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Portrait of Tönu Pullerits; Photo: Kennet Ruona

Tönu Pullerits

Professor

Portrait of Tönu Pullerits; Photo: Kennet Ruona

Charge Carrier Diffusion Dynamics in Multisized Quaternary Alkylammonium-Capped CsPbBr3Perovskite Nanocrystal Solids

Author

  • Sol Gutiérrez Álvarez
  • Weihua Lin
  • Mohamed Abdellah
  • Jie Meng
  • Karel Žídek
  • Tõnu Pullerits
  • Kaibo Zheng

Summary, in English

CsPbBr3 quantum dots (QDs) are promising candidates for optoelectronic devices. The substitution of oleic acid (OA) and oleylamine (OLA) capping agents with a quaternary alkylammonium such as di-dodecyl dimethyl ammonium bromide (DDAB) has shown an increase in external quantum efficiency (EQE) from 0.19% (OA/OLA) to 13.4% (DDAB) in LED devices. The device performance significantly depends on both the diffusion length and the mobility of photoexcited charge carriers in QD solids. Therefore, we investigated the charge carrier transport dynamics in DDAB-capped CsPbBr3 QD solids by constructing a bi-sized QD mixture film. Charge carrier diffusion can be monitored by quantitatively varying the ratio between two sizes of QDs, which varies the mean free path of the carriers in each QD cluster. Excited-state dynamics of the QD solids obtained from ultrafast transient absorption spectroscopy reveals that the photogenerated electrons and holes are difficult to diffuse among small-sized QDs (4 nm) due to the strong quantum confinement. On the other hand, both photoinduced electrons and holes in large-sized QDs (10 nm) would diffuse toward the interface with the small-sized QDs, followed by a recombination process. Combining the carrier diffusion study with a Monte Carlo simulation on the QD assembly in the mixture films, we can calculate the diffusion lengths of charge carriers to be μ239 ± 16 nm in 10 nm CsPbBr3 QDs and the mobility values of electrons and holes to be 2.1 (± 0.1) and 0.69 (± 0.03) cm2/V s, respectively. Both parameters indicate an efficient charge carrier transport in DDAB-capped QD films, which rationalized the perfect performance of their LED device application.

Department/s

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

Publishing year

2021-09-13

Language

English

Pages

44742-44750

Publication/Series

ACS Applied Materials and Interfaces

Volume

13

Issue

37

Document type

Journal article

Publisher

The American Chemical Society (ACS)

Topic

  • Condensed Matter Physics
  • Physical Chemistry

Keywords

  • carrier transport
  • charge transfer
  • CsPbBr
  • DDAB
  • diffusion lengths
  • quantum dot photovoltaics
  • ultrafast spectroscopy

Status

Published

ISBN/ISSN/Other

  • ISSN: 1944-8244