Development of Arsenic Doped Cd(Se,Te) Absorbers by MOCVD for Thin Film Solar Cells

Ochai Oklobia, Giray Kartopu, Stephen Jones, Peter Siderfin, B. Grew, Harrison Ka Hin Lee, W. Tsoi, Ali Abbas, John Walls, Deborah McGott, Matthew Reese, S. J. C. Irvine

Research output: Contribution to journalArticlepeer-review

11 Scopus Citations

Abstract

Recent developments in CdTe solar cell technology have included the incorporation of ternary alloy Cd(Se,Te) in the devices. CdTe absorber band gap grading due to Se alloying contributes to current density enhancement and can result in device performance improvement. Here we report Cd(Se,Te) polycrystalline thin films grown by a chamberless inline atmospheric pressure metal organic chemical vapour deposition technique, with subsequent incorporation in CdTe solar cells. The compositional dependence of the crystal structure and optical properties of Cd(Se,Te) are examined. Selenium graded Cd(Se,Te)/CdTe absorber structure in devices are demonstrated using either a single CdSe layer or CdSe/Cd(Se,Te) bilayer (with or without As doping in the Cd(Se,Te) layer). Cross-sectional TEM/EDS, photoluminescence spectra and secondary ion mass spectroscopy analysis confirmed the formation of a graded Se profile toward the back contact with a diffusion length of ~1.5 μm and revealed back-diffusion of Group V (As) dopants from the CdTe layer into Cd(Se,Te) grains. Due to the strong Se/Te interdiffusion, CdSe in the Se bilayer configuration was unable to form an n-type emitter layer in processed devices. In situ As doping of the Cd(Se,Te) layer benefited the device junction quality with current density reaching 28.3 mA/cm2. The results provide useful insights for the optimisation of Cd(Se,Te)/CdTe solar cells.

Original languageAmerican English
Article numberArticle No. 111325
Number of pages11
JournalSolar Energy Materials and Solar Cells
Volume231
DOIs
StatePublished - Oct 2021

Bibliographical note

Publisher Copyright:
© 2021

NREL Publication Number

  • NREL/JA-5K00-79902

Keywords

  • As doping
  • Cd(Se,Te)
  • CdSe
  • CdTe
  • MOCVD
  • Photovoltaics
  • Solar cells
  • Thin film

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