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Abstract:

Bilayer poly(3-hexylthiophene):[6,6]-phenyl C61-butyric acid methyl ester (PC61BM) [P3HT:PC61BM] organic field-effect transistors (OFETs) have been fabricated using a bottom-contact, bottom-gate (BCBG) architecture. By annealing these devices and monitoring the magnitude of the electron field-effect mobility, information about the diffusion properties of PC61BM in P3HT can be obtained. Using a solution to the one-dimensional diffusion equation and an application of percolation theory, a relationship between electron field-effect mobility, diffusion coefficient, and annealing time has been obtained. By applying this model to time-dependent mobility measurements, a rough approximation of 5 nm2s-1 has been made for the diffusion coefficient of PC61BM in P3HT at a temperature of 130°C. © 2011 American Physical Society.

Abstract:

We demonstrate that coherent random lasing can occur in solid-state dispersions of laser dyes 4-dicyanomethylene-2-methyl-6-(p-dimethylaminostyryl)- 4H-pyran and 4-dicyanomethylene-2-tert-butyl-6-(1,1,7,7-tetramethyljulolidin-4- yl-vinyl)-4H-pyran within a tris(8-hydroxy-quinolinato)aluminum matrix without the need for infiltrated scatterers. Random lasing thresholds as low as 90 μJ/cm2 are observed in 250 nm-thick films with 2-2.5 dye concentration. We find that the lasing threshold exhibits a power law decay with sample area, providing a simple test for the occurrence of random lasing. We discuss the implications of this result in the context of previous reports of lasing in these materials where feedback was provided by conventional optical resonators. © 2011 American Institute of Physics.

Abstract:

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. © 2011 American Institute of Physics.