An atomistic simulation of the liquid-crystalline phases of sexithiophene

Pizzirusso, Antonio; Savini, Matteo; Muccioli, Luca; Zannoni, Claudio

doi:10.1039/c0jm01284j

Cited by 63 publications

(112 citation statements)

References 66 publications

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“…The smectic order parameter is equal to 0.45, clearly confi rming the presence of a layered structure as suggested by the profi le of g ( r 12 ) plotted in Figure 5 c. This value is lower than in bulk T6 at the same temperature (0.52 in another study) [ 28 ] indicating that the confi nement partially disrupts the positional order along the director. Correspondingly, the layer spacing is measured to be d = 26.7 Å here, versus the bulk value of 26.2 Å.…”

Section: High Temperature Annealing Of the T6/c 60 (001) Interfacementioning

confidence: 67%

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From Chiral Islands to Smectic Layers: A Computational Journey Across Sexithiophene Morphologies on C₆₀

D’Avino

Muccioli

Zannoni

2014

Adv Funct Materials

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1wileyonlinelibrary.com in favorable cases by atomistic molecular dynamics (MD) simulations. [ 9,[13][14][15][16] Further development in improving the performance of OSC requires a deeper knowledge and ability to control the molecular organization at the interface between the materials playing the role of electron donor and acceptor. Important factors are the choice of donors and acceptors chemical nature, their morphology and the type of heterojunction, which currently consists of either a planar interface between two thin layers of donor and acceptor (bilayer cell, [ 17 ] possibly replicated) tandem cells, [ 18,19 ] or an interpenetrated bicontinuous arrangement where the D, A materials are microsegregated inside a single photoactive layer (bulk heterojunction or BHJ). [ 20,21 ] The orientation of donor and acceptor molecules at their interface and in particular the possibility of, say, "face-face" instead of "edge on" disposition of the respective aromatic moieties is of great importance for bilayer, as well as for BHJ cell performances. [ 22,23 ] As far as materials are concerned, both small molecules and polymers have and are being used. In general terms of efficiency polymer based devices, more extensively studied, have shown the best top performance, but small molecule cells are now showing similar results. [ 24,25 ] Small molecules have the advantage of being of a well-defi ned chemical composition: they can be easily purifi ed and their physical properties can be determined and controlled favoring a better reproducibility of solar cell performance with respect to the batch to batch variations often found in polymers. While chemical composition represents an essential aspect, polymorphism for crystalline materials or more generally the detailed molecular arrangement in space (e.g., the type of mesophase for liquid crystalline materials) [ 26 ] plays an important role. For small molecule materials these aspects can be thermodynamically controlled and well defi ned reaching equilibrium conditions at a certain temperature T , pressure P , and composition. However molecular organizations can very signifi cantly change in thin nanometric fi lms and, moreover, the fi lm preparation process can be a nonequilibrium one making the fi nal result even more diffi cult to predict.Here we wish to investigate the possibility of controlling morphology at a donor-acceptor interface prepared with a physical vapor deposition process, applying a methodology we have recently developed and applied to the deposition of pentacene From Chiral Islands to Smectic Layers: A Computational Journey Across Sexithiophene Morphologies on C 60Gabriele D'Avino , Luca Muccioli , and Claudio Zannoni* A theoretical investigation of the molecular organization at a sexithiophene (T6)-C 60 fullerene planar heterojunction, based on atomistic molecular dynamics, is presented, in which the effect of two different sample preparation processes on the resulting interface morphology is explored. First, the landing of T6 on C 60 (001) substrate is consid...

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Section: High Temperature Annealing Of the T6/c 60 (001) Interfacementioning

confidence: 67%

“…[ 28 ] The lowest energy full-trans structure is largely the most abundant at room temperature (83% and 72% in VD and LC samples, respectively), though bent conformers with one cis torsion have appreciable populations (see Table S2, Supporting Information).…”

Section: Analysis Of the Structures At Room Temperaturementioning

confidence: 97%

From Chiral Islands to Smectic Layers: A Computational Journey Across Sexithiophene Morphologies on C₆₀

D’Avino

Muccioli

Zannoni

2014

Adv Funct Materials

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“…[28][29][30][31][32][33] As a result, there have been a number of notable atomistic simulations of liquid crystals. 26,29,[33][34][35][36][37][38][39][40][41][42] Among these, only two have been performed on liquid crystal mixtures; one by Lansac et al on smectic mixtures of p,p -diheptylazobenzene (7AB) and 4-octyl-4 -cyanobiphenyl (8CB) molecules, 41 and the other by Pelaez and Wilson on a nematic mixture of E7, 42 which contains four components: 4-cyano-4 -n-pentyl-biphenyl (5CB), 4-cyano-4 -n-heptyl-biphenyl (7CB), 4-cyano-4 -n-octyloxy-biphenyl (80CB), and 4-cyano-4 -n-pentyl-p-terphenyl (5CT). Compared with nematic mixtures, smectic mixtures are more difficult to simulate at an atomistic level of detail.…”

