| Summary: | 碩士 === 國立交通大學 === 應用化學系碩博士班 === 100 === We have designed and synthesized a nitrogen-bridged pentacyclic structure, benzodi(pyrrolothiophene) (BDPT). Its corresponding distannyl monomer Sn-BDPT was copolymerized with four different acceptors, 2,1,3-benzothiadiazole (BT), 1,4-diketopyrrolo[3,4-c]pyrrole (DPP), N-ethylhexylthieno[3,4-c]pyrrole-4,6-dione (TPD-EH), and N-octylthieno[3,4-c]pyrrole-4,6-dione (TPD-C8) by Stille coupling to afford four alternating conjugated copolymers, PBDPTBT, PBDPTDPP, PBDPTTPD-EH, PBDPTTPD-C8, respectively.
These four conjugated copolymers exhibited good thermal stability with decomposition temperature (Td) ranging from 395 oC to 430 oC. The optical, electrochemical, and optoelectronic properties of the polymers varied significantly with respect to the electron-withdrawing ability of the acceptors. The optical band gap of these conjugated copolymers was estimated to be 1.25 eV, 1.52 eV, 1.77 eV, 1.79 eV for PBDPTDPP, PBDPTBT, PBDPTTPD-EH, PBDPTTPD-C8, respectively. This result indicates that the electron-withdrawing ability is in the order: DPP >BT >TPD. The LUMO energy levels of all the conjugated copolymer are higher than that of PC71BM, which assures that excitons can be efficiently dissociated at the interface between conjugated copolymers and PC71BM
Bulk heterojunction (BHJ) solar cell devices were fabricated to evaluate these polymers with the configuration of ITO/PEDOT:PSS/Copolymer:PC71BM/Ca/Al. The device based on PBDPTTPD-EH:PC71BM (1:3, in wt%) exhibited a highest PCE of 3.72% with a Voc of 0.75 V, a Jsc of 9.69 mA/cm2, and a fill factor of 51.2%.
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