Synthesis, Characterization and Mechanism Investigation of Poly(3-hexylthiophene-co-3-hexyloxythiophene) via Grignard Metathesis.
Date Issued
2008
Date
2008
Author(s)
Wu, Chun-Ching
Abstract
Poly(3-hexylthiophene-co-3-hexyloxythiophene) (P3HT-P3HOT) was synthesized using Grignard reaction, and confirm the inert structure by H NMR. And we do a series of experiments about the relationship of catalyst and molecular weight to study the mechanism of copolymerization, due to the effect of solubility, we find that the copolymerization only obey the GRIM chain-growth phenomenon below certain molecular weight, after is number the molecular won’t grow up even you reduce the amount of catalyst. And we find the real ratio of 3-alkoxythiophene is always 6~10% higher than feed ratio in different molar fraction of comonomer experiment. And we assume the phenomenon is because of the 3-alkoxythiophene has well degree of regiocontrol than 3-alkylthiophene. That is, 3-alkoxythiophene will form more react Grignard intermediate than 3-alkylthiophene. And we also use copolymerization equation and our result to calculate the monomer reactivity ratios r1 and r2, and r1 is equal to 1.2 and r2 is equal to 0.8, the multiple of r1 and r2 is equal to 0.96, indirectly prove the copolymerization is a random copolymerization rather than alternating or block copolymerization. We choose five different fraction of copolymers and detect in UV-vis, photoluminescenece(PL), cyclic voltammetry(CV), thermal gravimetric analysis(TGA), X-ray diffraction(XRD) and solar device. And when we add alkoxythiophene into our copolymer, it will be red shift in optical absorption because of the electro-donation property of alkoxythiophene, and the highest occupied molecule orbital (HOMO) increase and the band gap decrease when we increase the mole fraction of alkoxythiophene, in other words, we can control the HOMO and the band gap by controlling the mole fraction of alkoxythiophene. In TGA test of thermal stability, because the alkoxy is more oxidize, the thermal stability become worse when we increase the mole fraction of alkoxythiophene, and also the crystallinity in the copolymers. Finally , we use the copolymers on the active layer of the organic solar cell, due to the reason of HOMO increasing, the Voc become smaller and lower the efficiency.
Subjects
Poly(3-hexylthiophene-co-3-hexyloxythiophene)
P3HT-P3HOT
Grignard reaction
random copolymer
alkoxy-substituted thiophene
low band gap copolymer
Type
thesis
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