Showing papers on "Energy conversion efficiency published in 1993"
TL;DR: In this article, a novel method of fabricating a periodic domain structure with ideal laminar domains in LiNbO3 by applying an external field at room temperature is proposed.
Abstract: A novel method of fabricating a periodic domain structure with ideal laminar domains in LiNbO3 by applying an external field at room temperature is proposed. The method allows a high blue beam power of 20.7 mW and a high conversion efficiency of 600%/W cm2 to be obtained.
944 citations
TL;DR: In this article, Colloidal TiO[sub 2] electrodes were photosensitized with derivatives of chlorophyll and related natural porphyrins resulting in light harvesting and charge separation efficiencies comparable to those in natural photosynthesis.
Abstract: Colloidal TiO[sub 2] electrodes were photosensitized with derivatives of chlorophyll and related natural porphyrins resulting in light harvesting and charge separation efficiencies comparable to those in natural photosynthesis. The photocurrent action spectra of the electrodes correlate well with the absorption spectra of the dyes in solution. Incident photon to current efficiencies up to 83% are reached in the Soret peak at 400 nm with a 12-[mu]m-thick TiO[sub 2] film sensitized by copper mesoporphyrin IX, which corresponds to nearly unity quantum efficiency of charge separation when light reflection losses are taken into account. Photocurrent/voltage curves of TiO[sub 2] solar cells sensitized with copper chlorophyllin show an energy conversion efficiency of 10% for the red peak at 630 nm. Under simulated sunlight illumination, an open circuit photovoltage of 0.52 V and a short circuit current density of 9.4 mA/cm[sup 2] are measured. The overall energy conversion efficiency of the cell is 2.6% under these conditions, in part limited by ohmic losses at such high current densities. The comparison of different chlorophyll derivatives indicates that free carboxyl groups are important for adsorption and sensitization on TiO[sub 2]. However, conjugation of the carboxyl groups with the [pi] electron system of the chromophore is notmore » necessary for efficient electron transfer. Free bases, zinc, and even the nonfluorescent copper complexes of chlorophyllins and mesoporphyrin IX are efficient sensitizers for TiO[sub 2]. Cholanic acids as coadsorbates were found to be unique in improving both photocurrent and voltage of copper chlorophyllin sensitized cells. This effect is discussed by comparison with other coadsorbates. 23 refs., 3 figs., 1 tab.« less
826 citations
TL;DR: In this paper, the authors described the highest efficiency single junction thin-film cell reported to date with an active area efficiency of 14.8% with the cell structure n−ZnO/n−CdS/p−CuInSe2 deposited on a soda-lime glass substrate.
Abstract: An important milestone in the development of photovoltaic thin‐film solar cells is the achievement of 15% conversion efficiency. This letter describes the highest efficiency single junction thin‐film cell reported to date. An active area efficiency of 14.8% is obtained with the cell structure n‐ZnO/n‐CdS/p‐CuInSe2 deposited on a soda‐lime glass substrate. The current achievements are due to improved properties of the CuInSe2 layer and the heterojunctions compared to previously reported results. The rate and substrate temperature profiles used during the coevaporation process yield a relatively large‐grained material with very strong 〈112〉 orientation and low porosity. This results in reduced recombination rates, hence higher open circuit voltage and fill factor.
455 citations
TL;DR: In this article, an analysis was carried out of optical heterodyne conversion with an interdigitated-electrode photomixer made from low-temperature-grown (LTG) GaAs and pumped by two continuous-wave, frequency offset pump lasers.
Abstract: An analysis has been carried out of optical heterodyne conversion with an interdigitated‐electrode photomixer made from low‐temperature‐grown (LTG) GaAs and pumped by two continuous‐wave, frequency‐offset pump lasers. The analytic prediction is in excellent agreement with the experimental results obtained recently on a photomixer having 1.0‐μm‐wide electrodes and gaps. The analysis predicts that a superior photomixer having 0.2‐μm‐wide electrodes and gaps would have a temperature‐limited conversion efficiency of 2.0% at a low difference frequency, 1.6% at 94 GHz, and 0.5% at 300 GHz when connected to a broadband 100 Ω load resistance and pumped at hν=2.0 eV by a total optical power of 50 mW. The predicted 3‐dB bandwidth (193 GHz) of this photomixer is limited by both the electron‐hole recombination time (0.6 ps) of the LTG‐GaAs material and the RC time constant (0.5 ps) of the photomixer circuit.
