The surface potential near GBs shows negative band bending behaviors with about 300 meV of energy shift. In the current map, the dominant current flow path is observed through GBs, which is governed by minority carriers. Most of the electrical properties of the CZTSSe are very similar to
the CIGS, but we will study more the details to explain the physical and chemical properties in the interface of the CZTSSe thin films for high conversion efficiency. Acknowledgements This work was supported by the New & Renewable Energy of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant funded by the Korea government Ministry of Trade, Industry, and Energy (No. 20123010010130). References 1. Chen S, Gong XG, Walsh A, Wei S-H: Electronic structure and stability of quaternary chalcogenide semiconductors INK 128 chemical structure derived from cation cross-substitution of II-VI and I-III-VI 2 compounds. Phys Rev B 2009, 79:165211.CrossRef 2. Todorov TK, Tang J, Bag S, Gunawan O, Gokmen T, Zhu Y, Mitzi DB: Beyond 11% efficiency: characteristics of state-of-the-art see more Cu 2 ZnSn(S, Se) 4 solar cells. Adv Energy Mater 2013, 3:34–38.CrossRef
3. W-C H, Repins I, Beall C, DeHart C, To B, Yang W, Yang Y, Noufi R: Growth mechanisms of co-evaporated kesterite: a comparison of Cu-rich and Zn-rich composition paths. Prog Photovolt: Res Appl 2014, 22:35–43.CrossRef 4. Repins I, Beall C, Phospholipase D1 Vora N, DeHart C, Kuciauskas D, Dippo P, To B, Mann J, W-C H, Goodrich A, Noufi R: Co-evaporated Cu 2 ZnSnSe 4 films and devices. Sol Energy Mater Sol Cells 2012, 101:154–159.CrossRef
5. Hiroi H, Sakai N, Kato T, Sugimoto H: High voltage Cu 2 ZnSnS 4 submodules by hybrid buffer layer. In Proceedings of the IEEE Photovoltaic Specialists Conference 39th: 16–21 June 2013. Tampa, FL; 6. Katagiri H, Jimbo K, Maw WS, Oishi K, Yamazaki M, Araki H, Takeuchi A: Development of CZTS-based thin film solar cells. Thin Solid Films 2009, 517:2455–2460.CrossRef 7. Shin SW, Pawar SM, Park CY, Yun JH, Moon J-H, Kim JH, Lee JY: Studies on Cu 2 ZnSnS 4 (CZTS) absorber layer using different stacking orders in precursor thin films. Sol Energy Mater Sol Cells 2011, 95:3202–3206.CrossRef 8. Zoppi G, Forbes I, Miles RW, Dale PJ, Scragg JJ, Peter LM: Cu 2 ZnSnSe 4 thin film solar cells produced by selenization of magnetron sputtered precursors. Prog Photovolt: Res Appl 2009, 17:315–319.CrossRef 9. Scragg JJ, Ericson T, Fontané X, Izqierdo-Roca V, Pérez-Rodríguez A, Kubart T, Edoff M, Platze-Björkman C: Rapid annealing of reactively sputtered precursors for Cu 2 ZnSnS 4 solar cells. Prog Photovolt: Res Appl. 2014, 22:10–17.CrossRef 10. Momose N, Htay MT, Yudasaka T, Igarashi S, Seki T, Iwano S, Hashimoto Y, Ito K: Cu 2 ZnSnS 4 thin film solar cells utilizing sulfurization of metallic precursor prepared by simultaneous sputtering of metal targets.