Transamidation of dimethylformamide during alkylammonium lead triiodide film formation for perovskite solar cells

Michael V. Lee, Sonia R. Raga, Yuichi Kato, Matthew R. Leyden, Luis K. Ono, Shenghao Wang, Yabing Qi

Research output: Contribution to journalArticleResearchpeer-review

24 Citations (Scopus)

Abstract

Perovskite-based solar cells, typically CH3NH3PbI3, have reached power conversion efficiencies on par with single crystal silicon solar cells. Perovskite cells prepared with the most common perovskite solvent N,N-dimethylformamide (DMF) by different research groups exhibit disparate efficiencies and stability for nominally identical perovskite films. Although the differences can be related to processing conditions, a consistent physical cause for the differences has been lacking. Highly-sensitive time-of-flight secondary ion mass spectrometry (TOF-SIMS) reveals significant dimethylamine (DMA) included in perovskite films. TOF-SIMS and x-ray photoelectron spectroscopy results suggest DMA levels ranging from roughly 10-50%. Only the highest levels register as perovskite peak shifts in x-ray diffraction; lower levels are invisible. We propose that methylamine (MA) can react with DMF solvent by transamidation to produce dimethylamine (DMA), which then displaces some MA in perovskite crystals, see Fig. 1. Transamidation of DMF can be catalyzed by TiO2, Al2O3, water, or acid, but in perovskite films transamidation is inhibited by water.

Original languageEnglish
Pages (from-to)45-55
Number of pages11
JournalJournal of Materials Research
Volume32
Issue number1
DOIs
Publication statusPublished - 13 Jan 2017
Externally publishedYes

Keywords

  • chemical reaction
  • photovoltaic
  • secondary ion mass spectroscopy (SIMS)

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