Organometallic halide perovskites: Sharp optical absorption edge and its relation to photovoltaic performance

Stefaan De Wolf*, Jakub Holovsky, Soo Jin Moon, Philipp Löper, Bjoern Niesen, Martin Ledinsky, Franz Josef Haug, Jun Ho Yum, Christophe Ballif

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1367 Scopus citations

Abstract

Solar cells based on organometallic halide perovskite absorber layers are emerging as a high-performance photovoltaic technology. Using highly sensitive photothermal deflection and photocurrent spectroscopy, we measure the absorption spectrum of CH3NH3PbI3 perovskite thin films at room temperature. We find a high absorption coefficient with particularly sharp onset. Below the bandgap, the absorption is exponential over more than four decades with an Urbach energy as small as 15 meV, which suggests a well-ordered microstructure. No deep states are found down to the detection limit of ∼1 cm-1. These results confirm the excellent electronic properties of perovskite thin films, enabling the very high open-circuit voltages reported for perovskite solar cells. Following intentional moisture ingress, we find that the absorption at photon energies below 2.4 eV is strongly reduced, pointing to a compositional change of the material.

Original languageEnglish (US)
Pages (from-to)1035-1039
Number of pages5
JournalJournal of Physical Chemistry Letters
Volume5
Issue number6
DOIs
StatePublished - Mar 20 2014

Keywords

  • Urbach energy
  • absorption
  • band edge
  • bandgap
  • perovskites
  • solar cells
  • stability

ASJC Scopus subject areas

  • Materials Science(all)

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