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In recent years, the dielectric constant (εr) of organic semiconductors (OSCs) has been of interest in the organic photovoltaic (OPV) community due to its potential influence on the exciton binding energy. Despite progress in the design of high εr OSCs and the accurate measurement of the εr, the effects of the synthetic strategies on specific (opto)electronic properties of the OSCs remain uncertain. In this contribution, the effects of εr on the optical properties of five new C70 derivatives and [70]PCBM are investigated. Together with [70]PCBM, the derivatives have a range of εr values that depend on the polarity and length of the side chains. The properties of the singlet excitons are investigated in detail with steady-state and time-resolved spectroscopy and the exciton diffusion length is measured. All six derivatives show similar photophysical properties in the neat films. However, large differences in the crystallinity of the fullerene films influence the exciton dynamics in blend films. This work shows that design principles for OSCs with a higher εr can have a very different influence on the performance of traditional BHJ devices and in neat films and it is important to consider the neat film properties when investigating the optoelectronic properties of new materials for OPV. [ABSTRACT FROM AUTHOR]

Ambipolar charge transport in organic field-effect transistors based on the solution processible methanofullerene [6,6]-phenyl-C71-butyric acid methyl ester ([70]PCBM) is demonstrated. The electron mobility measured in the linear and saturated regimes is approximately equal and of the order of 1*10(super -3) cm(super 2)/V s.

Exciton diffusion and photoluminescence quenching in conjugated polymer/fullerene heterostructures are studied by time-resolved photoluminescence. It is observed that heterostructures consisting of a spin-coated poly(p-phenylene vinylene) (PPV)-based derivative and evaporated C60 are ill-defined as diffusion of C60 into the polymer, leading to an overestimation of the excition diffusion length.

Author(s): Erwin Mecher [1]; Francisco Gallego-Gómez [1, 2]; Hartwig Tillmann [3]; Hans-Heinrich Hörhold [3]; Jan C. Hummelen [4]; Klaus Meerholz (corresponding author) [1, 2] Among the various applications for reversible [...]

Experimental studies involving in situ preparation and trapping of a diazo compound enable the preparation of the isomers, (5,6) fulleroid and (6,6) methanofullerene. Kinetic studies reveal that the substrate concentration exerts no influence on the rate of conversion between these isomers. Cyclic voltammetry reveals that fulleroid undergoes reduction at 34 mV more positive potential than methanofullerene.

The family of soluble fullerene derivatives comprises a widely studied group of electron transporting molecules for use in organic electronic and optoelectronic devices. For electronic applications, electron transporting (n-channel) materials are required for implementation into organic complementary logic circuit architectures. To date, few soluble candidate materials have been studied that fulfill the stringent requirements of high carrier mobility and air stability. Here we present a study of three soluble fullerenes with varying electron affinity to assess the impact of electronic structure on device performance and air stability. Through theoretical and experimental analysis of the electronic structure, characterization of thin-film structure, and characterization of transistor device properties we find that the air stability of the present series of fullerenes not only depends on the absolute electron affinity of the semiconductor but also on the disorder within the thin-film. [ABSTRACT FROM AUTHOR]

An organic field-effect transistor with integrated proteins (Bio-FET) for sensing of sulfate ions is presented. A sulfate receptor was engineered to contain a thiol group for surface-anchoring without affecting its binding activity. The modified receptor was covalently coupled to a maleimide-functionalized polystyrene layer, and integrated as gate dielectric in a dual-gate transducer. The binding of sulfate ions in dry conditions was detected by a shift in the threshold voltage. Combined with surface density measurements by atomic force microscopy , an effective charge of -1.7q per protein was found, as expected from the Bio-FET operation model. [ABSTRACT FROM AUTHOR]

We demonstrate ambipolar charge transport in organic field-effect transistors based on the solution processible methanofullerene [6,6]-phenyl-C71-butyric acid methyl ester ([70]PCBM). The electron mobility measured in the linear and saturated regimes is approximately equal and of the order of 1×10-3 cm2/V s. In the linear regime, mobility is thermally activated with a strong gate bias dependence. The p-channel hole mobility is lower with a maximum value of 2×10-5 cm2/V s. The n- and p-channel operations are characterized by a low (∼|3| V) and a high (∼|50| V) switch-on voltage, respectively, with the on-off current ratio on the order of 104 for both channels. Although the present findings are qualitatively similar to those reported previously for C60-methanofullerene-based transistors, [70]PCBM devices are more stable and easier to reproduce. By making use of this property we are able to demonstrate functional unipolar and complementarylike logic circuits with promising operating characteristics. [ABSTRACT FROM AUTHOR]

A new method involving fulleroid to methanofullerene isomerization without hydrolysis and hydrolysis without rearrangement allows for the manipulation of a fulleroid functional derivative. This method is believed to be possible due to acetate and trifluoroacetate nucleophilicity differences and polarity differences between mediums. Methanofullerenes and fulleroids with 61st carbon phenyl and butanecarboxylate groups may be valuable for study as fullerene derivatives.