Showing papers on "Energy conversion efficiency published in 2005"
TL;DR: In this article, the luminescence properties of Eu2+-activated alkaline-earth silicon-oxynitrides have been studied in the BaO−SiO2−Si3N4 system, and a new BaSi2O2N2 compound was obtained having the monoclinic structure with lattice parameters.
Abstract: The luminescence properties of Eu2+-activated alkaline-earth silicon-oxynitrides have been studied In the BaO−SiO2−Si3N4 system, a new BaSi2O2N2 compound was obtained having the monoclinic structure with lattice parameters a = 14070(4) A, b = 7276(2) A, c = 13181(3) A, β = 10774(6)° All MSi2O2-δN2+2/3δ:Eu2+ (M = Ca, Sr, Ba) materials can be efficiently excited in the UV to visible region (370−460 nm), making them attractive as conversion phosphors for LED applications A blue-green emission at 490−500 is observed for BaSi2O2N2:Eu2+, yellow emission at 560 nm for CaSi2O2-δN2+2/3δ:Eu2+ (δ ≈ 0), and a green-yellow emission peaking from 530 to 570 nm for SrSi2O2-δN2+2/3δ:Eu2+ (δ ≈ 1), the position depending on the exact value of δ BaSi2O2N2:Eu2+ is the most promising conversion phosphor for white-light LEDs due to its high conversion efficiency for blue light from InGaN-based LEDs related to its very small Stokes shift
567 citations
TL;DR: In this article, the fundamental limits of organic solar cell efficiency were discussed, and the schemes that have been used to overcome many of these limitations were discussed in the last few years, including double and bulk heterojunctions, as well as tandem cells employing materials with high exciton diffusion lengths.
Abstract: We consider the fundamental limits to organic solar cell efficiency, and the schemes that have been used to overcome many of these limitations. In particular, the use of double and bulk heterojunctions, as well as tandem cells employing materials with high exciton diffusion lengths, is discussed.We show that in the last few years, a combination of strategies has led to a power conversion efficiency of ηp = 5.7% (under AM 1.5 G simulated solar radiation at 1 sun intensity) for tandem cells based on small-molecularweight materials, suggesting that even higher efficiencies are possible.We conclude by considering the ultimate power conversion efficiency that is expected from organic thinfilm solar cells.
482 citations
TL;DR: Versatile dyes based on benzothiadiazole and benzoselenadiazoles chromophores have been developed that perform efficiently in dye-sensitized solar cells.
440 citations
TL;DR: The observation of four-wave mixing phenomenon in a simple silicon wire waveguide at the optical powers normally employed in communications systems and the wavelength conversion for data rate of 10-Gbps using a 5.8-cm-long silicon wire is reported.
Abstract: We report the observation of four-wave mixing phenomenon in a simple silicon wire waveguide at the optical powers normally employed in communications systems. The maximum conversion efficiency is about -35 dB in the case of a 1.58-cm-long silicon wire waveguide. The nonlinear refractive index coefficient is found to be 9×10-18 m2/W. This value is not negligible for dense wavelength division multiplexing components, because it predicts the possibility of large crosstalk. On the other hand, with longer waveguide lengths with smaller propagation loss, it would be possible to utilize just a simple silicon wire for practical wavelength conversion. We demonstrate the wavelength conversion for data rate of 10-Gbps using a 5.8-cm-long silicon wire. These characteristics are attributed to the extremely small core of silicon wire waveguides.
415 citations
TL;DR: In this paper, a 3-junction InGaP/InGaAs/Ge concentrator solar cell with an efficiency of 37.4% (AM1.5G, 200-suns) has been fabricated.
380 citations
TL;DR: Ultramicroelectrode voltammetric, nanosecond laser transient absorbance, and photovoltaic measurements show that a high iodide concentration is required for dye regeneration to compete efficiently with charge recombination.
