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J Am Chem Soc. 2019 Apr 10;141(14):5972-5979. doi: 10.1021/jacs.9b00972. Epub 2019 Mar 27.

Enhanced Charge Transport in 2D Perovskites via Fluorination of Organic Cation.

Author information

1
National Renewable Energy Laboratory , Golden , Colorado 80401 , United States.
2
Department of Materials , Imperial College London , London SW72AZ , United Kingdom.
3
University of North Carolina at Chapel Hill , Chapel Hill , North Carolina 27599 , United States.
4
Renewable and Sustainable Energy Institute , University of Colorado Boulder , Boulder , Colorado 80309 , United States.
5
Department of Materials Science and Engineering , Yonsei University , Seoul 03722 , Korea.

Abstract

Organic-inorganic halide perovskites incorporating two-dimensional (2D) structures have shown promise for enhancing the stability of perovskite solar cells (PSCs). However, the bulky spacer cations often limit charge transport. Here, we report on a simple approach based on molecular design of the organic spacer to improve the transport properties of 2D perovskites, and we use phenethylammonium (PEA) as an example. We demonstrate that by fluorine substitution on the para position in PEA to form 4-fluorophenethylammonium (F-PEA), the average phenyl ring centroid-centroid distances in the organic layer become shorter with better aligned stacking of perovskite sheets. The impact is enhanced orbital interactions and charge transport across adjacent inorganic layers as well as increased carrier lifetime and reduced trap density. Using a simple perovskite deposition at room temperature without using any additives, we obtained a power conversion efficiency of >13% for (F-PEA)2MA4Pb5I16-based PSCs. In addition, the thermal stability of 2D PSCs based on F-PEA is significantly enhanced compared to those based on PEA.

PMID:
30882210
DOI:
10.1021/jacs.9b00972

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