Thienopyrazine電子施體-受體共軛高分子之合成、性質及其光電元件應用

Abstract

Listen

Translate article

Donor-acceptor conjugated polymers have been widely investigated in recent years. By optimization of donor and acceptor structures, the conjugated copolymers can exhibit broad absorption from visible region to near-infrared range for electronic and optoelectronic applications, such as light-emitting diodes, photovoltaic cells, and thin film transistor. However, the electronic and optoelectronic properties of thienopyrazine-based conjugated polymers have not been fully explored yet. The goal of this thesis is to investigate the effects of donor-acceptor or donor-acceptor-donor structures on the electronic properties of thienopyrazine based conjugated polymers. In chapter 2, the optical, electrochemical, and field effect charge transport properties of the new thienopyrazine-based alternating donor-acceptor conjugated copolymers were explored. The new copolymers, Poly[5-(2,5-bis(decyloxy)phenyl)-2,3- bis(4-(2-ethylhexyloxy)phenyl)thieno[3,4-b]pyrazine] (PDPTP), Poly[5-(9,9-dioctyl- 9H-fluoren-2-yl)-2,3-bis(4-(2-ethylhexyloxy)phenyl)thieno[3,4-b]pyrazine] (PFPTP), Poly[5-(9-(2-ethylhexyl)-9H-carbazol-3-yl)-2,3-bis(4-(2-ethylhexyloxy)phenyl)thieno[3,4-b]pyrazine] (PCPTP) and Poly[2,3-bis(4-(2-ethylhexyloxy)phenyl)-5-(thiophen-2-yl) thieno[3,4-b]pyrazine] (PTPTP) had excellent solubility and broad optical absorption bands with absorption maxima at 540-950nm in thin film. The PTPTP exhibits the smallest band gap (0.98eV), indicating a stronger intramolecular charge transfer. The four polymers show the low ionization potentials (4.57-4.99 eV) and high electron affinity (3.26-3.49eV). The hole mobilities of PDPTP, PCPTP, and PTPTP are 2.62×10-6, 2.74×10-5, and 2.00×10-4 cm2V-1s-1. PTPTP has the highest hole mobility due to low band gap and strong intramolecular charge transfer.The AFM topographic images of the copolymers show smooth and amorphous phases. From these results, intramolecular charge transfer might be main impact on hole mobility. In chapter 3, thienopyrazine-based donor-acceptor-donor alternating conjugated copolymers were synthesized. The copolymers including Poly[5-(5-(2,5-bis(decyloxy)-4-methylphenyl)thiophen-2-yl)-2,3-bis(4-(2-ethylhexyloxy)phenyl)-7-(5-methylthiophen-2-yl)thieno[3,4-b]pyrazine] (PDDTTP), Poly[5-(5-(9,9- dioctyl-9H-fluoren-2-yl)thiophen-2-yl)-2,3-bis(4-(2-ethylhexyloxy)phenyl)-7-(thiophen-2-yl)thieno[3,4-b]pyrazine] (PFDTTP), and Poly[2,3-bis(4-(2-ethylhexyloxy)phenyl)-5 ,7-di(thiophen-2-yl)thieno[3,4-b]pyrazine] (PDTTP) exhibit broad optical absorption bands (662-816nm) and small optical band gaps (1.15-1.57eV). All polymers exhibit reversible oxidation and reduction and low ionization potential (4.62-4.98 eV). The hole mobility of PDDTTP, PFDTTP, and PDTTP are 7.24×10-4, 1.61×10-3 and 1.16×10-3cm2V-1s-1. The hole mobility of PFDTTP is the highest probably due to the relatively smooth and amorphous phase in thin film. According to these results, thienopyrazine-based donor-acceptor-donor copolymers combine small band gap and high carrier mobility. Such polymers may have potential optoelectronic device applications, such as thin film transistor and photovoltaic cells.