Abstract: A 7.4% power conversion efficiency at air mass (AM) 1.5 full sunlight was reached with a mesoscopic solar cell employing a new binary ionic liquid electrolyte composed of 1-propyl-3-methylimidazolium iodide and 1-ethyl-3-methylimidazolium tricyanomethanide in conjunction with the amphiphilic ruthenium complex NaRu(4-carboxylic acid-4‘-carboxylate)(4,4‘-dinonyl-2,2‘-bipyridine)(NCS)2, coded as Z-907Na. Ultramicroelectrode voltammetric, nanosecond laser transient absorbance, and photovoltaic measurements show that a high iodide concentration is required for dye regeneration to compete efficiently with charge recombination. A surprisingly fast reductive quenching process is turned on in pure iodide melts. This channel is unproductive, explaining the lower photocurrents observed under these conditions.
378 citations
TL;DR: In this paper, the series-internal resistance of dye-sensitized solar cells was investigated with electrochemical impedance spectroscopy measurement based on an equivalent circuit of DSCs, and it was found that series internal resistance correlates positively with the sheet resistance of transparent conducting oxide and the thickness of the electrolyte layer and negatively with the roughness factor of the platinum counter electrode.
Abstract: With the aim of increasing conversion efficiency, the series-internal resistance of dye-sensitized solar cells (DSCs) was investigated with electrochemical impedance spectroscopy measurement based on an equivalent circuit of DSCs. It was found that series-internal resistance correlates positively with the sheet resistance of the transparent conducting oxide and the thickness of the electrolyte layer and negatively with the roughness factor of the platinum counter electrode. A cell sensitized with a black dye with series-internal resistance of 1.8Ωcm2 was fabricated and showed conversion efficiency of 10.2% when measured with a metal mask under an air mass of 1.5 sunlight.
328 citations
TL;DR: The results of the stability test indicated that the solar cell fabricated by the nitrogen-doped titania exhibited great stability and an 8% overall conversion efficiency has been achieved.
Abstract: A highly efficient dye-sensitized solar cell (DSC) was fabricated using a nanocrystalline nitrogen-doped titania electrode. The properties of the nitrogen-doped titania powder, film, and solar cell were investigated. The substitution of oxygen sites with nitrogen atoms in the titania structure was confirmed by X-ray photoemission spectroscopy (XPS). The UV-vis spectrum of the nitrogen-doped powder and film showed a visible light absorption in the wavelength range from 400 to 535 nm. An enhancement of the incident photon-to-current conversion efficiency (IPCE) in the range of 380-520 nm and 550-750 nm was observed. An 8% overall conversion efficiency has been achieved. The results of the stability test indicated that the solar cell fabricated by the nitrogen-doped titania exhibited great stability.
304 citations
TL;DR: The side ring acted as a spacer to efficiently prevent dye aggregation when adsorbed on the TiO2 surface, resulting in significant improvements of short-circuit photocurrent, open-circuits photovoltage, and fill factor compared with NKX-2586 that aggregated on theTiO2surface.
Abstract: A new coumarin dye, cyano-{5,5-dimethyl-3-[2-(1,1,6,6-tetramethyl-10-oxo-2,3,5,6-tetrahydro-1H,4H,10H-11-oxa-3a-aza-benzo[de]anthracen-9-yl)vinyl]cyclohex-2-enylidene}-acetic acid (NKX-2753), was prepared and characterized with respect to photophysical and electrochemical properties. It was employed as a dye sensitizer in dye-sensitized solar cells and showed efficient photon-to-electron conversion properties. The photocurrent action spectrum exhibited a broad feature with a maximum incident photon-to-electron conversion efficiency (IPCE) of 84% at 540 nm, which is comparable to that for the famous red dye RuL2(NCS)2 (known as N3), where L stands for 2,2‘-bipyridyl-4,4‘-dicarboxylic acid. The sandwich-type solar cell with NKX-2753, under illumination of full sun (AM1.5, 100 mW cm-2), produced 16.1 mA cm-2 of short-circuit photocurrent, 0.60 V of open-circuit photovoltage, and 0.69 of fill factor, corresponding to 6.7% of overall energy conversion efficiency using 0.1 M LiI, 0.05 M I2, 0.1 M guanidinium th...
