標題: Interplay between potassium doping and bandgap profiling in selenized Cu(In,Ga)Se-2 solar cells: A functional CuGa: KF surface precursor layer
作者: Cai, Chung-Hao
Chen, Rong-Zhi
Chan, Ting-Shan
Lu, Ying-Rui
Huang, Wei-Chih
Yen, Chao-Chun
Zhao, Kejie
Lo, Yu-Chieh
Lai, Chih-Huang
材料科學與工程學系
Department of Materials Science and Engineering
關鍵字: Cu(In Ga)Se-2;K doping;Ga grading;EXAFS;First-principle calculations;notch structure
公開日期: 1-May-2018
摘要: The progress of selenized Cu(In,Ga)Se-2 (CIGSe) solar cells is limited by low open-circuit voltage (Voc), which results from the Ga-deficient surface and undesirable bandgap profile after selenization. Controlling the Ga grading, especially on the CIGSe surface, is challenging but critical for further efficiency improvement. Here, the simple sputtering route with K incorporation is presented to engineer single-or double-graded bandgap. The K incorporation through sputtered precursors can considerably affect the Ga profile in CIGSe during selenization, essentially distinct from reported KF post-deposition treatment, in which the Ga profile keeps unchanged. Using synchrotron-based X-ray absorption spectroscopy and first-principle calculations, we verify that Ga diffusion via Cu vacancies is restrained due to the presence of K-Cu defects. Therefore, by introducing a CuGa:KF surface layer on the bi-layer precursors, the surface Ga content of CIGSe is increased effectively, achieving a notch-like Ga distribution after selenization. This unique CuGa: KF layer significantly boosts the Voc and yields over 15% efficiency, even with a low reactive Se vapor for selenization. Our approach, completely compatible with the existing fabrication process, offers a new direction for engineering band structure without sulfurization.
URI: http://dx.doi.org/10.1016/j.nanoen.2018.03.024
http://hdl.handle.net/11536/144847
ISSN: 2211-2855
DOI: 10.1016/j.nanoen.2018.03.024
期刊: NANO ENERGY
Volume: 47
起始頁: 393
結束頁: 400
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