Cette invention se rapporte a un dispositif electronique microminiaturise et a son procede de fab... more Cette invention se rapporte a un dispositif electronique microminiaturise et a son procede de fabrication, qui eliminent les defauts des dispositifs electroniques traditionnels en molecules de carbone et qui possedent des performances superieures a celles de ces dispositifs traditionnels. On utilise a cet effet un nanotube de carbone multicouche (10) comportant une couche semi-conductrice externe (1) et une couche metallique interne (2) recouverte partiellement par la couche semi-conductrice externe (1). Les electrodes de source et de drain (3, 5) en metal sont en contact avec les deux extremites du nanotube de carbone a semi-conducteur (1), respectivement. Une electrode de grille (4) en metal est en contact avec la couche metallique (2) du nanotube de carbone. Une couche isolante de grille est formee dans l'espace situe entre les couches semi-conductrices et metalliques (1, 2) du nanotube de carbone. Ainsi, on obtient un transistor a effet de champ a grille isolee. Ce nanotube ...
We demonstrated that, using laser irradiation in air, metallic single-walled carbon nanotubes (SW... more We demonstrated that, using laser irradiation in air, metallic single-walled carbon nanotubes (SWNTs) in carbon nanotube thin film can be preferentially destroyed to their semiconducting counterparts if SWNTs are not heavily bundled. Although all metallic SWNTs were not destroyed using the lasers with an excitation wavelength of 514.5nm and 632.8nm due to a large distribution of SWNTs diameter, it is clear that if SWNTs with a small distribution of diameter can be produced, it should be possible to destroy all of the metallic SWNTs using one or two lasers. [Huang et al. J.Phys.Chem.B, 2006, 110, 7316-20. and 4686-90.]
ABSTRACT Exciton engineering with carbon nanotubes and graphene for solar energy conversion: from... more ABSTRACT Exciton engineering with carbon nanotubes and graphene for solar energy conversion: from exciton antennae to nano-heterojunctions Michael S. Strano Charles and Hilda Roddey Associate Professor of Chemical Engineering 66-566 Department of Chemical Engineering 77 Massachusetts Avenue Cambridge, MA 02139-4307 Email: strano@MIT.EDU phone: (617) 324-4323 fax: (617) 258-8224 http://web.mit.edu/stranogroup/ Our laboratory has been interested in how low dimensional materials, such as single walled carbon nanotubes or graphene, can augment and enhance solar conversion efficiencies and demonstrate new photonic concepts. We will discuss two recent examples of our work in this space. In the first example, there is significant interest in combining carbon nanotubes with semiconducting polymers for photovoltaic applications because of potential advantages from smaller exciton transport lengths and enhanced charge separation. However, to date, bulk heterojunction (BHJ) devices have demonstrated relatively poor efficiencies, and little is understood about the polymer/nanotube junction. To investigate this interface, we fabricate a planar nano-heterojunction comprising well-isolated millimeter-long single-walled carbon nanotubes underneath a poly(3-hexylthiophene) (P3HT) layer (1). The resulting junctions display photovoltaic efficiencies per nanotube ranging from 3% to 3.82%, which exceed those of polymer/nanotube BHJs by a factor of 50-100. The increase is attributed to the absence of aggregate formation in this planar device geometry. It is shown that the polymer/nanotube interface itself is responsible for exciton dissociation. Typical open-circuit voltages are near 0.5 V with fill factors of 0.25-0.3, which are largely invariant with the number of nanotubes per device and P3HT thickness. A maximum efficiency is obtained for a 60 nm-thick P3HT layer, which is predicted by a Monte Carlo simulation that takes into account exciton generation, transport, recombination, and dissociation. We combine for the first time both optical T-matrix and kinetic Monte Carlo models to investigate the photocurrent generation in two state-of-the-art PHJ photovoltaics. The combined model takes into account the rates of exciton generation, transport, recombination and dissociation using literature values. By including the optical, electronic and structural properties of the different materials, we are able to predict the short-circuit current of recently reported P3HT/SWNT PHJ and also P3HT/PCBM PHJ solar cells from the literature. The experimental data for each of these devices show a maximum photocurrent output at a P3HT thickness of 60-65 nm, in contradiction to the expected value equal to the diffusion length of excitons in P3HT (8.5nm). The model demonstrates how a bulk exciton sink can explain this shifted maximum in the P3HT/SWNT case, whereas the maximum is mainly determined by PCBM interdiffusing in P3HT in the P3HT/PCBM case. This platform is promising for further understanding the potential role of polymer/nanotube interfaces for photovoltaic applications. In the second example, there has been renewed interest in solar concentrators and optical antennas for improvements in photovoltaic energy harvesting and new optoelectronic devices. We dielectrophoretically assemble single-walled carbon nanotubes (SWNTs) of homogeneous composition into aligned filaments that can exchange excitation energy, concentrating it to the centre of core–shell structures with radial gradients in the optical bandgap (2). We find an unusually sharp, reversible decay in photoemission that occurs as such filaments are cycled from ambient temperature to only 357 K, attributed to the strongly temperature-dependent second-orderAuger process. Core–shell structures consisting of annular shells of mostly (6, 5) SWNTs (Eg = 1.21 eV) and cores with bandgaps smaller than those of the shell (Eg = 1.17 eV (7,5)–0.98 eV (8,7)) demonstrate the concentration concept: broadband absorption in the ultraviolet–near-infrared wavelength regime provides quasi-singular photoemission at the (8, 7) SWNTs. This approach demonstrates the potential of specifically designed collections of nanotubes to manipulate and concentrate excitons in unique ways. * Ham MH, Paulus GLC, Lee CY, Song C, Kalantar-zadeh K, Choi W, Han JH and Strano MS: Evidence for High-Efficiency Exciton Dissociation at Polymer/Single-Walled Carbon Nanotube Interfaces in Planar Nano-heterojunction Photovoltaics. ACS NANO, 4 (2010) 6251-6259 * Han JH, Paulus GLC, Maruyama R, Jeng ES, Heller DA, Kim WJ, Barone PW, Lee CY, Choi JH, Ham MH, Song C, Fantini C, Strano MS: Exciton Antennas and Concentrators from Core-Shell and Corrugated Carbon Nanotube Filaments of Homogeneous Composition. NATURE MATERIALS, 9, 833 - 839 (2010).
