Synthesis And Properties Of Conjugated Polymers Based On Nitrogen Atoms In Isoindigo Derivatives

D-A conjugated polymers represent a class of promising semiconducting materials for organic field effect transistors.They have also attracted considerable attention due to their attractive advantages such as variety molecular designs,easy tuned energy levels,solution-processability,etc.The main chains of Isoindigo and its derivatives have good planarity and always exihibit excellent solubility and great OFETs performances among polymers based IID and its derivatives,which were one of the most investigated units.The energy levels can be tuned by choosing different donors and make different charge transport behaviors.In this paper,the thermal stability,optical properties,electrical properties and charge transport of N-Isoindigo derivatives as organic field effect transistor semiconductor materials were investigated.The main contents and conclusions are as follows:(1)From the Isoindigo and benzodipyrrolidone units,the C = C bond of IID was replaced and the benzodipyrrolidone(BDP)unit was used as a linkage.The benzene rings of IID were replaced by pyridine units,and a new acceptor unit BABDP was synthesized.The effective conjugated length was extended and the LUMO level was also decreased.Due to the additional N-substituted branched alkyl chains,more opportunities for materials solubility were also provided.Low bandgap conjugated polymers P1 and P2 were synthesized with TT and TVT as donors,the optical bandgaps are 1.26 eV and 1.23 eV,respectively.The devices of P1 and P2 were fabricated and characterized,exhibited amipolar transistor behaviors.The highest hole mobility and electron mobility of P1 are 6.67×10-2 cm2V-1s-1 and 1.81 ×10-1 cm2V-1s-1 respectively.The highest hole mobility and electron mobility of P2 are 1.97×10-1 cm2V-1s-1 and 1.74×10-1cm2V-1s-1,respectively.(2)As donors in D-A conjugated polymers can also have influence on HOMO and LUMO levels,2FBT and TCNT were chosen to prepare P3 and P4.The results of cyclic voltammetry show decreased HOMO and LUMO levels,which the LUMO comes to-4 eV.They exhibited typically n-type transistor behaviors under vacuum as organic layer in OFETs,where the highest electron mobility of P3 and P4 are 7.81 × 10-2 cm2V-1s-1 and 4.66×10-2cm2V-1s-1,respectively.