A study on the band structure of ZnO/CdS heterojunction for CIGS solar-cell application

Hana Sim, Jeongmin Lee, Seongjae Cho, Eou Sik Cho, Sang Jik Kwon

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24 Scopus citations

Abstract

In this paper, ZnO films were prepared by atomic layer deposition (ALD) and CdS films were deposited using chemical bath deposition (CBD) to form ZnO/CdS heterojunction. More accurate mapping of band arrangement of the ZnO/CdS heterojunction has been performed by analyzing its electrical and optical characteristics in depth by various methods including transmittance, x-ray photoemission spectroscopy (XPS), and ultraviolet photoemission spectroscopy (UPS). The optical bandgap energies (Eg) of ZnO and CdS were 3.27 eV and 2.34 eV, respectively. UPS was capable of extracting the ionization potential energies (IPEs) of the materials, which turned out to be 8.69 eV and 7.30 eV, respectively. The electron affinity (EA) values of ZnO and CdS calculated from IPE and Eg were 5.42 eV and 4.96 eV, respectively. Energy-band structures of the heterojunction could be accurately drawn from these parameters taking the conduction band offset (CBO) into account, which will substantially help acquisition of the full band structures of the thin films in the CIGS solar-cell device and contribute to the optimal device designs.

Original languageEnglish
Pages (from-to)267-275
Number of pages9
JournalJournal of Semiconductor Technology and Science
Volume15
Issue number2
DOIs
StatePublished - 1 Apr 2015

Bibliographical note

Publisher Copyright:
©Institute of Electronics Engineers of Korea. All rights reserved.

Keywords

  • Atomic layer deposition
  • CdS
  • Chemical bath deposition
  • CIGS solar cell
  • Conduction band offset
  • Heterojunction
  • Ionization potential energy
  • Transmittance
  • UPS
  • XPS
  • ZnO

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