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4.4 conclusions 59ties. The absorption spectrum of the ZnPc in the gas phaseis characterized by the Q band and Soret band, common toalmost all phthalocyanine and porphyrin molecules, fallingin the red part of the visible region (1.9 eV) and in the nearUV region (3.6 eV), respectively [102].These absorption peaks are well reproduced by TDDFPTcalculations (Figure 4.8 A) and are subjected to a relevantred shift (1.7 eV for the Q band and 3.1 eV for the Soretband) when the ZnPc molecules are on the ZnO surface[4] (Figure 4.8 B). As for the P3HT, long chains in generalare characterized by a strong absorption of visiblelight around 1.9-2.0 eV [103]. The P3HT oligomer here describedpresents a peak at 2.3 eV (Figure 4.8 E), which isred shifted at 2.1 eV when the P3HT interacts directly withthe ZnO (Figure 4.8 D), but is found almost untouched inthe ternary system (Figure 4.8 C). Therefore, the resultingoptical spectrum of the ternary system (Figure 4.8 C) ischaracterized by three strong absorption peaks spanningall the visible light range suggesting an optimal utilizationof the solar light.4.4 conclusionsIn conclusion, in this chapter we have described the propertiesof a hybrid ternary system in which the hybrid P3HT/ZnOinterface is functionalized by a optically active self-assembledorganic interlayer formed by macrocyclic ZnPc molecules.We have seen that the ZnPc molecules on ZnO, results in astable and ordered self-assembled monolayer. This molecularlayer act as an active electronic spacer between polymerand the metal oxide, potentially hindering the electronholerecombination process. Finally, the strong optical absorptionof the ZnPc and P3HT, indicates a optimal sensitizationof the ZnO substrate across all the visible lightrange.This system is an example of a novel architecture thatcan be designed by a multiscale predictive modeling whoseperformances are currently under experimental investigation.