Showing papers on "Energy conversion efficiency published in 1977"
TL;DR: In this article, a new principle for solar energy conversion is proposed and evaluated theoretically, and the optical path length in a triangular collector is computed, which offers the advantage of separating the various fractions of light and converting them with solar cells with different bandgaps.
Abstract: A new principle for solar energy conversion is proposed and evaluated theoretically. Collection and concentration of direct and diffuse radiation is possible by the use of a stack of transparent sheets of material doped with fluorescent dyes. High efficiency of light collection can be achieved by light guiding and special design of collectors. The optical path length in a triangular collector is computed. In combination with solar cells this type of collector offers the advantage of separating the various fractions of light and converting them with solar cells with different bandgaps. Theoretical conversion efficiency under optimum conditions is 32% for a system with four semiconductors. Thermal energy conversion offers several advantages over conventional collectors: High temperature and efficiency even under weak illumination, separation of heat transport and radiation collection, low thermal mass. Thermal efficiency is computed to be between 42% and 60%. Very attractive appear hybrid systems for generation of thermal and electric energy. An estimate of the economics of electricity generation shows that due to the concentration costs can be much lower than possible today. With the use of only silicon cells the breakeven point of $0.5/W is almost reached. Practical difficulties to be solved are: Synthesis of dyes with stringent requirements, identification of plastic materials with high transparency and development of solar cells with higher bandgaps.
638 citations
TL;DR: In this paper, the authors theoretically analyzes the spectral response of TiO/sub 2/ photoelectrolysis cells and determine the diffusion length of minority carriers in the photolysis of water.
Abstract: In all previous studies of the photoelectrolysis of water, very little attention has been paid to the carrier generation and transport properties of the optically active semiconductor electrode To gather such information the present work theoretically analyzes the spectral response of TiO/sub 2/ photoelectrolysis cells Comparison with experimental results allows us to determine the diffusion length of minority carriers in TiO/sub 2/ for the first time It is the hole transport that governs the spectral response curve, not the electron transport The quantum efficiency of carrier generation in TiO/sub 2/ electrodes in the photolysis mode can be increased to 80% by doping the crystals with Al The sunlight conversion efficiency has been raised to 13% from 04% reported earlier by others The spectral response of the device has been extended into the visible portion of the spectrum through sensitization of the TiO/sub 2/ with Cr dopant impurities, allowing hydrogen generation with visible light The photoelectrolytic processes associated with the impurity doped crystals are discussed 36 references
359 citations
TL;DR: In this article, the authors proposed an explanation for the operation of such solar cells based on the concept that they are minority-carrier nonequilibrium MIS tunnel diodes, and showed that a maximum theoretical efficiency of 21% is possible under AM2 illumination for high substrate doping and low interface defect density.
Abstract: Recent reports in the literature indicate that the introduction of an interfacial oxide layer in a Schottky barrier can greatly increase the photovoltaic conversion efficiency of such devices. We propose an explanation for the operation of such solar cells based on the concept that they are minority‐carrier nonequilibrium MIS tunnel diodes. Calculations of efficiency as a function of insulator thickness, substrate carrier concentration, surfaces states, and oxide charge are presented. These indicate that a maximum theoretical efficiency of 21% is possible under AM2 illumination for high substrate doping and low interface defect density.
191 citations
TL;DR: In this article, the photoresponse spectra of liquid junction solar cells were used to identify states due to imperfections at or near the surface of semiconductors in AM2 cells.
Abstract: States due to imperfections at or near surfaces of semiconductors in liquid junction solar cells can be identified by changes in the photoresponse spectra under short-circuit current conditions. These effects become dominant features in two-beam experiments with an intense pumping (laser) source and a weak modulated probing beam. The presence of these states can be correlated with drastic decreases in short-circuit currents, open-circuit voltages, fill factors, and maximum power conversion efficiencies of the cells. Elimination of the damaged surface regions by suitable etching allows AM2 solar conversion efficiencies of 1.3 and 7.2%, respectively, in the cells n-CdS/0.1F Na/sub 2/S--0.02F S-0.1F NaOH/C and n-CdSe/1F Na/sub 2/S--1F S-1F NaOH/C.
