High-efficiency Cu(In,Ga)Se ₂ (CIGSe) thin-film solar cells are typically fabricated by a multistage coevaporation process. The Cu-rich composition achieved during the second stage is known to favor the grain growth of the polycrystalline CIGSe film and has a beneficial effect on the solar cell performance. In this article, we analyze the effect of copper stoichiometry on the grain size of sputtered CIGSe absorbers and the efficiency of respective solar cells. CIGSe absorber layers were deposited on Mo-coated soda-lime glass substrates by pulsed hybrid reactive magnetron sputtering from Cu-poor and Cu-rich Cu-In-Ga targets and simultaneous Se evaporation. CIGSe films sputtered with the Cu-rich target show larger grain size and lead to better solar cell performance. Furthermore, we also introduce a two-stage process, which further increases the solar cell performance, consisting of an initial CIGSe layer deposited from the Cu-rich target followed by an indium-selenide postdeposition step. This two-stage process effectively eliminates the unwanted Cu _{2- x} Se impurity phase and renders the otherwise required and toxic KCN etching unnecessary.

中文翻译：

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Cu-In-Ga靶成分对混合溅射Cu(In,Ga)Se2太阳能电池的影响

高效Cu(In,Ga)Se ₂(CIGSe) 薄膜太阳能电池通常通过多级共蒸发工艺制造。已知在第二阶段获得的富铜成分有利于多晶 CIGSe 膜的晶粒生长，并对太阳能电池性能产生有益影响。在本文中，我们分析了铜化学计量对溅射 CIGSe 吸收剂的晶粒尺寸和各个太阳能电池效率的影响。CIGSe 吸收层通过脉冲混合反应磁控溅射从贫铜和富铜 Cu-In-Ga 靶材和同步 Se 蒸发沉积在 Mo 涂层的钠钙玻璃基板上。用富铜靶溅射的 CIGSe 薄膜显示出更大的晶粒尺寸并导致更好的太阳能电池性能。此外，我们还引入了两阶段工艺，进一步提高了太阳能电池的性能，包括从富铜靶沉积的初始 CIGSe 层，然后是硒化铟后沉积步骤。这种两阶段过程有效地消除了不需要的铜 _{2- x} Se 杂质相并使得原本需要的有毒 KCN 蚀刻变得不必要。