| 초록 |
We synthesized four donor- acceptor alternating low band gap copolymers by Suzuki and Stille polymerization. The polymers, P1-P4, were designed to find the structural effect of polymer backbones and solubilizing groups on optical and photovoltaic properties. They have thiophene and diketo-pyrrolo-pyrrole (DPP) moieties in the main chain and branched alkyl chains as solubilizing groups. P1-P4 polymers have UV-visible absorption peak in the range of 790 nm ~ 830 nm in film state. The optical band gap of P1-P4 was tuned in the range of 1.21 eV ~ 1.33 eV. The HOMO levels of four polymers are in the range from 5.26 eV to 5.48 eV. Photovoltaic devices incorporating the polymers, P1-P4, were fabricated in the conventional structure. P3 showed the best performance as an open circuit voltage (Voc) of 0.64 V, a short circuit current (Jsc) of 8.92 mA/cm2, a fill factor (FF) of 0.59 and power conversion efficiency (PCE) of 3.32% under AM 1.5 G illumination. |
