Exploitation Of Organic Optoelectronic Materials Based On Benzodithiophene And Benzothiadiazole

As compared with inorganic counterparts, organic optoelectronics including organic solar cells(OSCs), organic field-effect transistors(OFETs), and organic light-emitting diodes(OLEDs) have been regarded to have advantages of flexibility, light weight, solution-processability, and adaptability for fabrication of large area devices. The former two are inherent for organic materials, while the latter two should be well designed. Especially for the last one, it requires the material has a good filmformation capability.In this thesis work, we aimed to improve solubility and film-formation properties of our previously reported small optoelectronic molecule, BDT(Th BTTh)2 based benzodithiophene(BDT) and benzothiadiazole(BT), designed and synthesized a series of new materials through structural modification and derivation. The basic properties and optoelectronic performance of these new materials were also studied.In first part of work, we synthesized two optoelectronic isomers, BDT(DTBT)2 and BDT(DTBT)2-C6-inner, by integrating two additional hexyl side chains into both ends or the inner thiophene units of BDT(Th BTTh)2 molecule. It was found that:(1) Both BDT(DTBT)2 and BDT(DTBT)2-C6-inner possess better solubility than BDT(Th BTTh)2, and can self-assemble into fiber structures;(2) In solution, the conjugated backbone of BDT(DTBT)2-C6-inner is twisted, as evidenced by blue shift in its light absorption band. However, such twisted structure disappear in film state, and the molecule exhibits even stronger intermolecular interactions than conformation due to steric hindrance effect, it had stronger intermolecular interactions than BDT(DTBT)2;(3) The OFET hole mobility of BDT(DTBT)2 was 2.18×10-4 cm2/Vs, while the hole mobility of BDT(DTBT)2-C6-inner was 1.80×10-2 cm2/Vs, which was almost 100 times of the former;(4) The organic photovoltaic(OPV) performance of BDT(DTBT)2-C6-inner(the Power Conversion Efficiency(PCE) was 1.60%) was better than that of BDT(DTBT)2(PCE=0.78%).In second part of work, we synthesized three poly(rod-coil) polyesters P1, P2, and P3 by connecting the optoelectronic active segment of BDT(DTBT)2 and three different soft ester segments in an alternative fashion. It was found that the basic optoelectronic properties of P1, P2, and P3 are similar to those of BDT(DTBT)2. However, their film-formation capabilities have been greatly improved as compared to BDT(DTBT)2. The final solar cell device investigations revealed that the P3-based device with a large area showed a better performance than the BDT(DTBT)2-based although the situation was reverse in a smaller area scale.