以Top-Down技術製作硫化鐵奈米顆粒墨水暨奈米薄膜研究

A Facile Manufacturing Process of Pyrite Nanoparticles with Well-Dispersed Pyrite Nanosuspension for Photovoltaic Thin-Films by Top-Down Media Milling

邱士翔(Shih-Hsiang Chiu)

指導教授 ： 周麗新

國立清華大學/工學院/材料科學工程學系/碩士(2014年)

摘要

FeS2(Pyrite) 擁有地球含量豐富、無毒性組成元素、合宜的能隙(約0.95 eV)及高吸收係數(α>105 cm−1)等特性，適合作為薄膜太陽能電池吸收層材料，且以其高吸收係數，理論上極薄的厚度(低於100 nm)即可使用，然而因其純相晶體難被合成，目前的應用仍然有限。
本論文我們藉由化學合成法合成出高品質、似立方體的Pyrite以及鈷摻雜的Pyrite奈米顆粒，其平均顆粒尺寸約為50~100 nm，由於初合成之Pyrite顆粒過大且傾向聚集成大於100 nm之團聚物，因此無法將其製作成小於50 nm的平整連續薄膜。
為解決此問題，我們採用高轉速珠磨法來擊碎並分散Pyrite奈米顆粒，經過珠磨參數如珠磨轉速、Pyrite與分散劑(油胺)的比重的調整後，我們獲得最佳的珠磨參數並得到懸浮良好的Pyrite奈米顆粒懸浮液，並以此分散液旋轉塗佈出膜厚約為30 nm的Pyrite薄膜。珠磨最佳參數為濃度1 wt.% Pyrite混合液、珠磨轉速2500 rpm、Pyrite/Oleylamine重量比5、研磨40 分鐘。
最後，於硫氛圍下針對旋轉塗佈好的薄膜進行熱處理，以去除殘存於膜上之分散液及薄膜缺陷。並進行熱處理後薄膜的微結構與光電性質研究，發現微量鈷元素摻雜後的Pyrite薄膜，由原先P型轉變為N型。不論是否有摻雜鈷元素，兩者薄膜的載子濃度皆大於1017cm-3且光吸收係數於波長低於700 nm時大於2×〖10〗^5 cm-1。

關鍵字

二硫化鐵 ； 薄膜 ； 太陽能電池材料 ； 珠磨法

並列摘要

Iron pyrite (FeS2) is a promising photovoltaic absorber due to its earth abundance, non-toxic composition element, infrared band gap (Eg = 0.95 eV), and excellent photoabsorption characteristic (α>105 cm−1), which make it possible to allow the use of very thin (less than 100 nm) absorption layers. However, its use has been hindered because phase-pure pyrite nanocrystals are difficult to be synthesized.
In this work, by the means of chemical method, we synthesized cube-like Pyrite nanoparticles (NPs) and Co-doped Pyrite NPs with high quality and both of their size are around 50 to 100 nm. Since the NPs are big and tend to agglomerate to a size over 100 nm, they are unable to form smooth, continuous ultrathin films with thickness less than 50nm.
To solve this problem, bead mill at high milling speed was applied to smash the NPs into smaller pieces and then dispersed the agglomerate to yield well-dispersed pyrite NPs inks. After revising experimental parameters such as rotation speeds of rotor blade and weight ratio (WR) of Pyrite and surfactant(Oleylamine), we obtained the optimal experimental parameters to fabricate films with thickness about 30 nm by spin coating. The parameters are 1 wt. % pyrite slurry, rotor blade rotation speed at 2500 rpm, WR (Pyrite/OLA) of 5 and milling for 40 mins.
Eventually, we annealed the as-deposited Pyrite thin films under sulfur atmosphere in order to remove the surfactant and defects. Moreover, we investigated the microstructures and optoelectronic properties of these films, finding that Pyrite thin films transfer from P-type to N-type after doping a small amount of Cobalt. Also, the analytical result shows that both of their carrier concentration are above 1017 cm-3 and their photoabsorption coefficient are above 2×〖10〗^5 cm-1 for wavelength below 700 nm.

並列關鍵字

Pyrite ； thin films ； Solar cell materials ； bead mill

參考文獻

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