Synthesis And Optoelectronic Properties Of Conjugated Polymers Based On Diketopyrrolopyrrole Flanked With Pyridyl Unit

Solution processable π-conjugated polymers have gained much attention due to their specific advantages of light-weight, low-cost processing techniques and great potential for the mass-production of large-area flexible organic electronic products. Recent advantages of organic semiconducting polymers allowed for the systematically tunable optoelectronic properties through the delicate molecular design, which can provide optimum frontier molecular orbital levels, appropriate absorbance, favorable film morphology as well as high charge carrier mobility. One of the most extensively used strategies to construct conjugated polymers was the integration of the electron-rich donor（D） and the electron-deficient acceptor（A） units along the polymer backbone in an alternating fashion, which can result in excellent optoelectronic performances of conjugated polymers.Diketopyrrolopyrrole（DPP） unit has been extensively utilized as the electron-deficient building block for the construction of organic semiconductors due to its planar architecture and high charge carrier mobility. Moreover, diketopyrrolopyrrole can be chemically modified by introducing the different aromatic groups at the 3, 6 positions, which can adjust the absorbance and HOMO/LUMO energy levels.In chapter 2, two novel donor eacceptor π-conjugated copolymers（PTDPP-Ph, PTDPP-Py） comprising（E）-1,2-di（thiophen-2-yl）ethylene as the electron-donating unit, and diketopyrrolopyrrole flanked with phenyl or 2-pyridyl moiety as the electron-accepting unit were synthesized through Stille polymerization. The bulk heterojunction solar cells were fabricated using PTDPP-Ph, PTDPP-Py as the donor materials, respectively, and PC61 BM as the acceptor material. The polymer PTDPP-Ph exhibited power conversion efficiency of 2.51%（Voc= 0.95 V, Jsc= 5.20 m A cm-2,FF= 50.78%）; PTDPP-Py exhibited power conversion efficiency of 3.26%（Voc= 0.70 V, Jsc = 8.80 m A cm-2,FF = 52.93%）.In chapter 3, two novel regio-isomeric π-conjugated polymers（d-PDBPy, p-PDBPy） consisting of the pyridyl unit flanked by diketopyrrolopyrrole as the electron-accepting unit and2,5-bis（3-hexylthiophen-2-yl）thieno[3,2-b]thiophene as the electron donating unit were synthesized through Stille polymerization. The optoelectronic properties and HOMO/LUMO energy levels of polymers changed significantly by changing the pyridyl group orientation. Bottom gate and top-contact（BGTC） organic field effect transistors（OFET） based on polymers was fabricated, the polymers d-PDBPy and p-PDBPy exhibited holes mobility of 3.2×10-4 cm²V^-1 s^-1, 0.35 cm²V^-1 s^-1, respectively.In chapter 4, three novel π-conjugated polymers（PDBPy-T, PDBPy-TT, PDBPy-DTT） containing diketopyrrolopyrrole flanked with 2-pyridyl moiety as electron-accepting unit and extending the conjugated length of donor along the polymer chain. Bottom gate and top-contact（BGTC） organic field effect transistors（OFET） based on polymers was fabricated, the polymers PDBPy-T, PDBPy-TT and PDBPy-DTT exhibited a hole mobility of 3.0×10-4cm²V^-1 s^-1, 3.1×10-3 cm²V^-1 s^-1, 3.0×10-5 cm²V^-1 s^-1, respectively.