Section: Introductionmentioning

confidence: 99%

Atomistic simulations of liquid crystal mixtures of alkoxy substituted phenylpyrimidines 2PhP and PhP14

Yan

Earl

2012

The Journal of Chemical Physics

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We study liquid crystal mixtures of alkoxy substituted phenylpyrimidines 2-[4-(butyloxy)phenyl]-5-(octyloxy)pyrimidine (2PhP) and 2-[4-(tetradecyloxy)phenyl]-5-(tetradecyloxy)pyrimidine (PhP14) using molecular dynamics simulations at the all atom level. The molecular length of PhP14 is 1.8 times that of 2PhP, resulting in an interesting binary mixture phase diagram. Our simulations are composed of 1000-1600 molecules for a total of 80,000-130,000 atomic sites, with total simulation times of 60-100 ns. We first show that a pure 2PhP system self-assembles into isotropic, nematic, smectic A and smectic C phases, and a pure PhP14 system self-assembles into isotropic and smectic C phases. Binary mixtures of PhP14 and 2PhP display a stabilization of the smectic A phase at the expense of the smectic C and nematic phases. We determine that the concentration-induced phase transition from the smectic C to the smectic A phase in the mixture is driven by an out-of-layer fluctuation arrangement of the molecules. We also observe that the tilt angle in the smectic C phases formed in the mixtures is concentration dependent. The results of our simulations are in good agreement with the experimental findings of Kapernaum et al. [J. Org. Chem. 5, 65 (2009)], thus showing that atomistic simulations are capable of reproducing the phase behavior of liquid crystal mixtures and can also provide microscopic details regarding the mechanisms that govern phase stability.

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“…Preliminary observation of the dynamics of colloidal silica rods [17] in the smectic phase suggests larger values of D xy than D z . Interlayer diffusion is also studied by MD simulations in a model of rod-sphere mixture [18], hard-core spherocylinders [19], and in atomic detailed sexithiophene [20]. The ratio is much smaller for these simulated shorter particles (molecules), but still D z /D xy > 1 [18,20] or D z /D xy ≃ 1 [19] in the SmA phase.…”

Section: One-dimensional Hopping In Liquid Crystal Phasementioning

confidence: 99%

“…Interlayer diffusion is also studied by MD simulations in a model of rod-sphere mixture [18], hard-core spherocylinders [19], and in atomic detailed sexithiophene [20]. The ratio is much smaller for these simulated shorter particles (molecules), but still D z /D xy > 1 [18,20] or D z /D xy ≃ 1 [19] in the SmA phase. Experimental studies of thermotropic smectic phases show D xy /D z ≥ 1 [21].…”

Section: One-dimensional Hopping In Liquid Crystal Phasementioning

confidence: 99%

One-, Two-, and Three-Dimensional Hopping Dynamics

et al. 2013

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Hopping dynamics in glass has been known for quite a long time. In contrast, hopping dynamics in smectic-A (SmA) and hexatic smectic-B (HexB) liquid crystals (LC) has been observed only recently. The hopping in SmA phase occurs among the smectic layers (one-dimensionally), while hopping in HexB phase occurs inside the layers (two-dimensionally). The hopping dynamics in SmA and HexB liquid crystal phases is investigated by parallel soft-core spherocylinders, while three-dimensional hopping dynamics in inherent glassy states is investigated by systems of Weeks-Chandler-Andersen (WCA) spheres. The temperature dependence of diffusion coefficients of hopping in SmA phase can be described by the Arrhenius equation characteristic of activation process. In HexB LC phase, the diffusion coefficients saturate at higher temperatures. In a system of WCA spheres, the values and temperature dependence of diffusion coefficients depend on the observed states.

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An atomistic simulation of the liquid-crystalline phases of sexithiophene

Cited by 63 publications

References 66 publications

From Chiral Islands to Smectic Layers: A Computational Journey Across Sexithiophene Morphologies on C₆₀

From Chiral Islands to Smectic Layers: A Computational Journey Across Sexithiophene Morphologies on C₆₀

Atomistic simulations of liquid crystal mixtures of alkoxy substituted phenylpyrimidines 2PhP and PhP14

One-, Two-, and Three-Dimensional Hopping Dynamics

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An atomistic simulation of the liquid-crystalline phases of sexithiophene

Cited by 63 publications

References 66 publications

From Chiral Islands to Smectic Layers: A Computational Journey Across Sexithiophene Morphologies on C60

From Chiral Islands to Smectic Layers: A Computational Journey Across Sexithiophene Morphologies on C60

Atomistic simulations of liquid crystal mixtures of alkoxy substituted phenylpyrimidines 2PhP and PhP14

One-, Two-, and Three-Dimensional Hopping Dynamics

Contact Info

Product

Resources

About

From Chiral Islands to Smectic Layers: A Computational Journey Across Sexithiophene Morphologies on C₆₀

From Chiral Islands to Smectic Layers: A Computational Journey Across Sexithiophene Morphologies on C₆₀