Triiodide Attacks the Organic Cation in Hybrid Lead Halide Perovskites: Mechanism and Suppression

Junnan Hu, Zhaojian Xu, Tucker L. Murrey, István Pelczer, Antoine Kahn, Jeffrey Schwartz, Barry P. Rand

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

Abstract

Molecular I2 can be produced from iodide-based lead perovskites under thermal stress; triiodide, I3, is formed from this I2 and I. Triiodide attacks protic cation MA+- or FA+-based lead halide perovskites (MA+, methylammonium; FA+, formamidinium) as explicated through solution-based nuclear magnetic resonance (NMR) studies: triiodide has strong hydrogen-bonding affinity for MA+ or FA+, which leads to their deprotonation and perovskite decomposition. Triiodide is a catalyst for this decomposition that can be obviated through perovskite surface treatment with thiol reducing agents. In contrast to methods using thiol incorporation into perovskite precursor solutions, no penetration of the thiol into the bulk perovskite is observed, yet its surface application stabilizes the perovskite against triiodide-mediated thermal stress. Thiol applied to the interface between FAPbI3 and Spiro-OMeTAD (“Spiro”) prevents oxidized iodine species penetration into Spiro and thus preserves its hole-transport efficacy. Surface-applied thiol affects the perovskite work function; it ameliorates hole injection into the Spiro overlayer, thus improving device performance. It helps to increase interfacial adhesion (“wetting”): fewer voids are observed at the Spiro/perovskite interface if thiols are applied. Perovskite solar cells (PSCs) incorporating interfacial thiol treatment maintain over 80% of their initial power conversion efficiency (PCE) after 300 h of 85 °C thermal stress.

Original languageEnglish (US)
Article number2303373
JournalAdvanced Materials
Volume35
Issue number40
DOIs
StatePublished - Oct 5 2023

All Science Journal Classification (ASJC) codes

  • Mechanics of Materials
  • Mechanical Engineering
  • General Materials Science

Keywords

  • halide perovskite photovoltaic stability
  • interfacial thiol
  • triiodide-catalyzed perovskite degradation
  • triiodide–formamidinium complexes

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