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Title: Compositional effects in Ag 2 ZnSnSe 4 thin films and photovoltaic devices

Authors:
ORCiD logo; ; ; ; ; ; ;
Publication Date:
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
OSTI Identifier:
1420001
Grant/Contract Number:
EE0006334
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Acta Materialia
Additional Journal Information:
Journal Volume: 126; Journal Issue: C; Related Information: CHORUS Timestamp: 2018-02-09 04:14:14; Journal ID: ISSN 1359-6454
Publisher:
Elsevier
Country of Publication:
United States
Language:
English

Citation Formats

Gershon, Talia, Sardashti, Kasra, Lee, Yun Seog, Gunawan, Oki, Singh, Saurabh, Bishop, Douglas, Kummel, Andrew C., and Haight, Richard. Compositional effects in Ag 2 ZnSnSe 4 thin films and photovoltaic devices. United States: N. p., 2017. Web. doi:10.1016/j.actamat.2017.01.003.
Gershon, Talia, Sardashti, Kasra, Lee, Yun Seog, Gunawan, Oki, Singh, Saurabh, Bishop, Douglas, Kummel, Andrew C., & Haight, Richard. Compositional effects in Ag 2 ZnSnSe 4 thin films and photovoltaic devices. United States. doi:10.1016/j.actamat.2017.01.003.
Gershon, Talia, Sardashti, Kasra, Lee, Yun Seog, Gunawan, Oki, Singh, Saurabh, Bishop, Douglas, Kummel, Andrew C., and Haight, Richard. Wed . "Compositional effects in Ag 2 ZnSnSe 4 thin films and photovoltaic devices". United States. doi:10.1016/j.actamat.2017.01.003.
@article{osti_1420001,
title = {Compositional effects in Ag 2 ZnSnSe 4 thin films and photovoltaic devices},
author = {Gershon, Talia and Sardashti, Kasra and Lee, Yun Seog and Gunawan, Oki and Singh, Saurabh and Bishop, Douglas and Kummel, Andrew C. and Haight, Richard},
abstractNote = {},
doi = {10.1016/j.actamat.2017.01.003},
journal = {Acta Materialia},
number = C,
volume = 126,
place = {United States},
year = {Wed Mar 01 00:00:00 EST 2017},
month = {Wed Mar 01 00:00:00 EST 2017}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1016/j.actamat.2017.01.003

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  • Cited by 14
  • We observed efficient terahertz (THz) emission from sol-gel grown Cu{sub 2}ZnSnSe{sub 4} (CZTSe) thin films using THz time domain spectroscopy technique. The THz emission bandwidth exceeds 2 THz with a dynamic range of 20 dB in the amplitude spectrum. The THz emission amplitude from CZTSe is found to be independent of external magnetic fields. Comparing the polarity of THz emission waveforms of CZTSe and GaAs, we suggest that the acceleration of photo-carriers in the surface accumulation layer of CZTSe is the dominant mechanism of radiation emission. Optical excitation fluence dependence measurements show that the saturation fluence of the CZTSe thin filmmore » reaches 1.48 μJ/cm{sup 2}.« less
  • Cu{sub 2}ZnSnSe{sub 4} thin-films for photovoltaic applications are investigated using combined atom probe tomography and ab initio density functional theory. The atom probe studies reveal nano-sized grains of Cu{sub 2}Zn{sub 5}SnSe{sub 8} and Cu{sub 2}Zn{sub 6}SnSe{sub 9} composition, which cannot be assigned to any known phase reported in the literature. Both phases are considered to be metastable, as density functional theory calculations yield positive energy differences with respect to the decomposition into Cu{sub 2}ZnSnSe{sub 4} and ZnSe. Among the conceivable crystal structures for both phases, a distorted zinc-blende structure shows the lowest energy, which is a few tens of meVmore » below the energy of a wurtzite structure. A band gap of 1.1 eV is calculated for both the Cu{sub 2}Zn{sub 5}SnSe{sub 8} and Cu{sub 2}Zn{sub 6}SnSe{sub 9} phases. Possible effects of these phases on solar cell performance are discussed.« less
  • Cu{sub 2}ZnSnSe{sub 4} thin films, fabricated on bare or molybdenum coated glass substrates by magnetron sputtering and selenisation, were studied by a range of techniques. Photoluminescence spectra reveal an excitonic peak and two phonon replicas of a donor-acceptor pair (DAP) recombination. Its acceptor and donor ionisation energies are 27 and 7 meV, respectively. This demonstrates that high-quality Cu{sub 2}ZnSnSe{sub 4} thin films can be fabricated. An experimental value for the longitudinal optical phonon energy of 28 meV was estimated. The band gap energy of 1.01 eV at room temperature was determined using optical absorption spectra.
  • We report on atom probe tomography studies of the composition at internal interfaces in Cu{sub 2}ZnSnSe{sub 4} thin-films. For Cu{sub 2}ZnSnSe{sub 4} precursors, which are deposited at 320 °C under Zn-rich conditions, grain boundaries are found to be enriched with Cu irrespective of whether Cu-poor or Cu-rich growth conditions are chosen. Cu{sub 2}ZnSnSe{sub 4} grains are found to be Cu-poor and excess Cu atoms are found to be accumulated at grain boundaries. In addition, nanometer-sized ZnSe grains are detected at or near grain boundaries. The compositions at grain boundaries show different trends after annealing at 500 °C. Grain boundaries in the annealedmore » absorber films, which are free of impurities, are Cu-, Sn-, and Se-depleted and Zn-enriched. This is attributed to dissolution of ZnSe at the Cu-enriched grain boundaries during annealing. Furthermore, some of the grain boundaries of the absorbers are enriched with Na and K atoms, stemming from the soda-lime glass substrate. Such grain boundaries show no or only small changes in composition of the matrix elements. Na and K impurities are also partly segregated at some of the Cu{sub 2}ZnSnSe{sub 4}/ZnSe interfaces in the absorber, whereas for the precursors, only Na was detected at such phase boundaries possibly due to a higher diffusivity of Na compared to K. Possible effects of the detected compositional fluctuations on cell performance are discussed.« less