Engineering Grain Boundaries in Cu2ZnSnSe4 for Better Cell Performance: A First-Principle Study

Wan Jian Yin, Yelong Wu, Su Huai Wei, Rommel Noufi, Mowafak M. Al-Jassim, Yanfa Yan

Research output: Contribution to journalArticlepeer-review

140 Scopus Citations

Abstract

Through first-principle density functional theory (DFT) calculations, the atomic structure and electronic properties of intrinsic and passivated Σ3 (114) grain boundaries (GBs) in Cu2ZnSnSe4 (CZTSe) are studied. Intrinsic GBs in CZTSe create localized deep states within the band gap and thus act as Shockley-Read-Hall recombination centers, which are detrimental to cell performance. Defects, such as ZnSn (Zn atoms on Sn sites), Na+i (interstitial Na ions), and OSe (O atoms on Se sites), prefer to segregate into GBs in CZTSe. The segregation of these defects at GBs exhibit two beneficial effects: 1) eliminating the deep gap states via wrong bonds breaking or weakening at GBs, making GBs electrically benign; and 2) creating hole barriers and electron sinkers, promoting effective charge separation at GBs. The results suggest a unique chemical approach for engineering GBs in CZTSe to achieve improved cell performance. The intrinsic grain boundaries of Cu2ZnSnSe4 introduce deep gap states and act as Shockley-Read-Hall recombination centers. The segregation of defects such as ZnSn, Na+i, and OSe eliminates the gaps states and produces the band bending around grain boundaries. The efficiencies of Cu2ZnSnSe4-based solar cell are expected to be further enhanced by proper treatment at grain boundaries.

Original languageAmerican English
Article number1300712
Number of pages7
JournalAdvanced Energy Materials
Volume4
Issue number1
DOIs
StatePublished - 2014

NREL Publication Number

  • NREL/JA-5900-57974

Keywords

  • CuZnSnSe (CZTSe)
  • density functional theory
  • grain boundaries
  • photovoltaic cells

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