Optoelectronic Properties of Strontium and Barium Copper Sulfides Prepared by Combinatorial Sputtering

Andriy Zakutayev, Yanbing Han, Qun Zhang, Sebastian Siol

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29 Scopus Citations


Optically transparent materials with p-type electrical conductivity can facilitate the development of transparent electronics and improve the efficiency of photovoltaic solar cells. Sulfide materials represent an interesting alternative to oxides for these applications due to better hole transport properties. Here, transparent and conductive Ba-Cu-S thin films are prepared by combinatorial cosputtering and characterized for their composition, structure, and optoelectronic properties. The conductivity and transparency of these films are found to be strongly dependent on their chemical composition and the substrate temperature during growth. The conductivity of BaCu2S2 and BaCu4S3 can reach 53 S/cm (at 250 °C) and 74 S/cm (at 200 °C), respectively, which is higher than their solution processed/bulk counterparts. The 90% reflectance corrected transmittance is achieved in the wavelength range 600-1000 nm for BaCu2S2 and 650-1000 nm for BaCu4S3 (at 250 °C). These electrical and optical properties are comparable with other recently presented transparent p-type conductors, while the 200-350 °C processing temperature is low enough to be used in semiconductor devices with limited thermal budgets. Attempts have been made to synthesize the related Sr-Cu-S materials, following the theoretical suggestion of their potential as transparent p-type conductors, but these attempts resulted only in phase-separated SrS and CuxS phases. Alloying BaCu2S2 with Sr on the Ba site on the other hand increases the conductivity to >100 S/cm while only slightly compromising the transparency of the material. To explain the difference between the Ba and the Sr containing copper sulfides, the lower bounds on the SrCu2S2 and SrCu4S3 formation enthalpies are estimated. While the doping of the Ba-Cu-S materials presented here is too large for application in transparent electronics, it is promising for potential use as p-type contact layers in thin film solar cells.

Original languageAmerican English
Pages (from-to)8239-8248
Number of pages10
JournalChemistry of Materials
Issue number19
StatePublished - 10 Oct 2017

Bibliographical note

Publisher Copyright:
© 2017 American Chemical Society.

NREL Publication Number

  • NREL/JA-5K00-70119


  • optoelectronic properties
  • photovoltaics
  • transparent electronics


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