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Weihua Lin. Portrait.

Weihua Lin

Postdoctoral fellow

Weihua Lin. Portrait.

Electronic Structure and Trap States of Two-Dimensional Ruddlesden–Popper Perovskites with the Relaxed Goldschmidt Tolerance Factor

Author

  • Mingli Liang
  • Weihua Lin
  • Zhenyun Lan
  • Jie Meng
  • Qian Zhao
  • Xianshao Zou
  • Ivano E. Castelli
  • Tönu Pullerits
  • Sophie E. Canton
  • Kaibo Zheng

Summary, in English

Two-dimensional Ruddlesden–Popper perovskites (2D RPPs) have been considered as promising building blocks for optoelectronic applications owing to optical properties comparable to the ones of 3D perovskites, together with superior stability. In addition, the more flexible structure adopted by such perovskites leads to a relaxation of the Goldschmidt tolerance factor (τ) requirement. Herein, we compare the crystalline and electronic structures, as well as the photophysics of two 2D perovskite single crystals (n-BA)2(MA)2Pb3I10 (BMAPI) and (n-BA)2(EA)2Pb3I10 (BEAPI) (n-BA = n-butylamine) containing small A-cations (MA, methylammonium) and large A-cations (EA, ethylammonium), respectively. The latter presents a relaxed τ (τEA > 1) compared with the requirement of a stable phase in 3D perovskites (τ < 1). Such relaxed τ is beneficial from the structural flexibility of the long organic cation bilayer and the pronounced lattice distortions in the 2D perovskite structures. We further elucidate how the greater lattice distortions concurrently modulate the electronic structure as well as trap densities in these 2D RPPs. The electronic band gap (Eg) of BEAPI (2.08 ± 0.03 eV) is ∼0.17 eV larger than the one of BMAPI (1.91 ± 0.03 eV). This is mainly because of a shift in the valence band maximum associated with the expansion of the Pb–I bond length in BEAPI. In addition, the overall trap state densities for BMAPI and BEAPI are calculated to be ∼2.18 × 1016 and ∼3.76 × 1016 cm–3, respectively, as extracted from the time-resolved photoluminescence studies. The larger trap density in BEAPI can be attributed to the stronger interfacial lattice distortion that sets in when large EA cations are contained into the inorganic crystal lattice.

Department/s

  • Chemical Physics
  • NanoLund: Centre for Nanoscience
  • eSSENCE: The e-Science Collaboration

Publishing year

2020

Language

English

Pages

1402-1412

Publication/Series

ACS Applied Electronic Materials

Volume

2

Issue

5

Document type

Journal article

Publisher

The American Chemical Society (ACS)

Topic

  • Materials Chemistry
  • Condensed Matter Physics (including Material Physics, Nano Physics)

Status

Published

ISBN/ISSN/Other

  • ISSN: 2637-6113