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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