New Type Of Porphyrin -) Imide Molecules Array Synthesis And Photoelectric Performance Study

Porphyrin derivatives are ideal substitutes of chlorophyll molecule in study of artificial photosynthesis, which possess unique structural and property characteristics. Perylenediimides exhibit excellent photothermal and chemical stability,they can be easily chemically modified and own outstanding photoelectric properties. Porphyirn-perylene molecular arrays are constructed by linking porphyrin and perylene moieties in a certain way, and excellent photoelectric performances will be obtained.On the basis of the recent domestic and foreign progress in the field of porphyirn-perylene molecular arrays were summarized, the review showed the promising applications of these arrays in the molecular photo-electric devices especially in the photo-electric transfer aspect, and raised three existed fundamental problems:(1) the synthetic routes are long and inefficient with low yield, as a result, there are relatively few candidates of the arrays; (2) the reports on the aggregation states of the porphyrin-perylene arrays are rare; (3) the researches on the properties of the arrays focuses on the photophysics and photochemistry characteristics, and researches on the arrays for applications to the photo-electric devices including the organic solar cells are few. A research strategy was accordingly proposed for this thesis:it emphasized on the design and synthesis of porphyrin-perylene arrays, on the investigation of the electronic structures and aggregation states, the research work mainly concerned the charge/energy transfer processes in the arrays, and the photo-to-electricity conversion properties of this arrays in photoelectrochemical cell and organic film solar cell are studied preliminarily.Using the Sonogashira coupling reaction, two novel porphyrin-perylene molecular arrays PDI-ZnPOR2 and PDI-ZnPOR4 were synthesized. The intermediate compounds and target molecular arrays was characterized by FT-IR,1HNMR and elemental analysis. The conditons of synthesis were also discussed. The chemical structures of the arrays were further proved by the results of ESI-MS and the X-ray Phtoelectron Spectroscopy.The electronic structures of the two porphyrin-perylene arrays have been investigated by the UV-vis absorption spectroscopy and cyclic voltammetry (CV). The absrorption of array PDI-ZnPOR2 mainly exhibits the features of porphyrin absorption, and it shows two additional absorption peaks in the long-wavelength region, which indicates relatively strong electronic interactions exsits between the porphyrin moiety and perylene moiety in the ground state; While the absorption of array PDI-ZnPOR4 is a simple superposion of those of the molecular components, this indicates that the electronic interaction between the molecular components in the array is weak in the ground state. The electrochemistry behavior of the two arrays showed reversible oxidation and reduction processes; In additionally, the band gap of the array PDI-ZnPOR2 and PDI-ZnPOR4 by calculation were 1.57 eV and 1.59 eV, repectively, the low band-gap feature make the the two arrays have potential applications in the fields of organic semiconductor and solar cells.Photoinduced electron-transfer and energy transfer processes of arrays PDI-ZnPOR2 and PDI-ZnPOR4 in dilute solutions have been investigated in detail, and the decay mechanism of the excited states were explored. Selectively excited porphyrin chromophore at 430 nm, molecular arrays exhibits weak porphyrin emission, and the fluorescence intensity are considerably reduced compared to the reference compound. This indicated photoinduced electron transfer process from porphyrin units to perylene units in these arrays. Exciting perylene chromophore at 560 nm, significant fluorescence quenching of the perylene moiety was observed, arrays only showed weak porphyrin emission, and compared to reference compound, the fluorescence intensity was considerably decreased. This reveals the existence of the photoinduced energy transfer processes from perylene to porphyrin, following the electron transfer process from the excited porphyrin to the perylene. These results indicated the efficient photoinduced intramolecular electron transfer processes either the porphyrin was excited or the perylene was excited. In polar solvent THF, the array exhibits much stronger queching than that in nonpolar solvent toluene, which further confirmed the existence of the efficient electron transfer porphyrin units to perylene moiety. The results of the time-resolved fluorescence spectroscopy also proved that the light induced intramolecular electron transfer really occurred in these arrays.The aggregated states of these arrays in different solvents were researched by SEM and TEM. The structures of the aggregated morphology differ with the variation of the solvents, which indicated the occurrence of the solvent-induced molecular aggregate states variation. The results of the XRD reveal the solid states of the arrays are amorphous. Measurements of thermogravimetry (TG) and differential scanning calorimetry (DSC) exhibits the two arrays has good thermal and physical stability, which satisfy the demand for preparation of organic solar cells.Molecular arrays PDI-ZnPOR2 and PDI-ZnPOR4 possess excellent light harvesting performance, the results of the lightinduced electronic spin resonance of arrays in film states indicates that lightinduced intramolecular electron transfer occurs, which makes the two arrays showing their potential applications in lightinduced charge separate devices. On these bases, we fabricated photoelectrochemical cells and organic film solar cells based on the two arrays, and made preliminarily researches on the photo-to-electric properties of these devices. Obvious photovoltaic effect of the film working electrode was discovered in the photoelectrochemical cell, and rapid and steady photocurrent was generated upon illumination by simulated solar light. Single layer solar cells using arrays PDI-ZnPOR2 and PDI-ZnPOR4 as active layer were fabricated by solution spin. Under air mass (AM) 1.5 simulated solar illumination, the power conversion efficiencies (PCE) of the single layer device using PDI-ZnPOR2 and PDI-ZnPOR4 as active layer has a much lower PCE. The reason for this poor PCE lies in that in the arrays, the perylene core was surrounded by porphyrin moieties, therefore, the transporting channel might be disrupted, which increased the recombination probabilities of the electrons and holes.The research work on solar cell devices based on the porphyrin-perylene arrays remain to be improved, and due to limits in experiment conditions and time, an in-depth study on relationships between aggregates morphology and device perfomances are needed in future studies; The photoelectric conversion efficiency is rather low, therefore, further experiments concerning optimization of device performances are under way. Preliminary research work in the respect provide basis for study in application of porphyrin-perylene arrays in organic solar cells.