Synthesis And Investigation Of D-A Conjuated Polymers Based On Benzo[1,2-b:4,5-b’]Dithiophene

Solar energy is a kind of inexhaustible clean energy. With the depletion of fossil energy and the deterioration of the environment, solar cells which can transform solar energy to electrical have become a new research hotspot. Due to its low cost, light weight, and potential use in flexible devices, polymer solar cells have attracted much attention. Although the PCE has been more than 10%, but it is still not enough for the commercial application. Design and synthesis of novel materials become the focus of polymer solar cells.In this thesis, we respectively introduced 2-alkoxythienyl and 2-alkylthiothienyl substituent on the central benzene core of BDT and two donor units M1 and M2 were synthesized. And then synthesized two DPP based acceptor units M3 and M4 with furan or thiophene as π-bridge, respectively. M1 and M2 used as donor units were copolymerized with M3, M4 respectively. And four kinds of polymers, whose absorption were in the near-infrared region, were obtained:PBDTT-O-FDPP, PBDTT-S-FDPP, PBDTT-O-TDPP and PBDTT-S-TDPP. Ml and M2 used as donor units were copolymerized with TPD respectively. And two kinds of polymers, which had high open-circuit voltage, were obtained. M1 and M2 used as donor units were copolymerized with BT and BT(F) respectively. And four kinds of polymers, whose absorption covered the maximum light intensity and maximum photon-pass region, were obtained: PBDTT-O-BT, PBDTT-S-BT, PBDTT-O-BT(F) and PBDTT-S-BT(F). Nevertheless, when BT and BT(F) were used as acceptor units, the polymers’solubility was not well. So we introduced 2-hexylthiophene as π-bridge in the main chain. M1, M2 were copolymerized with BTT(6) respectively. And PBDTT-O-BTT(6) and PBDTT-S-BTT(6) were obtained.By TGA, UV-Vis and CV, their properties were studied. The results showed that the thermal decomposition temperatures of these polymers were more than 300℃; Band gaps were below 2.0 eV, which means they are all belongs to the narrow band gap materials; HOMO energy level is relatively low, which can help to obtain higher Voc.The 12 polymers were used as donor, while PCBM were used as acceptor, to prepare bulk heterojunction solar cells.And then investigated their photovoltaic performance. Among them, the photovoltaic performance of PBDTT-O-TDPP, PBDTT-S-TPD and PBDTT-S-BTT(6) were good. PCE of them were 4.58%,4.63% and 5.55%, respectively. Among them, the PCE of PBDTT-S-BTT(6) was the highest. It said design and synthesis donor materials, whose absorption coverage the maximum light intensity and luminous flux, and have high absorption coefficient,was the best method to improve PCE.