Synthesis And Properties Of Organic Functional Molecules Based On Naphthodithiadiazole

As the critical components of dye-sensitized solar cells(DSSCs)and perovskite solar cells(PSCs),organic functional molecules are applied as the sensitizer and hole-transporting material,respectively,affecting the photovoltaic performance to considerable extent.Benzothiadiazole,benzodithiadiazole,and benzotriazole are widely used as the electron-withdrawing segment in the design of organic functional molecules.Recently,fused ring heteroaromatics,such as naphthothiadiazole and naphthodithiadiazole groups,have attracted some attentions due to their high electron-withdrawing capabilities.However,the regulation of these electron-withdrawing groups on dye properties is still need to be investigated in detail.Thus,herein,naphthothiadiazole and naphthodithiadiazole groups have been applied as the electron acceptor in the design of organic functional molecules,which are applied as the sensitizer and hole-transporting material in DSSCs and PSCs,respectively.The effects of various on the properties of organic functional molecules have been investigated systematically.In the first chapter,the development of dye-sensitized and perovskite solar cells have been introduced.The recent research progress of organic dyes based on different acceptor groups have been reviewed in detail.The design ideas and research contents of this thesis are proposed.In the second chapter,three D-A-?-A sensitizing dyes,coded as CS-70-72,have been designed and synthesized,utilizing benzothiadiazole,naphthadiazole,and naphthodithiadiazole as the auxiliary acceptor groups,respectively.The target compounds are obtained through Ullmann condensation reaction,SUZUKI coupling reaction,and substitution reaction.All chemical structures of the target compounds and intermediates are characterized by ¹H NMR,¹³C NMR and FT-IR.In the third chapter,the photophysical,electrochemical,and photovoltaic properties of the CS-70-72 are investigated to evaluate the effect of different auxiliary acceptor groups on the properties of the dyes.With the enhancement of electron-withdrawing capability,the LUMO energy level of CS-71-72 are selectively stabilized thus resulting in the reduction of energy band gap.Compared with the reference dye CS-70,CS-71-72,with naphthothiadiazole and naphthodithiadiazole,respectively,as the auxiliary acceptor group,presents a red-shifted absorption band of 64 and 46 nm,which effectively expands the spectral absorption range and improves light harvesting capability.Moreover,the electron injection efficiency of CS-71-72 is higher than that of CS-70.Finally,the device based of CS-72 exhibited the best photovoltaic performance among three sensitizers.In the fourth chapter,two D-A-D hole-transporting materials,coded as CS-82-83,have been designed and synthesized,utilizing benzothiadiazole and naphthodithiadiazole as the acceptor groups,respectively.The target compounds are obtained through one-step Ullmann condensation reaction.All chemical structures of the target compounds and intermediates are characterized by ¹H NMR,¹³C NMR and FT-IR.UV-Vis absorption spectroscopy,fluorescence emission spectroscopy,cyclic voltammetry,and thermogravimetric analysis tests are used to evaluate the performance of hole-transporting materials.Compared with the reference hole-transporting material CS-82,CS-83 with naphthodithiadiazole as the acceptor group has a red-shifted absorption band of 42 nm,which effectively expands the spectral absorption range.The introduction of naphthodithiadiazole group can also reduce the HOMO energy level,which is beneficial to improve the photovoltage.Moreover,thermogravimetric analysis shows that the introduction of naphthodithiadiazole acceptor group improves the thermal stability of hole-transporting material.Chapter 5,conclusions.Multiple organic functional molecules have been designed and synthesized by through introducing various acceptor groups into the molecular skeleton.It's found that different acceptor groups could effectively control the molecular properties,as well as the photovoltaic performance of the devices,providing a meaningful reference for the design of organic functional molecule in the future.