WALAILAK JOURNAL OF SCIENCE AND TECHNOLOGY

Volume 15, No. 11, Month NOVEMBER, Year 2018, Pages 811 - 817

Effects of organic linkers on energy gaps of covalent based triazine frameworks

Kamonrat KASORNMALA, Vittaya AMORNKITBAMRUNG, Pornjuk SREPUSHARAWOOT

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The Covalent Triazine Frameworks (CTFs) were successfully synthesized from the experiments. They usually consist of triazine ring covalently bonded with organic linkers. CTF-Benzene was defined in case of the organic linker be benzene ring. Moreover, 5 different types of organic linkers, namely, Napthalene, Quinoline, Quinoxaline, Anthracene and Acridine were chosen to connect to the boroxine ring and these structures are abbreviated as CTF-Naphthalene, CTF-Quinoline, CTF-Quinoxaline, CTF-Anthracene and CTF-Acridine, respectively. In the present study, the structural parameters, the density of states and energy bands of these structures were investigated by means of the first-principles calculations. For the CTF-Benzene structure, it shows an indirect band gap structure with energy gap of 1.86 eV. By considering the electron density at the states of valence band maximum and conduction band minimum, it was found that the electrons are only localized on the benzene ring. Hence, the optical property of this structure directly related to type of organic linker. This leads us to calculate the optical property of various types of the organic linker in order to adjust the optical property in the Covalent based Triazine Frameworks. According to CTF- Naphthalene, CTF-Quinoline and CTF-Quinoxaline structures, we found that the energy gap ranges from 1.0 to 1.5 eV. Moreover, our calculations revealed that the energy gaps of CTF- Anthracene CTF-Acridine are 0.40 and 0.75 eV, respectively. Based on these results, it is clearly seen that the optical band gaps of these CTF structures can be adjustable in range of 0.4 - 2.5 eV depending on the type of organic linker. Finally, we believed that these newly generated structures might be useful for both photovoltaic and solarcell applications.

Keywords

Covalent Triazine Frameworks, organic linkers, optical bandgaps, first-principles calculations, electron density

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