Synthesis And Properties Of Thiophene-Coupled Perylene Imides Derivatives

Peryleneimide materials have become a new research hotspot in the field of electron acceptor materials in the OSC field due to their many advantages.However,the photoelectric conversion efficiency of PDI-based BHJ solar cells is not ideal.One of the main reasons is that PDI easily forms large-scale crystals due to its rigid molecular configuration [49].Efforts to solve the large-scale accumulation of PDI in the active layer of the battery are mainly focused on three strategies:(1)The development of monomeric PDI by introducing large groups at the imide position and adjacent or harbor positions.(2)Coupling two or more PDI units through aromatic groups in the ortho-port or bay position;(3)Designing twisted PDI with three-dimensional(3D)molecular configuration through different 3D central cores.In addition to creating distorted structures,the π-π conjugation of the entire molecule should also be considered.In summary,the development of perylene imide acceptor materials should proceed from the following points:(i)Non-planar,appropriately twisted spatial structure to reduce the degree of aggregation of PDI molecules(ii)Narrow band gap molecules,larger molar extinction coefficient And wider spectral absorption;(iii)higher LUMO energy level;(iv)efficient exciton dissociation and diffusion process,resulting in higher short-circuit current.Based on the above strategies,a series of peryleneimide derivatives were designed and synthesized in this paper,and their photoelectric properties were studied.1.Designed and synthesized thiophene coupled and closed-loop PDI diploid 2PDI-Th and fused-2PDI-Th,and studied their excited state and kinetic properties.Both 2PDI-Th and fused-2PDI-Th have strong visible light absorption,with maximum molar extinction coefficients of 61000 and 68000 L · mol-1cm-1,respectively;in terms of fluorescence,the fluorescence quantum yield of 2PDI-Th is only 0.02,while-2PDI-Th is 0.17,and the fluorescence spectrum of 2PDI-Th indicates that it forms an excimer.The fluorescence lifetime test shows that the fluorescence lifetime of 2PDI-Th is 840 ps,and the fluorescence lifetime of fused-2PDI-Th is 3.3 ns.Their femtosecond transient spectroscopy proved that 2PDI-Th did form an excimer state and then transitioned to the triplet state.The fused-2PDI-Th traverses directly to the triplet state through singlet systems.Nanosecond transient spectroscopy shows that the triplet lifetimes of 2PDI-Th and fused-2PDI-Th are 22 and 68 μs,respectively.The above results indicate that the excited state properties of the two are significantly different.2.Designed and synthesized dimers S-Th-2PDI and fused-S-Th-2PDI.It can be drawn from the absorption spectrum that fused-S-Th-2PDI has a wider light absorption range,and S-Th-2PDI has a higher light absorption intensity.In electrochemical analysis,S-Th-2PDI has two reduction peaks,and fused-S-Th-2PDI has four reduction peaks,indicating that both have strong electron nucleophilicity,but fused-S-Th-2PDI Have stronger electronic acceptance3.The fused-ob-Th-4PDI tetrameric PDI tetramer was designed and synthesized.It can be drawn from the absorption spectrum that fused-ob-Th-4PDI has a wide light absorption range and a high light absorption intensity.It can be seen from the fluorescence spectrum that the peak shape is broadened and a certain red shift occurs,and its fluorescence quantum yield is only extremely low 0.011,indicating that the fluorescence is greatly quenched.In electrochemical analysis,fused-ob-Th-4PDI has five reversible reduction waves and has a very strong ability to accept electrons.The calculated LUMO value of fused-ob-Th-4PDI is-3.75 eV and HOMO value is-5.98 eV.