The Synthesis Of A-D-A Type Conjugated Small-Molecule And Properties Of Solution-Processed Organic Field Effect Transistors

Small molecule design based on donor?D?and receptor?A?units is an effective method for fabrication of high-performance semiconductor devices.A-D-A small molecule combines the advantages of small molecule and polymer,and avoids the disadvantages of uncontrollable molecular weight of polymer and big difference between batches.This type of small molecule has relatively high molecular weight and large size,which makes it have good solution processing performance and excellent film forming performance.In this paper,we designed and synthesized a series of A-D-A small molecular materials with dinindendithiophene[3,2-b]thiophene?IDTT?as the donor unit and benzodiazepine dipyrrolidone?IDD?and pyridine dipyrrolidone?IDD-N?as the acceptor units,and systematically studied the relationship between the molecular structure and the performance of OFETs.?1?Rigid IDTT was designed and synthesized as the donor?D?unit,and the IDD molecules with electron absorption ability were selected and the small molecules IDTT-IDD and IDTT-IDD-N with strong electron absorption ability were introduced as the receptor units at the end of the envelope.It was found that the introduction of an N atom into the IDD unit enhanced the planarity and structural ordering of the molecule through non-covalent interaction,which had a significant effect on the small molecule.The non-substituted small molecule?IDTT-IDD?did not show any field-effect properties,while the solution-processable OFET based on IDTT-IDD-N obtained a hole mobility of up to 7.7 cm ² V^–1 s^–1,with an average mobility of 6.1cm ² V^–1 s^–1.?2?Due to the excellent field effect performance observed by IDTT-IDD-N,the effect of alkyl side chains on the performance of OFETs was further studied by changing the length of the alkyl side chains of the receptor IDD-N.Eight A-D-A small molecular materials?IDTT-IDD-N-C1?C8?were synthesized,in which the number of carbon atoms in the side chain of the linear alkyl group was 1-8.The results showed that the other small molecules had similar optical and electrochemical properties except the material of the methyl side chain,and all showed excellent field-effect properties.It is also found that there is an approximate odd-even effect between the mobility and the number of carbon atoms in the side chain of the alkyl group.