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2.2 p3ht assembling and intermolecular forces 21Figure 2.5.: Static interaction between two P3HT chains at differentinterdigitation distances.Figure 2.6.: Perspective-view (left), top-view (center) and side-view(right) of P3HT equilibrium structures. The white boxrepresent the othorombic unit cell with the correspondinglattice parameters (figures from [3]).give rise to a larger edge-to-edge distance corresponding tominimum A of a = 15.8 Å and b = 8.0 Å (correspondingto a thiophene-thiophene distance of 4 Å) in Figure 2.7.The above analysis permits to conclude that the P3HTassembling is mainly driven by the π − π interaction [3].2.2 p3ht assembling and intermolecular forcesDue to the fact that in vacuo the ruling interaction betweentwo polymer chains is the π − π one, it is possibleto build two-dimensional P3HT structures formed bychains stacked on top of each other. This structure (hereafternamed h-foils) have hydrophobic surfaces exposingthe hexyl chains (see Figure 2.3 left).Two different foils interact attractively and can spontaneouslyorganize into bilayers [3]. The thiophene rings inthe resulting structure turn out to be tilted, as a result of
22 p3ht - poly(3-hexylthiophene)Figure 2.7.: Energy landscapes obtained by MP for the bulk P3HTstructure. The lattice parameters are referred to the equilibriumvalues a 0 and b 0 while the total energy is referredto the energy of two unbound chains (figure from [3]).a long-range interaction with the other foil (Figure 2.8 toppanels) [3]. In particular, it was found that the thiophenerings belonging to adjacent h-foils formed in a zigzag-likeconfiguration less interdigitated (16.2 Å) with respect tothe ideal minimum energy phase. Such a value is in agreementwith the experimental results [82].On the other hand, in presence of a planar surface stronglyinteracting with the polymer (e.g. with a binding energyfor the face-on polymer comparable with the π − π interaction)it is likely that P3HT molecules will align on the substrateforming s-foils (see Figure 2.3 right) [3]. The polymeris expected to further grow according to a layer-by-layermechanism as depicted in Figure 2.8 bottom panel .2.3 p3ht crystalline bulk phasesIn the present work, in order to study the crystallinityof the polymer bulk phase, we calculate a functional of theatomic positions, hereafter named S(q):S(q) = 1 N∣N∑j=1f j · e −iq·x j∣(2.1)where x j are the coordinates of the j-th atom, N is the numberof atoms and |q| = 2π /λ is any possible wave vector.
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 42 and 43: 2.3 p3ht crystalline bulk phases 23
Page 44 and 45: 2.5 nanocrystalline p3ht 25Figure 2
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
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M O L E C U L A R D Y N A M I C SAa
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A.1 molecular dynamics 75a.1.2The t
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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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