Intrinsic point defects and complexes in the quaternary kesterite semiconductor Cu2 ZnSnS4

Shiyou Chen, Ji Hui Yang, X. G. Gong, Aron Walsh, Su Huai Wei

Research output: Contribution to journalArticle

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Abstract

Current knowledge of the intrinsic defect properties of Cu2 ZnSnS4 (CZTS) is limited, which is hindering further improvement of the performance of CZTS-based solar cells. Here, we have performed first-principles calculations for a series of intrinsic defects and defect complexes in CZTS, from which we have the following observations. (i) It is important to control the elemental chemical potentials during crystal growth to avoid the formation of secondary phases such as ZnS, CuS, and Cu2 SnS3. (ii) The intrinsic p -type conductivity is attributed to the CuZn antisite which has a lower formation energy and relatively deeper acceptor level compared to the Cu vacancy. (iii) The low formation energy of many of the acceptor defects will lead to the intrinsic p -type character, i.e., n -type doping is very difficult in this system. (iv) The role of electrically neutral defect complexes is predicted to be important, because they have remarkably low formation energies and electronically passivate deep levels in the band gap. For example, [Cu Zn - + Zn Cu +], [V Cu - + Zn Cu +], and [Zn Sn 2- +2 Zn Cu +] may form easily in nonstoichiometric samples. The band alignment between Cu2 ZnSnS4, CuInSe2 and the solar-cell window layer CdS has also been calculated, revealing that a type-II band alignment exists for the CdS/ Cu2 ZnSnS4 heterojunction. The fundamental differences between CZTS and CuInSe2 for use in thin-film photovoltaics are discussed. The results are expected to be relevant to other I2 -II-IV-VI4 semiconductors.

Original languageEnglish
Article number245204
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume81
Issue number24
DOIs
Publication statusPublished - 2010 Jun 8

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Point defects
point defects
Semiconductor materials
energy of formation
Defects
defects
Solar cells
solar cells
alignment
Chemical potential
Crystallization
Crystal growth
Vacancies
Heterojunctions
heterojunctions
crystal growth
Energy gap
Doping (additives)
Thin films
conductivity

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics
  • Electronic, Optical and Magnetic Materials

Cite this

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abstract = "Current knowledge of the intrinsic defect properties of Cu2 ZnSnS4 (CZTS) is limited, which is hindering further improvement of the performance of CZTS-based solar cells. Here, we have performed first-principles calculations for a series of intrinsic defects and defect complexes in CZTS, from which we have the following observations. (i) It is important to control the elemental chemical potentials during crystal growth to avoid the formation of secondary phases such as ZnS, CuS, and Cu2 SnS3. (ii) The intrinsic p -type conductivity is attributed to the CuZn antisite which has a lower formation energy and relatively deeper acceptor level compared to the Cu vacancy. (iii) The low formation energy of many of the acceptor defects will lead to the intrinsic p -type character, i.e., n -type doping is very difficult in this system. (iv) The role of electrically neutral defect complexes is predicted to be important, because they have remarkably low formation energies and electronically passivate deep levels in the band gap. For example, [Cu Zn - + Zn Cu +], [V Cu - + Zn Cu +], and [Zn Sn 2- +2 Zn Cu +] may form easily in nonstoichiometric samples. The band alignment between Cu2 ZnSnS4, CuInSe2 and the solar-cell window layer CdS has also been calculated, revealing that a type-II band alignment exists for the CdS/ Cu2 ZnSnS4 heterojunction. The fundamental differences between CZTS and CuInSe2 for use in thin-film photovoltaics are discussed. The results are expected to be relevant to other I2 -II-IV-VI4 semiconductors.",
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Intrinsic point defects and complexes in the quaternary kesterite semiconductor Cu2 ZnSnS4 . / Chen, Shiyou; Yang, Ji Hui; Gong, X. G.; Walsh, Aron; Wei, Su Huai.

In: Physical Review B - Condensed Matter and Materials Physics, Vol. 81, No. 24, 245204, 08.06.2010.

Research output: Contribution to journalArticle

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AU - Yang, Ji Hui

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AU - Walsh, Aron

AU - Wei, Su Huai

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AB - Current knowledge of the intrinsic defect properties of Cu2 ZnSnS4 (CZTS) is limited, which is hindering further improvement of the performance of CZTS-based solar cells. Here, we have performed first-principles calculations for a series of intrinsic defects and defect complexes in CZTS, from which we have the following observations. (i) It is important to control the elemental chemical potentials during crystal growth to avoid the formation of secondary phases such as ZnS, CuS, and Cu2 SnS3. (ii) The intrinsic p -type conductivity is attributed to the CuZn antisite which has a lower formation energy and relatively deeper acceptor level compared to the Cu vacancy. (iii) The low formation energy of many of the acceptor defects will lead to the intrinsic p -type character, i.e., n -type doping is very difficult in this system. (iv) The role of electrically neutral defect complexes is predicted to be important, because they have remarkably low formation energies and electronically passivate deep levels in the band gap. For example, [Cu Zn - + Zn Cu +], [V Cu - + Zn Cu +], and [Zn Sn 2- +2 Zn Cu +] may form easily in nonstoichiometric samples. The band alignment between Cu2 ZnSnS4, CuInSe2 and the solar-cell window layer CdS has also been calculated, revealing that a type-II band alignment exists for the CdS/ Cu2 ZnSnS4 heterojunction. The fundamental differences between CZTS and CuInSe2 for use in thin-film photovoltaics are discussed. The results are expected to be relevant to other I2 -II-IV-VI4 semiconductors.

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