Circularly Polarized Photoluminescence from Chiral Perovskite Thin Films at Room Temperature

Daniele Di Nuzzo (Corresponding author), Linsong Cui, Jake L. Greenfield, Baodan Zhao, Richard H. Friend, Stefan C.J. Meskers

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

Hybrid organic-inorganic perovskites allow the synthesis of high-quality, nanostructured semiconducting films via easily accessible solution-based techniques. This has allowed tremendous development in optoelectronic applications, primarily solar cells and light-emitting diodes. Allowed by the ease of access to nanostructure, chirality has recently been introduced in semiconducting perovskites as a promising way to obtain advanced control of charge and spin and for developing circularly polarized light sources. Circular polarization of photoluminescence (CPL) is a powerful tool to probe the electronic structure of materials. However, CPL in chiral perovskites has been scarcely investigated, and a study in bulk thin films and at room temperature is still missing. In this work, we fabricate bromine-based chiral perovskites by using a bulky chiral organic cation mixed with CsBr, resulting in Ruddlesden-Popper perovskite thin films. We measure CPL on these films at room temperature and, by using unpolarized photoexcitation, we record a degree of circular polarization of photoluminescence in the order of 10-3 and provide a full spectral characterization of CPL. Our results show that chirality is imparted on the electronic structure of the semiconductor; we hypothesize that the excess in polarization of emitted light originates from the charge in the photogenerated Wannier exciton describing an orbit in a symmetry-broken environment. Furthermore, our experiments allow the direct measurement of the magnetic dipole moment of the optical transition, which we estimate to be ≥0.1 μB. Finally, we discuss the implications of our findings on the development of chiral semiconducting perovskites as sources of circularly polarized light.

Original languageEnglish
Pages (from-to)7610-7616
Number of pages7
JournalACS Nano
Volume14
Issue number6
DOIs
Publication statusPublished - 23 Jun 2020

Keywords

  • chiral semiconductors
  • chirality
  • chiroptical spectroscopy
  • circularly polarized luminescence
  • excitons
  • hybrid perovskites
  • magnetic dipole moment

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