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Article Citation - WoS: 5Citation - Scopus: 7Design of Novel Tellurium and Selenium Containing Semiconducting Polymers Using Quantum Mechanical Tools(Elsevier, 2017) Kaya, Birnur; Kayi, HakanStructural, optical and electronic properties of the two novel donor-acceptor-donor type conjugated polymers based on 4,7-di(selenophen-2-yl)benzo[c][1,2,5]selenadiazole (SeSeSe) and 4,7-di(tellurophen-2-yl)benzo[c][1,2,5]telluradiazole (TeTeTe) are investigated by means of quantum chemical calculations utilizing conventional and long-range corrected hybrid functionals. The lowest energy structures of the SeSeSe and TeTeTe monomers and oligomers are revealed through conformational analysis, while their electronic properties are obtained from density functional theory (DFT) molecular orbital calculations and optical properties are obtained from the time dependent DFT (TD-DFT) calculations for UV-vis absorption spectra. Electronic band gaps that directly affect the semiconducting properties of these novel polymers are calculated by using linear regression analysis of DFT data, and also periodic boundary conditions calculations (PBC-DFT). Our results indicate that SeSeSe and TeTeTe polymers have considerably lower band gap values than that of their furan-, thiophene-, benzooxadiazole- and benzothiadiazole-based analogs. The novel SeSeSe and TeTeTe polymers with improved optical and electronic properties may have an important role in the near future, especially for the optoelectronic and photovoltaic applications. (C) 2016 Elsevier B.V. All rights reserved.Article Citation - WoS: 10Citation - Scopus: 9A Computational Study on 4,7-Di(furan Monomer and Its Oligomers(Springer, 2014) Kayi, Hakan; Kayı, Hakan; Kayı, Hakan; Chemical Engineering; Chemical EngineeringThe energy gap, Eg, between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy levels that determines the electronic and optical properties of 4,7-di(furan-2yl)benzo[c][1,2,5]thiadiazole (FSF) polymer is calculated by performing quantum chemical calculations. First, we theoretically investigated the most stable conformers of FSF monomer and its corresponding oligomers at the B3LYP/6-31G(d) and B3LYP/LANL2DZ levels of theory. We reveal the theoretical molecular structure of this very recently synthesized novel monomer and its oligomers for the first time in the literature. Our results from the B3LYP/6-31G(d) calculations indicated that FSF polymer has a low HOMO-LUMO gap of 1.55 eV to be in good agreement with the experiments. Experimental design and synthesis of novel conjugated polymers require time-consuming and expensive procedures. The findings from this study are promising for the use of computational methods in the design of the novel conjugated polymers, and help to narrow the materials to be used in design and synthesis of conjugated polymers with desired properties.Article Citation - WoS: 9Citation - Scopus: 10A Theoretical Investigation of 4,7-Di(furan Donor-Acceptor Type Conjugated Polymer(Elsevier, 2015) Kayi, Hakan; Elkamel, AliQuantum chemical calculations are performed using density functional theory (DFT) to investigate the HOMO-LUMO energy gap of the 4,7-di(furan-2-yl)benzo[c][1,2,5]selenadiazole-based (FSeF) donor-acceptor type conjugated polymer which ascertains the optoelectronic properties and plays a crucial role, especially in polymeric solar cell applications. In this paper, the most stable conformers of the FSeF monomer and its corresponding oligomers are investigated at the B3LYP/Def2TZV and B3LYP/LANL2DZ levels of theory, and their molecular structures are revealed. The band gap of the polymer is determined by linear-fitting and extrapolation of the DFT data. This gap is found to be 1.44 eV and 1.45 eV by the B3LYP/Def2TZV, and B3LYP/LANL2DZ with PCM calculations, respectively. Our theoretical findings related to the band gap of the FSeF polymer (PFSeF) are in good agreement with other experimental studies in the literature and, hence, the theoretical methods used in this study are promising for the design of similar donor-acceptor type novel conjugated polymers. (C) 2014 Elsevier B.V. All rights reserved.
