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Liquid-phase encapsulation of α-sexithiophene (6T) molecules inside individualized single-walled carbon nanotubes (SWCNTs) is investigated using Raman imaging and spectroscopy. By taking advantage of the strong Raman response of this system, we probe the encapsulation isotherms at 30 and 115 °C using a statistical ensemble of SWCNTs deposited on a oxidized silicon substrate. Two distinct and sequential stages of encapsulation are observed: Stage 1 is a one-dimensional (1D) aggregation of 6T aligned head-to-tail inside the nanotube, and stage 2 proceeds with the assembly of a second row, giving pairs of aligned 6Ts stacked together side-by-side. The experimental data are fitted using both Langmuir (type VI) and Ising models, in which the single-aggregate (stage 1) forms spontaneously, whereas the pair-aggregate (stage 2) is endothermic in toluene with formation enthalpy of ΔHpair= (260 ± 20) meV. Tunable Raman spectroscopy for each stage reveals a bathochromic shift of the molecular resonance of the pair-aggregate, which is consistent with strong intermolecular coupling and suggestive of J-type aggregation. This quantitative Raman approach is sensitive to roughly 10 molecules per nanotube and provides direct evidence of molecular entry from the nanotube ends. These insights into the encapsulation process guide the preparation of well-defined 1D molecular crystals having tailored optical properties.

We investigated the performance of carbon nanotube (CNT) array electrodes applied to n-type and ambipolar phenyl-C61-butyric acid methyl ester (PCBM) thin film transistors on a SiO2dielectric substrate. Compared to conventional Au electrodes, CNT arrays provide better injection efficiency, improved switching behavior, higher electron mobility, and lower contact resistance. Experiments on ambipolar PCBM transistors indicate that the injection performance is enhanced by the electrostatics of the CNT contacts, which promotes electron and hole tunneling across Schottky barriers at the PCBM/nanotube interface. The use of CNT arrays is a valid replacement to low workfunction metals, which are often reactive in air and difficult to process. Our work paves the way for a widespread use of carbon nanotube array electrodes in high-performance n-type and p-type organic thin film transistors.