391 citations
TL;DR: In this paper, the authors proposed a semi-empirical method to determine the optimum aperture size and operating temperature of a solar cavity-receiver for which its energy conversion efficiency is maximized.
242 citations
TL;DR: Optical-to-optical conversion efficiencies of as high as 32% with a slope efficiency of 44% were obtained with a novel diode-bar, side-pumped laser cavity design and aperturing effects by the laser rod were found to limit the effects of nonuniform gain on the laser mode.
Abstract: Optical-to-optical conversion efficiencies of as high as 32% with a slope efficiency of 44% were obtained with a novel diode-bar, side-pumped laser cavity design. A slab geometry with a single, high-angle-of-incidence reflection was used to extract gain from near the pump face of a Nd:YVO(4) bar that absorbed strongly at the pump wavelength. Small-signal gains of greater than 8 cm(-1) and pulse energies of as much as 3.2 mJ were obtained in an almost TEM(00) mode. Aperturing effects by the laser rod were found to limit the effects of nonuniform gain on the laser mode.
168 citations
TL;DR: In this article, the electrical and optical properties of poly(p -phenylene-vinylene) and light emitting devices based on this polymer were investigated, and it was shown that the Schottky junction is not necessary for the observation of electroluminescence in conjugated polymers.
162 citations
TL;DR: In this article, the authors demonstrate a new technique for enhancing the absorption of high-intensity, ultrashort-duration laser pulses by solids, such as gold gratings and gold clusters.
Abstract: We demonstrate a new technique for enhancing the absorption of high‐intensity, ultrashort‐duration laser pulses by solids. Targets consisting of gold gratings and gold clusters were found to absorb greater than 90% of the incident high‐intensity laser light. This is in contrast to less than 10% absorption by flat surfaces. As a result of this strong coupling of the laser to a high‐density plasma, conversion efficiency of laser energy to x rays of greater than 1% was observed for x rays above 1 keV. Efficiency of nearly 25% was observed for emissions greater than 30 eV. These conversion efficiencies are more than an order of magnitude greater than those measured from flat targets.
133 citations
TL;DR: By controlling the relative polarization of the two fields, this work can control the mixing efficiency and produce coherent extreme ultraviolet (XUV) radiation polarized orthogonally to the strong driving field.
Abstract: Production of sum-frequency radiation and even'' harmonics from the mixed 1[omega] (1053 nm) and 2[omega] (527 nm) field is observed and compared to measurements of the relative conversion efficiency of the independent fields. By controlling the relative polarization of the two fields, we can control the mixing efficiency and produce coherent extreme ultraviolet (XUV) radiation polarized orthogonally to the strong driving field. Extension to produce XUV radiation of arbitrary polarization is discussed.
128 citations
TL;DR: In this paper, a traveling-wave parametric generator with angular tuning with the use of ZnGeP2 and GaSe crystals pumped by 100-ps pulses from an actively mode-locked Er laser (λ ≈ 3 μm) is reported.
Abstract: Traveling-wave parametric generators with angular tuning with the use of ZnGeP2 and GaSe crystals pumped by 100-ps pulses from an actively mode-locked Er laser (λ ≈ 3 μm) are reported. The continuous-tuning range achieved was 4–10 μm (ZnGeP2; length, 12 mm) and 3.5–18 μm (GaSe; length, 12 mm) in a type-I interaction, with a quantum conversion efficiency of a few percent. In the case of ZnGeP2 (length, 42 mm) and type-II phase matching, the pump threshold was 0.35 GW/cm2 and the quantum efficiency achieved was 17.6%, corresponding to an output peak power of 3 MW near 5–6 μm.
