Oxidation in Tin Halide Perovskites: Influence of Acidic and Basic Additives

Tareq Hossain, Syed Joy, Kiera Draffen, Ralph Bright, Stephen Johnson, Kenneth R. Graham

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

Tin-containing halide perovskites (Sn-HPs) are promising alternatives to their lead-containing counterparts; however, Sn-HPs suffer from higher defect concentrations due to the oxidation of Sn2+ to Sn4+. To minimize oxidation, improve film morphology, and reduce defect concentrations, additives that interact with SnI2 are typically incorporated into Sn-HP precursor solutions. These additives are often acidic, yet acidic conditions tend to be more oxidizing. In this work, we determine how oxidation of Sn-HP precursors is influenced by the chemical environment in solution, including the presence of acidic and basic additives, solvent system, oxygen exposure, and water exposure. We find that strong Brønsted-Lowry acids increase oxidation of SnI2 and I-, whereas addition of basic salts decreases oxidation. When the solvent system contains dimethyl sulfoxide (DMSO), a conventional solvent used for the fabrication of Sn-HPs, strong acids lead to the fast oxidation of SnI2 at room temperature. Through the use of 119Sn and 1H NMR, UV-vis absorbance, and controlled atmosphere exposure, we propose oxidation reactions that depend on the chemical environment, including the presence of DMSO, oxygen, water, and acidic additives. Because of the less oxidizing conditions, Sn-HP films processed with basic salts display increased performance in perovskite solar cells relative to when the conjugate acid is used or no additive is included.

Original languageEnglish
Pages (from-to)12334-12342
Number of pages9
JournalACS Applied Energy Materials
Volume6
Issue number24
DOIs
StatePublished - Dec 25 2023

Bibliographical note

Publisher Copyright:
© 2023 American Chemical Society

Keywords

  • additives
  • halide perovskite
  • oxidation
  • solar cell
  • tin perovskite
  • Urbach energy

ASJC Scopus subject areas

  • Chemical Engineering (miscellaneous)
  • Energy Engineering and Power Technology
  • Electrochemistry
  • Materials Chemistry
  • Electrical and Electronic Engineering

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