Synthesis and properties of novel phosphonic acid containing-poly(alkylthiophene)/TiO2 hybrid materials
Date Issued
2006
Date
2006
Author(s)
Chou, Shih-Chi
DOI
zh-TW
Abstract
Polythiophenes have been widely used as photo-sensitizer and electron donor materials in polymer solar cells, because of their excellent optoelectronic properties and high charge-carrier mobility. However, the inherent incompatibility of organic polymers and inorganic particles frequently causes severe phase separation upon physical mixing, thus leading to poor photo-induced charge transfer efficiency. In this study, a series of novel polythiophene-TiO2 hybrid materials were synthesized by the sol-gel reaction of titanium alkoxide precursor in the presence of phosphonic acid-containing poly(3-hexylthiophene) to increase the interactions between TiO2 particles and conjugated polymer chains.
2,5-Dibromo-3-(ω-bromoalkyl)thiophenes bearing different chain-lengths of alkyl side groups were synthesized by reacting 3-bromothiophene with 1,ω-dibromoalkane, followed by the bromination with NBS. Then, the terminal bromide group on thiophene monomer was converted to the phosphonate moiety by reacting with P(OEt)3 via the Michaelis-Arbuzov rearrangement. Finally, the phosphonate-containing regioregular polythiophenes were synthesized by the McCullough method using 2,5-dibromo-3-hexylthiophene and 2,5-dibromo-3-(ω- alkylphosphonate)thiophene as monomers. The chemical structures of monomers and polymers were characterized using 1H NMR and 31P NMR analyses. GPC was employed to investigate the molecular weight characteristics of polymers.
Polythiophene-TiO2 hybrid materials were prepared by the in-situ sol-gel reaction of titanium isopropoxide in the CHCl3 solution of polythiophene or phosphonate-bearing polythiophene. The bonding formation between phosphonic acid and TiO2 were confirmed by the FT-IR and solid state 31P NMR spectra of hybrids. Both SEM and TEM micrographs demonstrated that the presence of phosphonic-acid groups effectively prevents the macroscopic phase separation during the so-gel reaction, and showed that the size of TiO2 particles ranges from 5 to 20 nm. Moreover, the TEM pictures of hybrid materials revealed that TiO2 particles were better distributed inside the polythiophene matrix as the chain length of the alkyl side-arm increases to 10 carbons. Herein, a homogeneous and transparent hybrid material was successfully prepared, and the compatibility between TiO2 and polythiophene was greatly enhanced.
Subjects
太陽能電池
溶膠凝膠法
聚烷基噻
吩
solar cell
bulk heterojunction
polythiophene
phosphonic acid
Type
thesis
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