| Organic solar cells（OSCs）have attracted enormous attention by researchers due to its merits of solution-processing,low-cost and adjustable molecular structures.One of the most important layers in OSCs is the active layer blended with p-type semiconductor donor and n-type semiconductor acceptor,which could affect the device performance directly via material selection.With the development of non-fullerene acceptors（NFAs）,the device performance of OSCs improves rapidly in recent years.Compared to fullerene acceptors,the modular structure of NFAs is convenient for functionalized modification and building the relationship between molecular structure and device performance,which could help us fabricate high-efficiency OSCs.Theβposition of fused cores in Y-series acceptors is one of the promising modification sites which can effectively regulate photovoltaic performance.Since theβposition of thieno[3,2-b]thiophene in fused core is difficult to modify,the side-chain engineering of Y-series NFAs usually starts from the expensive3-bromothieno[3,2-b]thiophene,which is highly complex for synthesis.Therefore,the research on the structure-performance relationship of side-chain engineering of Y-series NFAs is relatively few.In this thesis,we construct a simple and efficient method for side-chain engineering through hydrogen-bromine migration to synthesize a variety of small molecular acceptors（SMAs）with different 2D-conjugated side chains and discuss the structure-performance relationship in depth.Further,our effect provides a new idea for polymerized small molecular acceptors.Inspired by this idea,we design and synthesize several polymer acceptors（PAs）based on side-chain engineering.The main research contents are as follows:1.We successfully introduce bromine atom on theβposition of thienothiophene based on Y-series molecules via hydrogen-bromine migration,which paves the way for easier side-chain modification.Based on this method,we design and synthesize three acceptors with different benzene conjugated side chains.Among these three acceptors,CY5,functionalized with meta-substituted and branched alkoxylphenyl side chains,achieves an impressive power conversion efficiency above 17%when paring with polymer donor PM6.Subsequently,we systematically investigated the influence of meta-substitution and branched side chains on device performance.We find that these two factors could work together to obtain appropriate intermolecular packing and device morphology,contributing to high device performance.2.On the basis of previous side-chain modification method,we design and synthesize two Y-series molecules with thiophene thioalkyl and alkoxy side chains named CY6 and CY7 respectively to discuss the effect of introducing heteroatoms into side chains on device performance.Surprisingly,the photovoltaic efficiency based on PM6:CY6 achieves 16.23%,with a high Jsc of26.67 m A cm-2 and FF of 74.84%.Besides,the CY7-based OSCs display a high power conversion efficiency（PCE）above 15%.We find that introducing sulfur atom could enhance the miscibility between the donor and acceptor to obtain appropriate morphology and help exciton dissociation and carrier transport,achieving a high PCE eventually.3.Hydrogen-bromine migration could not only achieve efficient side-chain modification,but also provide a new idea for polymerized small molecular acceptors.We design and synthesize a series of PAs with different conjugated side chains and find that PAs via extending the length of side chains have wider absorption and narrower electrochemical bandgap.In addition,we synthesize novel polymer acceptor PCY4 via shoulder polymerization and find that it could be used in OSCs as a new type of PAs after rudimentary characterization.Our research also provides the theory foundation and direction for further side-chain engineering of PAs. |
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