The Role of Dimethylammonium in Bandgap Modulation for Stable Halide Perovskites

Giles Eperon, Kevin Stone, Laura Mundt, Tracy Schloemer, Severin Habisreutinger, Sean Dunfield, Laura Schelhas, Joseph Berry, David Moore

Research output: Contribution to journalArticlepeer-review

67 Scopus Citations

Abstract

Halide perovskites with bandgaps of 1.70-1.85 eV are of interest for multijunction photovoltaics. Mixing halides on the X site of the ABX3-structured perovskite system is a common way to reach these bandgaps, but this method introduces phase segregation pathways, limiting photovoltage. Recently, a new strategy for increasing the bandgap has been introduced, where cations normally too large to fit into the lattice, but compensated by smaller cations, are substituted on the A site. The mechanism underlying the increase of the bandgap with this strategy remained an open question. Here, we show that by partial substitution of the large dimethylammonium (DMA) cation at the A site of FAxCs1-xPbIyBr3-y perovskites, a bandgap increase is observed not only when DMA is compensated by smaller Cs cations but also when only DMA is added, which is accompanied by an expansion of the crystal lattice. Our experimental findings suggest that adding DMA is causing an unexpected tilt in the perovskite octahedra, increasing the bandgap. Efficient solar cells based on 1.73 eV DMA-incorporated materials are extremely stable, retaining 96% of their original efficiency over 2200 h at 85 °C in the dark and 92% of their original efficiency after operation at 60 °C for 500 h. This octahedral tilting strategy is a promising route for attaining efficient and stable wide bandgap perovskite solar cells.

Original languageAmerican English
Pages (from-to)1856-1864
Number of pages9
JournalACS Energy Letters
Volume5
Issue number6
DOIs
StatePublished - 2020

Bibliographical note

Publisher Copyright:
Copyright © 2020 American Chemical Society.

NREL Publication Number

  • NREL/JA-5900-76813

Keywords

  • bandgap modulation
  • dimethylammonium
  • halide perovskites

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