115 citations
TL;DR: In this paper, two unmodified industrial CMOS processes have been used for the integration of highly interdigitated pn structures, and under forward bias these pn junctions emit narrow-band infrared light at 1160 nm with an electrical-to-optical power conversion efficiency of typically 10 −4.
Abstract: Two different unmodified industrial CMOS processes have been used for the integration of highly interdigitated pn structures. Under forward bias these pn junctions emit narrow-band infrared light at 1160 nm with an electrical-to-optical power conversion efficiency of typically 10 −4 . The same junctions show broad-band visible-light emission between 450 and 800 nm in the avalanche breakdown region under reverse bias with efficiencies of the order of 10 −8 . This is already enough for a first few practical applications as light-emitting devices (LEDs). No satisfactory explanation for this emission efrect, fitting all the experimentally observed electro-optical and physical properties of our silicon LEDS, has been found yet.
TL;DR: In this paper, a photovoltaic measurement on the diodes at various light intensities from 1 to 40 mW/cm2 showed power conversion efficiencies of about 0.04, 0.57 and 0.88%, respectively, at a light intensity of 1 mW /cm2 (which, for doped PAns, are comparable with that of HCl-doped (CH)x, 1% at 7 mW
TL;DR: In this paper, the operating characteristics of a pulsed β-barium borate optical parametric oscillator, pumped at 355 nm by a single-mode Nd:YAG laser, are described.
Abstract: The operating characteristics of a pulsed β-barium borate optical parametric oscillator, pumped at 355 nm by a single-mode Nd:YAG laser, are described. This device operates with high conversion efficiency (up to 61%) and high output energy (>100 mJ) over most of its wide tuning range (0.41–2.7 μm). Continuous narrow-band tuning over as wide a range as 140 cm−1 is achieved by injection seeding with light from a tunable pulsed dye laser. The spectroscopic potential of this narrow-band β-barium borate optical parametric oscillator is demonstrated by recording photoacoustic spectra of acetylene gas in the near-infrared spectral range.
10 May 1993
TL;DR: In this paper, high efficiency CdTe/CdS solar cells have been prepared on glass substrates by the chemical bath deposition process (CBD) to a thickness of 500-1200 /spl Aring/m.
Abstract: High efficiency CdTe/CdS solar cells have been prepared on glass substrates. The CdS films are deposited on SnO/sub 2/ coated 7059 glass substrates by the chemical bath deposition process (CBD) to a thickness of 500-1200 /spl Aring/. The CdTe films are deposited by the close-spaced sublimation (CSS) technique to a thickness of 4-8 /spl mu/m. Doped-graphite paste is used as the ohmic contact to the CdTe. The substrate temperature used for the deposition of the CdTe films appears to be an important parameter for the junction formation process. It is believed to be critical in the formation of an interface Cd/sub x/S/sub 1-x/Te mixed crystal layer. The heat treatment of the CdS films in hydrogen is also an important processing step, and it must be modified as the thickness of the CdS films is decreased in order to maintain high fill factors. High photocurrents in conjunction with high open-circuit voltages and fill factors are achieved by properly adjusting the annealing conditions of thin CdS films. The open-circuit voltage, short-circuit current, and fill factor of the best device were 843 mV, 25.1 mA/cm/sup 2/, and 74.5% respectively, corresponding to a conversion efficiency of 15.8% as measured under AM1.5 conditions at the National Renewable Energy Laboratory. >
TL;DR: In this article, a second-harmonic generation (SHG) was performed in ion-implanted planar waveguides in KTiOPO4 using type 2 zero order mode phase matching at a wavelength of ∼ 1.07 μm.
Abstract: Second‐harmonic generation (SHG) has been successfully performed in ion‐implanted planar waveguides in KTiOPO4. The waveguides were formed by helium implantation, and SHG was achieved using type 2 zero order mode phase matching at a wavelength of ∼1.07 μm. The results indicate that the high nonlinearity of the material remains in the guiding region after ion implantation. The conversion efficiency in a typical guide is estimated at ∼25% for ∼1 μJ pulsed excitation. At a lower input power level, the harmonic green output from the waveguide is 20 times higher than that from the bulk for the same amount of fundamental power. This clearly demonstrates the advantage of using waveguides in achieving frequency doubling for integrated optical devices.
