Enhanced p-Type Doping in Polycrystalline CdTe Films: Deposition and Activation

Brian McCandless, Wayne Buchanan, Gowri Sriramagiri, Christopher Thompson, Joel Duenow, David Albin, Soren A. Jensen, John Moseley, M. Al-Jassim, Wyatt K. Metzger

Research output: Contribution to journalArticlepeer-review

24 Scopus Citations

Abstract

An in situ nonequilibrium method to increase hole density in polycrystalline CdTe thin films to 1016 cm-3 using group V substitution on Te is presented. Single-phase CdTe films doped with P, As, and Sb were deposited at 550 °C at 100-200 nm/s onto moving cadmium sulfide/high resistance transparent buffer layer/transparent conductive oxide/glass superstrates by vapor transport deposition in Cd overpressure from high purity compound sources. Doping levels before and after activation were determined by capacitance-voltage analysis of diagnostic devices. Secondary ion mass spectrometry depth profiling confirmed dopant incorporation levels of 1017-1018 atoms/cm3 in as-deposited films. Electronic activation was carried out by post-deposition annealing in Cd or CdCl2 vapor with fast cooling, increasing acceptor concentrations to >1015 cm-3 for P and >1016 cm-3 for As and Sb, compared with mid-1014 cm-3 acceptor levels for undoped CdTe films. The activation methods are compatible with post-deposition processing presently used for high-efficiency CdTe solar cells. For the dopants As and Sb, the acceptor concentration increased by substitutional AsTe and SbTe formation, respectively, which was validated by cathodoluminescence spectroscopy.

Original languageAmerican English
Article number8671701
Pages (from-to)912-917
Number of pages6
JournalIEEE Journal of Photovoltaics
Volume9
Issue number3
DOIs
StatePublished - May 2019

Bibliographical note

Publisher Copyright:
© 2019 IEEE.

NREL Publication Number

  • NREL/JA-5K00-73937

Keywords

  • CdTe
  • doping
  • photovoltaic
  • thin film

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