| Organic semiconductor materials have attracted extensive attention due to their potential applications in large-area,low-cost,flexible electronic devices.Conjugated polymer semiconductors are favored because of their excellent solution processability and film forming properties.A lot of research works have been done in developing high performance organic polymer semiconductors.However,the development of new highperformance D-A polymers is at a standstill because the monomers that construct high performance D-A polymers often require demanding,poisonous,and tedious syntheses that deviate from the ultimate vision desired for organic electronics with a simple and low-cost platform.Recently,random and regular terpolymer strategy is promising and efficient candidates to overcome the standstill,and accelerate the development of new conjugated polymers.In this dissertation,based on random or regular copolymerization strategies,the properties of the conjugated polymers were adjusted through both of side chain engineering and main chain modification.The main contents include the following aspects:In the first part,random copolymerization is employed to finely tune the transport behavior of terpolymers by side chain engineering and BIBDF incorporation.Two series of terpolymers have been synthesized by varying both the branching positions in side chain and BIBDF content in main chain.The spectral absorption,electrochemical behavior,microstructure,and electrical performance in organic field effect transistors have been systematically studied.The results reveal that as the side chain branching positions is far away from the backbone,the lamellar packing and ?-? interactions of molecular was enhanced,and the mobility increased.Furthermore,the influence of BIBDF content was studied under the optimal side chain,which suggests that proper ratio BIBDF can also promote the molecular packing,crystallinity and electrical properties of terpolymers.For instance,C33P2.5 polymer,with optimal side chain branching position and BIBDF content,exhibited maximum mobility of 7.01 cm2 V-1 s-1,which is three times higher than the reference polymer C11P3.75 and C30P0.The current study presents a novel route to maximize the performance of conjugated terpolymers and provides a baseline for further research on high-performance conjugated polymers for a wide array of applications.In the second part,nitrogen atom was introduced to the random conjugated polymer backbone,and investigated the effect of heteroatom modification on the transport properties of the random terpolymers.First,introducing nitrogen atom in the acceptor unit BIBDF could enhance its electron-withdrawing ability and obtain NBIBDF.It was found that incorporation of a small amount of NBIBDF can increase the hole mobility of the random terpolymer.When the proportion of NBIBDF reaches 20%,the random polymer begins to transform from hole transport materials to bipolar transport materials.Next,nitrogen atom was further introduced into the isoindigo unit and a series of random all-aza-conjugated polymers were synthesized.When the ratio of aza-isoindigo and NBIBDF in the main chain achieved 1:1,the random aza-conjugated polymer is converted from hole transport materials to balanced bipolar transport material.The hole and electron mobility were 0.057 and 0.050 cm2 V-1 s-1,respectively.GIXRD studies exhibited that the introduction of nitrogen atoms can not only reduce the molecule orbital energy level,but also promote the interaction between molecules.As the nitrogen atoms increase,the ?-? stacking distance between main chains becomes closer.In the third part,a new ?-extended electron-deficient unit,6,6?-(5,5?-N,N'-(2-ethylhexyl)-isoindigo-6,6'-diyl)bis(thiophene-5,2-diyl))bis(2,5-bis(2-decyltetradecyl)-3-(thiophen-2-yl)pyrrolo[3,4-c]-pyrrole-1,4(2H,5H)-dione)(2DPPI)was designed and synthesized.Three new D-A conjugated polymers were then synthesized based on 2DPPI unit and different electron-donors thiophene,thieno[3,2-b]thiophene and 2,2'-bithiophene.Their photophysical properties,electrochemical behaviors,field-effect characteristics,thin-films morphologies,and photothermal conversion performances were systematically investigated.All three polymers displayed broad and strong absorption in the near infrared region.Compared with the corresponding DPP-based polymers,the 2DPPIbased polymers possess deeper the highest occupied molecular orbital and the lowest unoccupied molecular orbital levels and narrower band gap due to the introduction of large acceptor formed by IID and DPP.The OTFT devices based on three polymers were fabricated,and their field-effect performance were characterized under ambient conditions.After annealing,P2DPP-BT showed the maximum hole mobility of 0.224 cm2 V-1 s-1 and an electron mobility of 0.033 cm2 V-1 s-1.The corresponding microstructure and morphology analyses revealed that P2DPPI-BT showed more ordered molecular stacking,lamellar packing and well-interconnected larger domains,all of which are favorable to the carrier transport.In addition,the photothermal test reviews that all three polymer films can effectively convert near infrared light to heat,and P2DPPI-TT has the highest photothermal conversion efficiency of 25.6%.Furthermore,P2DPPI-TT was successfully used for tuning cholesteric liquid crystal reflective band under the irradiation of near infrared light. |
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