| Summary: | 碩士 === 國立臺灣大學 === 高分子科學與工程學研究所 === 101 === Isoindigo is a kind of nature dye, and it is renewable and available from plants. Isoindigo-based low-band gap conducting polymers have high absorption coefficient, crystallinity, and power conversion efficiency(PCE). We focus on developing this type of polymers for solar cell application. The polymers(PnTI) are designed to have different length of thiophene(nT) as donor unit and iosindigo(I) as acceptor unit. We synthesize four polymers of P3TI, P4TI, P5TI, and P6TI by Stille coupling, characterizing their optical property, electrical property, crystallinity and PCE systematically. The Properties of polymers are affected by the amount of side chain, the length of thiophene, and the symmetry of donor unit. As the amount of side chain on donor unit decreases, the UV-Vis absorption of polymers increases. As the length of thiophene increases, the HOMO and LUMO of PnTI rise. The P4TI and P6TI contain centrosymmetric donor unit, which exhibits higher crystallinity than that of axisymmetry of P3TI and P5TI. When the amount of side chain on donor unit increases, the crystallinity of PnTI becomes lower. Thus, the order of crystallinity is P4TI>P6TI>P3TI>P5TI. The solar cell fabricated from the blend of P6TI and fullerene derivative PC71BM reaches the best PCE of 7.24% among PnTIs. This is the highest record in the field of isoindigo-based polymer solar cell, according to our best knowledge. The PCE is expected to increase to more than 10% of commercial viable value by optimizing the polymer compositions and device structures.
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