TL;DR: In this paper, a low-temperature grown GaAs interdigitated-electrode photomixer is used to generate coherent power at microwave frequencies, achieving an output power of 200 μW (−7 dBm) with two 70mW modes of a Ti:Al2O3 laser.
Abstract: A low‐temperature‐grown GaAs interdigitated‐electrode photomixer is used to generate coherent power at microwave frequencies. An output power of 200 μW (−7 dBm) is generated by pumping the photomixer with two 70‐mW modes of a Ti:Al2O3 laser, separated in frequency by 200 MHz. This represents an optical‐to‐microwave conversion efficiency of 0.14%, which is within 50% of a prediction based on optical‐heterodyne theory. When two lasers are used and the frequency of one is tuned with respect to the other, the output frequency of the photomixer increases smoothly and the output power is nearly constant up to 20 GHz. At higher frequencies the power decays because of parasitic capacitance.
Patent•
NGK1
TL;DR: In this article, a method for accurately and precisely detecting deterioration of a catalyst and measuring a conversion efficiency for HC/CO/NOx by using an oxygen sensor and an air/fuel ratio sensor disposed on the upstream and downstream sides of the catalyst, respectively.
Abstract: The invention provides a method for accurately and precisely detecting deterioration of a catalyst and measuring a conversion efficiency of a catalyst for HC/CO/NOx by using an oxygen sensor and an air/fuel ratio sensor disposed on the upstream and downstream sides of the catalyst, respectively. The catalyst is determined to be deteriorating when an output amplitude of the air/fuel ratio sensor becomes greater than a predetermined value. The conversion efficiency of the catalyst is determined based on a predetermined relationship between the output amplitude and the mean converted rate of HC/CO/NOx.
TL;DR: In this paper, an eye-safe source at 1.61 μm with 2.1% wall plug efficiency is demonstrated by use of a Nd:YAG-pumped KTP optical parametric oscillator with total peak power conversion efficiency of 70% and an energy conversion efficiency.
Abstract: An eye-safe source at 1.61 μm with 2.1% wall-plug efficiency is demonstrated by use of a Nd:YAG-pumped KTP optical parametric oscillator with total peak-power conversion efficiency of 70% and an energy conversion efficiency of 47%. Similar efficiencies are obtained when one employs a Nd:YLF laser as the pump source, but the signal wavelengths move into the defined eye-safe band at 1.54 and 1.55 μm. We also demonstrate 1.54-μm operation, for noncritical phase matching, with the 1.064-μm pump by propagating along the y axis of the KTP crystal.
TL;DR: Intensity scaling suggests that laser spot size and two-dimensional expansion are important for optimizing x-ray production at these low-irradiation intensities.
Abstract: X-ray production in the region ~ 13 nm from laser-produced plasmas has been investigated as a source for projection x-ray lithography. The dependence of x-ray conversion efficiency on target material, intensity, and pulse length has been studied by using a 0.53-μm laser with a maximum of 0.3 J. A conversion efficiency of 1% into a 0.3-nm bandwidth has been demonstrated for Sn targets at intensities of ~ 1011 W/cm2 by using a 7.5-ns pulse. Intensity scaling suggests that laser spot size and two-dimensional expansion are important for optimizing x-ray production at these low-irradiation intensities.
TL;DR: In this paper, the authors describe a CIGS-based solar cell that demonstrates an open-circuit voltage approaching 700 mV and a total area conversion efficiency of 12.2%.
Abstract: An important development in polycrystalline Cu(In,Ga)Se2 (CIGS) thin‐film photovoltaic solar cells is the attainment of a high voltage device simultaneous with state‐of‐the‐art conversion efficiency. This letter describes a CIGS‐based solar cell that demonstrates an open‐circuit voltage (Voc) approaching 700 mV and a total‐area conversion efficiency of 12.2%. The high value of Voc was achieved by grading In/Ga through the absorber by a computer‐controlled physical vapor deposition (PVD) process that utilizes variable metal fluxes.
