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Frank, Anna; Grunwald, Jan; Breitbach, Benjamin; Scheu, Christina (2018): Facile and Robust Solvothermal Synthesis of Nanocrystalline CuInS2 Thin Films. In: Nanomaterials, Vol. 8, No. 6, 405
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Abstract

This work demonstrates that the solvothermal synthesis of nanocrystalline CuInS2 thin films using the amino acid l-cysteine as sulfur source is facile and robust against variation of reaction time and temperature. Synthesis was carried out in a reaction time range of 3-48 h (at 150 degrees C) and a reaction temperature range of 100-190 degrees C (for 18 h). It was found that at least a time of 6 h and a temperature of 140 degrees C is needed to produce pure nanocrystalline CuInS2 thin films as proven by X-ray and electron diffraction, high-resolution transmission electron microscopy, and energy-dispersive X-ray spectroscopy. Using UV-vis spectroscopy, a good absorption behavior as well as direct band gaps between 1.46 and 1.55 eV have been determined for all grown films. Only for a reaction time of 3 h and temperatures below 140 degrees C CuInS2 is not formed. This is attributed to the formation of metal ion complexes with l-cysteine and the overall slow assembly of CuInS2. This study reveals that the reaction parameters can be chosen relatively free;the reaction is completely nontoxic and precursors and solvents are rather cheap, which makes this synthesis route interesting for industrial up scaling.