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

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...

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Veröffentlicht in:Energy & environmental science 2021-09, Vol.14 (9), p.484-4846
Hauptverfasser: De Keersmaecker, Michel, Armstrong, Neal R, Ratcliff, Erin L
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Sprache:eng
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Zusammenfassung: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 MAPbI 3 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 × 10 17 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". A solid-state, operando approach for defect quantification with respect to an internal energy reference using an optically and X-ray transparent electrolyte that can be easily removed.
ISSN:1754-5692
1754-5706
DOI:10.1039/d1ee01525g