Evolution of Na—S(—O) Compounds on the Cu2ZnSnS4 Absorber Surface and Their Effects on CdS Thin Film Growth

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• 作者：Yi Ren ; Jonathan J. S. Scragg ; Marika Edoff ; Jes K. Larsen ; Charlotte Platzer-Björkman
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2016
• 出版时间：July 20, 2016
• 年：2016
• 卷：8
• 期：28
• 页码：18600-18607
• 全文大小：505K
• 年卷期：0
• ISSN：1944-8252

文摘

Formation of Na-containing surface compounds is an important phenomenon in the Cu₂ZnSnS₄ (CZTS) quaternary material synthesis for solar cell applications. Still, identification of these compounds and the understanding of their potential influence on buffer layer growth and device performance are scarce. In this work, we discovered that the evolution of Na—S(—O) compounds on the CZTS surface substantially affect the solution/CZTS interface during the chemical bath deposition of CdS buffer film. We showed that Na₂S negatively affects the growth of CdS, and that this compound is likely to form on the CZTS surface after annealing. It was also demonstrated that the Na₂S compound can be oxidized to Na₂SO₄ by air exposure of the annealed CZTS surface or be removed using water dipping instead of the commonly used KCN etching process, resulting in significantly better quality of the CdS layer. Lastly, 6.5% CZTS solar cells were fabricated with air exposure treatment without incorporation of the KCN etching process. This work provides new insight into the growth of the CdS/CZTS interface for solar cell applications and opens new possibilities for improving likewise Cd-free buffer materials that are grown with a similar chemical bath deposition process.