TITLE:
Effect of Organic Dopants in Dimetallophthalocyanine Thin Films: Application to Optoelectronic Devices
AUTHORS:
María Elena Sánchez-Vergara, Santiago Osorio-Lefler, Pablo Osorio-Lefler, José Ramón Álvarez-Bada
KEYWORDS:
Organic Semiconductors, Thin Films, Optical Properties, Electrical Properties, Optoelectronic Devices
JOURNAL NAME:
Advances in Materials Physics and Chemistry,
Vol.9 No.4,
April
26,
2019
ABSTRACT:
Semiconductor films of organic, doped
dimetallophthalocyanine M2Pcs (M = Li, Na) on different substrates
were prepared by synthesis and vacuum evaporation. Tetrathiafulvalene (TTF) and
tetracyanoquinodimethane (TCNQ) were used as dopants and the structure and
morphology of the semiconductor films were studied using IR spectroscopy, X-ray
diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray
Spectroscopy (EDS). The absorption spectra recorded in the ultraviolet-visible region for the deposited films showed the Q and Soret bands related to the electronic π-π* transitions in M2Pc molecules. Optical characterization of
the films indicates electronic transitions characteristic of amorphous thin
films with optical bandgaps between 1.2 and 2.4 eV. Finally,
glass/ITO/doped M2Pc/Ag thin-film devices were produced and their
electrical behavior was evaluated by using
the four-tip collinear method. The devices manufactured from Na2Pc have a small rectifying effect, regardless of the organic dopant used, while
the device manufactured from Li2Pc-TCNQ presents ohmic-like behavior at low voltages, with an insulating
threshold around 19 V. Parameters such as the hole mobility (μ), the concentration of
thermally-generated holes (p0),
the concentration of traps per unit of energy (P0) and the total trap concentration (Nt(e)) were also determined for the Li2Pc-TTF device.