Design,Synthesis And Properties Of Poly(diketopyrrolopyrrole-alt-terchalcogenophene)s

The solution processability and mechanical flexibility of conjugated polymers（CPs）enable their applications in ultralow-cost and large-area electronics.To date,significant progress has been made in CP-based organic thin film transistors（OTFTs）.However,to meet the needs of future commercialization,several issues of CPs,such as low mobility,low solubility,and complicated structures,still to be addressed.In the current thesis,a series of diketopyrrolopyrrole（DPP）-based CPs,i.e.,poly（DPP-alt-terchalcogenophene）s,were designed and synthesized.Structure-properties correlation was studied in detail by UV-vis-NIR absorption spectra,atomic force microscopy,X-ray diffraction and small-angle neutron scattering,and high mobility CPs soluble in non-chlorinated solvents were obtained.With o-xylene or anisole as processing solvent,high mobility p-channel OTFT devices were fabricated via bar-coating.The results will promote the development of polymer semiconductors.The main results are as follows:1.Increasing the density of alkyl side chains is an effective strategy to improve thesolubility of CPs in non-chlorinated solvents.The solubility of a poly（DPP-alt-terthiophene）carrying 4-hexyldodecyl chains,named as PDPPT3-HDO,in o-xylene is above 50 mg m L^-1.With this solvent,OTFT devices with the maximum mobility of9.24 cm²V^-1s^-1 were fabricated via bar-coating.The devices showed characteristics of ideal field-effect transistor,yielding mobility reliability factor as high as 87%.2.Seven poly（DPP-alt-terthiophene）s with terbutylsilylalkyl side chains were synthesized and the effects of the position of Si branching point on their properties were investigated.Film microstructures and OTFT performance can be tuned by varying the number of C-atom between Si and conjugated backbone.The polymer Si C6 that has a hexyl spacer between Si and conjugated backbone exhibited the best device performance.Si C6-based bar-coated OTFT devices processed with o-xylene showed mobility up to 2.69 cm²V^-1s^-1 in saturation regime.3.Nine poly（DPP-alt-terchalcogenophene）s via combinations of furanyl-DPP,thienyl-DPP,selenophenyl-DPP and furan,thiophene,selenophene comonomers were synthesized to investigate the chalcogen effect on the solubility,microstructure and charge transport property of the polymers.OTFT devices of all nine CPs can be fabricated with non-chlorinated solvents.The TDPP-Se based devices via bar-coating with o-xylene/tetralin showed the best device performance,with reliable mobility above10 cm²V^-1s^-1 in saturation regime.The CPs based on FDPP are also soluble in more environmentally benign solvent anisole.With this solvent,FDPP-F based OTFT devices with mobility up to 3.50 cm²V^-1s^-1 in saturation regime were fabricated.4.Molecular mass-dependent properties of TDPP-Se were studied in detail.TDPP-Se samples with different molecular weights all adopt 1D rod-like aggregation structures of relatively constant radius in deuterated 1,2-dichlorobenzene,while the length increases monotonically with molecular mass.Highly aligned and ordered films of the polymers that form the rod-like aggregates with the length/radius ratio of～20 can be fabricated via bar-coating.The bar-coated devices of P-41k(M_n=41 kg mol^-1)showed the best performance,and reliable mobility up to 13.8 cm²V^-1s^-1 in saturation regime has been demonstrated.