Synthesis And Photovoltaic Properties Of Two-Dimensional Conjugated Polymers With Tunable Conjugated Side Chains

Recently, the research of polymer solar cells （PSCs） has become research focusin the field of energy and material, PSCs have developed very rapidly over the pastdecades. But its practical application is also limited by such as material properties,device. High performance donor materials are needed for its practical application.Synthesis of the polymers with deep HOMO levels is an efficient strategy to achievepolymer soalr cell with high PCE.In this dissertation, we designed a new series of two-dimensional conjugatedpolymers （P1-P4） based on a benzo[1,2-b:4,5-b′]dithiophene （BDT） unit and athiophene unit with a pendant acceptor group. The thiophene unit with tunablependant electron-deficient groups is used for efficiently tuning the properties of thepolymers. We also studied the connection between polymer structure and performance.The main contents of this dissertation are as follows:1. Monomer （M1, M2, M3, M4） was prepared by Friedel-Crafts acylationreaction, Suzuki coupling reaction, NBS bromination reaction, Knoevenagelcondensation reaction with many kinds of raw materials; Monomer M5was preparedby Amidation, Cyclization, Alkylation, and reaction with trimethyltin chloride. All thestructures of the monomers and the intermediates were characterized by¹H NMR.And we discussed the reaction of the monomers and the intermediates.2. P1-P4were prepared by copolymerization of BDT with thiophene-monomerswith side conjugated chain through the Stille coupling reations. And we discussed thereaction of the polymers.3. All polymers were characterized by Solubility test, GPC, UV-vis absorptionspectra and CV. And the results show that P1-P4have good solubility, appropriatemolecular weight and good thermal stability. The results of UV-vis absorption spectraand CV show that P1-P4have broad absorption, so they can obtain more solar photon,which contributes to raise the Jscof PSCs. P1-P4possess low HOMO energy levels（-5.32eV^-5.38eV）, which can afford high Voc（more than0.92V）. The resultsshow that acceptor groups were introduced into the polymers, which can induce theabsorption edge red-shifted and low the energy level of HOMO. Among all of thepolymers, the molecular structure of P2has the good coplanarity, so P2has goodoptical and electrochemical properties. 4. PSC devices with a configuration ofITO/PEDOT:PSS/Polymer:PC₆₁BM/Ca/Al were fabricated. The results of the devicemeasurements show that the bulk heterojunction polymer solar cell based on P1-P4exhibits good PCE of0.90%,1.89%0.95%,1.45%, respectively. P2exhibits the bestPCE of1.89%with an impressively high V_ocof0.93V, a J_scof3.51mA/cm²and a FFof49%.