Optical and Structural Properties of High-Efficiency Epitaxial Cu(In,Ga)Se2 Grown on GaAs

Harvey Guthrey, Andrew Norman, Mowafak Al-Jassim, Jiro Nishinaga, Shigeru Niki, Hajime Shibata

Research output: Contribution to journalArticlepeer-review

14 Scopus Citations


Photovoltaic devices based on Cu(In,Ga)Se2 (CIGS) typically employ polycrystalline thin films as the absorber layer. This is because, to date, the highest conversion efficiencies have been attained with polycrystalline CIGS films. Recently, Nishinaga et al. presented an epitaxial CIGS thin-film solar cell grown on a GaAs (100) substrate with a conversion efficiency of 20.0%. In this contribution, we study the optical and structural properties of this high-efficiency epitaxial film, along with others with different compositions using cathodoluminescence spectrum imaging and transmission electron microscopy. A comparison of the high-efficiency epitaxial film and a traditional polycrystalline film with a similar global composition reveals significant differences in microstructure and uniformity of emission properties despite similar performance. The analysis of epitaxial films with a higher gallium concentration indicates that the emission characteristics and nature of extended defects in epitaxial CIGS films are strongly dependent on the gallium content. The results presented here provide evidence that, with further optimization, photovoltaic conversion efficiencies of epitaxial CIGS films could exceed those of polycrystalline CIGS.

Original languageAmerican English
Pages (from-to)3150-3160
Number of pages11
JournalACS Applied Materials and Interfaces
Issue number2
StatePublished - 15 Jan 2020

Bibliographical note

Publisher Copyright:
Copyright © 2019 American Chemical Society.

NREL Publication Number

  • NREL/JA-5K00-72576


  • cathodoluminescence
  • CIGS microscopy
  • defect characterization
  • epitaxial CIGS
  • solar cell
  • TEM


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