Molecular Orbital-Based Verification of Conductivity of Tetramethylammonium Pentaiodide and Pentaiodide-Based Electrolytes in Dye-Sensitized Solar Cells. Issue 10 (1st January 2015)

• Record Type: Journal Article
• Authors: Yanagida, Shozo; Yanagisawa, Susumu; Segawa, Hiroshi
• Is Part Of: Journal of the Electrochemical Society. Volume 162:Issue 10(2015)
• Page Start: E263
• Page End: E270
• Publication Date: 2015-01-01
• Subjects: anisotropic -- DFT -- DSC -- hopping -- iodine -- molecular modeling -- semiconducting; Electrochemistry -- Periodicals; 541.3705
• DOI: 10.1149/2.0701510jes
• Languages: English
• ISSNs: 0013-4651

Abstract

Abstract : In order to verify the electrical conductivity of tetramethylammonium pentaiodide (TAPI, I5 − (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 I5 − and with I5 − N(CH3 )4 + confirms the formation of I5 − integrated complexes of respective I5 − &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 I5 − net via van der Waals and coulomb interactions (vdW&Clb) in I5 − -based electrolytes. The narrow energy gap (0.3 ∼ 0.35 eV) and the spin density on SOMO of the radical anions of [(I5 − N(CH3 )4 + )2 ] − and [I5 − &I5 − N(CH3 )4 + ] − explain that the I5 − N((CH3 )4 + -derived self-integrated I5 − cluster nets become semiconducting and the photo-formed electron is transported effectively through SOMOs on I5 − units of the electron-carrying clusters of [I5 − &I5 − N(CH3 )4 + ] .− and [(I5 − N(CH3 )4 + )2 ] − . The DFT-based molecular modeling verifies reasonably the semi-conductivity of I5 − -based DSC electrolytes.