Synthesis,Photovoltaic Properties Of BODIPY Sensitizers And Cosensitization Of BODIPY And Porphyrin Sensitizers

In this work,BODIPY was chosen as framework,and series of D-?-A BODIPY dyes had been designed and synthesized and employed in DSSC?dye-sensitised solar cell?.Based on the study on the co-sensitization of BODIPY dye 2-6b and porphyrin dye PorD,a BODIPY-Porphyrin dyad was designed and synthesized to obtain better light harvesting efficiency.The main contents of this thesis were listed as following:?1?BODIPY framework 2-3 had been synthesized by using 2,4-dimethylpyrrole and methyl-4-formylbenzoate as the starting materials via condensation reaction,oxidation-reaction with DDQ and coordination reaction with BF3·OEt2 successively.Subsequently,BODIPY dyes 2-6a 2-6d were obtained by Knoevenagel reaction between compound 2-3 and corresponding aromatic aldehyde?e.g.4-?diphenylamino?benzaldehyde,4-?9H-carbazol-9-yl?benzaldehyde,4-?5H-dibenzo[b,f]azepin-5-yl?benzaldehyde and 4-?10,11-dihydro-5H-dibenzo[b,f]azepin-5-yl?benzaldehyde?followed by hydrolysis of COOMe group.The structures of dyes 2-6a 2-6d had been characterized by 1H-NMR and MS spectra,and their optical,electrochemical and photovoltaic properties had been measured to investigate the influence of different triarylamine donors on the optical,electrochemical properties and photovoltaic performances of sensitizers 2-6a 2-6d.The best performance was realized for the cell based on rigid BODIPY sensitizer 2-6b with a fluorescence quantum yield of 0.516 and a fluorescence lifetime of 4.02 ns,resulting in a short circuit photocurrent density of 14.10 mA·cm-2 and an overall conversion efficiency of 4.42%,which was fairly good results achieved for boron BODIPY type sensitizer-based solar cell.It was believed that locking of phenyl rings of triphenylamine donors lowered the nonradiative energy loss caused by the rotation and vibration of phenyl rings,which in turn facilitate the intramolecular charge transfer between the donor and the BODIPY core.The results revealed that the BODIPY sensitizer with a greater fluorescence quantum yield and longer fluorescence lifetime would lead to the better photovoltaic performance.?2?Dyes Por-?-BODIPY and Por-meso-BODIPY had been designed and synthesized via Knoevenagel reaction between BODIPY framework 2-3 and zinc?beta or meso?formylated tetraphenylporphyrin followed by hydrolysis of COOMe group,and their structures had been characterized by 1H-NMR and MS spectra.The introduction of porphyrin ring not only enhanced the light absorption in higher energy region of dyes Por-?-BODIPY and Por-meso-BODIPY,but also broadened the photoabsorption region of BODIPY dyes.However,Por-?-BODIPY sensitized solar cell obtained only a photon to current conversion efficiency of 1.91% because of H-aggregation.Though Por-meso-BODIP sensitized solar cell gave a better Jsc?short-circuit current density?of 11.83 mA·cm-2 than 2-6b based solar cell,only 3.55% of photon to current conversion efficiency was realized because of lower Voc?open voltage?resulting from bigger molecular volume.?3?Porphyrin dye PorD was chosen for co-sensitization with dye 2-6b,two dyes had complementary absorption spectrum.For co-sensitization of PorD and 2-6b,the optimized molar ratio of sensitizing dye solution between PorD : 2-6b was found to be 0.5 : 1,and the best photoelectric conversion efficiency of 5.06% was obtained,which was 14.7 percent higher than that of single dye?PorD : ? = 2.96% or 2-6b : ? = 4.42%?sensitized solar cell.The reason for a higher Jsc of PorD / 2-6b co-sensitized solar cell was twofold: reciprocal inhibition of dye aggregation,and F?rster resonance energy transfer from dye PorD to dye 2-6b.But the Voc of PorD / 2-6b co-sensitized solar cell decreased somewhat,which limited the further improvement of the photovoltaic performance.?4?A BODIPY-Porphyrin dyad dye 5-9 had been designed and synthesized via Suzuki cross coupling reaction of PorD chromophore and 2-6b chromophore,and structures of intermediates target dye molecule had been characterized by 1H-NMR and MS spectra.UV-vis absorption spectrum revealed the absorption spectrum of dye 5-9 was possessed of characteristic absorption bands of both dyes PorD and 2-6b,the light harvesting abilitiy PorD / 2-6b co-sensitized photoanode was significantly superior to single dye?PorD or 2-6b?sensitized photoanode.However,intramolecular F?rster resonance energy transfer from porphyrin chromophore to BODIPY chromophore of dye 5-9 was presented,and the direction of energy transfer was contrary to that of photo-induced electron injection,which was adverse to electron injection of excited 5-9 into the TiO₂ conduction band.Consequently,dye 5-9 sensitized solar cell gave a Jsc of 5.10 mA·cm-2,a Voc of 475 mV,and only a total photoelectric conversion efficiency of 1.50%.