Intrinsic Surface Passivation of CdTe

Matthew Reese, Craig Perkins, Teresa Barnes, Steven Johnston, Darius Kuciauskas, Timothy Gessert, Wyatt Metzger, Stuart Farrell, James Burst

Research output: Contribution to journalArticlepeer-review

110 Scopus Citations

Abstract

Recombination is critically limiting in CdTe devices such as solar cells and detectors, with much of it occurring at or near the surface. In this work, we explore different routes to passivate p-type CdTe surfaces without any intentional extrinsic passivation layers. To provide deeper insight into the passivation routes, we uniquely correlate a set of characterization methods: surface analysis and time-resolved spectroscopy. We study two model systems: nominally undoped single crystals and large-grain polycrystalline films. We examine several strategies to reduce surface recombination velocity. First, we study the effects of removing surface contaminants while maintaining a near-stoichiometric surface. Then we examine stoichiometric thermally reconstructed surfaces. We also investigate the effects of shifting the surface stoichiometry by both "subtractive" (wet chemical etches) and "additive" (ampoule anneals and epitaxial growth) means. We consistently find for a variety of methods that a highly ordered stoichiometric to Cd-rich surface shows a significant reduction in surface recombination, whereas a Te-rich surface has high recombination and propose a mechanism to explain this. While as-received single crystals and as-deposited polycrystalline films have surface recombination velocities in the range of 105-106-cm/s, we find that several routes can reduce surface recombination velocities to <2.5-�-104-cm/s.

Original languageAmerican English
Article number155305
Number of pages12
JournalJournal of Applied Physics
Volume118
Issue number15
DOIs
StatePublished - 21 Oct 2015

Bibliographical note

Publisher Copyright:
� 2015 AIP Publishing LLC.

NREL Publication Number

  • NREL/JA-5K00-64478

Keywords

  • CdTe
  • lifetime
  • surface passivation
  • surface recombination
  • time-resolved photoluminescence (TRPL)

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