Effects of substrate curvature on the adsorption of poly(3-hexylthiophene) on single-walled carbon nanotubes

Goh, Rachel; Motta, Nunzio; Bell, John; Waclawik, Eric R.

doi:10.1063/1.2168514

Cited by 45 publications

(34 citation statements)

References 22 publications

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“…In terms of the geometry of rr-P3HT in the presence of SWNTs, previous reports on nanohybrids prepared using techniques similar to that described in this work have indicated experimentally (through scanning probe microscopic techniques) as well as computationally, a natural tendency for the rr-P3HT to wrap around SWNTs due to π-π type super-molecular interactions. 10,[21][22][23][24] To ascertain this fact further and to obtain a better understanding of the non-covalent functionalization process, optical absorption, valence and core level X-ray spectroscopy (XPS) measurements were carried out on the rr-P3HT/s-SWNT nanohybrid system. A representative UV-Vis absorbance spectrum for rr-P3HT/s-SWNT nanohybrids in 1,2-dichlorobenzene is shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

Hybrid Carbon Nanotube Networks as Efficient Hole Extraction Layers for Organic Photovoltaics

et al. 2012

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Transparent, highly percolated networks of regio-regular poly(3-hexylthiophene) (rr-P3HT) wrapped semiconducting single walled carbon nanotubes (s-SWNT) are deposited and the charge transfer processes of these nanohybrids are studied using spectroscopic and electrical measurements. The data discloses hole doping of s-SWNTs by the polymer, challenging the prevalent electron doping hypothesis. Through controlled fabrication, high to low-density

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Section: Resultsmentioning

confidence: 99%

Hybrid Carbon Nanotube Networks as Efficient Hole Extraction Layers for Organic Photovoltaics

et al. 2012

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“…Recently, there are two types of materials that have attracted significant amount of attention as dispersants to assist carbon nanotube dispersion. One of these materials is the conjugated polymers, such as poly(m-phenylene vinylene), [17,18] poly(3-alkylthiophene), [19,20] and poly(arylene ethynylene). [21,22] These polymers stabilize carbon nanotubes by forming strong p-p stack interactions with carbon nanotube walls.…”

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Dispersion of Pristine Carbon Nanotubes Using Conjugated Block Copolymers

et al. 2008

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Despite many of the intriguing and excellent electrical, mechanical and optical properties of carbon nanotubes (CNTs), [1,2] extensive applications of these nanomaterials are still limited. One of the main challenges in carbon nanotube research field is the dispersion and stabilization of CNTs in different solvent media and polymer matrices. The as-synthesized CNTs are often bundled together due to strong van der Waals interactions between the nanotubes. There have been three most widely used methods to disperse CNTs into solvents and polymer matrices: [3] physical blending, [4][5][6] chemical functionalization, [7][8][9][10][11] and dispersants-assisted dispersion. [12][13][14][15][16] Each of these methods has its own advantages and disadvantages. For physical blending using mechanical forces such as sonication, although simple and cost effective, the dispersion quality is often the poorest. The so-dispersed nanotubes will quickly precipitate out again when sonication stops. For chemical modification and functionalization, CNTs are treated with strong oxidizing reagents to form functional groups such as carboxylic acids on the nanotube walls. CNTs can be made water or organic solvent soluble, depending on the modification degree and further molecular moieties attached to the nanotubes. Although most effective as a dispersion method, such treatment inevitably disrupts the long range p conjugation of the nanotube, often leads to decreased electrical conductivity, diminished mechanical strength, and other undesired properties. In the dispersants-assisted dispersion, a third component chemical is mixed with CNTs in solutions. Through sonication, the CNTs are mechanically de-bundled and then stabilized by a dispersant chemical through noncovalent interactions, therefore, avoiding the destruction of the chemical structures, electronic and mechanical properties of the carbon nanotubes. Recently, there are two types of materials that have attracted significant amount of attention as dispersants to assist carbon nanotube dispersion. One of these materials is the conjugated polymers, such as poly(m-phenylene vinylene), [17,18] poly(3-alkylthiophene), [19,20] and poly(arylene ethynylene). [21,22] These polymers stabilize carbon nanotubes by forming strong p-p stack interactions with carbon nanotube walls. However, the thus-formed dispersions have limited solubility and stability because the conjugated polymers themselves face solubility and miscibility issues due to the strong inter-chain p-p interactions. A second family of interesting materials with potential for third componentassisted carbon nanotube dispersion are block copolymers. [23][24][25] In general, the block copolymer is designed in such a way that one block of the polymer will form a close interaction with the carbon nanotube walls, while the other block(s) will provide the solubility to the exfoliated nanotubes by forming a steric barrier or repulsion interaction between polymer-wrapped nanotubes.[26] So far, a wide range of charged and neutral block copoly...

