Defect quantification in metal halide perovskites: The solid-state electrochemical alternative

Michel De Keersmaecker, Neal R. Armstrong, Erin L. Ratcliff

Research output: Contribution to journalArticlepeer-review

Abstract

Electrochemical methodologies are routinely used to determine energetics and defect density in semiconductor materials under operando conditions. For metal halide perovskites, electrochemical methods are restricted to a limited group of non-solvent electrolytes. This challenge is circumvented via a "peel and stick"solid electrolyte that can contain redox active species, is transparent to visible and X-ray photons for simultaneous characterizations, and can be removed for quantification of near-surface composition and energetics using photoelectron spectroscopies. Defects are qualified for both near-stoichiometric and over-stoichiometric MAPbI3 films using controlled hole and electron injection, afforded through potential modulation with respect to a calibrated internal reference. Inclusion of mid-gap redox probes (ferrocene) allows for probing density of states, whereby electron transfer reversibility is shown to be dependent upon the number of ionized defects at the perovskite's band edges. A detailed Coulombic analysis is provided for determination of defect energetics and densities, with a near-stoichiometric film exhibiting a defect density of ∼2 × 1017 cm-3 at 0.1 eV above the valence band. We predict that this easily implemented three-electrode platform will be translatable to operando characterization of a range of semiconductor materials, including thin film perovskites, (in)organic semiconductors, quantum dots, and device stacks, where the removable solid electrolyte functions as the "top contact".

Original languageEnglish (US)
Pages (from-to)4840-4846
Number of pages7
JournalEnergy and Environmental Science
Volume14
Issue number9
DOIs
StatePublished - Sep 2021

ASJC Scopus subject areas

  • Environmental Chemistry
  • Renewable Energy, Sustainability and the Environment
  • Nuclear Energy and Engineering
  • Pollution

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