Synthesis And Characterization Of Organic Small Molecule Receptors Modified With Electron-donating Groups

The society is in the era of high-speed development,the rapid consumption of non renewable energy forces people to develop other effective new energy technologies,such as nuclear energy,geothermal energy and solar energy,they are all new energy with unlimited development potential.The low-cost,environment-friendly and easy to manufacture organic photovoltaic(OPV)cell is an effective way of using solar energy.It is found that the main receptor materials in the past ten years are fullerenes and their derivatives From the previous research of organic photovoltaic materials.but their visible light absorption is weak,hard to purify,the cost is high,the morphology stability is poor and it is not easy to modify and other shortcomings are obvious,and the efficiency of organic photovoltaic cells based on fullerene receptor(FA)has also reached the bottleneck,it is hard to make breakthrough progress.Therefore,the design and synthesis of non fullerene acceptor(NFA)materials have attracted extensive attention.Through chemical structure tailoring and continuous optimization of device technology,the efficiency of organic photovoltaic cells composed of NFA and polymer donor materials has exceeded that of fullerene derivatives.In recent two years,it has been reported that the device efficiency of non fullerene small molecules as acceptor materials has been increasing,which has exceeded 17%.NFA materials are mainly based on ITIC heavy ring acceptors.Researchers have carried out a lot of experiments in the optimization design of such molecules.The photovoltaic properties of the receptor molecules can be adjusted by changing the central skeleton structure,the side chain substituent group,the end group and the bridging unit.this molecular structure is generally acceptor donor acceptor A-D-A type,which has advantages over perylene diimide and dithiophene pyrrole pyrrole pyrrole diketone in spectral response and device efficiency,but whether its structural type is optimal remains to be discussed,so the development of new receptor materials needs to be further developed.In the second chapter,the A-D-A-D-A small molecule receptor GQIC is synthesized by using the dithiopheno furan ring with strong electron donating ability instead of cyclopentadiethiophene,which is connected with benzothiadiazole as the central framework and combines with ninhydrin end group.The spectral response of the small molecule GQIC after the change of the molecular structure has been greatly broadened.The absorption band edge of the film is 910 nm,which is 109 nm more red shifted than the ITIC.The energy levels of the highest occupied orbit(HOMO)andthe lowest unoccupied orbit(LUMO)are-5.44 /-4.02 ev respectively.The aggregation behavior and photovoltaic performance of molecules are different from those of ITIC.The introduction of F atom can effectively regulate the molecular energy level and optical band gap,enhance the light collection ability of the molecule and improve the short-circuit current density(JSC).In Chapter 3,the introduction of F atom on the indanone end group of small molecule is used to synthesize GQIC-4FIC.Compared with GQIC nonfluorinated small molecules,the absorption edge of fluorinated molecules has a red shift of 10 nm,and the energy level of the molecule has a significant decrease,with the HOMO/LUMO energy levels of-5.61 /-3.92 eV,respectively.The stacking and crystallizing properties of the molecules changed.In the fourth chapter,we synthesized ITOR-IC series of small molecule acceptors with excellent photoelectric performance according to the literature,matched them with donor material PM6,made photovoltaic devices and compared them,and optimized the device process.In view of whether there is fluorine atom or not,and the effect of fluorine atom substitution on small molecule spectral absorption,electrochemistry,dielectric constant and so on,we studied dielectric The correlation between the constants and the photoelectric properties of the devices.ITOR-4FIC not only has the highest epsilon r5.1 in three materials(4.03 in ITOR-IC and 4.46 in ITOR4F-IC),but also has the best PCE of 11.1% in the device combined with donor PM6.