Na incorporation and diffusion in CuIn1-xGaxSe2

Angus Rockett, M. Bodegard, Karin Granath, Lars Stolt

Research output: Contribution to journalConference articlepeer-review

Abstract

CuIn1-xGaxSe2 based solar cells deposited by vapor phase techniques show significant improvement in performance when Na is present at the growth surface. Evidence is just becoming available concerning how the Na participates in the change in device performance. This work reports on the distribution of Na in CIGS in as grown device-type films, in Na-free films implanted with Na and the effects of annealing of these layers. CIGS thin films were deposited by four-source evaporation and analyzed by secondary ion mass spectroscopy (SIMS) and X-ray photoelectron spectroscopy. Samples were ion implanted and analyzed before and after annealing at 420°C. Na segregates rapidly out of CIGS at normal physical vapor deposition temperatures. No Na diffusion at room temperature was observed in samples after six months. The segregation drives Na both to the surface of polycrystalline layers and into the Mo substrate. The segregation ratio for the CIGS/Mo interface is approx. 10 at 400°C and approx. 100 at 600°C. Small Na-rich regions can also occur inside CIGS layers. In spite of these observations, Na leads to a strong (112) preferred orientation of CIGS and apparently improves the performance of devices.

Original languageEnglish (US)
Pages (from-to)985-987
Number of pages3
JournalConference Record of the IEEE Photovoltaic Specialists Conference
StatePublished - Dec 1 1996
EventProceedings of the 1996 25th IEEE Photovoltaic Specialists Conference - Washington, DC, USA
Duration: May 13 1996May 17 1996

ASJC Scopus subject areas

  • Control and Systems Engineering
  • Industrial and Manufacturing Engineering
  • Electrical and Electronic Engineering

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