| 1. |
- Hu, Tianyu, et al.
(author)
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Steric hindrance induced low exciton binding energy enables low-driving-force organic solar cells
- 2024
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In: Aggregate. - 2692-4560 .- 2766-8541. ; In Press
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Journal article (peer-reviewed)abstract
- Exciton binding energy (Eb) has been regarded as a critical parameter in charge separation during photovoltaic conversion. Minimizing the Eb of the photovoltaic materials can facilitate the exciton dissociation in low-driving force organic solar cells (OSCs) and thus improve the power conversion efficiency (PCE); nevertheless, diminishing the Eb with deliberate design principles remains a significant challenge. Herein, bulky side chain as steric hindrance structure was inserted into Y-series acceptors to minimize the Eb by modulating the intra- and intermolecular interaction. Theoretical and experimental results indicate that steric hindrance-induced optimal intra- and intermolecular interaction can enhance molecular polarizability, promote electronic orbital overlap between molecules, and facilitate delocalized charge transfer pathways, thereby resulting in a low Eb. The conspicuously reduced Eb obtained in Y-ChC5 with pinpoint steric hindrance modulation can minimize the detrimental effects on exciton dissociation in low-driving-force OSCs, achieving a remarkable PCE of 19.1% with over 95% internal quantum efficiency. Our study provides a new molecular design rationale to reduce the Eb.
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| 2. |
- Sun, Fengbo, et al.
(author)
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1,5-Diiodocycloctane: a cyclane solvent additive that can extend the exciton diffusion length in thick film organic solar cells
- 2024
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In: Energy and Environmental Sciences. - 1754-5692 .- 1754-5706. ; 17:5, s. 1916-1930
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Journal article (peer-reviewed)abstract
- The short exciton diffusion length associated with most state-of-the-art organic semiconductors used in organic solar cells (OSCs) imposes severe limits on the exciton transport in the larger donor/acceptor domains and the exciton dissociation at the interface, which hinder further improvements in the power conversion efficiencies (PCE) of the thick-film devices. In this study, a new cyclane, 1,5-diiodocycloctane (DICO), was employed as a solvent additive to effectively extend the exciton LD within the bulk-heterojunction blend, which can function with the multiple photovoltaic materials system. Due to the great enhancement of molecular stacking and exclusively large domain sizes of photovoltaic materials with the assistance of the DICO additive, the trap density in devices is significantly reduced, thereby nearly doubling the LD in the thick film OSCs. Notably, the DICO-processed PM6/L8-BO-based OSC showed high thickness tolerance for the bulk-heterojunction (BHJ) layer, delivering a high PCE of 19.1% in the case of a 110 nm thick film and still maintaining an excellent PCE of 17.2% in the case of a 300 nm thick film. Crucially, a noticeably increased stability of the multiple materials system was observed in the DICO-processed OSCs. These findings enrich the additive family with new cyclane systems to extend the exciton LD in thick film OSCs with high performance.
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