ABSTRACT There has been renewed interest in solar concentrators and optical antennae for improvem... more ABSTRACT There has been renewed interest in solar concentrators and optical antennae for improvements in photovoltaic energy harvesting and new opto-electronic devices. In this work, we dielectrophoretically assemble single-walled carbon nanotubes (SWNTs) of homogeneous composition into aligned filaments that can exchange excitation energy, concentrating it to the center of core-shell structures with radial gradients in the optical band gap. We find an unusually sharp, reversible decay in photoemission that occurs as such filaments are cycled from ambient to only 353 K, attributed to the strongly temperature dependent second order Auger process. Core-shell structures consisting of annular shells of mostly (6,5) SWNT (Eg = 1.20 eV ) and cores with bandgaps smaller than those of the shell (Eg = 1.02 eV (11,3) to 0.98 eV (8,7)) demonstrate the concentration concept: broad band absorption in the ultraviolet (UV) - near-infrared (nIR) wavelength regime provides singular photoemission at the (8,7) SWNT. This approach demonstrates the potential of specifically designed collections of nanotubes to manipulate and concentrate excitons in unique ways.
Cette invention se rapporte a un dispositif electronique microminiaturise et a son procede de fab... more Cette invention se rapporte a un dispositif electronique microminiaturise et a son procede de fabrication, qui eliminent les defauts des dispositifs electroniques traditionnels en molecules de carbone et qui possedent des performances superieures a celles de ces dispositifs traditionnels. On utilise a cet effet un nanotube de carbone multicouche (10) comportant une couche semi-conductrice externe (1) et une couche metallique interne (2) recouverte partiellement par la couche semi-conductrice externe (1). Les electrodes de source et de drain (3, 5) en metal sont en contact avec les deux extremites du nanotube de carbone a semi-conducteur (1), respectivement. Une electrode de grille (4) en metal est en contact avec la couche metallique (2) du nanotube de carbone. Une couche isolante de grille est formee dans l'espace situe entre les couches semi-conductrices et metalliques (1, 2) du nanotube de carbone. Ainsi, on obtient un transistor a effet de champ a grille isolee. Ce nanotube ...
We demonstrated that, using laser irradiation in air, metallic single-walled carbon nanotubes (SW... more We demonstrated that, using laser irradiation in air, metallic single-walled carbon nanotubes (SWNTs) in carbon nanotube thin film can be preferentially destroyed to their semiconducting counterparts if SWNTs are not heavily bundled. Although all metallic SWNTs were not destroyed using the lasers with an excitation wavelength of 514.5nm and 632.8nm due to a large distribution of SWNTs diameter, it is clear that if SWNTs with a small distribution of diameter can be produced, it should be possible to destroy all of the metallic SWNTs using one or two lasers. [Huang et al. J.Phys.Chem.B, 2006, 110, 7316-20. and 4686-90.]
