Design And Synthesis Of Near Infrared Small Molecules Based On Conjugation-extended Bisindole

As a kind of green energy technology,organic solar cells have attracted great attention in scientific and industrial circles in the past 20 years.In recent years,the development of non-fullerene acceptors has greatly promoted the efficiency of organic solar cells.For organic solar cells,the range of light absorption in the active layer has a direct effect on the efficiency.In the first part of this thesis,we focus on the design and synthesis of novel near infrared small molecule dyes.Based on the bisindole with strong electron donating ability,we extended its conjugated skeleton to obtain 8-membered heteroacene,and further synthesized the A-D-A type small molecule dyes（DNIC series）.At the same time,the DNTIC series w synthesized by inserting alkoxyethiophene between the thickened ring and the dicyano group.The thermal characterization shows that these new A-D-A small molecules have good thermal stability and certain crystallinity.Importantly,both DNIC and DNTIC series show good light absorption in the near infrared region.However,unexpectedly,the absorption of DNTIC was not red-shifted compared to DNIC,but blue-shifted by about 15-20 nm,which isprobably due to deterioration of the overall molecular flatness caused by the introduction of alkoxyethiophene..Notably,the absorption edge of the DNIC is 1030 nm,while the absorption edge of the fluorinated and chlorinated DNIC is 1052 nm and 1068 nm,respectively,which is more than 250nm redshifted than that of the corresponding A-D-A small molecule receptor based on carbazole ring extension.Interestingly,compared to Y6(λ_onset=930 nm),these novel small molecule acceptors ir have absorption spectra redshifted by more than 100 nm.The corresponding device application in organic photovoltaic is in progress.In the second part of the thesis,we focus on employing the supramolecular host-guest structure strategy to construct organic near infrared materials.Using carbazole as a donor unit,we have synthesized two kinds of electron-rich cyclophanes,C-Cb and CC-Cb,with different cavities Cyclophanes based on bisindole were synthesized by Suzuki coupling method.The single crystal structure of C-Cb shows that the two carbazole units in the cyclopane do not form a face to face bu a slip stacking,resulting in a cavity size of 4.9?.Further UV absorption and fluorescence titration experiments showed that electron-deficient units could enter C-Cb cavity.The obvious CT absorption peak also indicates the charge transfer between the electron rich cavity and the electron deficient unit in the host and guest.By utilizing electron-deficient units with different electron affinity,we can modulate the location of CT absorption.The subject and object research of this part of work has not been fully characterized and is continuing to improve.