Charge transfer excitons in a donor–acceptor amphidynamic crystal: the role of dipole orientational order

MacDonald, J. W.; Piana, Giacomo; Comin, Massimiliano; Hauff, Elizabeth von; Kociok‐Köhn, Gabriele; Bowen, Chris; Lagoudakis, Pavlos G.; D’Avino, Gabriele; Como, Enrico Da

doi:10.1039/d0mh01044h

Cited by 10 publications

(16 citation statements)

References 38 publications

(41 reference statements)

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“…For instance, Prof. Y. W. Zhong et al reported the synthesis of light-harvesting triblock nanorods via the stepwise co-assembly of polypyridyl Ir(III) and Ru(II) metallophosphors at low acceptor doping ratios. Among them, the organic cocrystal engineering can be used as a promising tool for the fabrication of OHSs owing to their huge material categories and diverse intermolecular interactions 40 – 42 . A facile approach for the fabrication of OHSs has been previously reported, through which the OHSs are successfully fabricated via the hierarchical self-assembly process from the cocrystals of DPEpe-BrFTA and DPEpe-F 4 DIB, realizing the precise manipulation for the length ratio of different emissive part in the triblock nanowires by tuning the noncovalent interactions (hydrogen bond and halogen bond) 43 .…”

Section: Introductionmentioning

confidence: 99%

Lattice-mismatch-free growth of organic heterostructure nanowires from cocrystals to alloys

Wang

et al. 2022

Nat Commun

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Organic heterostructure nanowires, such as multiblock, core/shell, branch-like and related compounds, have attracted chemists’ extensive attention because of their novel physicochemical properties. However, owing to the difficulty in solving the lattice mismatch of distinct molecules, the construction of organic heterostructures at large scale remains challenging, which restricts its wide use in future applications. In this work, we define a concept of lattice-mismatch-free for hierarchical self-assembly of organic semiconductor molecules, allowing for the large-scale synthesis of organic heterostructure nanowires composed of the organic alloys and cocrystals. Thus, various types of organic triblock nanowires are prepared in large scale, and the length ratio of different segments of the triblock nanowires can be precisely regulated by changing the stoichiometric ratio of different components. These results pave the way towards fine synthesis of heterostructures in a large scale and facilitate their applications in organic optoelectronics at micro/nanoscale.

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Section: Introductionmentioning

confidence: 99%

Lattice-mismatch-free growth of organic heterostructure nanowires from cocrystals to alloys

Wang

et al. 2022

Nat Commun

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“…8,9 Enhanced charge-transfer character is typically exhibited by higher-energy excitations in the presence of sufficiently long donor chains. 8 This situation is not very favorable to photocurrent generation, in contrast to so-called chargetransfer excitons, [10][11][12][13][14] which feature electrons and holes localized on opposite sides of the donor/acceptor interface. 13,15 However, these excitations are typically weak, due to the small spatial overlap between the involved wave-functions.…”

Section: Introductionmentioning

confidence: 99%

“…Nonetheless, cluster models show their limitations when long-range correlations become predominant. 14,[19][20][21][22][23][24][25] These effects are intrinsically present in organic samples with crystalline order, and give rise to the unique electronic and optical characteristics of these materials. [26][27][28][29][30][31][32][33][34][35][36][37][38][39] In this paper, we show how long-range interactions impact on the electronic and optical properties of organic donor/acceptor co-crystals.…”

Section: Introductionmentioning

confidence: 99%

Long-Range Order Promotes Charge-Transfer Excitations in Donor/Acceptor Co-Crystals

