Unraveling interface characteristics of Zn(O,S)/Cu(In,Ga)Se2 at nanoscale: Enhanced hole transport by tuning band offsets

Juran Kim, Jayeong Kim, Eunji Ko, Ha Kyung Park, Seokhyun Yoon, Dae Hyung Cho, Woo Jung Lee, Yong Duck Chung, William Jo

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


Environment-friendly Cu(In,Ga)Se2 (CIGS) solar cells requires the replacement of Cd-containing buffers with non-toxic materials. Zn(O,S) buffers have been developed and yielded even better efficiency than CdS-buffered CIGS thin-film solar cells [23.35%, Ref. [6]]. In this work, we studied band offsets of Zn(O,S) and CIGS interfaces. The Cd-free buffer layers were deposited with 1.0%, 1.3%, and 1.6% oxygen (O2) gas partial pressure during the deposition. Effects of the oxygen partial pressure on the structure and electronic properties of the devices were investigated by micro-Raman scattering spectroscopy and Kelvin probe force microscopy, respectively. We achieved depth-profiling of spatial work function mapping across the interface between the absorbers and the buffers. The best efficiency sample, grown using 1.3% of oxygen, showed 80 mV spike-like band offsets. We propose that the efficiency can be improved through tailoring of the band offsets at the interface as well as improving the absorber and the buffer materials.

Original languageEnglish
Article number144782
JournalApplied Surface Science
StatePublished - 15 Apr 2020

Bibliographical note

Funding Information:
This research was supported by the Technology Development Program to Solve Climate Changes of the National Research Foundation (NRF) of Korea ( 2016M1A2A2936784 and 2016M1A2A2936754 ), the DGIST R&D Program (19-BD-05) funded by the Ministry of Science, ICT & Future Planning, Republic of Korea , and the Basic Science Research Program ( 2018R1A6A1A03025340 ) of the NRF of Korea funded by the Ministry of Education.

Publisher Copyright:
© 2019


  • Cu(In
  • Ga)Se thin-film solar cells
  • Kelvin probe force microscopy (KPFM)
  • Micro-Raman scattering spectroscopy
  • Zn(O,S) buffer layer


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