Research in organic electronics has included advances in materials, devices, and processes. Device architectures, increasingly complex circuitry, reliable fabrication methods, and new semiconductors are enabling the incorporation of organic electronic components in products including OLED displays and flexible electronic paper.

Pentacene-based thin-film integrated circuits patterned only with polymeric shadow masks and powered by near-field coupling at radio frequencies of 125 kHz and above 6 MHz have been demonstrated. Sufficient amplitude modulation of the rf field was obtained to externally detect a clock signal generated by the integrated circuit. The circuits operate without the use of a diode rectification stage. This demonstration provides the basis for more sophisticated low-cost rf transponder circuitry using organic semiconductors.

We show novel and selective means to modify the dielectric surfaces in organic TFTs. Modification schemes include alkylphosphonic acid monolayers that have a strong affinity for alumina surfaces. Monolayers form robust, extremely uniform thin films and are deposited through simple spin-coating with a dilute solution of the monolayer precursor in solvent. Adding monolayers to organic TFTs has resulted in polycrystalline devices with mobilities nearly equal to single-crystal values while maintaining acceptable values of other device parameters (for example, the threshold voltage, on/off ratio, and subthreshold slope) required for fully functional integrated circuits.

We report here methods of surface modification and device construction which consistently result in lab-scale pentacene-based TFTs with mobilities at or above 5 cm2/Vs. Surface modifications include polymeric ultrathin films presenting a passivated interface on which the semiconductor can grow. High performance TFTs have been fabricated on a variety of dielectric materials, both organic and inorganic, and are currently being implemented in manufacturable constructions. Our surface modifications have also proven useful for substituted pentacene materials and for a variety of other organic semiconductors. In addition, we report an all organic active layer, rf-powered integrated circuit. Further experiments and statistical analyses are underway to explain the elevated mobility in our samples, and efforts have been made to confirm these results through collaboration.

We present the results of two studies:  (1) a comparison of force−distance (F−D) profiles obtained by atomic force microscopy (AFM) and the surface forces apparatus (SFA) for a poly(2-vinylpyridine)−polystyrene (PVP−PS) brush in good solvent; (2) a series of F−D profiles for a poly(4-tert-butylstyrene)−sodium poly(styrene-4-sulfonate) (PtBS−NaPSS) brush as a function of aqueous NaCl concentration. The AFM force profiles of the neutral PVP−PS brush are less steep than the corresponding surface forces data in the regime of high brush compression, in agreement with a recent molecular simulation study that indicated the tip would splay polymer chains and penetrate the brush. We also observe a bimodal distribution of interaction distances for the AFM force profiles of the PVP−PS brush which we ascribe to the tip sampling regions of higher and lower chain density during consecutive force measurements. AFM F−D profiles of the PtBS−NaPSS brush show a strong dependence of interaction distance on NaCl concentration, and a plot of interaction distance vs salt concentration shows predicted power law behavior. Images of both the PVP−PS and PtBS−NaPSS brushes show that the chain density is not uniform which gives rise to variations in the interaction distances measured by AFM. By facilitating measurements of local force profiles, AFM complements SFA measurements of interfacial forces and allows measurement of brush heterogeneity.