Gradually increasing dielectric constants (up to 6.3) are obtained for a series of PCPDTTPD polymers.

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.

A method for accurately measuring the relative dielectric constant (εr) of thin films of soft, organic materials is described. The effects of the bombardment of these materials with hot Al atoms, the most commonly used top electrode, are mitigated by using electrodes fabricated from eutectic gallium–indium (EGaIn). The geometry of the electrode is defined by injection into microchannels to form stable structures that are nondamaging and that conform to the topology of the organic thin film. The εr of a series of references and new organic materials, polymers, and fullerene derivatives was derived from impedance spectroscopy measurements for both Al and EGaIn electrodes showing the specific limitations of Al with soft, organic materials and overcoming them with EGaIn to determine their dielectric properties and provide realistic values of εr.