편편하고 강직한 구조를 기본으로 한 새로운 공액고분자의 합성 및 광전변환특성에 대한 연구

Abstract

Regioregular poly(3-hexylthiophene) (P3HT) has been proven to be one of the successful electron donors for polymer bulk heterojunction (BHJ) solar cells. The regioregularity of P3HT plays an important role in the performance of solar cells because the regularity strongly associate with the morphology of thin film. The spectral overlap of the polymer with solar spectrum is also important factor for solar cell performance. To better match the solar spectrum, low-band gap polymers have been synthesized for polymer solar cells; however very few of them give a power conversion efficiency (PCE) of more than 5%. The low efficiency is probably due to the nonplanar structure of the polymer, which is detrimental for the close packing of polymer chains in the solid state. Here, we demonstrate a strategy for designing planar polymers with better chain packing in film to facilitate charge carrier transport for photovoltaic application. The π-conjugated polymers with low-band gap based on 2,7-dibromofluorenone and 2-(2,7-dibromo-fluoren-9-ylidene)-malononitrile were synthesized by the Heck coupling and Suzuki coupling reactions. Also, we synthesized a series of low band gap polymers with very planar geometry based dialkoxyphenanthrene, 2,1,3-benzothiadiazole and thiophene by the Suziki coupling and Stille coupling reaction. All polymers were soluble in common organic solvents such as chloroform, chlorobenzene, dichlorobenzene and toluene. The band gap of polymers were estimated UV-Vis spectroscopy and cyclic voltammogram between 1.7 ~ 2.6 eV. The BHJ type photovoltaic cells were fabricated with polymer and PCBM ([6,6]-phenyl-C61-butyric acid methyl ester). The efficieny of solar cells based on the low band gap polymers are ca. 0.1 ~ 0.2%. In this thesis, we report the synthesis and characterization of new polymer.