Synthesis of Supported Single-Crystalline Organic Nanowires by Physical Vapor Deposition (original) (raw)
Related papers
Heterostructures Based on Porphyrin/Phthalocyanine Thin Films for Organic Device Applications
Phthalocyanines and Some Current Applications, 2017
Multilayer or blend heterostructures based on porphyrins and phthalocyanines were obtained on different substrates using VTE and MAPLE methods. Stacked structures based on ZnPc and C60 with NTCDA were prepared by VTE on ITO/glass, their current value being increased by the deposition of the materials in an inverted configuration or by using ITO/PEDOT:PSS as a substrate. Multilayer structures comprising ZnPc and NTCDA were fabricated by MAPLE on an AZO/glass. Treating the AZO in oxygen plasma, a higher current value was obtained for the deposited heterostructures. The oxygen plasma treatment can increase the work function of the AZO resulting in a decrease of the energetic barrier from AZO/organic interface and finally improving the charge transport. Stacked layers or blend heterostructures having ZnPc, MgPc and TPyP were deposited by MAPLE on ITO/PET. In the case of those containing MgPc and TPyP, an increase in the current value (in dark) was obtained for the blend compared to the stacked layer configuration. For those with ZnPc and TPyP, under illumination, a photovoltaic effect was observed for the blend structure. All heterostructures are featured by a large absorption in the visible domain of the solar spectrum and suitable electrical properties for their use in OPV applications.
Langmuir, 2010
We present for the first time a general vacuum process for the growth of supported organic nanowires formed by π-conjugated molecules, including metalloporphyrins, metallophthalocyanines, and perylenes. This methodology consists on a one-step physical vapor deposition of the π-conjugated molecules. The synthesis is carried out at controlled temperature on substrates with tailor morphology which allows the growth of organic nanowires in the form of squared nanofibers and nanobelts. The study of the nanowires by electron diffraction and HRTEM combining with the results of a theoretical analysis of the possible arrangement of the π-conjugated molecules along the nanowires reveals that the nanowires show a columnar structure along the fiber axis consisting of π-stacked molecules having a herringbone-like arrangement. The formation of these nanowires on different substrates demonstrates that the growth mechanism is independent of the substrate chemical composition. An in-depth phenomenological study of the formation of the nanowires drives us to propose a growth mechanism based on a crystallization process. Furthermore, the growth method allows the fabrication of two particular 1D heterostructures: binary and open core@shell organic nanofibers.
Nano Research, 2014
We report on large work function shifts induced by the coverage of several organic semiconducting (OSC) films commonly used in organic light emitting diodes (OLEDs) and organic photovoltaics (OPVs) with a porphyrin aggregated layer. The insertion between the organic film and the aluminum cathode of an aggregated layer based on the meso-tetrakis(1-methylpyridinium-4-yl) porphyrin chloride (porphyrin 1), with its molecules adopting a face-to-face orientation parallel to the organic substrate, results in a significant shift of the OSC work function towards lower values due to the formation of a large interfacial dipole and induces large enhancement of either the OLED or OPV device efficiency. OLEDs based on poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(1,4-benzo-2,1',3-thiadiazole)] (F8BT) and incorporating the porphyrin 1 at the cathode interface exhibited current efficiency values up to 13.8 cd/A, an almost three-fold improvement over the efficiency of 4.5 cd/A of the reference device. Accordingly, OPVs based on poly(3hexylthiophene) (P3HT), [6,6]-phenyl-C 61 butyric acid methyl ester (PC 61 BM) and porphyrin 1 increased their external quantum efficiencies to 4.4% relative to 2.7% for the reference device without the porphyrin layer. The incorporation of a layer based on the zinc meso-tetrakis (1-methylpyridinium-4-yl)porphyrin chloride (porphyrin 2), with its molecules adopting an edge-to-edge orientation, also introduced improvements, albeit more modest in all cases, highlighting the impact of molecular orientation.
The Conductance of Porphyrin-Based Molecular Nanowires Increases with Length
Nano Letters
High electrical conductance molecular nanowires are highly desirable components for future molecular-scale circuitry, but typically molecular wires act as tunnel barriers and their conductance decays exponentially with length. Here, we demonstrate that the conductance of fused-oligo-porphyrin nanowires can be either length independent or increase with length at room temperature. We show that this negative attenuation is an intrinsic property of fused-oligo-porphyrin nanowires, but its manifestation depends on the electrode material or anchor groups. This highly desirable, nonclassical behavior signals the quantum nature of transport through such wires. It arises because with increasing length the tendency for electrical conductance to decay is compensated by a decrease in their highest occupied molecular orbital− lowest unoccupied molecular orbital gap. Our study reveals the potential of these molecular wires as interconnects in future molecular-scale circuitry.
