Class Of Dopants Research Articles

Thermally Activated Aromatic Ionic Dopants (TA‐AIDs) Enabling Stable Doping, Orthogonal Processing and Direct Patterning

AbstractDoping plays a critical role in organic electronics, and dopant design has been central in the development of functional and stable doping. In this study, there is departure from conventional molecular dopants and a new class of dopants are reported – aromatic ionic dopants (AIDs). AIDs consist of a pair of aromatic cation and anion that are responsible for molecular doping reaction and charge balancing separately. It is shown that the first AID made from cycloheptatrienyl (tropylium) cation and pentacyanocyclopentadienide anion (PCCp), abbreviated as T‐PCCp, can function as an effectivep‐type dopant to dope polydioxythiophenes. Here, tropylium cation induces the doping reaction while the PCCp anion stabilizes the generated polarons and bipolarons. With T‐PCCp, a highly doped (≈120 S/cm) and stable system is achieved up to 150 °C, an orthogonal (sequential)solution processing resulting from the immiscibility of the dopant and the polymer host, and a high‐resolution direct micropatterning with laser writing resulted from a thermally activated doping process.

Unraveling the mechanism behind air instability in thin semiconducting polymer layers p-doped with molybdenum dithiolene complexes

Doping efficiency and stability are crucial requirements for the integration of doped organic semiconductors in optoelectronic devices. This work presents a detailed experimental study on the air stability of p-doped systems based on a low-bandgap polymer, poly[(4,8-bis-(2-ethylhexyloxy)-benzo(1,2-b:4,5-b’)dithiophene)-2,6-diyl-alt-(4-(2-ethylhexanoyl)-thieno[3,4-b]thiophene-)-2-6-diyl) (PBDTTT-c) doped with a strong molecular p-dopant, i.e. molybdenum tris[1-(trifluoroethanoyl)-2-(trifluoromethyl) ethane-1,2-dithiolene] (Mo(tfd-COCF3)3). The electrical conductivity and the optical absorption are measured for different dopant concentrations in argon atmosphere, and their variations monitored as a function of the air exposure time. The results indicate a clear instability under ambient air related to a dedoping process, which is particularly pronounced in ultra-thin (< 50 nm) doped layers. By evaluating the stability of the p-doped polymer layers under different atmospheres (ambient air, anhydrous air and argon), the detrimental impact of moisture and/or O2(H20)n complexes is highlighted. X-ray Photoelectron Spectroscopy (XPS) revealed that the p-doping instability in ambient air can be assigned to changes in the oxidation state of the metallic center as well as to an intrinsic degradation of the dopant molecule. This study unravels an important degradation mechanism with this class of dopants that should be taken under consideration and solved for future integration of ultrathin p-doped layers in printed electronic devices.

Hydrogen-Bond-Induced Microstructural Transition of Ionic Micelles in the Presence of Neutral Naphthols: pH Dependent Morphology and Location of Surface Activity

The effect of naphthols and methoxynaphthalenes on the microstructure transition of cetyltrimethylammonium bromide (CTAB) micelles is studied. Although the surface activities of these two types of organic dopants are strong, methoxynaphthalenes failed to promote spherical to worm-like micellar transition and to impart viscoelasticity to the aqueous CTAB solution, presumably due to their inability to form unique H-bonds with interfacial water. The micropolarity of OH sites of micelle-embedded naphthols is measured by observing the pK(a) shift at the micellar surface relative to bulk water. On the basis of spectroscopic and other data, the microstructures formed by both classes of dopants at the micellar surface are predicted. On the basis of hydroxyaromatic dopants, a simple and effective route to design pH-responsive viscoelastic worm-like micelles and the vesicles of single tail cationic surfactant (CTAB) is reported. Results are confirmed by observing cryogenic transmission electron microscopy (cryo-TEM) images.

Polyaniline doped by a new class of dopants, benzoic acid and substituted benzoic acid: synthesis and characterization

This work reports on a new class of dopants, benzoic acid and substituted benzoic acids such as 2-hydroxybenzoic acid, 2-chlorobenzoic acid, 4-nitrobenzoic acid, 2-methoxybenzoic acid, 3-methylbenzoic acid, 4-methylbenzoic acid, 3-aminobenzoic acid and 4-aminobenzoic acid, for polyaniline. Benzoic acids can be used to dope polyaniline by mixing benzoic acid (or a substituted benzoic acid) with polyaniline in the common solvent 1-methyl-2-pyrrolidone. Properties of benzoic acid doped polyaniline salts are studied using Fourier transform infra-red, X-ray diffraction spectroscopy, scanning electron microscopy, thermogravimetric analysis and conductivity measurements. The conductivity of polyaniline-benzoic acid salt was found to be high (10−2 S/cm) when compared to polyaniline-substituted benzoic acid salts (10−3–10−5 S/cm). Copyright © 2005 John Wiley & Sons, Ltd.

Optical activation of ion implanted and annealed GaN

Ion implantation and the associated annealing was investigated using luminescence and absorption measurements to demonstrate the efficacy of implantation for introducing various classes of dopants into GaN. A wide range of implantation and annealing studies were performed with several dopant species (Zn, Nd, Er, Ar). Room temperature ion implantation was performed on MOCVD grown GaN samples at energies between 200 and 400 keV with doses ranging from 1 × 1013 to 1 × 1015 cm−2. Conventional furnace annealing in flowing NH3 or N2 resulted in good recovery of implantation damage at an annealing temperature of 1000°C for 90 min. However, surface degradation became evident for annealing in an NH3 environment at temperatures above 1000°C. Low temperature photoluminescence showed that the optical activation of the Zn, and the rare earth elements, Er and Nd, was optimum in the NH3 annealing environment at 1000°C.

‘Organic metals’. New classes of p-type dopants for converting polyacetylene, (CH)xinto the ‘metallic’ state

When ca. 85%cis films of the semiconducting polymer, ‘polyacetylene,’(CH)x, are treated with H2SO4, HClO4, (NO2)(SbF6), (NO)(SbCl6), and (NO2)(BF4) two new classes of dopants are introduced to give golden, flexible films exhibiting high conductivities characteristic of the metallic state.