294 citations
TL;DR: In this paper, a high-boiling-point solvent, 1,2,4-trichlorobenzene, instead of chloroform for spin-coating, was used to obtain a threefold increase in solar power conversion efficiency in devices based on CdSe tetrapods and poly(p-phenylenvinylene) derivative OC1C10-PPV.
Abstract: Solution-processed photovoltaic devices based on blends of conjugated polymers and inorganic semiconductor tetrapods show high efficiencies due to the good electron transport perpendicular to the plane of the film. Here, we show that by using a high-boiling-point solvent, 1,2,4-trichlorobenzene, instead of chloroform for spin-coating, we can typically obtain a threefold increase in solar power conversion efficiency in devices based on CdSe tetrapods and the poly(p-phenylenvinylene) derivative OC1C10-PPV. The optimized devices show AM1.5 solar power conversion efficiencies of typically 2.1% with some devices as high as 2.8%. The results can be explained by the occurrence of vertical phase separation which leads to an optimal structure for charge collection. Evidence for this structure is obtained by environmental scanning electron microscopy, photocurrent action spectra measurements, time-resolved photoluminescence, and spectroscopic measurements of exciton dissociation and charge-carrier recombination.
277 citations
TL;DR: The results showed that the bilayer architecture, rather than enhanced light harvesting within the inverse opal structures, is responsible for the bulk of the gain in IPCE.
Abstract: The mechanism of enhancing the light harvesting efficiency of dye-sensitized TiO2 solar cells by coupling TiO2 inverse opals or disordered scattering layers to conventional nanocrystalline TiO2 films has been investigated. Monochromatic incident photon-to-current conversion efficiency (IPCE) at dye-sensitized TiO2 inverse opals of varying stop band wavelengths and at disordered titania films was compared to the IPCE at bilayers of these structures coupled to nanocrystalline TiO2 films and to the IPCE at nanocrystalline TiO2 electrodes. The results showed that the bilayer architecture, rather than enhanced light harvesting within the inverse opal structures, is responsible for the bulk of the gain in IPCE. Several mechanisms of light interaction in these structures, including localization of heavy photons near the edges of a photonic gap, Bragg diffraction in the periodic lattice, and multiple scattering events at disordered regions in the photonic crystal or at disordered films, lead ultimately to enhance...
TL;DR: In this article, the effects of bulk and interface recombination for a broad range of absorber band-gap energies assuming that the Ga/In ratio primarily affects the conduction band were investigated.
TL;DR: Powerful coherent emission around the plasma oscillation frequency can be produced from a laser wakefield through linear mode conversion, suitable for high-field applications and a simple way to measure the wakefield produced for particle acceleration.
Abstract: Powerful coherent emission around the plasma oscillation frequency can be produced from a laser wakefield through linear mode conversion. This occurs when the laser pulse is incident obliquely to the density gradient of inhomogeneous plasmas. The emission spectrum and conversion efficiency are obtained analytically, which are in agreement with particle-in-cell simulations. The emission can be tuned to be a radiation source in the terahertz region and with field strengths as large as a few GV/m, suitable for high-field applications. The emission also provides a simple way to measure the wakefield produced for particle acceleration.
TL;DR: In this paper, a polymer blend solar cell with an external quantum efficiency of more than 30% and a high overall energy conversion efficiency (ECE) under white light illumination (100 mW/cm2) of up to 1.7% using a blend of M3EH−PPV (poly[2,5-dimethoxy-1,4-phenylene-1.2-ethenylene-2-methoxy,5-(2-ethylhexyloxy)−(1, 4)-phenylene)]) and CN−ether−PP
Abstract: We report on polymer blend solar cells with an external quantum efficiency of more than 30% and a high overall energy conversion efficiency (ECE) under white light illumination (100 mW/cm2) of up to 1.7% using a blend of M3EH−PPV (poly[2,5-dimethoxy-1,4-phenylene-1,2-ethenylene-2-methoxy-5-(2-ethylhexyloxy)−(1,4-phenylene-1,2-ethenylene)]) and CN−ether−PPV (poly[oxa-1,4-phenylene-1,2-(1-cyano)ethenylene-2,5-dioctyloxy-1,4-phenylene-1,2-(2-cyano)ethenylene-1,4-phenylene]). We attribute these high efficiencies to the formation of a vertically composition graded structure during spin coating. Photoluminescence measurements performed on the blend layers indicated the formation of exciplexes between both types of polymers, which we propose to be one factor preventing even higher efficiencies.
