| Summary: | 碩士 === 國立中央大學 === 化學學系 === 105 === The photovoltical performance of a P-type conjugated polymer can be tuned by changing the molecular structure and weight. In this study, 8-bis(5-ethylhexyl)thiophen-2-yl)-2,6-di(thiophen-2-yl)benzo[1,2-b:4,5-b'] dithiophene was used as a donor unit and bromo-2,3-bis(4-(hexyloxy) phenyl)pyrido[3,4-b]pyrazine was used as an acceptor to construct the copolymer P11. Furthermore, an electron-withdrawing alkylthio chain was attached on the donor to form P12, or adding electron-withdrawing fluorine atoms on the acceptor to prepare P14. P15 has alkylthio chain on the donor and fluorine on the acceptor. Combining these four new copolymers with P9 and P10 (without thiophenebridge) prepared in our lab before, the properties- photovoltical performance relationship were investigated. The results showed that the conjugation length of P11 and P12 which containing thiophene bridge was longer than P9 and P10, respectively therefore the corresponding solar cells have higher Jsc value. P15 has higher molecular weight, large absorption coefficient, good crystallinity and forms an interpenetrating bicontinuous network when blend with PC61BM. As a result, inverted cell based on P15 copolymer exhibits the highest Jsc value (11.70 mA/cm2), FF value (0.53) and conversion efficiency (4.50%) amongst the copolymers studied in this thesis. In addition, increasing the molecular weight of P2 by using the fresh prepared Pd(PPh3)4 as a catalyst, or by Soxhlet extraction of P15 with high polar solvent. We have proved the copolymers with higher molecular weight have the efficiency (P2:1.67%, P15:4.31%) higher than that of copolymers with lower molecular weight (P2:0.91%, P15:2.43%).
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