Co-Solvent Enhanced Zinc Oxysulfide Buffer Layers in Kesterite Copper Zinc Tin Selenide Solar Cells

K. Xerxes Steirer, Rebekah L. Garris, Jian V. Li, Michael J. Dzara, Paul F. Ndione, Kannan Ramanathan, Ingrid Repins, Glenn Teeter, Craig L. Perkins

Research output: Contribution to journalArticlepeer-review

26 Scopus Citations


A co-solvent, dimethylsulfoxide (DMSO), is added to the aqueous chemical "bath" deposition (CBD) process used to grow ZnOS buffer layers for thin film Cu2ZnSnSe4 (CZTSe) solar cells. Device performance improves markedly as fill factors increase from 0.17 to 0.51 upon the co-solvent addition. X-ray photoelectron spectroscopy (XPS) analyses are presented for quasi-in situ CZTSe/CBD-ZnOS interfaces prepared under an inert atmosphere and yield valence band offsets equal to -1.0 eV for both ZnOS preparations. When combined with optical band gap data, conduction band offsets exceed 1 eV for the water and the water/DMSO solutions. XPS measurements show increased downward band bending in the CZTSe absorber layer when the ZnOS buffer layer is deposited from water only. Admittance spectroscopy data shows that the ZnOS deposited from water increases the built-in potential (Vbi) yet these solar cells perform poorly compared to those made with DMSO added. The band energy offsets imply an alternate form of transport through this junction. Possible mechanisms are discussed, which circumvent the otherwise large conduction band spike between CZTSe and ZnOS, and improve functionality with the low-band gap absorber, CZTSe (Eg = 0.96 eV).

Original languageAmerican English
Pages (from-to)15355-15364
Number of pages10
JournalPhysical Chemistry Chemical Physics
Issue number23
StatePublished - 2015

Bibliographical note

Publisher Copyright:
© 2015 the Owner Societies.

NREL Publication Number

  • NREL/JA-5K00-63824


  • admittance
  • buffers
  • conduction band
  • Cu2ZnSnSe4
  • CZTS
  • CZTSe
  • defects
  • kesterite
  • photoelectron spectroscopic (UPS)
  • solar cells
  • UPS
  • UV-VIS
  • XPS


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