TL;DR: High conversion efficiency can be achieved with nonlinear crystals of relatively low nonlinear coefficient for cw harmonic generation for the situation in which both fundamental and harmonic waves are resonant.
Abstract: Conversion efficiency for cw harmonic generation is calculated for the situation in which both fundamental and harmonic waves are resonant Compared with the situation of a singly resonant cavity at the fundamental, the doubly resonant geometry can lead to an increase of the effective nonlinear coefficient High conversion efficiency can thus be achieved with nonlinear crystals of relatively low nonlinear coefficient and with modest pump power for the fundamental input,
TL;DR: In this paper, the second-harmonic power and the integral of the second harmonic power with respect to the fundamental wavelength at a wavelength scan were investigated for quasi-phase-matching waveguides, and it was concluded that the inhomogeneities in the effective index, the absence of domain inversion in some regions along the waveguide, and the suppression of the nonlinearity that is due to the proton exchange process are the most important imperfections to deal with in the future optimization of the domain-inversion process and waveguide formation.
Abstract: The generation of coherent blue light by frequency doubling of radiation from semiconductor lasers in quasi-phase-matching lithium niobate waveguides has recently been demonstrated, but with a conversion efficiency significantly lower than the theoretically predicted value. We have experimentally investigated the performance of some quasi-phase-matching waveguides by measurements of the second-harmonic power and the integral of the second-harmonic power with respect to the fundamental wavelength at a wavelength scan. These experimental results are combined with a theoretical analysis. It is concluded that the inhomogeneities in the effective index, the absence of domain inversion in some regions along the waveguide, and the suppression of the nonlinearity that is due to the proton exchange process are the most important imperfections to deal with in the future optimization of the domain inversion process and the waveguide formation.
TL;DR: In this paper, the dependence of conversion efficiency on target material, intensity, wavelength, and pulse width is determined using absolutely calibrated detectors using laser produced plasmas as a source for soft x-ray projection lithography.
Abstract: Laser‐produced plasmas are investigated as a source for soft x‐ray projection lithography. The dependence of conversion efficiency on target material, intensity, wavelength, and pulse width is determined using absolutely calibrated detectors. Conversion efficiency greater than 1% into a 2.2 eV bandwidth is demonstrated for Sn targets, fulfilling the system source requirements.
TL;DR: In this paper, a theory of terahertz optical-frequency conversion using highly nondegenerate four-wave mixing (FWM) in an injection-locked semiconductor laser is presented, using small-signal analysis.
Abstract: A theory of terahertz optical-frequency conversion using highly nondegenerate four-wave mixing (FWM) in an injection-locked semiconductor laser is presented, using small-signal analysis. The optical frequency conversion can be realized through the use of cavity-enhanced highly nondegenerate FWM in an injection-locked semiconductor laser in a range of 1-THz detuning frequency between the pump and the probe waves, when the probe frequency is tuned close to one of the resonance modes. The frequency conversion is mainly attributed to the nonlinear gain effect. The maximum bandwidth of the converted signal is increased by shortening the laser cavity length. The frequency conversion efficiency is asymmetrical with respect to both the zero detuning frequency and the resonance mode where the converted signal appears. The theoretical results agree with experiments. >
Abstract: Direct conversion of thermal energy into electrical energy using a photovoltaic cell is called thermophotovoltaic energy conversion. One way to make this an efficient process is to have the thermal energy source be an efficient selective emitter of radiation. The emission must be near the band-gap energy of the photovoltaic cell. One possible method to achieve an efficient selective emitter is the use of a thin film of rare-earth oxides. The determination of the efficiency of such an emitter requires analysis of the spectral emittance of the thin film including scattering and reflectance at the vacuum-film and film-substrate interfaces. Emitter efficiencies (power emitted in emission band/total emitted power) in the range 0.35-0.7 are predicted. There is an optimum optical depth to obtain maximum efficiency. High emitter efficiencies are attained only for low (less than 0.05) substrate emittance values, both with and without scattering. The low substrate emittance required for high efficiency limits the choice of substrate materials to highly reflective metals or high-transmission materials such as sapphire.
