Iron Pyrite Thin Films Synthesized from an Fe(acac)3 Ink

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• 作者：Sean Seefeld ; Moritz Limpinsel ; Yu Liu ; Nima Farhi ; Amanda Weber ; Yanning Zhang ; Nicholas Berry ; Yon Joo Kwon ; Craig L. Perkins ; John C. Hemminger ; Ruqian Wu ; Matt Law
• 刊名：The Journal of the American Chemical Society
• 出版年：2013
• 出版时间：March 20, 2013
• 年：2013
• 卷：135
• 期：11
• 页码：4412-4424
• 全文大小：706K
• 年卷期：v.135,no.11(March 20, 2013)
• ISSN：1520-5126

文摘

Iron pyrite (cubic FeS₂) is a promising candidate absorber material for earth-abundant thin-film solar cells. Here, we report on phase-pure, large-grain, and uniform polycrystalline pyrite films that are fabricated by solution-phase deposition of an iron(III) acetylacetonate molecular ink followed by sequential annealing in air, H₂S, and sulfur gas at temperatures up to 550 掳C. Phase and elemental compositions of the films are characterized by conventional and synchrotron X-ray diffraction, Raman spectroscopy, Auger electron spectroscopy, secondary ion mass spectrometry, and X-ray photoelectron spectroscopy (XPS). These solution-deposited films have more oxygen and alkalis, less carbon and hydrogen, and smaller optical band gaps (E_g = 0.87 卤 0.05 eV) than similar films made by chemical vapor deposition. XPS is used to assess the chemical composition of the film surface before and after exposure to air and immersion in water to remove surface contaminants. Optical measurements of films rich in marcasite (orthorhombic FeS₂) show that marcasite has a band gap at least as large as pyrite and that the two polymorphs share similar absorptivity spectra, in excellent agreement with density functional theory models. Regardless of the marcasite and elemental impurity contents, all films show p-type, weakly activated transport with curved Arrhenius plots, a room-temperature resistivity of 1 惟 cm, and a hole mobility that is too small to measure by Hall effect. This universal electrical behavior strongly suggests that a common defect or a hole-rich surface layer governs the electrical properties of most FeS₂ thin films.