Density functional theory study of electronic band structures of fluorene-based conjugated polymers

Ling, Lin (2007) Density functional theory study of electronic band structures of fluorene-based conjugated polymers. Masters thesis, Memorial University of Newfoundland.

[img] [English] PDF - Accepted Version
Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission.

Download (8MB)


Alternating triphenylamine-fluorene, TPAFn (n=2,3), and fluorene-oxadiazole copolymers OxFn (n=2,3) are important components of novel high-efficiency multilayer polymeric blue light-emitting diodes [1]. In this work we investigate their electronic structure properties using a computational approach. For comparison and calibration purposes we also perform the calculations for poly(acetylene) (PA). The band gaps (E gap’s) and band widths (E width’s) are studied with the Hartree-Fock (HF) and density functional theory (DFT) approaches. The polymers are treated as one-dimensional (1D) infinite conjugated chains with periodic boundary condition. We consider a number of DFT exchange correlation functionals: B3LYP, O3LYP, OB95, PBEPBE, PBE1PBE and TPSSTPSS and employ the 6-31G* basis set and 32 k points in most of our calculations. We compare our results with experimental values whenever possible. The results show that HF method overestimates the band gap of trans-PA by 2.0 eV while the DFT theory underestimates it by 0.20 eV or more. In all DFT calculations with various functionals, B3LYP, O3LYP, OB95, PBEPBE, PBE1PBE and TPSSTPSS, all band gaps are direct and the best agreement with experiment is obtained with the B3LYP and O3LYP functionals for the fluorene-based polymers. The variation of bond length alternations (BLA's) and dipole moments as related to band gaps are discussed.

Item Type: Thesis (Masters)
Item ID: 8800
Additional Information: Includes bibliographical references (leaves 116-124)
Department(s): Science, Faculty of > Physics and Physical Oceanography
Date: 2007
Date Type: Submission
Library of Congress Subject Heading: Conjugated polymers--Electric properties; Density functionals; Energy bands; Fluorene--Electric properties; Hartree-Fock approximation; Light emitting diodes--Electric properties; Polyacetylenes--Electric properties

Actions (login required)

View Item View Item


Downloads per month over the past year

View more statistics