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Weihua Lin. Portrait.

Weihua Lin

Postdoctoral fellow

Weihua Lin. Portrait.

N-doping of nonfullerene bulk-heterojunction organic solar cells strengthens photogeneration and exciton dissociation

Author

  • Jiaqi Xie
  • Weihua Lin
  • Guillermo C. Bazan
  • Tõnu Pullerits
  • Kaibo Zheng
  • Ziqi Liang

Summary, in English

N-type doping of the bulk-heterojunction layer in nonfullerene organic solar cells allows to effectively ameliorate inferior electron transportation by filling traps and optimizing electron pathways, leading to a better balance of charge transport in device. This mechanism, however, provides an incomplete understanding of the stronger photogeneration, long-lived excitons and simultaneously increased short-circuit current density (JSC) and open-circuit voltage (VOC) that also benefit from the n-doping. Herein we investigate how molecular n-dopant impacts the optical characteristics, intermolecular packing behavior, charge carrier dynamics and photovoltaic performance in the nonfullerene-based blend. When incorporating a prototypical n-type dopant N-DMBI into a benchmark PM6:Y6 blend, the crystallization of PM6/Y6 is facilitated and the crystal coherence length is elongated, which is correlated with the optical absorbance enhancement. N-doping is unveiled to prolong exciton lifetime by retarding germinate recombination (GR) both at donor/acceptor (D/A) interfaces and within constituent domains by dilating interspace, reducing trap states and decreasing exciton binding energy. Despite slower interfacial charge transfer across the enlarged D/A interspace due to dopant intercalation, exciton dissociation remains highly effective due to the impeded interfacial GR. Consequently, the champion inverted cell at an optimal N-DMBI content delivers a decent efficiency of 15.34%, which is among the highest of the state-of-the art analogous PM6:Y6-based binary cells. Such improvement is largely ascribed to the concurrent increase of JSC (up to 26.41 mA cm−2) and VOC (up to 0.86 V) in comparison to the undoped device.

Department/s

  • LTH Profile Area: Nanoscience and Semiconductor Technology
  • Chemical Physics
  • NanoLund: Centre for Nanoscience
  • LTH Profile Area: Photon Science and Technology

Publishing year

2022-08

Language

English

Pages

18845-18855

Publication/Series

Journal of Materials Chemistry A

Volume

10

Issue

36

Document type

Journal article

Publisher

Royal Society of Chemistry

Topic

  • Other Physics Topics

Status

Published

ISBN/ISSN/Other

  • ISSN: 2050-7488