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3.5 p3ht/zno interface: low deposition rate 37surface. For the low density case a better matching can beobtained. For this reason, in order to favor the order at theinterface, we generate our atomistic model by using s-foilswith interdigitation distance 15.8 Å.The s-foil is let to relax on the surface under the attractiveinteraction with the ZnO substrate. We find that theinitial interdigitation distance is affected during the formationof the interface. The initial value is preserved only forthe first P3HT layers and the polymer disorder increaseswith the distance from ZnO (see Figure 3.4 and Figure 3.5).Figure 3.5.: Final configuration of the LDR system at low temperature.The above visual analysis is confirmed quantitatively bycalculating the structure factor of the polymer in the threex, y and z direction. In particular the peak in y and x directionare lowered with respect to the ideal s-crystal (compareFigure 3.6 left and middle with Figure 2.10 top andmiddle). The lowering of S z in top-right panel of Figure 3.6and its broadening, indicates an increasing disorder in theπ − π direction.The interface has been also studied at room temperature(annealing at 300 K by Nosé-Hoover thermostat). Itis found that the first polymer layer remains fixed to thesurface because of the strong ZnO-polymer interaction butthe disorder induced by thermal fluctuations affects subsequentlayers (see Figure 3.7). This is indicated by thelowering of S y in the bottom-middle panel of Figure 3.6.Moreover, the S z peak shift to lower q values indicates anincrease of the interplanar distance (from 4 to 4.5 Å) inducedby temperature.
38 polymer/semiconductor interfaceFigure 3.6.: Structure factor in the three crystallographic directionsfor the LDR interface at low (top) and room temperature(bottom).Figure 3.7.: Final configuration of the LDR system at 300 K.3.6 p3ht/zno interface: high deposition rateThe HDR interface is generated by putting a previouslyformed P3HT s-crystal (with same dimension of the LDRfinal model) at 7 Å of distance from the ZnO surface(see Figure 3.8 upper panel) and relaxing (Figure 3.8 lowerpanel).Different HDR interface models are possible dependingon the crystallographic polymer plane that interacts withthe ZnO surface. We choose in particular the 010 and the100 planes and we refer to them by 010 HDR and 100 HDRhybrid interfaces, respectively. In the 010 HDR interface,the polymer nanocrystal is deposited on the substrate inthe face-on configuration and the π − π channels are perpendicularto the surface, as in the LDR case (Figure 3.8).
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 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 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
Page 98 and 99: A.2 the force field 79Waals interac
Page 100 and 101: A.3 methods 81tional Theory (DFT) l
Page 102 and 103: B I B L I O G R A P H Y[1] http://w
Page 104 and 105: ibliography 85[17] J. D. Servaites,
Page 106 and 107:
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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