| The growing demand for renewable energy as an alternative to fossil fuels has accelerated the emergence of organic solar cells(OSC).In an era of portable and wearable electronic devices,organic solar cells in particular exhibit advantages such as light mass,translucency,mechanical flexibility,and low cost processable manufacturing.In the past decade,organic solar cells have developed rapidly with the development of high-efficiency conjugated active layer materials,device structures and interfacial buffer layer materials,therefore the photovoltaic conversion efficiency(PCE)has exceeded 18%.Despite the surprising increase in performance,even exceeding the benchmark efficiency threshold of 15% for commercialization,there are still some issues that limit its commercialization.The use of mostly hazardous halogenated organic solvents,such as chloroform(CF),chlorobenzene(CB)and1,2-dichlorobenzene(o-DCB),which are not only hazardous to human health but also detrimental to creating a friendly environment,is one of the biggest obstacles to industrial-scale manufacturing of state-of-the-art organic solar cells.However,the solubility of highly efficient conjugated materials in green solvents is very limited and will form large aggregates that are not easy to process and handle.Therefore,the development of processing based on environmentally friendly solvents will be a major task in the field of organic solar cells.In order to realize the green solvent friendly processing,this paper on the one hand is to design new polymer donor materials that can be processed at room temperature with non-halogenated solvents based on the molecular structure;On the other hand,an elastomer is introduced into the interface buffer layer material processed by the water/alcohol green solvent to construct a flexible composite cathode interface buffer layer material.The main research of this thesis is as follows:In the first work,by introducing different amounts of the third structural unit bis(2-hexyldecyl)5,5’’’-dibromo-3’’,4’-difluoro-[2,2’:5’,2’’:5’’,2’’’-tetrathiophene]-3,3’’’-dicarboxylate(4T2FC)with ester groups and self-assembling properties into the highly crystalline polymer donor Pff BT4T-2OD,two polymer donor Pff BT4T-4T2FC-9/1 and Pff BT4T-4T2FC-4/1 were designed and synthesized.The advantage of this design is that the aggregation of the terpolymer can be effectively optimized by regulating the content of 4T2 FC units,and the introduction of ester units on the side chains of4T2 FC units can significantly improve the solubility of both terpolymers in non-halogenated solvents.The results show that both terpolymers have excellent room temperature processing properties in both halogen and non-halogen solvents.The devices based on the Pff BT4T-4T2FC-9/1:PC61BM active layer blend achieves a high efficiency of 9.11% by room temperature processing with the green solvent1,2,4-trimethylbenzene(TMB)with 1-phenylnaphthalene(PN),which is comparable to the efficiency of processing with CB solvent.Notably,the efficiency of 9.11% is one of the highest values reported for organic solar cells based on fullerene systems processed in non-halogenated solvents without any post-treatment at room temperature.In the second work,based on the water/alcohol green solvent processing efficient cathode interface buffer layer(PDINN)and organic elastomer polyurethane(PU)are combined to form a composite interface layer material through physical blending.The aim is to add different proportions of elastomer PU to make the interface layer material maintain good photoelectric properties after repeated bending.After adding PU into PDINN,the device efficiency based on PM6:Y6 system reaches15.43%,and the Young’s modulus decrease with the increase of PU content.These results show that the addition of PU can obtain very considerable device efficiency and significantly improve its mechanical bending performance.This composite material provides ideas for the large-scale preparation and production of flexible organic solar cells in the future. |
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