TL;DR: In this paper, the authors applied liquid phase epitaxy to thin film photovoltaics based on silicon and applied this method for about 20μm-thick solar cells with high efficiencies.
Abstract: Liquid phase epitaxy provides a new impetus for thin film photovoltaics based on silicon; we apply this method for about 20‐μm‐thick solar cells with high efficiencies. The analysis of internal quantum efficiency measurements reveals that the open circuit voltages around 660 mV arise from an excellent electronic quality of our thin silicon films. Their effective minority carrier diffusion lengths range up to 317 μm, a value that exceeds the thickness of the layers by an order of magnitude. The conversion efficiencies exceed 14% with a record value of 14.7% for a 16.8‐μm‐thick epitaxial layer without special antireflecting coatings. The high open circuit voltages promise a possible boost of the efficiency toward 20% by applying light trapping schemes to optimize the short circuit current.
TL;DR: In this article, an efficient monolithic Q-switched Nd:MgO:LiNbO3 waveguide laser operating at 1.085 μm was reported.
Abstract: An efficient monolithic Q-switched Nd:MgO:LiNbO3 waveguide laser operating at 1.085 μm is reported. Q-switched pulses of 350 W peak power and 300 ps width are obtained for less than 15 mW of CW 0.814 μm coupled pump power. This source was frequency-doubled in an external quasiphase-matched LiNbO3 waveguide yielding 12 W pulses at 0.54 μm with a 15% conversion efficiency.
10 May 1993
TL;DR: In this paper, the impurity photovoltaic (IPV) effect for improving silicon solar cell efficiency was investigated and shown to lead to improved solar cell energy conversion efficiency.
Abstract: This paper presents a theoretical investigation of the impurity photovoltaic (IPV) effect for improving silicon solar cell efficiency. The authors' approach is better than previous analyses because of the improved treatment of generation and recombination via impurities, and because it includes the effects of optical competition and light trapping. The approach is applied to indium as the IPV effect impurity incorporated into an idealised silicon solar cell. The analysis is based on experimentally determined parameters for indium. Improvements of cell current, subgap spectral response and energy conversion efficiency are quantified. Their analysis reveals the importance of light trapping and proper selection of indium and dopant concentrations. For the first time, the IPV effect is shown to lead to improved solar cell efficiency. >
TL;DR: In this paper, a new solar cell structure named HIT (Heterojunction with Intrinsic Thin layer) has been developed based on new artificially constructed junction (ACJ) technology.
Abstract: A new solar cell structure named HIT (Heterojunction with Intrinsic Thin layer) has been developed based on new artificially constructed junction (ACJ) technology. In this structure a non-doped a-Si thin layer was inserted between the p(a-Si)/n(c-Si) heterojunction, improving the output characteristics and achieving a conversion efficiency of 18.1%. This structure was applied to cast polycrystalline silicon solar cells of a practical size. A high conversion efficeincy of 13.6% was obtained with a cell size of 10 cm × 10 cm using various technologies, including hydrogen plasma passivation.
TL;DR: In this article, a GaAlAs tapered amplifier seeded by a laser diode is frequency doubled in a 12.4mm-long KNbO3 crystal to generate 62 mW of 429 nm continuous wave emission, corresponding to a conversion efficiency of 1.1%/W
Abstract: Diffraction limited emission of a GaAlAs tapered amplifier seeded by a laser diode is frequency doubled in a 12.4‐mm‐long KNbO3 crystal to generate 62 mW of 429 nm continuous wave emission, corresponding to a conversion efficiency of 1.1%/W cm. Reductions in the conversion efficiency due to nonuniform temperature distribution caused by blue‐enhanced infrared absorption were characterized.