Synthesis And Device Performance Of New Organic Semiconductor Materials

Organic semiconductors are the focus of intense investigation for the promise of low-cost manufacturing,ease of processing,mechanical flexibility and versatility in chemical synthesis,which have been utilized as active layers in the construction of organic field-effect transistors(OFETs),organic light-emitting diodes(OLEDs),and organic photovoltaics(OPVs).The performances of these electronic devices,such as mobility,power conversion efficiency,and stability,are highly dependent on the intrinsic structures of these materials.It is of great significance to develop new organic semiconductors and device of them.Given this,new organic semiconductors were prepared and applied as active layers in the construction of organic field-effect transistors or organic photovoltaics.The main points of this thesis include the following two aspects:1. Dibenzothienopyrroles(DBTP)possess an extended?-conjugated system with benzene rings fused thiophene rings,leading to a much deeper the highest occupied molecular orbital(HOMO)energy levels.However,OFETs results show poor charge transport based on DBTP molecules.To solve the problem of poor charge transport,Benzofuran was introduced to optimize the skeleton.The results show that the introduction of a benzofuran unit enhances the planarity and conjugation of heteroacenes leading to strong molecular aggregation and denser?-?stacking,resulting in better charge transport properties with the linear hole mobility of 0.025 cm~2/Vs,the saturation mobility of 0.062 cm~2/Vs,the threshold voltage of-30 V and switch ratio of3×10~3 for the OTFTs.2. Bithiophene imide is a classic electron-deficient N-type semiconductor material.When applied as the acceptor materials in all-PSCs,the power conversion efficiencies(PCE)is very low for its weak absorption in the visible region.To solve the absorption problems,thieno[3,4-B]pyrazine are excellent precursors for the production of promising low band gap?-conjugated polymers and copolymerization with bithiophene imide and bithiophene imide derivative.For comparison,the other two random polymers containing benzothiadiazole or isoindigotin were also synthesized.The all-PSCs based on bulk heterojunction blends with pyrazine random terpolymer as acceptor and PTB7-Th as donor give a high power conversion efficiency value of 7.35%with an open-circuit voltage of 1.02 V,a short-circuit current density of 13.28 m A/cm~2,and a fill factor of 54%.The results demonstrate that designing of the random terpolymer acceptors with thieno[3,4-B]pyrazine component is an effective strategy for obtaining high-performance photovoltaic acceptor materials.