Synthesis And Properties Of Polymer Soler Cell Materials

With the growing of energy crisis, the use of sunlight has been paid muchattention. Polymer solar cells have attracted considerable attention due to their lightweight, simple fabrication, low cost and good flexibility. However, the efficiency ofpolymer solar cells is still significantly lower than inorganic solar cells. To improvethe efficiency, most of the efforts have been devoted to the design and synthesis ofnew conjugated polymers with strong, broad absorption band and high charge-carriesmobility. In this thesis, a series of novel D-A copolymers were designed andsynthesized. The structure of polymers was characterized by1H NMR and13C NMR.The molecular weight of polymers was measured by the GPC method. Thermalstability, photophysical and electrochemical properties of polymers were also studied.Thiophene, benzene, triphenylamine and diphenylamine are well-knownfunctional groups. Based on this information, a series of benzothiadiazole(BT)derivatives with thiophene vinyl, benzene vinyl, triphenylamine vinyl anddiphenylamine vinyl units as conjugated side chains were designed and synthesized.Subsequently, copolymers of PBDBDT1, PBDBDT2, PBDBDT3, PBDBDT4andPBDBDT5based on benzothiadiazole derivatives and benzo[1,2-b:4,5-b’]-dithiophene(BDT) derivatives with alkoxy as side chains were synthesized via theStille coupling reaction. They have good thermal stability and their thermaldecomposition temperature have reached about330℃. These polymers have twoabsorption peaks in the UV-vis region, the maximum absorption peaks of polymerfilms are located at601nm,597nm,603nm,587nm and606nm, respectively. Theyshow broad absorption band, and the absorption spectra of these five polymers havecovered with visible spectra. From the results of electrochemical cyclic voltammetry,these five polymers have low bandgaps and are almost agreed well with opticalbandgaps.Benzo[1,2-b:4,5-b’]dithiophene derivatives with thiophene as side chains weresynthesized, which were introduced into BT-based polymer main chains.Subsequently, five novel D-A copolymers were synthesized via the Stille couplingreaction. They have good thermal stability and their thermal decompositiontemperature have reached about400℃. PBTBDT1, PBTBDT2, PBTBDT3,PBTBDT4and PBTBDT5have three absorption peaks in the UV-vis region, the maximum absorption peaks of polymer films are located at620nm,604nm,613nm,604nm and613nm, respectively. They show broad absorption band, and theabsorption spectra of these five polymers have covered with visible spectra. Thesepolymers have low bandgaps and are almost agreed well with optical bandgaps.Compared with the polymers based on benzo[1,2-b:4,5-b’]-dithiophene derivativeswith alkoxy as side chains, the polymers based on benzo[1,2-b:4,5-b’]dithiophenederivatives with thiophene as side chains have broader absorption band.A series of conjugated polymers based on benzothiadiazole derivatives aselectron acceptor and bithieno[3,2-b:2’,3’-e]pyridine as electron donor, PBDTP1,PBDTP2, PBDTP3, PBDTP4and PBDTP5, were synthesized. These polymers showgood thermal stability. From UV-vis absorption spectrum, the maximum absorptionpeaks of PBDTP1, PBDTP2, PBDTP3, PBDTP4and PBDTP5films are located at597nm,578nm,574nm,530nm and544nm, respectively. They have broad absorptionband, and the absorption spectra of these five polymers have covered with visiblespectra. From the results of electrochemical cyclic voltammetry, PBDTP1, PBDTP2,PBDTP3, PBDTP4and PBDTP5have low bandgaps and are almost agreed well withoptical bandgaps.