Direct probing of gap states and their passivation in halide perovskites by high-sensitivity, variable energy ultraviolet photoelectron spectroscopy

Igal Levine, Hisao Ishii, Kohei Shimizu, Alberto Lomuscio, Michael Kulbak, Carolin Rehermann, Arava Zohar, Mojtaba Abdi-Jalebi, Baodan Zhao, Susanne Siebentritt, Fengshuo Zu, Norbert Koch, Antoine Kahn, Gary Hodes, Richard H. Friend, David Cahen

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

Direct detection of intrinsic defects in halide perovskites (HaPs) by standard methods utilizing optical excitation is quite challenging, due to the low density of defects in most samples of this family of materials (≤1015 cm-3 in polycrystalline thin films and ≤1011 cm-3 in single crystals, except melt-grown ones). While several electrical methods can detect defect densities <1015 cm-3, such as deep level transient spectroscopy (DLTS) or thermally stimulated current (TSC), they require preparation of ohmic and/or rectifying electrical contacts to the sample, which not only poses a challenge by itself in the case of HaPs but also may create defects at the contact-HaP interface and introduce extrinsic defects into the HaP. Here, we show that low-energy photoelectron spectroscopy measurements can be used to obtain directly the energy position of gap states in Br-based wide-bandgap (Eg > 2 eV) HaPs. By measuring HaP layers on both hole- and electron-contact layers, as well as single crystals without contacts, we conclude that the observed deep defects are intrinsic to the Br-based HaP, and we propose a passivation route via the incorporation of a 2Dforming ligand into the precursor solution.

Original languageEnglish (US)
Pages (from-to)5217-5225
Number of pages9
JournalJournal of Physical Chemistry C
Volume125
Issue number9
DOIs
StatePublished - Mar 11 2021

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

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