Issue 9, 2021

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

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”.

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

Supplementary files

Article information

Article type
Communication
Submitted
19 May 2021
Accepted
23 Jul 2021
First published
24 Jul 2021

Energy Environ. Sci., 2021,14, 4840-4846

Author version available

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

M. De Keersmaecker, N. R. Armstrong and E. L. Ratcliff, Energy Environ. Sci., 2021, 14, 4840 DOI: 10.1039/D1EE01525G

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