Theoretical Analysis and Applications of Donor-Acceptor Conjugated Polymer Systems
Date Issued
2005
Date
2005
Author(s)
Pai, Chia-Ling
DOI
en-US
Abstract
Donor-acceptor conjugated polymer systems are potential used to tune the electronic and optoelectronic properties. In this thesis, the electronic and optoelectronic properties of two donor-acceptor conjugated polymer systems are explored: (1) theoretical analysis on the geometries and electronic properties of donor-acceptor alternating conjugated polymers based on 3,4-ethylenedioxythiophene (EDOT) and thiophene (T). (2) photophysical properties of fluorene based donor-acceptor conjugated polymer blends.
In the theoretical analysis on EDOT and T based donor-acceptor alternating conjugated polymers, the torsional angle, intramolecular charge transfer, bridge length, and bond length alternation were analyzed and correlated with the electronic properties. It was found that the geometries of the studied materials were significantly affected by the ring size and intramolecular charge transfer. The HOMO level, LUMO level, and band gap of the studied model compounds were well controlled by the acceptor strength. However, the electronic properties of the studied polymer showed a significant different trend with the acceptor strength due to the geometrical transformation. The model compound of EDOT-TP and T-TP has the aromatic geometry but is transformed to the quinoid geometry for large intramolecular charge transfer. The small bond length alternation and large acceptor strength in the EDOT-BDP polymer also results in the smallest Eg of 0.7 eV among the studied polymers. The theoretical results suggest that both the acceptor strength and the stable geometry contribute significantly to the electronic properties of donor-acceptor alternating conjugated polymers.
In the fluorene based conjugated polymer blends, photophysical properties of six blend systems were studied through UV-Vis absorption and photoluminescence spectra. Efficient energy transfer has been observed in blend system (I): F6PY and F6BT, and system (II): F6PY and F8T2. PL efficiencies could reach as high as 31.1 % and 15.6 % by adding only 5 wt% of F6BT or 10 wt% of F8T2 into F6PY, respectively. It suggests that the blend approach has the potential in enhancing the luminescence efficiency from the homopolymer. However, the PL emission of the F6TP blend system (III) ~ (V) did not show an enhancement as the systems (I) and (II). The PL quenching due to the heavy atom effects of sulfur or n→
Subjects
電子施體/受體
DFT
賽吩
fluorene
Fö
rster能量轉移
conjugated polymer
Donor-Acceptor
thiophene
polymer blends
rster energy transfer
Type
thesis
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