Guerrini,

Valencia,

Cocchi

2021

Preprint

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Electronic and optical properties of doped organic semiconductors are dominated by local interactions between donor and acceptor molecules. However, when such systems are in crystalline form, long-range order competes against short-range couplings. In a first-principles study on three experimentally resolved bulk structures of quaterthiophene doped by (fluorinated) tetracyanoquinodimethane, we demonstrate the crucial role of long-range interactions in donor/acceptor co-crystals. The band structures of the investigated materials exhibit direct band-gaps decreasing in size with increasing amount of F atoms in the acceptors. The valence-band maximum and conductionband minimum are found at the Brillouin zone boundary and the corresponding wavefunctions are segregated on donor and acceptor molecules, respectively. With the aid of a tight-binding model, we rationalize that the mechanisms responsible for these behaviors, which are ubiquitous in donor/acceptor co-crystals, are driven by long-range interactions. The optical response of the analyzed co-crystals is highly anisotropic.The absorption onset is dominated by an intense resonance corresponding to a chargetransfer excitation. Long-range interactions are again responsible for this behavior, which enhances the efficiency of the co-crystals for photo-induced charge separation and transport. In addition to this result, which has important implications in the rational design of organic materials for opto-electronics, our study clarifies that cluster models, accounting only for local interactions, cannot capture the relevant impact of long-range order in donor/acceptor co-crystals.

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“…7,8 for review), these methods are per se insufficient to address the full complexity of these materials. Since the turn of the century, ab initio calculations have tremendously contributed to understand the electronic transport, and optical properties of organic semiconductors, [9][10][11][12] and, in combination with model Hamiltonians, they have offered unprecedented insight into the excitations of these systems 13,14 , including electron-phonon coupling. 15,16 Charge-transfer (CT) excitons at donor-acceptor interfaces are considered prime intermediates for electron-hole pair dissociation and free-carriers generation.…”

mentioning

confidence: 99%

“…15,16 Charge-transfer (CT) excitons at donor-acceptor interfaces are considered prime intermediates for electron-hole pair dissociation and free-carriers generation. 14 To enhance the understanding of the microscopic nature of CT excitons in molecular composites, crystalline oligomeric model systems, especially organic co-crystals, are of particular interest, as they provide precise structural information on internal interfaces between the various components, which can be used to obtain correlations between structural and optoelectronic properties. While molecular cluster models allow to reproduce qualitatively some of the key features of these materials, [17][18][19][20] a full-fletched computational analysis of the electronic and optical response of co-crystals with appropriate state-of-the-art methods still represents a numerical challenge.…”

mentioning

confidence: 99%

Polarization Resolved Optical Excitation of Charge-Transfer Excitons in PEN:PFP Co-Crystalline Films: Limits of Non-Periodic Modelling

Günder,

Valencia,

Guerrini

et al. 2021

Preprint

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Charge-transfer excitons (CTX) at organic donor/acceptor interfaces are considered important intermediates for charge separation in photovoltaic devices. Crystalline model systems provide microscopic insights into the nature of such states as they enable microscopic structure-property investigations. Here, we use angular-resolved UV/Vis absorption spectroscopy to characterize the CTX of crystalline pentacene:perfluoro-pentacene (PEN:PFP) films allowing to determine the polarization of this state. This analysis is complemented by first-principles many-body calculations, performed on the three-dimensional PEN:PFP co-crystal, which confirm that the lowest-energy excitation is a CTX. Analogous simulations performed on bimolecular clusters are unable to reproduce this state. We ascribe this failure to the lack of long-range interactions and wave-function periodicity in these cluster calculations, which appear to remain a valid tool for modelling properties of organic materials ruled by local intermolecular couplings.

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Charge transfer excitons in a donor–acceptor amphidynamic crystal: the role of dipole orientational order

Abstract: Large amplitude motions in molecular solids are responsible for anomalous electrical characteristics in amphidynamic crystals. We study the effect of orientational dipolar disorder on charge transfer excitons (CTEs) in a...

Cited by 10 publications

References 38 publications

Lattice-mismatch-free growth of organic heterostructure nanowires from cocrystals to alloys

Lattice-mismatch-free growth of organic heterostructure nanowires from cocrystals to alloys

Long-Range Order Promotes Charge-Transfer Excitations in Donor/Acceptor Co-Crystals

Polarization Resolved Optical Excitation of Charge-Transfer Excitons in PEN:PFP Co-Crystalline Films: Limits of Non-Periodic Modelling

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