TCNQ molecular semiconductor of the Cu(II)TAAB macrocycle: Optical and electrical properties

M. E. Sánchez Vergara, R. Salcedo, Bertha Molina, R. Carrera-Téllez, J. R. Álvarez-Bada, A. Hernández-García, V. Gómez-Vidales

Research output: Contribution to journalArticlepeer-review

2 Scopus citations

Abstract

The present study reports the doping of a semiconducting molecular material through the formation of hydrogen bonds between the macrocycle Cu(II)(TAAB) and the electronic acceptor TCNQ. According to density functional theory (DFT) calculations and electron paramagnetic resonance (EPR) analysis, the doped compound has the shape of a distorted square pyramid, with four nitrogen atoms in the equatorial position and the apical oxygen atom from the water ligands. These water molecules can generate strong hydrogen bonds with TCNQ and the TAAB metallic complex. Thin films of copper molecular material were obtained through high vacuum evaporation and were structurally characterized by IR spectroscopy, EPR and scanning electron microscopy (SEM). Additionally, the absorption coefficient (α) and photon energy (hν) were calculated from UV–vis spectroscopy and used to determine the optical activation energy in each film, from which its semiconducting behavior was established. An important aspect to consider is that the presence of hydrogen bonds is essential to establish the semiconducting nature of these species; this chemical behavior, as well as the resulting electronic mobility, have been studied by DFT theoretical calculations, which reinforce the experimental conclusion of a relationship between Cu(II)TAAB and TCNQ moieties generated by a weak bond. Finally, I–V characteristics have been obtained from a glass/ITO/doped molecular semiconductor/Ag device using Ag and ITO electrodes. Results for the copper-based device show that, at low voltages, the conduction process is of an ohmic nature while, at higher voltages, space-charge-limited current (SCLC) is found. It is highly probable that the doping effect in TCNQ favors electronic transport due to the formation of conduction channels caused by dopant-favored anisotropy.

Original languageEnglish
Pages (from-to)158-166
Number of pages9
JournalSpectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy
Volume200
DOIs
StatePublished - 5 Jul 2018

Keywords

  • DFT calculations
  • Electrical properties
  • Optical properties
  • Semiconductor molecular material
  • Thin film

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