Design And Synthesis Of Conjugated Polymers For Solar Cells And Field-Effect Transistors

During the development process of organic electronics, the design and synthesis of polymer semiconducting materials is one of the hot researches in materials chemistry fields. The chemical and physical properties of polymers can be controlled by reasonable tuning the chemical structures. In this dissertation, with the goal to develop new type and high performance polymer semiconductors, I designed and synthesized a series of conjugated polymers which can be used in different electronic devices, and systematically investigated the relationship between the structure and properties.1. A series of quinoxalinoporphyrin-based D-?-A copolymers with carbazole as donor unit and oligothiophene as ?-bridge were designed and synthesized. Porphyrin was applied in an edge-fused fashion to form quinoxalino[2,3-b']porphyrin moiety as a new acceptor unit for the first time and the steric hindrance between the porphyrin and neighboring units was effectively reduced. All the polymers displayed a broad absorption over the entire spectrum of visible light without miss absorption region between Soret and Q bands. The influences of the ?-bridge and the central Zn ion on the electronic and photovoltaic properties were investigated and discussed in detail. At last, bulk heterojunction (BHJ) polymer solar cells (PSCs) based on P(C-TT-QP) yielded power conversion efficiencies (PCEs) of 2.5%, which was the highest value for porphyrin-based conjugated polymers reported in literature.2. A broad band-gap copolymer PzNDTTPD based on "zig-zag" naphthodithiophene and thieno[3,4-c]pyrrole-4,6-dione was designed and synthesized. PzNDTTPD exhibits a narrow absorption and deep HOMO energy level, with an optical band gap of 2.04eV. PSCs based on PzNDTTPD showed a Voc of 0.91V and PCE of 5.26%. Both the parameters are the highest values for conjugated polymers with a band gap over 2.0eV, indicating that PzNDTTPD may be a promising candidate for the high-bandgap material used in tandem PSCs3. Two D-A copolymers, PzNDTDTBT and PzNDTDTBO, using "zig-zag" naphthodithiophene as an electron-rich unit and benzodiathiazole or benzoxadiazoleas an electron-deficient one, were designed and synthesized. Both copolymers possess good solubility, high thermal stability, broad absorption, as well as low bandgap (1.76eV), and exhibit not only high field-effect mobilities but also high photovoltaic properties. The hole mobilities reached 0.43 and 0.34cm2 V-1 s-1 for PzNDTDTBT and PzNDTDTBO-based organic field-effect transistors (OFETs), respectively. Bulk heterojunction solar cells fabricated by using PzNDTDTBT or PzNDTDTBO as electron donor and PC71BM as acceptor show a power conversion efficiency of3.22% and 5.07%, respectively.4. A versatile 2-D conjugated polymer PNDTP-DPP containing alkylphenyl substituted naphthodithiophene was designed and synthesized. PNDTP-DPP exhibits good solubility and crystallinity with a ?-? stacking of 3.73A. Investigaion of the OFETs and PSCs demonstrated a promising PCE of 4.11% and a high hole mobility of up to 0.86cm2 V-1 s-1.5. A series of D-A copolymers containing "zig-zag" naphthodifuran donor unit, with diketopyrrolopyrrole or isoindigo as the electron-deficient unit were designed and synthesized. Through the side-chain engineering and main-chain modification, OFETs based on PNDF3DPP-C24 and PNDF3IID-C24 exhibited high hole mobilities of 2.02 and 1.87cm2 V-1 s-1 even without a heat treatment. After annealing at 120?, increased hole mobilities up to 5.31 and 3.35cm2 V-1 s-1 were achieved, which are the highest hole mobilitied for naphthodichalcogenophene-based conjugated polymers.6. Four D-A copolymers, using 5,10-didodecyl-naphtho[1,2-b:5,6-b']dithiophene or 5,10-didodecyl-naphtho[1,2-b:5,6-b']difuran as an electron-rich unit and benzodiathiazole or benzoxadiazole as an electron-deficient one, were designed, synthesized and characterized. Based on the similar polymer main chain skeleton structure, detailed systematical investigation was conducted for studying the effect of the S/O atoms (atomistic band gap engineering) on the optical, electrochemical, and morphological properties of the polymers, as well as the subsequent performance of the OFETs fabricated from these copolymers. Relative OFETs based on these polymers showed typical p-type transporting characteristics, and hole mobilities ranging from 0.20 to 0.32cm2 V-1 s-1 were obtained at last.