Reaching a Double-Digit Dielectric Constant with Fullerene Derivatives

Abstract

The dielectric constant (εr) of organic semiconductors is a key material parameter for improving device performance in the field of organic electronics. However, the effect of the dielectric constant on the electronic and optoelectronic properties of materials remains unclear due to the scarcity of known organic semiconductors with an εr value higher than 6. Herein, the optical and electronic properties of a homologous series of fullerene derivatives with high εr are studied. The low frequency (<106 Hz) εr is extracted from the capacitance measured using impedance spectroscopy, and the effect of length (n) and geometrical arrangement of the polar ethylene glycol (EG) side chains is investigated. The εr is found to correlate with length for the symmetrical Bingel adducts, whereas for the unsymmetrical branched-EG chain adducts there is no significant difference between the two EG chain lengths. For BTrEG-2, the εr reaches 10, which is an unprecedented value in monoadduct fullerene derivatives. These materials open up new possibilities of studying the effect of εr in organic electronic devices such as organic photovoltaics, organic thermoelectrics, and organic field-effect transistors.

Innovative Method for Longer Effective Corrosion Inhibition Time: Controlled Release Oil Palm Empty Fruit Bunch Hemicellulose Inhibitor Tablet

“…The decrease in capacitance value is typically caused by the reduction of the dielectric constant ( ε ) and/or the thickening of the double layer. Organic compounds typically have lower dielectric constant values ( ε ≈ 3–4) compared to water ( ε ≈ 80), owing to their outstanding electrical insulating properties [ 68 , 69 ]. Since the molecules of EFB-H displace water molecules on the metal surface upon adsorption, the overall electric conductance drops, and thus restricting the electrical current flow through the double layer [ 62 ].…”

Structure-induced optoelectronic properties of phenothiazine-based materials

“…The reasons for such modest mobility lie in the typically low dielectric constants of organic semiconductors and to the non-planar structure of PTZ, which inhibits molecular aggregation. In literature, a few successful attempts 113,114 to improve the charge mobilities (410 À2 cm 2 V À1 s À1 ) of building blocks other than PTZ were reported. For example, a few recent studies have shown that, with the insertion of polar glycol side chains, it is possible to significantly increase the dielectric constant of the fullerene derivatives without compromising their optical properties, electrical mobility, and energy levels.…”

“…For example, a few recent studies have shown that, with the insertion of polar glycol side chains, it is possible to significantly increase the dielectric constant of the fullerene derivatives without compromising their optical properties, electrical mobility, and energy levels. 114 We foresee that similar strategies could be applied also to the PTZ core. The flexible polar glycol side chains enhance the crystallinity of thin films with small stacking distance (Fig.…”

Resolving Donor–Acceptor Interfaces and Charge Carrier Energy Levels of Organic Semiconductors with Polar Side Chains

“…Replacement of alkyl by EG chains has been found to increase the doping efficiency of organic semiconductors in thermoelectric devices—mostly due to an increased host–dopant miscibility, [ 3–5 ] to allow for mixed ionic‐electronic conduction, [ 1,6 ] to decrease the π–π stacking distance of polymer backbones, [ 7 ] and to increase the dielectric constant. [ 8–11 ] The increase in the dielectric constant of organic semiconductors has been proposed as a strategy to increase the performance of organic photovoltaics (OPVs). [ 12 ] Although EG side chains in particular have found ample use in achieving organic materials with increased dielectric constants, [ 8–11,13–15 ] this has not yet resulted in OPV devices achieving higher efficiencies.…”

“…[ 8–11 ] The increase in the dielectric constant of organic semiconductors has been proposed as a strategy to increase the performance of organic photovoltaics (OPVs). [ 12 ] Although EG side chains in particular have found ample use in achieving organic materials with increased dielectric constants, [ 8–11,13–15 ] this has not yet resulted in OPV devices achieving higher efficiencies. [ 14 ] A microscopic understanding is paramount to rationalize the effect of polar side chains in blends of organic semiconductors.…”