Synthesis And Study On OFET Properties Of Benzene-Fused Heterocyclic Isoindigo Compounds

The advantages of organic semiconductor include the adjustable structures and properties via various organic synthetic method and the ability to construct flexible electronic devices. These organic semiconductors can be solution-processable, thus avoid sophositicated techniques such as vacuum deposition and photolithography in fabricating devices. Organic field-effect transistor (OFET) materials (especially n-type and ambipolar) based on small molecules still face enormous challenges, such as the stability in ambient conditions and low charge-carrier mobility. Isoindigo (a structural isomer of indigo) like Pyrrolo[3,4-c]pyrrole-1,4-(2H,5H)-dione (DPP), is an electron-deficient symmetrical nitrogen-containing pigment with two conjugated lactam rings. After decades of research, isoindigo derivatives emerged as novel and efficient building blocks for OFET materials.This work is focused on the synthesis of extended conjugated systems based on isoindigo core and their applications in the OFETs, More specifically, it includes the following aspects:Synthesis and OFET application study of isoindigo fused with benzothiophene and benzofuran.Start from an commercial available compounds, after multi-step reaction, ultimately, two extended conjugated system with isoindigo core, namely C20-DBTII and C20-DBFⅡ, were obtained.The optoelectronic properties of C20-DBTII and C20-DBFII were measured and theoretical calculations were performed to explain the difference in UV-vis absorption and we come to a conclusion:C20-DBTII and C20-DBFII maybe become good OFET materials.OFET devices based on C20-DBTⅡ and C20-DBFII were fabricated via solution spin-coating. The two compounds exhibit good ambipolar and n-type properties respectively at ambient conditions. OFETs based on the C20-DBFII show n-channel behaviour with electron mobility up to 0.074 cm2 V-1 s-1 in ambient conditions. This is the first report on the OFET application of the extended conjugated small molecule based on isoindigo core. These results showed isoindigo derivatives are applicable not only in polymeric systems, but also in small-molecular systems for OFET materials.Synthesis and optoelectronic properties of new non-chlorinated benzene-fused heterocyclic isoindigo.Compared to the previous chapter, non-chlorinated benzene-fused heterocyclic isoindigo were synthesized by a simpler method, and a series of derivatives with different alkyl side-chain were synthesized.Optical and electrical properties of these compounds were studied, and the performance of different alkyl-substituted compounds were compared. Although no further study on their OFET performance, we predict that they might be good OFET material candidates based on their photoelectric properties.