ABSTRACT Exciton engineering with carbon nanotubes and graphene for solar energy conversion: from... more ABSTRACT Exciton engineering with carbon nanotubes and graphene for solar energy conversion: from exciton antennae to nano-heterojunctions Michael S. Strano Charles and Hilda Roddey Associate Professor of Chemical Engineering 66-566 Department of Chemical Engineering 77 Massachusetts Avenue Cambridge, MA 02139-4307 Email: strano@MIT.EDU phone: (617) 324-4323 fax: (617) 258-8224 http://web.mit.edu/stranogroup/ Our laboratory has been interested in how low dimensional materials, such as single walled carbon nanotubes or graphene, can augment and enhance solar conversion efficiencies and demonstrate new photonic concepts. We will discuss two recent examples of our work in this space. In the first example, there is significant interest in combining carbon nanotubes with semiconducting polymers for photovoltaic applications because of potential advantages from smaller exciton transport lengths and enhanced charge separation. However, to date, bulk heterojunction (BHJ) devices have demonstrated relatively poor efficiencies, and little is understood about the polymer/nanotube junction. To investigate this interface, we fabricate a planar nano-heterojunction comprising well-isolated millimeter-long single-walled carbon nanotubes underneath a poly(3-hexylthiophene) (P3HT) layer (1). The resulting junctions display photovoltaic efficiencies per nanotube ranging from 3% to 3.82%, which exceed those of polymer/nanotube BHJs by a factor of 50-100. The increase is attributed to the absence of aggregate formation in this planar device geometry. It is shown that the polymer/nanotube interface itself is responsible for exciton dissociation. Typical open-circuit voltages are near 0.5 V with fill factors of 0.25-0.3, which are largely invariant with the number of nanotubes per device and P3HT thickness. A maximum efficiency is obtained for a 60 nm-thick P3HT layer, which is predicted by a Monte Carlo simulation that takes into account exciton generation, transport, recombination, and dissociation. We combine for the first time both optical T-matrix and kinetic Monte Carlo models to investigate the photocurrent generation in two state-of-the-art PHJ photovoltaics. The combined model takes into account the rates of exciton generation, transport, recombination and dissociation using literature values. By including the optical, electronic and structural properties of the different materials, we are able to predict the short-circuit current of recently reported P3HT/SWNT PHJ and also P3HT/PCBM PHJ solar cells from the literature. The experimental data for each of these devices show a maximum photocurrent output at a P3HT thickness of 60-65 nm, in contradiction to the expected value equal to the diffusion length of excitons in P3HT (8.5nm). The model demonstrates how a bulk exciton sink can explain this shifted maximum in the P3HT/SWNT case, whereas the maximum is mainly determined by PCBM interdiffusing in P3HT in the P3HT/PCBM case. This platform is promising for further understanding the potential role of polymer/nanotube interfaces for photovoltaic applications. In the second example, there has been renewed interest in solar concentrators and optical antennas for improvements in photovoltaic energy harvesting and new optoelectronic devices. We dielectrophoretically assemble single-walled carbon nanotubes (SWNTs) of homogeneous composition into aligned filaments that can exchange excitation energy, concentrating it to the centre of core–shell structures with radial gradients in the optical bandgap (2). We find an unusually sharp, reversible decay in photoemission that occurs as such filaments are cycled from ambient temperature to only 357 K, attributed to the strongly temperature-dependent second-orderAuger process. Core–shell structures consisting of annular shells of mostly (6, 5) SWNTs (Eg = 1.21 eV) and cores with bandgaps smaller than those of the shell (Eg = 1.17 eV (7,5)–0.98 eV (8,7)) demonstrate the concentration concept: broadband absorption in the ultraviolet–near-infrared wavelength regime provides quasi-singular photoemission at the (8, 7) SWNTs. This approach demonstrates the potential of specifically designed collections of nanotubes to manipulate and concentrate excitons in unique ways. * Ham MH, Paulus GLC, Lee CY, Song C, Kalantar-zadeh K, Choi W, Han JH and Strano MS: Evidence for High-Efficiency Exciton Dissociation at Polymer/Single-Walled Carbon Nanotube Interfaces in Planar Nano-heterojunction Photovoltaics. ACS NANO, 4 (2010) 6251-6259 * Han JH, Paulus GLC, Maruyama R, Jeng ES, Heller DA, Kim WJ, Barone PW, Lee CY, Choi JH, Ham MH, Song C, Fantini C, Strano MS: Exciton Antennas and Concentrators from Core-Shell and Corrugated Carbon Nanotube Filaments of Homogeneous Composition. NATURE MATERIALS, 9, 833 - 839 (2010).
ABSTRACT There has been renewed interest in solar concentrators and optical antennae for improvem... more ABSTRACT There has been renewed interest in solar concentrators and optical antennae for improvements in photovoltaic energy harvesting and new opto-electronic devices. In this work, we dielectrophoretically assemble single-walled carbon nanotubes (SWNTs) of homogeneous composition into aligned filaments that can exchange excitation energy, concentrating it to the center of core-shell structures with radial gradients in the optical band gap. We find an unusually sharp, reversible decay in photoemission that occurs as such filaments are cycled from ambient to only 353 K, attributed to the strongly temperature dependent second order Auger process. Core-shell structures consisting of annular shells of mostly (6,5) SWNT (Eg = 1.20 eV ) and cores with bandgaps smaller than those of the shell (Eg = 1.02 eV (11,3) to 0.98 eV (8,7)) demonstrate the concentration concept: broad band absorption in the ultraviolet (UV) - near-infrared (nIR) wavelength regime provides singular photoemission at the (8,7) SWNT. This approach demonstrates the potential of specifically designed collections of nanotubes to manipulate and concentrate excitons in unique ways.
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Papers by Ryuichiro Maruyama