TL;DR: In this paper, the authors have fabricated organic solar cells with blends of regioregular poly(3-hexylthiophene) (P3HT) and 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C61 (PCBM) as electron donor and electron acceptor, respectively.
Abstract: We have fabricated organic solar cells with blends of regioregular poly(3-hexylthiophene) (P3HT) and 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C61 (PCBM) as electron donor and electron acceptor, respectively. Blend composition and device annealing effects were investigated with optical absorption and photoluminescence spectroscopy, atomic force microscopy, photocurrent spectroscopy, and current-voltage characteristic measurements on devices under monochromatic or air mass (AM) 1.5 simulated solar light illumination. The highest efficiency was achieved for the 1:1 (P3HT:PCBM) weight ratio composition. The good performance is attributed to an optimized morphology that enables close intermolecular packing of P3HT chains. Inferior performance for the 1:2 composition is attributed to poorer intermolecular packing with increased PCBM content, while phase segregation on a sub-micron scale was observed for the 1:4 composition. The power conversion efficiency (AM 1.5) was doubled by the thermal annealing of devices at 140∘C to reach a value of 1.4%.
TL;DR: Use of a new ionic liquid crystal, 1-dodecyl-3-methylimidazolium iodide, and iodine as an electrolyte of dye-sensitized solar cells leads to a high short circuit photocurrent density and a high light-to-electricity conversion efficiency, due to a self-assembled structure of the imidazlium cations, resulting in high conductivity of the electrolyte.
TL;DR: In this paper, a tris-8-hydroxy-quinolinato aluminum (Alq3) instead of bathocuproine (BCP) is adopted as the buffer of the device, resulting in 150 times longer lifetime.
TL;DR: In this paper, the InGaP/(In)GaAs/Ge-based multijunction solar cells have been improved up to 29-30% and 31-32% by technologies, such as double-hetero wide band-gap tunnel junctions, combination with Ge bottom cell with the first hetero-growth layer, and precise lattice-matching to Ge substrate by adding 1% indium to the conventional GaAs lattice match structure.
Abstract: The conversion efficiency of InGaP/(In)GaAs/Ge -based multijunction solar cells has been improved up to 29–30% (AM0) and 31–32% (AM1·5G) by technologies, such as double-hetero wide band-gap tunnel junctions, combination with Ge bottom cell with the InGaP first hetero-growth layer, and precise lattice-matching to Ge substrate by adding 1% indium to the conventional GaAs lattice-match structure. Employing a 1·95 eV AlInGaP top cell should improve efficiency further. For space use, radiation resistance has been improved by technologies such as introducing of an electric field in the base layer of the lowest-resistance middle cell, and EOL current matching of sub-cells to the highest-resistance top cell. A grid structure and cell size have been designed for concentrator applications in order to reduce the energy loss due to series resistance, and 38% (AM1·5G, 100–500 suns) efficiency has been demonstrated. Furthermore, thin-film structure which is InGaP/GaAs dual junction cell on metal film has been newly developed. The thin-film cell demonstrated high flexibility, lightweight, high efficiency of over 25% (AM0) and high radiation resistance. Copyright © 2005 John Wiley & Sons, Ltd.
TL;DR: In this article, the authors investigated the possibility of constructing a two-stage solar-to-electric energy converter with high-temperature second stage, having the overall conversion efficiency of 30-40%.
TL;DR: A photon-to-thermal energy conversion nanosystem based the near-infrared irradiation of one-dimensional gold nanoparticles (nanorods) is highly efficient and tunable to the incident wavelength, suitable for potential use in multicolor detection on biochips and related sensors and as ideal contrasting agents for optoacoustic biomedical imaging applications.
