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2.5 nanocrystalline p3ht 25Figure 2.10.: S(q) for an ideal s-crystal and for a bulk relaxed at 1K and 300 K. The direction x is parallel to the backbone(top panel), the y corresponds to the interdigitation (middlepanel) and the z to the π − π (bottom panel).faces and the modifications in the polymer caused by thepresence of the inorganic substrate. In particular, the interdigitationbetween the molecules has an effect on matchingthe lattice parameters of the substrate, affecting the depositionof the polymer and the order at the interface.We study P3HT nanocrystals of different dimensions inorder to investigate the possible dependence of the interdigitation(that is the distance between h-foils) on the sizeof polymeric nanoparticles. To this aim, we build a seriesof model nanostructures by putting together s-foils and h-foils composed by polymer chains each formed by sixteenthiophenes. The initial interdigitation distance is chosen tobe the same of a perfect crystalline bulk (15.8 Å [3]). InFigure 2.13 is reported an example of the system studied.Table 2.1 (columns 1 and 2) reports the size of the systemschosen for the analysis: the symbol s indicates thenumber of s-foils (growing in the z direction) while h in-
26 p3ht - poly(3-hexylthiophene)Figure 2.11.: Configuration of a P3HT 010 (top) and 100 (bottom)surfaces after a low temperature relaxation (left) and aroom temperature annealing (right).dicates the number of h-foils (growing in the y direction)(see Figure 2.13). For each nanocrystal we perform a relaxationby annealing the system at low temperature. Thedistances between the h-foils (i.e. interdigitation) are reportedin column 3 of Table 2.1. In some cases we studythe nanocrystals resulting by applying the periodic boundaryconditions (pbc) in one or two directions, by allowingrelaxations in the corresponding cell dimensions.First of all we note that there exists a non-monotonic dependenceof the lattice parameter on the size of the nanocrystals.Table 2.1 shows that for pbc along h and s (an infiniteslab of width 16T), the distance between h-foils is the maximum,reaching one of the distances previously identifiedfor the intedigitation of two infinite polymer chains (16 Å).If pbc are applied only along one direction, the interdigitationdistance is smaller (from 13 to 14.6 Å with anexception at 18 Å). Furthermore, whenever the pbc arepresent, the zigzag-like conformation is observed in the relaxednanocrystals similarly to the case of the infinite bulk.As for the finite systems with no pbc, they always giverise to a reduction of the interdigitation distance with respectto the slab, but there is a non-monotonic dependenceon the size. Lower values are found for the nanocrystalscomposed by eight or sixteen s-foils (12.57 Å), while thosecomposed by four s-foils give higher interdigitation distances(up to 16.11 Å). Furthermore, these latter turn outto be the more ordered (see Figure 2.13 compared with Figure2.15). The increase of the size in the z direction (s) is
Page 1 and 2: Università degli Studi di Cagliari
Page 4: A C K N O W L E D G M E N T SI woul
Page 7 and 8: example of a novel class of systems
Page 10 and 11: C O N T E N T S1 introduction 11.1
Page 12 and 13: L I S T O F F I G U R E SFigure 1.1
Page 14 and 15: List of FiguresxiiiFigure 2.15 Init
Page 16 and 17: List of FiguresxvFigure 4.6Figure 4
Page 18: Figure 5.7Figure 5.8Figure A.1Figur
Page 21 and 22: 2 introduction1-3 eV) and the trans
Page 23 and 24: 4 introductionorder in such a compl
Page 25 and 26: 6 introductionprocesses that need t
Page 27 and 28: 8 introduction1.2 physical factors
Page 29 and 30: 10 introductionrecovered by the int
Page 31 and 32: 12 introductionA cheap and environm
Page 33 and 34: 14 introductiondensed phases [63, 7
Page 36 and 37: P 3 H T - P O LY ( 3 - H E X Y LT H
Page 38 and 39: 2.1 mechanism of assembling and mor
Page 40 and 41: 2.2 p3ht assembling and intermolecu
Page 42 and 43: 2.3 p3ht crystalline bulk phases 23
Page 46 and 47: 2.5 nanocrystalline p3ht 27Table 2.
Page 48 and 49: 2.6 conclusions 29Figure 2.13.: Ini
Page 50 and 51: P O LY M E R / S E M I C O N D U C
Page 52 and 53: 3.3 adhesion of a single p3ht molec
Page 54 and 55: 3.4 p3ht/zno interface 35surface (t
Page 56 and 57: 3.5 p3ht/zno interface: low deposit
Page 58 and 59: 3.6 p3ht/zno interface: high deposi
Page 64 and 65: 3.7 effective model for the transpo
Page 66 and 67: 3.8 conclusions 47As for the low te
Page 68 and 69: T E R N A RY Z N O / Z N P C / P 3
Page 70 and 71: 4.1 self assembling of znpcs on zno
Page 72 and 73: 4.2 polymer interaction with znpcs
Page 74 and 75: 4.3 electronic and optical properti
Page 76 and 77: 4.3 electronic and optical properti
Page 78 and 79: 4.4 conclusions 59ties. The absorpt
Page 80 and 81: I N T E R A C T I O N B E T W E E N
Page 82 and 83: 5.2 solvent thf interaction with zn
Page 88 and 89: 5.3 conclusions 69γ L/L ∼ 0.112
Page 90 and 91: C O N C L U S I O N SIn this thesis
Page 92 and 93: M O L E C U L A R D Y N A M I C SAa
Page 94 and 95:
A.1 molecular dynamics 75a.1.2The t
Page 96 and 97:
A.2 the force field 77Finally, τ t
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A.2 the force field 79Waals interac
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A.3 methods 81tional Theory (DFT) l
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B I B L I O G R A P H Y[1] http://w
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ibliography 85[17] J. D. Servaites,
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ibliography 87Zakeeruddin, and M. G
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ibliography 89Phys. Chem. Chem. Phy
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ibliography 91[65] D. J. Binks and
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ibliography 93cells,” Energy Envi
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ibliography 95[97] C. Ingrosso, A.
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ibliography 97298.15 k,” Journal
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ibliography 99charges. am1-bcc mode
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colophonThis document was typeset u
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