화학공학소재연구정보센터
Journal of the Electrochemical Society, Vol.162, No.10, E263-E270, 2015
Molecular Orbital-Based Verification of Conductivity of Tetramethylammonium Pentaiodide and Pentaiodide-Based Electrolytes in Dye-Sensitized Solar Cells
In order to verify the electrical conductivity of tetramethylammonium pentaiodide (TAPI, I-5(-)(N(CH3)(4)(+))) crystal, molecular orbital configurations and energy structures of the electron-carrying state TAPI packing unit (TAPI-6) are examined by density functional theory (DFT). The narrow energy gap of the electron-carrying state radical anion of [TAPI-6].(-) proves the semi-conductivity of TAPI together with the aligned configuration of singly occupied molecular orbital (SOMO) and the spin density distribution on SOMO. The molecular orbital analysis of the electron-accepted states of the vertical fragment unit of [TAPI-4](.-) and the coplanar fragment unit of [TAPI-3](.-) rationalize the anisotropic semiconducting property in TAPI. DFT-based molecular modeling for molecular integration of I5-N(CH3)(4)(+) with I-5(-) and with I5-N(CH3)(4)(+) confirms the formation of I-5(-) integrated complexes of respective I-5(-)&I5-N(CH3)(4)(+) and (I5-N(CH3)(4)(+))(2). The degenerate HOMO and LUMO in (I5-N(CH3)(4)(+))(2) suggest expanding integration of I-5(-) net via van der Waals and coulomb interactions (vdW&Clb) in I-5(-)-based electrolytes. The narrow energy gap (0.3 similar to 0.35 eV) and the spin density on SOMO of the radical anions of [(I5-N(CH3)(4)(+))(2)](-) and [I-5(-) &I5-N(CH3)(4)(+)](-) explain that the I5-N((CH3)(4)(+)-derived self-integrated I-5(-) cluster nets become semiconducting and the photo-formed electron is transported effectively through SOMOs on I-5(-) units of the electron-carrying clusters of [I-5(-) &I5-N(CH3)(4)(+)](.-) and [(I5-N(CH3)(4)(+))(2)](-). The DFT-based molecular modeling verifies reasonably the semi-conductivity of I-5(-)-based DSC electrolytes. (c) The Author(s) 2015. Published by ECS. All rights reserved.