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“…In recent work, Schuettfort et al 19 synthesized a highly purified nanohybrid structure consisting of a SWNT coated with a monolayer of P3HT. In these purified nanohybrids, the P3HT organizes into a sheathlike morphology on the tubes, aligned at an approximate angle of 48°with respect to the SWNT axis 20 and at a distance of twice the van der Waals radius (0.34 nm) from the nanotube; 19 this is shown schematically in Figure 1b. In addition, a small number of isolated P3HT nanocrystals of typical dimensions of 3-5 nm are observed attached to the P3HT sheath enveloping the tubes, as shown by atomic force microscopy (AFM) ( Figure 1c, 19 ) and transmission electron microscopy (TEM) 11 im-ages.…”

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Ultrafast Charge Separation at a Polymer−Single-Walled Carbon Nanotube Molecular Junction

et al. 2010

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We have investigated the charge photogeneration dynamics at the interface formed between single-walled carbon nanotubes (SWNTs) and poly(3-hexylthiophene) (P3HT) using a combination of femtosecond spectroscopic techniques. We demonstrate that photoexcitation of P3HT forming a single molecular layer around a SWNT leads to an ultrafast (∼430 fs) charge transfer between the materials. The addition of excess P3HT leads to long-term charge separation in which free polarons remain separated at room temperature. Our results suggest that SWNT-P3HT blends incorporating only small fractions (1%) of SWNTs allow photon-to-charge conversion with efficiencies comparable to those for conventional (60:40) P3HT-fullerene blends, provided that small-diameter tubes are individually embedded in the P3HT matrix.KEYWORDS Carbon nanotube, P3HT, charge separation, molecular junction O rganic photovoltaic (OPV) cells have been demonstrated as low-cost alternatives to silicon-based cells, offering the possibility of low temperature "reel-to-reel" fabrication, necessary for viable large-scale power generation.1 The majority of OPV devices utilize exciton dissociation at the interface between two materials which exhibit a type-II heterojunction alignment, 2 resulting in interfacial charge separation and free polarons in the materials. However, it has been shown that for many OPV materials such as polymer-polymer blends, exciton dissociation leads to the formation of an interfacial bound geminate charge pair, termed an exciplex. [3][4][5][6][7] This species can be strongly bound and long-lived, significantly lowering charge separation efficiencies. studies demonstrating that a type-II heterojunction only exists for certain interfaces, such as between small diameter semiconducting SWNTs and regioregular poly(3-hexylthiophene) (P3HT). Even for such blends, energy transfer from the polymer to the SWNTs may compete effectively against charge transfer.In this letter, we show that charge transfer across the interface between individually dispersed SWNTs wrapped in a monolayer sheath of P3HT occurs on an ultrafast (430 fs) time scale. Generated charge pairs relax into a bound interfacial charge-transfer state or via nonradiative recombination of excitons within the nanotubes and no long-lived free polarons are observed. However, in the presence of an excess P3HT network, charge separation at room temperature is long-lived and comparable to that in a conventional P3HT-fullerene blend. This is the first time such blends have been studied using femtosecond time resolution, and we observe a charge transfer time three-magnitudes faster than reported previously. 17,18 In addition, significant long-term charge separation is observed for the first time in SWNTpolymer blends. We conclude that charge separation is only possible if small-diameter semiconducting tubes are individually embedded in an excess P3HT matrix. Our findings explain the poor polymer-SWNT device behavior to date and provide a promising route to incorporation of SWNTpolymer blen...

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Effects of substrate curvature on the adsorption of poly(3-hexylthiophene) on single-walled carbon nanotubes

Cited by 45 publications

References 22 publications

Hybrid Carbon Nanotube Networks as Efficient Hole Extraction Layers for Organic Photovoltaics

Hybrid Carbon Nanotube Networks as Efficient Hole Extraction Layers for Organic Photovoltaics

Dispersion of Pristine Carbon Nanotubes Using Conjugated Block Copolymers

Ultrafast Charge Separation at a Polymer−Single-Walled Carbon Nanotube Molecular Junction

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