Abstract: A photon-to-thermal energy conversion nanosystem based the near-infrared irradiation of one-dimensional gold nanoparticles (nanorods) is highly efficient and tunable to the incident wavelength. Using ambient photothermal detection, we observed a temperature rise of ca. 30 degrees C upon irradiating an aliquot of an aqueous nanoparticle suspension with a laser for 5 s. The temperature can be elevated even higher by embedding the particles into a poorly thermally conducting solid medium. The illuminated area of a sample containing nanorod particles embedded in a polyurethane matrix can be heated to >100 degrees C upon irradiation for 1 min. This optothermal conversion efficiency can be turned on selectively by tuning the wavelength to match that of the surface plasmon resonance of the particles. This specificity, with respect to the wavelength of the incident light, makes these highly efficient, particle-based, optothermal nanoconvertors suitable for potential use in multicolor detection on biochips and related sensors and as ideal contrasting agents for optoacoustic biomedical imaging applications.
TL;DR: In this paper, the photoactive layer of small-molecule organic semiconductor tetracene∕C60 heterojunction was used for solar cells and the external power conversion efficiency of the devices under AM 1.5 solar illumination at 100mW∕cm2 (1 sun) is 2.3±0.5% with relatively high open-circuit voltage (Voc=0.58± 0.06V).
Abstract: We report organic solar cells fabricated with small-molecule organic semiconductor tetracene∕C60 heterojunction as the photoactive layer. The external power conversion efficiency of the devices under AM 1.5 solar illumination at 100mW∕cm2 (1 sun) is 2.3±0.5% with relatively high open-circuit voltage (Voc=0.58±0.06V) compared to most of the other small-molecular donor-acceptor (D-A) heterojunction solar cells reported so far. Using atomic force microscopy and x-ray diffraction we found that tetracene thin films consist of submicron-sized grains with rough surface and well defined molecular order. Therefore, using high mobility polycrystalline tetracene thin films for D-A heterojunction devices dramatically increases area of tetracene and C60 interface for exciton diffusion to reduce the recombination.
TL;DR: Results clearly show that the formation of a molecular assembly between fullerene and multi-porphyrin arrays with a polypeptide backbone controls the electron transfer efficiency in the supramolecular complex, which is essential for the light-energy conversion.
Abstract: Organic photovoltaic cells using supramolecular complexes of porphyrin−peptide oligomers (porphyrin-functionalized α-polypeptides) with fullerene demonstrate remarkable enhancement in the photoelectrochemical performance as well as broader photoresponse in the visible and near-infrared regions by increasing the number of porphyrin units in α-polypeptide structures. A high power conversion efficiency (η) of 1.3% and a maximum incident photon-to-photocurrent efficiency (IPCE) of 42% were attained using composite clusters of porphyrin−peptide octamer and fullerene. These results clearly show that the formation of a molecular assembly between fullerene and multi-porphyrin arrays with a polypeptide backbone controls the electron transfer efficiency in the supramolecular complex, which is essential for the light-energy conversion.
TL;DR: In this paper, vertical aligned CdTe nanorods were fabricated by electrodeposition and were applied for the active layer of solar cells after being combined with poly(3-octylthiophene) (P3OT), a conjugated polymer.
Abstract: Vertically aligned CdTe nanorods were fabricated by electrodeposition and were applied for the active layer of solar cells after being combined with poly(3-octylthiophene) (P3OT), a conjugated polymer. The electrodeposited CdTe showed an n-type behavior with the electric resistivity and the electron density of 2×106Ωcm, 1.3×1010cm−3, respectively. Quantum efficiency curve of the hybrid solar cells exhibited a peak at the same wavelength as the optical absorption for CdTe nanorods. The hybrid solar cells demonstrated a power conversion efficiency of 1.06%, whereas the efficiency was only 0.0006% without the nanorods.
TL;DR: The possibility for up-scaling the energy of sub-ps THz pulses generated by tilted pulse front excitation using 150-fs-long 500 muJ optical pump pulses at 800 nm up to 240 nJ THz pulse energy has been demonstrated.
