不同的蝕刻時間都會對表面孔洞尺寸造成很大的影響，而孔洞尺寸的理想範圍大概是在2μm左右，如此抗反射層以及最後的電極網印才能較完美的與粗糙化表面接觸，降低反射率以及接觸電阻。最後共燒完成後，背面鋁漿形成的BSF厚度根據SEM量測顯示為4~5μm。而最後的I-V特性量測，我們發現雖然效率可以完全達到業界的水準，但Rsh都偏低導致Voc也偏低，很有可能是因為本研究使用的矽晶表面倒金字塔結構的尺寸太小，導致表面存在過多的缺陷之故。

關鍵字

製絨；倒金字塔結構

並列摘要

In addition to improving the efficiencies of solar cells, the reduction of process cost is also an important issue. This thesis mainly discusses a new chemical wet etching method for texturing the surfaces of single crystalline silicon solar cells, in which inverted pyramids are formed on the surfaces without using a metal catalyzed chemical etching(MCCE) method. The MCCE texturing technique recently developed is relatively expensive in forming either porosities or inverted pyramids. On the contrary, the chemical wet etching method discussed in this paper does not require any metal to achieve the desired size of the inverted pyramids. After inverted pyramids are formed on the surface, we then use POCl3 to form an n+ layer on the front surface. Next, a PECVD SiNx layer is deposited on the front surface and used as an anti-reflection layer. Finally, Al paste and silver paste are, respectively, screen-printed on the back and front surfaces of the silicon solar wafer, followed by a co-firing process. This paper also presents SEM photographs to show the surface morphologies. Different solutions or different etching times will have an influence on the size and distribution uniformity of the inverted pyramids. Several solar cells are fabricated to show the comparison of the devices with different surface morphologies. It is found that the group of solar cells with uniformly-distributed inverted pyramids of ~900nm in size have a highest conversion efficiency of 19.16% on average.