Structure And Properties Of Conjugated Polymers Based On Isoindigo And Its Derivatives

Organic thin film transistor has the advantages of light weight, low price, good solution processing and good flexibility, which makes it show the potential application prospect in building low cost, large area and full flexible optoelectronic device. Conjugated polymer is the material basis of organic thin film transistor. It is very important to design and synthesize new conjugate polymer material with good comprehensive performance to improve the performance and mobility of organic thin film transistor. In this paper, a series of low energy bandgap conjugated polymers based on isoindigo and its derivatives have low energy bandgap and low HOMO energy levels of the composites were synthesized. We studied the relationship between structure and performance of isoindigo, the main contents are as follows:?1? In the second chapter, we used 2,2'-Bithiophene ?DT? as the electron donor unit, isoindigo ?IID? and isoindigo derivative ?BIBDF? containing benzodifuranone as the electron acceptor unit, synthesized a series of random conjugated polymers containing different acceptor materials, and studied the effect of the polymer backbone structure on its properties. The BIBDF unit has a stronger electron-withdrawing ability and better planarity than the IID unit, which enhances the interaction between the polymer's D-A structure and reduces the polymer HOMO level. However, the poor solubility of BIBDF, will affect the accumulation of polymers, thus affecting its performance. The study found that the reasonable combination of different receptor units, can combine the advantages of different receptor units. We found that the BIBDF content of 3.75% of the acceptor unit, the polymer to obtain the best performance and good solubility, the hole mobility reached 2.93 cm²V^-1s^-1.?2? In the third chapter, we use 5,5'-bis?tributylstannyl?-3,3'-bis?dodecyl?-2,2'-bithiophene and 2,2'-Bithiophene ?DT?as donor units, isoindigo ?IID? as acceptor unit, synthesize polymer P1and P2, and use BIBDF as the acceptor unit, synthesize polymer P3,P4, and investigated the effects of the alkyl side chains of the polymer donor units on the properties of the conjugated polymers. The results show that the alkyl chain of the donor unit has a great influence on the accumulation of isoindigo-based polymer, but the effect on the BIBDF-based polymer is small, because the BIBDF unit has a large conjugated planar structure,strong electron absorption ability, make the ?-? stack between the donor and acceptor units closer together, so the alkyl side chain has little effect on its stacking. The polymer P1 and P4 are p-type materials with a maximum hole mobility of 0.91 and 5.18×10-3 Cm²V^-1s^-1,respectively. Polymer P2 exhibits pure electron properties in vacuum with a maximum electron mobility of 1.74 cm2V-1S-1, showing bipolar characteristics in air, the highest electron mobility was 1.45 cm²V^-1s^-1, the hole mobility was 0.47 cm2V-1s- 1; Polymer P3 exhibits bipolar characteristics in vacuum with a maximum electron mobility of 1.08cm²V^-1s^-1 and a maximum hole mobility of 0.30 cm²V^-1s^-1.