| Summary: | 碩士 === 國立交通大學 === 材料科學與工程學系所 === 104 === In this study, in order to investigate the characteristics of bulk heterojunction polymer solar cell through changing polymer alkyl side chains, we use benzodithiophene (BDT) with alkyl thienyl side chains as electron donor, thiophene as π-bridge, and benzooxadiazole (BO) as electron acceptor. By changing the alkyl side chains of BDT and BO into linear or branched structure, we synthesize a series of donor-π-acceptor (D-π-A) conjugated polymers－PBDTTC8TBOC8C8 (P1), PBDTTC8TBOEHEH (P2), PBDTTC8TBOC8EH (P3), PBDTTEHTBOC8C8 (P4), PBDTTEHTBOEHEH (P5), PBDTTEHTBOC8EH (P6) respectively. We systematically compare the physical, chemical, photovoltaic, structural packing, and morphological properties.
P1 has the highest thermal stability, number-average molecular weights (Mn), and weight-average molecular weights (Mw). P1, P2, P3, and P4 films tend to form face-on packing structures which is beneficial to carrier transfer orthogonally, thus show enhanced shortcut current (Jsc). P2 and P3 have low-lying HOMOs, leading to high open circuit voltage (Voc) which are 0.93 V and 0.90 V, respectively. These high Voc cause P2 and P3 to achieve power conversion efficiency (PCE) of 6.5% and 6.8%. P4 exhibit the widest FWHM owing to its broad absorption range with more obvious red shift, and its λonset is 706 nm. The Jsc and PCE of P4 are 15.7 mA/cm2 and 7.5%.
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