Design,Synthesis And Properties Of Interfacial Materials Based On Perylene Diimides And Naphthalene Diimides

Organic solar cells(OSCs)have attracted extensive research and development for the advantages of low cost,flexibility,convenient fabrication and suitability for large-scale production.In the past few years,great progress has been made in improving the photovoltaic performance of OSCs.For small-area devices,the highest power conversion efficiency(PCE)have reached 15.7%in single-junction binary devices and surpassed 17%in tandem devices.To further improve device performance,researchers are continually designing novel active layer materials,optimizing device processing,or finding stable device structures.Since organic solar cells are usually made of multiple layers,good connections at the interface of which are critical to achieving high conversion efficiency.The interfacial engineering is an effective strategy for realizing the good device performance for some advantages of interfacial materials,including compatible ohmic contact,matched energy levels between the photoactive layer and the electrode,and improved selectivity towards electrons or holes while blocking others.Among various interfacial materials,organic interfacial materials have been extensively studied due to their low-temperature solution processability.Organic solar cells with complete solution preparation have been realized by introducing organic interfacial materials and using printable Ag electrodes.In addition,the structural diversity of organic interfacial materials allows us to regulate their optoelectronic properties,such as bandgap,energy levels,and carrier mobility,which are critical to device performance.Compared to polymers,small molecule interfacial materials exhibit inherent advantages for their simple synthesis and purification steps,well-defined structures,and perfect batch repeatability.The main work of this thesis is made of the following three parts.The first part is the synthesis of amino and ammonium bromide modified perylene diimide derivatives and their effects on the interfacial modification properties for polymer solar cells(Chapter 2).The second part is the synthesis of amine oxide modified perylene diimide derivatives and their effects on the interfacial modification properties for polymer solar cells(Chapter 3).The third part is about the synthesis of the nuclear-substituted water/alcohol-soluble naphthalene diimide derivatives and their effects on the interfacial modification properties for polymer solar cells(Chapter 4).Chapter 1:Firstly,the development history,device structure and basic working principle of organic solar cells are introduced.Then,the development of cathode interfacial materials in recent years is summarized.Also,perylene diimide and naphthalene diimide derivatives and their characteristics are sketched.Finally,based on the interfacial materials of perylene diimide and naphthalene diimide,the design ideas and main research contents of this thesis are proposed.Chapter 2:The side groups of phenyl(Ph),biphenyl(BPh),m-terphenyl(DPP)and tetraphenylethene(TPE)with gradually increased sizes were introduced into the bay area of perylene diimide to obtain PDI-N?P4P-N with different molecular configurations.Subsequently,the five compounds reacted with excess bromoethane to yield ammonium bromide modified PDI-NBr?P4P-NBr.These ten compounds were used as cathode interfacial layers(CILs)for non-fullerene polymer solar cells to systematically study the effect of chemical modification of PDI on their molecular conformation and device performance.Chapter 3:On the basis of Chapter 2,five compounds of PDI-NO?P4P-NO modified by amine oxide were obtained by changing the ion pair of PDI-NBr?P4P-NBr.These five compounds were used as cathode interfacial layers for non-fullerene polymer solar cells.Compared to the device without any interfacial layer,the PDI-NO series modified devices have improved efficiency.Among them,P1P-NO based devices exhibited the best photovoltaic performance:V_oc was 0.940 V,J_sc was 17.47 m A cm^-2,and FF was 70.35%,the PCE of which increased by 49%(7.78%:11.56%)compared to the device without cathode interfacial layers.By increasing the thickness of the interfacial layer,P1P-NO was found to exhibit insensitivity to film thickness.When the film thickness of the interfacial layer was gradually increased,the device efficiency didn't show a sharp drop.What's more,the stability of the P1P-NO device is greatly improved compared to the PDI-NO device.Chapter 4:Three nuclear-substituted water/alcohol-soluble naphthalene diimide derivatives of NDI-N,NDI-NBr and NDI-NO were designed and synthesized by introducing different polar side chains on both sides of the naphthalene dimide core,with the aim to enhance water/alcohol-solubility and adjust the energy levels of NDI molecules.These three water/alcohol-soluble naphthalene diimide derivatives were used as cathode interfacial layers for fullerene and non-fullerene polymer solar cells.In the fullerene system,three molecules exhibited similar interfacial modification properties,with PCE exceeding 9%.Among them,NDI-NBr modified devices demonstrated the best device performance compared to those without interfacial layer devices,and the corresponding increased PCE by 49%(6.32%:9.41%).The interfacial materials show great differences in non-fullerene organic solar cells,where NDI-N modified devices exhibit optimal device performance with PCE of 10.27%.