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T E R N A RY Z N O / Z N P C / P 3 H T S Y S T E M4Contents4.1 Self assembling of ZnPcs on ZnO surface504.1.1 Interaction of a single ZnPc withthe ZnO surface 504.1.2 Aggregation of ZnPc on ZnO 514.2 Polymer interaction with ZnPcs functionalizedZinc Oxide 534.3 Electronic and optical properties of thesystem 554.3.1 Electronic level alignment 554.3.2 Charge densities and recombination574.3.3 Absorption spectra 584.4 Conclusions 59The use of interlayers between the inorganic and theorganic components of hybrid interfaces has great potentialin order to engineer photovoltaic properties. Several attempshave been made in this direction, as already rewiedin section 1.2. Such interlayers can reduce the charge recombination,enlarge the light absorbed spectrum and increasethe compatibility between the polymer and the substrate[44, 45, 46, 47].In this chapter we study the anchoring, energetics andassembling of a particular kind of phthalocyanine, the zincphthalocyanine (ZnPc), on the ZnO surface. We choose Zn-Pcs for their tendency to aggregate on metal oxides [5]forming self-assembled monolayers strongly bound to thesurface. This property allows the use of these moleculesas interlayer in hybrid systems without using anchoringgroups that can modify the properties of the interface.The ternary system ZnO/ZnPc/P3HT is investigated fromthe morphological point of view together with the analysisof its electronic and optical properties.49
50 ternary zno/znpc/p3ht system4.1 self assembling of znpcs on zno surface4.1.1 Interaction of a single ZnPc with the ZnO surfaceThe first step in our work is to create the ZnO/ZnPcsinterface by MPMD. To this aim, we study first of all theattraction of a single ZnPc molecule on the ZnO surface.Since its electronic properties will be studied at DFTlevel, we choose to use a ZnO surface coming from an abinitio optimization of a crystal slab formed by six atomiclayers of bulk ZnO parallel to the (10¯10) plane, and we donon relax the atoms positions during classical moleculardynamics simulations. The DFT surface, reproduce in a betterway some features of the 10¯10 ZnO wurtzite structuresuch as the upward shift of the oxygens in the ZnO surfacedimers. The details of the theoretical method to treat thissurface are reported in section A.3.The interaction between the ZnO surface and a ZnPcmolecule relaxed on it, is reported in Figure 4.1 as a functionof the relative distance between molecule and surface.The bound state is characterized by the molecule at 1.96Å from the surface with a binding energy of 2.2 eV. Themolecule is slightly rotated with respect to the ZnO dimersand not perfectly planar.Figure 4.1.: Interaction between a ZnPc molecule and the ZnO surfaceas a function of the distance.The lack of planarity in the molecule is due to the coulombicinteraction between the central Zn atom of the moleculeand the oxygen of the surface [56] and can be observedby relaxing the system by both DFT (Figure 4.2 left) or
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Università degli Studi di Cagliari
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A C K N O W L E D G M E N T SI woul
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example of a novel class of systems
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C O N T E N T S1 introduction 11.1
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L I S T O F F I G U R E SFigure 1.1
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List of FiguresxiiiFigure 2.15 Init
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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 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 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
Page 108 and 109: ibliography 89Phys. Chem. Chem. Phy
Page 110 and 111: ibliography 91[65] D. J. Binks and
Page 112 and 113: ibliography 93cells,” Energy Envi
Page 114 and 115: ibliography 95[97] C. Ingrosso, A.
Page 116 and 117: 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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