Enhanced Conductivity in CZTS/Cu2‿i>xSe Nanocrystal Thin Films: Growth of a Conductive Shell

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• 作者：Lasantha Korala ; J. Tyler McGoffin ; Amy L. Prieto
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2016
• 出版时间：February 24, 2016
• 年：2016
• 卷：8
• 期：7
• 页码：4911-4917
• 全文大小：497K
• ISSN：1944-8252

文摘

Poor charge transport in Cu₂ZnSnS₄ (CZTS) nanocrystal (NC) thin films presents a great challenge in the fabrication of solar cells without postannealing treatments. We introduce a novel approach to facilitate the charge carrier hopping between CZTS NCs by growing a stoichiometric Cu₂Se shell that can be oxidized to form a conductive Cu_2–xSe phase when exposed to air. The CZTS/Cu₂Se core/shell NCs with varying numbers of shell monolayers were synthesized by the successive ionic layer adsorption and reaction (SILAR) method, and the variation in structural and optical properties of the CZTS NCs with varying shell thicknesses was investigated. Solid-phase sulfide ligand exchange was employed to fabricate NC thin films by layer-by-layer dip coating and a 2 orders of magnitude rise in dark conductivity (∼10^–3 S cm^–1 at 0 monolayer and ∼10^–1 S cm^–1 at 1.5 monolayers) was observed with an increase in the number of shell monolayers. The approach described herein is the first key step in achieving a significant increase in the photoconductivity of as-deposited CZTS NC thin films.