Abstract: The possibility for up-scaling the energy of sub-ps THz pulses generated by tilted pulse front excitation is demonstrated. Using 150-fs-long 500 μJ optical pump pulses at 800 nm up to 240 nJ THz pulse energy has been achieved. For a 1.2 mm2 pump spot area, the energy conversion efficiency of pump energy to THz pulse energy had a maximum of 5 × 10-4 at 300 μJ pump pulse energy. The corresponding photon conversion efficiency amounts to 10 %. For comparison, the maximum attainable THz pulse energy was limited to 3.1 nJ if a line focusing excitation geometry was utilized. This limit was reached at 32 μJ pump energy. For the latter configuration the THz energy dropped for larger pump energies. The tilted pulse front excitation allows further up-scaling of the THz pulse energy by using a larger pump spot size and still stronger pump pulses.
TL;DR: In this paper, an organic photovoltaic cell based on a tin(II) phthalocyanine (SnPc)∕C60 donor/acceptor heterojunction with sensitivity at wavelengths of λ>900nm was described.
Abstract: We describe an organic photovoltaic cell based on a tin(II) phthalocyanine (SnPc)∕C60 donor/acceptor heterojunction with sensitivity at wavelengths of λ>900nm. We find that the low hole mobility in polycrystalline thin films of SnPc, μh=(2±1)×10−10cm2∕Vs, prevents the use of thick layers, leading to low fill factors and therefore low-power conversion efficiencies. However, owing to its large absorption coefficient, a 50-A-thick layer of SnPC yields solar cell external quantum efficiencies of up to 21% at λ=750nm. With the double heterostructure of indium-tin oxide/100A copper phthalocyanine/50A SnPc∕540A C60∕75A bathocuproine/Ag, we obtain a power conversion efficiency of (1.0±0.1)% under 1 sun standard AM1.5G solar illumination and efficiencies of (1.3±0.1)% under intense (10 suns) standard AM1.5G solar illumination.
TL;DR: In this article, the authors present recent results on the growth and characterization of CuInGaSe2 (CIGS) thin film solar cells by the three-stage process and show that a conversion efficiency of 19.3% and 18.4% has been achieved for solar cells made from absorbers with band gap values of 1.15 and 1.21 eV.
TL;DR: The ionic conductivity of polymer electrolytes and their interfacial contact with dye-attached TiO2 particles were enhanced markedly by the addition of amorphous oligomer into polymer electrolyte, resulting in very high overall energy conversion efficiency.
TL;DR: In this paper, the performance of small-molecular weight organic double heterojunction donor-acceptor bilayer solar cells is studied as a function of the purity of the donor material, copper phthalocyanine (CuPc).
TL;DR: In this paper, the authors report the characteristics of polymer-nanocrystalline solar cells fabricated using an environmentally friendly water-soluble polythiophene and TiO2 in a bilayer configuration.
Abstract: We report the characteristics of polymer∕nanocrystalline solar cells fabricated using an environmentally friendly water-soluble polythiophene and TiO2 in a bilayer configuration. The cells were made by dropping the polymer onto a TiO2 nanocrystalline film and then repeatedly sweeping a clean glass rod across the polymer as it dried. The devices showed an open circuit voltage of 0.81 V, a short circuit current density of 0.35mA∕cm2, a fill factor of 0.4, and an energy conversion efficiency of 0.13%. The water-soluble polythiophene showed significant photovoltaic behavior and the potential for use in solar cells.
TL;DR: A rigorous theory of third-harmonic generation in optical waveguides is introduced and applied to design a micro-fiber waveguide for efficient generation of third -harmonic radiation from infrared lasers.
Abstract: We introduce a rigorous theory of third-harmonic generation in optical waveguides and apply it to design a micro-fiber waveguide for efficient generation of third-harmonic radiation from infrared lasers. Phase-matching with efficient mode overlap is achieved in micro-fibers having a diameter roughly equal to half of the fundamental wavelength. Using a typical solid-state or fiber laser for pumping, high conversion efficiency is possible in only a few centimeters of a micro-fiber.