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

Xie, Jiaqi ; Lin, Weihua LU ; Bazan, Guillermo C. ; Pullerits, Tõnu LU ; Zheng, Kaibo LU and Liang, Ziqi (2022) In Journal of Materials Chemistry A 10(36). p.18845-18855
Abstract

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... (More)

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.

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author
; ; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Journal of Materials Chemistry A
volume
10
issue
36
pages
11 pages
publisher
Royal Society of Chemistry
external identifiers
  • scopus:85138619889
ISSN
2050-7488
DOI
10.1039/d2ta05078a
language
English
LU publication?
yes
id
4e2f0385-606f-4576-b265-4ceaa80b653a
date added to LUP
2022-12-20 12:11:24
date last changed
2023-11-21 14:18:02
@article{4e2f0385-606f-4576-b265-4ceaa80b653a,
  abstract     = {{<p>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 (J<sub>SC</sub>) and open-circuit voltage (V<sub>OC</sub>) 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 J<sub>SC</sub> (up to 26.41 mA cm<sup>−2</sup>) and V<sub>OC</sub> (up to 0.86 V) in comparison to the undoped device.</p>}},
  author       = {{Xie, Jiaqi and Lin, Weihua and Bazan, Guillermo C. and Pullerits, Tõnu and Zheng, Kaibo and Liang, Ziqi}},
  issn         = {{2050-7488}},
  language     = {{eng}},
  number       = {{36}},
  pages        = {{18845--18855}},
  publisher    = {{Royal Society of Chemistry}},
  series       = {{Journal of Materials Chemistry A}},
  title        = {{N-doping of nonfullerene bulk-heterojunction organic solar cells strengthens photogeneration and exciton dissociation}},
  url          = {{http://dx.doi.org/10.1039/d2ta05078a}},
  doi          = {{10.1039/d2ta05078a}},
  volume       = {{10}},
  year         = {{2022}},
}