| 1. |
- Han, Ziqi, et al.
(författare)
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Regulating the miscibility of donors/acceptors to manipulate the morphology and reduce non-radiative recombination energy loss enables efficient organic solar cells
- 2024
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Ingår i: Journal of Materials Chemistry C. - : ROYAL SOC CHEMISTRY. - 2050-7526 .- 2050-7534.
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Tidskriftsartikel (refereegranskat)abstract
- Due to the high exciton binding energy and relatively low charge carrier mobilities of organic photovoltaic materials, it is crucial to optimize the active layer morphology of organic solar cells (OSCs) to well juggle exciton dissociation and charge carrier transport, and inhibit charge carrier recombination for high power conversion efficiencies (PCEs). Herein, we efficiently improve the crystallinity and miscibility of fused ring electron acceptors (FREAs) via lengthening the side chains and developing four FREAs, BTP-nC8, BTP-C8, BTP-C12 and BTP-C20. The dual functions of lengthening the side chains of FREAs make PM6:FREA blend films present the tendency of first improving then deteriorating in crystallinity, phase separation, domain purity and thus charge carrier dynamics, which leads the JSC and FF of PM6:FREA-based OSCs to show the same trend along with the side-chain length of FREAs. More importantly, enhancing the miscibility between PM6 and FREA facilitates the spatial registry to reduce the formation and recombination rate of triplet excitons in the PM6:FREA blend films, thus inhibiting the non-radiative recombination for decreased Delta Enr, and then increasing VOC in OSCs. Among them, PM6:BTP-C8 based OSCs well balance the multiple impacts of lengthening the side chains to achieve the highest PCE of 17.77%. This work demonstrates that it is important to finely control the crystallinity and miscibility of organic photovoltaic materials to achieve high PCEs in OSCs. The miscibility and crystallinity of fused ring electron acceptors is regulated to study the effects on the morphology and energy loss of organic solar cells (OSCs). BTP-C8 based OSCs juggle multiple impacts to gain the best efficiency.
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| 2. |
- Gao, Bin, et al.
(författare)
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Spectral identification of fullerene C82 isomers
- 2007
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 127:16, s. 164314-1-164314-8
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Tidskriftsartikel (refereegranskat)abstract
- Ultraviolet photoelectron spectra (UPS) of C-82 isomers have been calculated using hybrid density functional theory in combination with the Gelius model [Proceedings of the International Conference on Electron spectroscopy, edited by D. A. Shirley (North-Holland, Amsterdam, 1972), p. 311; J. Electron Spectrosc. Relat. Phenom. 5, 985 (1974)]. The calculated UPS spectra are found to be isomer dependent and in good agreement with the experimental counterparts. Near-edge x-ray absorption fine structure (NEXAFS), x-ray photoelectron spectroscopy (XPS), x-ray emission spectroscopy, and the resonant inelastic x-ray scattering (RIXS) spectra of three important isomers [3(C-2), 6(C-s), and 9(C-2v)] have also been simulated. Strong isomer dependence has also been found for NEXAFS, XPS, and RIXS spectra.
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| 3. |
- Lin, Yuze, et al.
(författare)
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Balanced Partnership between Donor and Acceptor Components in Nonfullerene Organic Solar Cells with > 12% Efficiency
- 2018
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Ingår i: Advanced Materials. - : WILEY-V C H VERLAG GMBH. - 0935-9648 .- 1521-4095. ; 30:16
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Tidskriftsartikel (refereegranskat)abstract
- Relative to electron donors for bulk heterojunction organic solar cells (OSCs), electron acceptors that absorb strongly in the visible and even near-infrared region are less well developed, which hinders the further development of OSCs. Fullerenes as traditional electron acceptors have relatively weak visible absorption and limited electronic tunability, which constrains the optical and electronic properties required of the donor. Here, high-performance fullerene-free OSCs based on a combination of a medium-bandgap polymer donor (FTAZ) and a narrow-bandgap nonfullerene acceptor (IDIC), which exhibit complementary absorption, matched energy levels, and blend with pure phases on the exciton diffusion length scale, are reported. The single-junction OSCs based on the FTAZ:IDIC blend exhibit power conversion efficiencies up to 12.5% with a certified value of 12.14%. Transient absorption spectroscopy reveals that exciting either the donor or the acceptor component efficiently generates mobile charges, which do not suffer from recombination to triplet states. Balancing photocurrent generation between the donor and nonfullerene acceptor removes undesirable constraints on the donor imposed by fullerene derivatives, opening a new avenue toward even higher efficiency for OSCs.