133 citations
TL;DR: In this article, an epitaxial growth of CdS on pCdTe wafers was extensively studied, and properties of the cells were extensively studied; the best cell exhibited a solar conversion efficiency of 10.5% under illumination by sunlight (AM1.3, 68 mW/cm2), and 6.0% under simulated sunlight, which was attributed to the reduction in both the series resistance and surface recombination.
Abstract: CdS–CdTe solar cells were prepared by epitaxial growth of CdS on pCdTe wafers, and properties of the cells were extensively studied. The cells have a junction structure of nCdS–(n or i)CdTe–pCdTe. Formation of the (n or i) layer is due to diffusion of In into CdTe; the thickness of the layer was 0.5 µm in the most efficient cell. The best cell exhibited a solar conversion efficiency of 10.5% under illumination by sunlight (AM1.3, 68 mW/cm2), and 6.0% under illumination by a simulated sunlight (AMO). The high efficiency is attributed to the reduction in both the series resistance and surface recombination, which results from the presence of the heavily doped CdS layer on the wafer. The cell is not humidity sensitive and is stable in the forward bias test, These results suggest strongly that practically useful solar cells can be manufactured from this type of junction.
116 citations
TL;DR: Experiments are described illustrating enhanced photon trapping and efficient energy transfer in mixed-dye planar solar concentrators containing, for example, Rhodamine 6G and Coumarin 6.
Abstract: Experiments are described illustrating enhanced photon trapping and efficient energy transfer in mixed-dye planar solar concentrators containing, for example, Rhodamine 6G and Coumarin 6. These concentrators intercept more of the solar spectrum to give an enhanced photon-flux gain that exceeds the single-dye concentrator. It is also shown that the energy absorbed by the donor dye is transferred efficiently into the emitting acceptor by two competing processes.
116 citations
TL;DR: The performance of photogalvanic cells for the direct conversion of solar energy to electrical energy depends on the cell photochemistry, the homogeneous kinetics, the mass transport, the electrode kinetics and the load on a cell as discussed by the authors.
Abstract: The performance of photogalvanic cells for the direct conversion of solar energy to electrical energy depends on the cell photochemistry, the homogeneous kinetics, the mass transport, the electrode kinetics and the load on the cell. The variation of the power output with the concentrations of the redox couples, their transport and kinetic parameters and the dimensions of the cell is found. The power conversion efficiency of the optimal cell could be as large as 18% but it is unlikely that all the necessary conditions can be met. A more realistic estimate of the maximum power conversion efficiency that could be achieved from a photogalvanic cell is between 5 and 9%.
108 citations
TL;DR: In this paper, it was shown that for a single photochemical system operating at 20°C in sunlight not attenuated by the atmosphere, this efficiency cannot exceed 29% and for a solar converter composed of two photochemical systems, it can reach 41%.
Abstract: Entropy and unavoidable irreversibility place a limit on the efficiency of photochemical solar energy conversion which is substantially lower than that placed by the first law of thermodynamics alone. Shockley and Queisser’s ’’detailed balance limit’’ on the efficiency of p‐n‐junction photovoltaic devices is a special case of this general thermodynamic limit on the efficiency of all quantum‐utilizing solar energy converters. For a single photochemical system operating at 20 °C in sunlight not attenuated by the atmosphere, this efficiency cannot exceed 29%. Under the same conditions, the efficiency of a solar converter composed of two photochemical systems can reach 41%.
99 citations
TL;DR: In this paper, a detailed model of the CdS-Cu 2 S solar cell was used to analyze design limits of cell configurations based on present laboratory technology, and the parameters controlling the short-circuit current, open-circuits voltage, and fill factor were obtained.
Abstract: A detailed model of the CdS-Cu 2 S solar cell was used to analyze design limits of cell configurations based on present laboratory technology. The parameters controlling the short-circuit current, open-circuit voltage, and fill factor are treated. The limits for each of these factors is obtained. The results indicate that the attainable conversion efficiency of the CdS-Cu 2 S solar cell extrapolating from the present processing technology is roughly 10 percent, as compared to a theoretical efficiency of 16 percent, if no losses occurred. A similar analysis for a cell using Cd 1-x Zn x S in place of CdS yields an attainable efficiency of 15 percent and a theoretical efficiency of over 26 percent. The model identifies those processing parameters which must be improved in order to optimize cell efficiency. Once technology is improved, the processing parameters will be reassessed with an aim towards increasing the maximum attainable efficiency.