Porphyrin-Phthalocyanine Nanorods (P-PcNR) formed by Electrostatic Self-Assembly
Porphyrin-Phthalocyanine nanorods had been formed by electrostatic self-assembly of two oppositely charged 4complexes. The negatively charged complex was meso-tetra-4-phenylsulfonated porphyrin (H TPPS ) and the two 2 4 positively charged complex were tin and indium complexes of tetra {2,(3)-(2-mercaptopyridine) phthalocyaninato}(MTSPyPc). The transmission electron microscope (TEM) images of the colloid suspension of the aggregate confirmed formation of nanorods while their electron spectra showed that the molecules formed J-aggregation.
Ultralong Copper Phthalocyanine Nanowires with New Crystal Structure and Broad Optical Absorption
ACS Nano, 2010
The development of molecular nanostructures plays a major role in emerging organic electronic applications, as it leads to improved performance and is compatible with our increasing need for miniaturisation. In particular, nanowires have been obtained from solution or vapour phase and have displayed high conductivity 1, 2 or large interfacial areas in solar cells. 3 In all cases however, the crystal structure remains as in films or bulk, and the exploitation of wires requires extensive post-growth manipulation as their orientations are random. Here we report copper phthalocyanine (CuPc) nanowires with diameters of 10-100 nm, high directionality and unprecedented aspect ratios. We demonstrate that they adopt a new crystal phase, designated η-CuPc, where the molecules stack along the long axis. The resulting high electronic overlap along the centimetre length stacks achieved in our wires mediates antiferromagnetic couplings and broadens the optical absorption spectrum. The ability to fabricate ultralong, flexible metal phthalocyanine nanowires opens new possibilities for applications of these simple molecules.
Ring-expanded porphyrins as an approach towards highly conductive molecular semiconductors
Chemical Physics Letters, 1993
As an approach to obtainiq molecular semiconductors with high conductivity, it was attempted to lower the activation energy of conduction by enlargiqthe n-conjugated system in porphyrin materials. An anthraporphyrin (ZnTAnP) has been synthesized for the fast time, and the spectroscopic, electrochemical and semiconductive properties have been characterized as a function of increasing molecular size, in the order: tetraphenylporphyrin (ZnTPP), tetrabenzoporphyrin (ZnTBP), tetranaphthaloporphyrin (ZnTNP), and ZnTAnP. With enlargement of the macrocycle, the Q band shifts to the red, and the absolute values of oxidation and reduction potentials become smaller. Room temperature conductivities of air-doped ZnTPP, ZnTBP, ZSNP, and ZnTAnP thin films are < lo-", 4~ lo-lo, 3~ lo-' and 1 x lo-' W' cm-', respectively. The smaller conductivity of ZnTAnP appears due to the formation of a stable charge transfer complex with oxygen.
Self-Assembled Molecular Nanowires for High-Performance Organic Transistors
ACS Applied Materials & Interfaces
While organic semiconductors provide tantalising possibilities for low-cost, lightweight , flexible electronic devices, their current use in transistors-the fundamental building block-is rather limited as their speed and reliability is not competitive with their inorganic counterparts, and is simply too poor for many practical applications. Through self-assembly, highly ordered nanostructures can be prepared that have more competitive transport characteristics, but no simple, scalable method has been discovered that can produce devices based on such nanostructures. Here we show how transistors of self-assembled molecular nanowires can be fabricated using a scalable, gradient sublimation technique, which have dramatically improved characteristics compared to their thin film counterparts, both in terms of performance and stability. Nanowire devices based on copper phthalocyanine have been fabricated with threshold voltages as low as-2.1 V, high on/off ratios of 10 5 , small sub-threshold swings of 0.9 V/decade and mobilities of 0.6 cm 2 /Vs, and lower trap energies as deduced from temperature-dependent properties-in line with leading organic semiconductors involving more complex fabrication. High-performance transistors manufactured using our scalable deposition technique, compatible with flexible substrates, could enable integrated all-organic chips implementing conventional as well as neuromorphic computation and combining sensors, logic, data storage, drivers and displays.
Metal Octaethylporphyrin Nanowire Array and Network toward Electric/Photoelectric Devices
A vapor transfer deposition method was developed to fabricate metal (metal ) Co, Ni, Cu, Zn, Mg) octaethylporphyrin (MOEP) nanowire arrays in large area on a variety of substrates. The formation process of MOEP nanowire arrays was investigated by time-dependently terminating deposition at various stages, based on which, a vaporization-condensation-recrystallization (VCR) mechanism was proposed to understand the formation of nanowires and thus guide the synthesis of three-dimensional (3D) sea urchin-like nanowire assemblies and two-dimensional (2D) nanowire networks. As application examples of these porphyrin nanostructures, the porphyrin nanowires demonstrated a good field emission property and the photoelectric device based on the 2D MOEP nanowire network was fabricated, showing a good light-induced signal amplification behavior.