Abundance of CuZn + SnZn and 2CuZn + SnZn defect clusters in kesterite solar cells

S. Chen, L.-W. Wang, A. Walsh, X. G. Gong, S.-H. Wei

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Abstract

Kesterite solar cells show the highest efficiency when the absorber layers (Cu ZnSnS [CZTS], Cu ZnSnSe [CZTSe] and their alloys) are non-stoichiometric with Cu / (Zn + Sn) ≈ 0.8 and Zn / Sn ≈ 1.2. The fundamental cause is so far not understood. Using a first-principles theory, we show that passivated defect clusters such as Cu + Sn and 2 Cu+ Sn have high concentrations even in stoichiometric samples with Cu/(ZnSn) and Zn/Sn ratios near 1. The partially passivated Cu+ Sn cluster produces a deep donor level in the band gap of CZTS, and the fully passivated 2Cu+ Sn cluster causes a significant band gap decrease. Both effects are detrimental to photovoltaic performance, so Zn-rich and Cu, Sn-poor conditions are required to prevent their formation and increase the efficiency. The donor level is relatively shallower in CZTSe than in CZTS, which gives an explanation to the higher efficiency obtained in Cu ZnSn (S, Se) (CZTSSe) cells with high Se content.
LanguageEnglish
Article number223901
JournalApplied Physics Letters
Volume101
Issue number22
DOIs
StatusPublished - 26 Nov 2012

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Chen, S., Wang, L-W., Walsh, A., Gong, X. G., & Wei, S-H. (2012). Abundance of CuZn + SnZn and 2CuZn + SnZn defect clusters in kesterite solar cells. Applied Physics Letters, 101(22), [223901]. DOI: 10.1063/1.4768215

Abundance of CuZn + SnZn and 2CuZn + SnZn defect clusters in kesterite solar cells. / Chen, S.; Wang, L.-W.; Walsh, A.; Gong, X. G.; Wei, S.-H.

In: Applied Physics Letters, Vol. 101, No. 22, 223901, 26.11.2012.

Research output: Contribution to journalArticle

Chen, S, Wang, L-W, Walsh, A, Gong, XG & Wei, S-H 2012, 'Abundance of CuZn + SnZn and 2CuZn + SnZn defect clusters in kesterite solar cells' Applied Physics Letters, vol 101, no. 22, 223901. DOI: 10.1063/1.4768215
Chen S, Wang L-W, Walsh A, Gong XG, Wei S-H. Abundance of CuZn + SnZn and 2CuZn + SnZn defect clusters in kesterite solar cells. Applied Physics Letters. 2012 Nov 26;101(22). 223901. Available from, DOI: 10.1063/1.4768215
Chen, S. ; Wang, L.-W. ; Walsh, A. ; Gong, X. G. ; Wei, S.-H./ Abundance of CuZn + SnZn and 2CuZn + SnZn defect clusters in kesterite solar cells. In: Applied Physics Letters. 2012 ; Vol. 101, No. 22.
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