95 citations
TL;DR: In this paper, pressure sintered electrodes of cadmium selenide subsequently doped with Cadmium vapor have shown solar energy conversion efficiencies approaching /sup 3/sub 4/ of those of single crystal specimens in sunlight experiments.
Abstract: Pressure sintered electrodes of cadmium selenide subsequently doped with cadmium vapor have shown solar energy conversion efficiencies approaching /sup 3///sub 4/ of those of single crystal specimens in sunlight experiments. The cell CdSe/1F Na/sub 2/S-1F S-1F NaOH/C has operated at 5.1% conversion efficiency under AM2 conditions with polycrystalline electrodes. The relatively small sacrifice of efficiency from single crystal values of 7.5 +- 0.5% suggests the possibility of substantial cost advantage. The temperature and pressure conditions, cadmium doping procedure, material characterization, and the voltammetric behavior of the cell are discussed.
TL;DR: In this paper, the semiconductor liquid junction cell n- GaAs/0.8 M K 2 Se-0.1 M K2 Se 2 -1M KOH/C has been shown to attain 9 percent photovoltaic power conversion efficiency in sunlight.
Abstract: The semiconductor liquid junction cell n- GaAs/0.8 M K 2 Se-0.1 M K 2 Se 2 - 1 M KOH/C has been shown to attain 9 percent photovoltaic power conversion efficiency in sunlight. Accelerated tests under 3100°K light sources of several solar intensities indicate very low photocorrosion currents and high output stability.
IBM1
TL;DR: Photoelectrolytic decomposition of water with visible irradiation is demonstrated in a cell made of p-type gallium phosphide as the cathode and platinum as the anode, and the results are discussed in terms of a composite energy diagram.
Abstract: Photoelectrolytic decomposition of water with visible irradiation is demonstrated in a cell made of p-type gallium phosphide as the cathode and platinum as the anode. A maximum energy conversion efficiency of 0.1 percent is achieved with an external bias of 1.3 volts. The stability of the electrode is demonstrated, and the results are discussed in terms of a composite energy diagram.
IBM1
TL;DR: In this article, a semiconductor electrode with a bandgap in the visible part of the spectrum that can serve in the catalytic photodecomposition of water was explored.
Abstract: In an effort to find a semiconductor electrode with a bandgap in the visible part of the spectrum that can serve in the catalytic photodecomposition of water, different systems were explored. The first was sputtered thin films of wide bandgap semiconductor materials such as TiO/sub 2/, SnO/sub 2/, Nb/sub 2/O/sub 3/, Al/sub 2/O/sub 3/, and Si/sub 3/N/sub 4/ on low bandgap, n-type semiconductors such as GaAs and GaAlAs. Scanning electron micrographs showed that corrosion is greatly reduced but continues by diffusion of the electrolyte through the film, undermining the film by pit formation in the low bandgap semiconductor. There was no evidence for hole conduction through the film. The second system employed p-type GaP as the cathode and Pt as the anode. It was observed that this cell catalytically photoelectrolyzes water with conversion efficiency of 0.1%. The efficiency of the device is a strong function of crystal orientation, surface treatment, and purity of the crystal. The results are explained in terms of an energy diagram of the entire system. Areas for possible improvement are mentioned.
TL;DR: In this article, the epitaxial growth of CdS on p-type InP using the close-spaced technique has been used to obtain good rectification and photovoltaic properties.
Abstract: Heterojunction solar cells have been made by epitaxial growth of CdS on p-type InP using the close-spaced technique. Good rectification and photovoltaic properties have been observed in the cells grown on the (110) face of InP. The characteristics of the most efficient cell are Voc = 807 mV, the fill factor = 0.74 and the power conversion efficiency = 14.4% under the solar input of 77 mW/cm2. The photovoltaic properties of the cells obtained in this experiment are better than those reported elsewhere, and this is attributed to the superiority of the growth system to those of others in points that the junction is formed at relatively high temperature in a short time.
