Design And Synthesis Of Novel Singlet Fission Materials Based On Peryleneimide Framework

Singlet fission is an effective multi-exciton generation down-conversion photophysical process,and is the most promising approach to break through the traditional single-cell organic solar cell theoretical photoelectric conversion efficiency SQ(Shockley-Queisser)limit.In this thesis,the typical organic industrial dyes perylene diimide and vat orange 3 which are cheap and easy to obtain are used as the basic unit to design and synthesize A-D-A type perylene diimide derivatives and vat orange 3 ring derivatives.The femtosecond transient absorption spectra is used to systematically investigate singlet fission properties of the molecules.The thesis includes the following parts:1.The A-D-A type perylene diimide derivatives PDI-1T and PDI-2T were designed and synthesized,and their properties of singlet fission were studied by a series of optical characterizations.We tested the transient absorption spectra and kinetic behaviors of the perylene diimide derivatives by means of femtosecond ultrafast spectroscopy,indicating that both PDI-1T and PDI-2T undergo intramolecular singlet fission process in solution.2.The effects of solvent polarity,concentration and aggregation state on the intramolecular singlet fission process in PDI-1T and PDI-2T solutions were systematically investigated.The results show that PDI-1T is more prone to undergo singlet exciton fission behavior in the strong polar solvent 1,4-dioxane.It is speculated that the singlet exciton is synergistically promoted by the appropriate electron coupling and A-D-A molecular structure.Singlet fission process of molecular PDI-1T and PDI-2T was not observed in the solid film.It is speculated that the molecular packing modes are more closely in the solid film,resulting in too strong intermolecular coupling.There are other approachs to compete with the singlet fission process.3.The DBBN and BPBN derivatives were designed and synthesized,and their optical properties were studied.Femtosecond transient absorption experiments show that neither DBBN nor BPBN has experienced intermolecular singlet fission process under the experimental conditions.At the same time,it was found that molecular BPBN is a novel piezochromic material,which can show pressure response under static pressure conditions and mechanical grinding conditions.4.The pyimidazole derivative PyI-TPA and the divinyl derivative OPV-TPA were designed and synthesized,and their pizochromic properties under static pressure were investigated.The preliminary in-situ high pressure Raman experiment showed that the PyI-TPA and OPV-TPA molecules did not show obvious pressure response.