Tuning the Band Gap of Cu2ZnSn(S,Se)4 Thin Films via Lithium Alloying

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• 作者：Yanchun Yang ; Xiaojiao Kang ; Lijian Huang ; Daocheng Pan
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2016
• 出版时间：March 2, 2016
• 年：2016
• 卷：8
• 期：8
• 页码：5308-5313
• 全文大小：402K
• ISSN：1944-8252

文摘

Alkali metal doping plays a crucial role in fabricating high-performance Cu(In,Ga)(S,Se)₂ and Cu₂ZnSn(S,Se)₄ (CZTSSe) thin film solar cells. In this study, we report the first experimental observation and characterizations of the alloyed Li_xCu_2–xZnSn(S,Se)₄ thin films. It is found that Cu⁺ ions in Cu₂ZnSn(S,Se)₄ thin films can be substituted with Li⁺ ions, forming homogeneous Li_xCu_2–xZnSn(S,Se)₄ (0 ≤ x ≤ 0.29) alloyed thin films. Consequently, the band gap, conduction band minimum, and valence band maximum of Li_xCu_2–xZnSn(S,Se)₄ thin films are profoundly affected by Li/Cu ratios. The band alignment at the Li_xCu_2–xZnSn(S,Se)₄/CdS interface can be tuned by changing the Li/Cu ratio. We found that the photovoltaic parameters of the Li_xCu_2–xZnSn(S,Se)₄ solar cell devices are strongly influenced by the Li/Cu ratios. Besides, the lattice constant, carrier concentration, and crystal growth of Li_xCu_2–xZnSn(S,Se)₄ thin films were studied in detail.