Formation of a K—In—Se Surface Species by NaF/KF Postdeposition Treatment of Cu(In,Ga)Se2 Thin-Film Solar Cell Absorbers

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• 作者：Evelyn HandickPatrick Reinhard ; Regan G. WilksFabian Pianezzi ; Thomas Kunze ; Dagmar Kreikemeyer-Lorenzo ; Lothar Weinhardt ; Monika Blum ; Wanli Yang ; Mihaela Gorgoi ; Eiji Ikenaga ; Dominic Gerlach ; Shigenori Ueda ; Yoshiyuki Yamashita ; Toyohiro Chikyow ; Clemens Heske ; Stephan Buecheler ; Ayodhya N. Tiwari ; Marcus Bär
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2017
• 出版时间：February 1, 2017
• 年：2017
• 卷：9
• 期：4
• 页码：3581-3589
• 全文大小：558K
• ISSN：1944-8252

文摘

A NaF/KF postdeposition treatment (PDT) has recently been employed to achieve new record efficiencies of Cu(In,Ga)Se₂ (CIGSe) thin film solar cells. We have used a combination of depth-dependent soft and hard X-ray photoelectron spectroscopy as well as soft X-ray absorption and emission spectroscopy to gain detailed insight into the chemical structure of the CIGSe surface and how it is changed by different PDTs. Alkali-free CIGSe, NaF-PDT CIGSe, and NaF/KF-PDT CIGSe absorbers grown by low-temperature coevaporation have been interrogated. We find that the alkali-free and NaF-PDT CIGSe surfaces both display the well-known Cu-poor CIGSe chemical surface structure. The NaF/KF-PDT, however, leads to the formation of bilayer structure in which a K—In—Se species covers the CIGSe compound that in composition is identical to the chalcopyrite structure of the alkali-free and NaF-PDT absorber.