The role of point defects in PbS, PbSe and PbTe: a first principles study

Wun-Fan Li, Chang-Ming Fang, M. Dijkstra, M.A. van Huis

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

Intrinsic defects are of central importance to many physical and chemical processes taking place in compound nanomaterials, such as photoluminescence, accommodation of off-stoichiometry and cation exchange. Here, the role of intrinsic defects in the above mentioned processes inside rock salt (RS) lead chalcogenide systems PbS, PbSe and PbTe (PbX) was studied systematically using first principles density functional theory. Vacancy, interstitial, Schottky and Frenkel defects were considered. Rock salt PbO was included for comparison. The studied physical properties include defect formation energy, local geometry relaxation, Bader charge analysis, and electronic structure. The defect formation energies show that monovacancy defects and Schottky defects are favoured over interstitial and Frenkel defects. Schottky dimers, where the cation vacancy and anion vacancy are adjacent to each other, have the lowest defect formation energies at 1.27 eV, 1.29 eV and 1.21 eV for PbS, PbSe and PbTe, respectively. Our results predict that a Pb monovacancy gives rise to a shallow acceptor state, while an X vacancy generates a deep donor state, and Schottky defects create donor-acceptor pairs inside the band gap. The surprisingly low formation energy of Schottky dimers suggests that they may play an important role in cation exchange processes, in contrast to the current notion that only single point defects migrate during cation exchange.
Original languageEnglish
Article number355801
Number of pages15
JournalJournal of physics. Condensed matter
Volume27
Issue number35
DOIs
Publication statusPublished - 17 Aug 2015

Keywords

  • density functional theory
  • lead chalcogenides
  • point defect
  • defect state
  • photoluminescence
  • off-stoichiometry
  • cation exchange

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