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Energy level offsets determine the interplay between charge and energy transfer in all-small-molecule organic solar cells

Wen, Guanzhao ; Hu, Rong ; Feng, Junyi ; Peng, Jun ; Chen, Zhifeng ; Zhang, Chengyun ; Zhao, Ningjiu ; Zou, Xianshao LU ; Chen, Zhe and Liu, Cuihong , et al. (2023) In Chemical Engineering Journal 475.
Abstract

All-small-molecule organic solar cells (ASM OSCs) hold great promise in OSCs owing to their defined structures, simple purification, and good reproducibility, but are challenging for further improved efficiency. The energy level strategy has been broadly applied to obtain a better performance; however, a comprehensive understanding of the effects of energy level offset on photoexcitation dynamics in ASM OSCs is rarely studied. Herein, for Y-series molecules (Y6, Y10, Y5, and BTP-4F-12) based ASM OSCs, the effect of energy level offset on charge photogeneration was investigated using steady-state and time-resolved spectroscopies. We found that both energy and charge transfer could occur in blend films. A method to quantitatively analyze... (More)

All-small-molecule organic solar cells (ASM OSCs) hold great promise in OSCs owing to their defined structures, simple purification, and good reproducibility, but are challenging for further improved efficiency. The energy level strategy has been broadly applied to obtain a better performance; however, a comprehensive understanding of the effects of energy level offset on photoexcitation dynamics in ASM OSCs is rarely studied. Herein, for Y-series molecules (Y6, Y10, Y5, and BTP-4F-12) based ASM OSCs, the effect of energy level offset on charge photogeneration was investigated using steady-state and time-resolved spectroscopies. We found that both energy and charge transfer could occur in blend films. A method to quantitatively analyze the contribution of charge and energy transfer processes was developed. For BTR-Cl:Y6 with the highest LUMO level offset, ∼ 23% of photogenerated excitons in donor dissociated via “energy transfer and the subsequent charge transfer” pathway, suggesting that the energy transfer in blend films should also be considered. And for the hole transfer, the excitons in Y-series molecules can only be effectively dissociated when the HOMO energy level offset is higher than 0.11 eV. Besides, a higher energy level offset would also suppress carrier recombination in ultrafast timescale. These results may shed light on the design of ASM OSCs.

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publishing date
type
Contribution to journal
publication status
published
subject
keywords
ASM OSCs, Charge photogeneration, Energy level offsets
in
Chemical Engineering Journal
volume
475
article number
145939
publisher
Elsevier
external identifiers
  • scopus:85171464187
ISSN
1385-8947
DOI
10.1016/j.cej.2023.145939
language
English
LU publication?
yes
id
444eb0c0-317e-44b8-8bfb-e2d4ae1057ad
date added to LUP
2023-12-07 09:05:43
date last changed
2023-12-07 09:06:04
@article{444eb0c0-317e-44b8-8bfb-e2d4ae1057ad,
  abstract     = {{<p>All-small-molecule organic solar cells (ASM OSCs) hold great promise in OSCs owing to their defined structures, simple purification, and good reproducibility, but are challenging for further improved efficiency. The energy level strategy has been broadly applied to obtain a better performance; however, a comprehensive understanding of the effects of energy level offset on photoexcitation dynamics in ASM OSCs is rarely studied. Herein, for Y-series molecules (Y6, Y10, Y5, and BTP-4F-12) based ASM OSCs, the effect of energy level offset on charge photogeneration was investigated using steady-state and time-resolved spectroscopies. We found that both energy and charge transfer could occur in blend films. A method to quantitatively analyze the contribution of charge and energy transfer processes was developed. For BTR-Cl:Y6 with the highest LUMO level offset, ∼ 23% of photogenerated excitons in donor dissociated via “energy transfer and the subsequent charge transfer” pathway, suggesting that the energy transfer in blend films should also be considered. And for the hole transfer, the excitons in Y-series molecules can only be effectively dissociated when the HOMO energy level offset is higher than 0.11 eV. Besides, a higher energy level offset would also suppress carrier recombination in ultrafast timescale. These results may shed light on the design of ASM OSCs.</p>}},
  author       = {{Wen, Guanzhao and Hu, Rong and Feng, Junyi and Peng, Jun and Chen, Zhifeng and Zhang, Chengyun and Zhao, Ningjiu and Zou, Xianshao and Chen, Zhe and Liu, Cuihong and Zhang, Wei}},
  issn         = {{1385-8947}},
  keywords     = {{ASM OSCs; Charge photogeneration; Energy level offsets}},
  language     = {{eng}},
  month        = {{11}},
  publisher    = {{Elsevier}},
  series       = {{Chemical Engineering Journal}},
  title        = {{Energy level offsets determine the interplay between charge and energy transfer in all-small-molecule organic solar cells}},
  url          = {{http://dx.doi.org/10.1016/j.cej.2023.145939}},
  doi          = {{10.1016/j.cej.2023.145939}},
  volume       = {{475}},
  year         = {{2023}},
}