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| 4. |
- Lin, Yuze, et al.
(författare)
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Mapping Polymer Donors toward High-Efficiency Fullerene Free Organic Solar Cells
- 2017
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Ingår i: Advanced Materials. - : WILEY-V C H VERLAG GMBH. - 0935-9648 .- 1521-4095. ; 29:3
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Tidskriftsartikel (refereegranskat)abstract
- Five polymer donors with distinct chemical structures and different electronic properties are surveyed in a planar and narrow-bandgap fused-ring electron acceptor (IDIC)-based organic solar cells, which exhibit power conversion efficiencies of up to 11%.
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| 5. |
- Liu, Lei, et al.
(författare)
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The structural determination of endohedral metallofullerene Gd@C-82 by XANES
- 2008
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Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1359-7345 .- 1364-548X. ; :4, s. 474-476
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Tidskriftsartikel (refereegranskat)abstract
- Although the Gd ion in Gd@C-82 has been shown to lie above the C-C bond on the C-2 axis as an anomalous structure from the MEM/Rietveld analysis, the present XANES study reveals that it lies above the hexagon on the C-2 axis as a normal structure, and Gd oscillates around its equilibrium position with an amplitude increasing with temperature increase.
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| 6. |
- Wu, Bo, et al.
(författare)
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The Effect of the Polyaromatic Hydrocarbon in the Formation of Fullerenes
- 2020
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Ingår i: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 59:10, s. 3942-3947
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Tidskriftsartikel (refereegranskat)abstract
- Tremendous advances in nanoscience have been made since the discovery of fullerenes. However, the short timescale of the growth process and high-energy conditions of synthesis result in severe constraints to investigation of the mechanism of fullerene formation. In this work, we attempted to reveal the formation process by analyzing the variation in the yield of fullerenes under different conditions. Experiments and theoretical analysis show that the formation of fullerenes could be affected by the addition of polycyclic aromatic compounds. It is proposed that the formation of C-60 during arc-discharge synthesis is fragment assembling, while the yield of C-2m (m=35, 38, 39) is strongly enhanced by building-block splicing. In addition, several features of the building blocks are put forward to predict the extent of their influence to the formation of larger fullerenes C-2n (n >= 42). This work not only provides essential insight into the formation process of fullerenes, but more importantly also paves the way to improving the yield of larger fullerenes selectively.
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| 7. |
- Wu, Bo, et al.
(författare)
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Visible-Light Photoexcited Electron Dynamics of Scandium Endohedral Metallofullerenes : The Cage Symmetry and Substituent Effects
- 2015
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 137:27, s. 8769-8774
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Tidskriftsartikel (refereegranskat)abstract
- Endohedral metallofullerenes (EMFs) have become an important class of molecular materials for optoelectronic applications. The performance of EMFs is known to be dependent on their symmetries and characters of the substituents, but the underlying electron dynamics remain unclear. Here we report a systematic study on several scandium EMFs and representative derivatives to examine the cage symmetry and substituent effects on their photoexcited electron dynamics using ultrafast transient absorption spectroscopy. Our attention is focused on the visible-light (530 nm as a demonstration) photoexcited electron dynamics, which is of broad interest to visible-light solar energy harvesting but is considered to be quite complicated as the visible-light photons would promote the system to a high-lying energy region where dense manifolds of electronic states locate. Our ultrafast spectroscopy study enables a full mapping of the photoinduced deactivation channels involved and reveals that the long-lived triplet exciton plays a decisive role in controlling the photoexcited electron dynamics under certain conditions. More importantly, it is found that the opening of the triplet channels is highly correlated to the fullerene cage symmetry as well as the electronic character of the substituents.
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| 8. |
- Zhao, Fuwen, et al.
(författare)
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Highly efficient fused ring electron acceptors based on a new undecacyclic core
- 2021
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Ingår i: Materials Chemistry Frontiers. - : ROYAL SOC CHEMISTRY. - 2052-1537. ; 5:4, s. 2001-2006
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Tidskriftsartikel (refereegranskat)abstract
- Two FREAs, IUIC-O and IUIC-T, based on an undecacyclic core were developed. IUIC-T having a higher extinction coefficient affords aligned energy levels with PBDB-T, finer nanoscale morphology and more orderly molecular stacking, thus achieving more efficient exciton dissociation and charge transport. Therefore, the PBDB-T:IUIC-T based OSC gains a higher PCE of 13.05%.
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