TL;DR: In this article, CdS films were used as photovoltaic detectors with an absolute quantum efficiency of 80% at a wavelength of 5800 A and a solar power conversion efficiency of 5% when they are exposed to the solar light whose intensity is 71 mW/cm2.
Abstract: p‐CuGaSe2/n‐CdS heterojunctions have been prepared by depositing CdS films on p‐type CuGaSe2 single crystals whose initial resistivity was 10−2 Ω cm and changed to 1 Ω cm after the CdS film deposition. The CdS films, which were grown by a multisources method, exhibit a room‐temperature resistivity of 0.1 Ω cm. The absolute quantum efficiency of these devices as photovoltaic detectors reaches the value of 80% at a wavelength of 5800 A. As solar cells, these heterojunctions at 25 °C display a solar power conversion efficiency of 5% when they are exposed to the solar light whose intensity is 71 mW/cm2. When the heterojunctions are directly polarized, they emit light in a broad band which is centered at ∼7700 A. An external electroluminescent emission efficiency of about 0.05% has been measured at liquid‐nitrogen temperature.
TL;DR: In this article, the intensity Raman emission at 585 nm has been observed from Ba vapor pumped by the XeF laser and the near-unit photon conversion efficiency was measured.
Abstract: Intense Raman emission at 585 nm has been observed from Ba vapor pumped by the XeF laser. Near‐unit photon conversion efficiency was measured.
TL;DR: In this paper, a dye laser arrangement in which superposition of both cw and pulsed excitation permits to get a single mode pulsed tunable laser light beam was presented.
IBM1
TL;DR: In this article, the effect of grain size on the short-circuit current and AM1 efficiency of polycrystalline thin film InP, GaAs, and Si Schottky barrier solar cells was investigated.
Abstract: Numerical calculations have been made of the effect of grain size on the short-circuit current and the AM1 efficiency of polycrystalline thin film InP, GaAs, and Si Schottky barrier solar cells. Si cells 10 µm thick are at best 8 percent efficient for 100-µm grain sizes; 25-µm-thick Si cells can be about 10 percent efficient for this grain size. GaAs cells 2 µm thick can be 12 percent efficient for grain sizes of 3 µm or greater.
TL;DR: The theory and experimental status of energy conversion using photoelectrochemical devices is reviewed in this article, where two classes of devices are considered: photo-electrolysis cells and electrochemical photovoltaic cells.
TL;DR: In this article, an experimental and theoretical investigation of energy conversion in the three-photon parametric interaction of ultrashort light packets is made both in the constant pump field approximation and for strong energy exchange between packets.
Abstract: An experimental and theoretical investigation is made of energy conversion in the three-photon parametric interaction of ultrashort light packets Calculations are made both in the constant pump field approximation and for strong energy exchange between packets A parametric two-stage oscillator generating ultrashort light pulses is described: it has an energy conversion efficiency of 12%, a line width of the output radiation of 4–5 cm–1, and a high pulse repetition frequency (up to 25 Hz) A parametric small-signal gain of 109–1010 can be achieved The competition between stimulated Raman scattering (STRS) and stimulated parametric scattering, observed in a number of nonlinear crystals (α-HIO3, KDP, LiIO3), is discussed The characteristics of picosecond optical parametric oscillators (OPO's) using α-HIO3, KDP, LiIO3, and LiNbO3 crystals are given An automatic measuring system incorporating amplitude analyzers, a data terminal, and a computer has been developed to investigate the energy and temporal characteristics
TL;DR: In this paper, the authors presented a cell with an open-circuit voltage of 0.63 V, a quantum efficiency of 1.82, a fill factor of 2.66, and a solar efficiency of 7.9 percent, in which the CdS is covered with an indium-tinoxide coating and then with an antireflection coating.
Abstract: n-CdS-p-CdTe heterojunctions have been prepared by close-spaced vapor transport of p-CdTe films onto single crystal n-CdS, by vacuum evaporation of n-CdS films onto single crystal p-CdTe, and by solution spraying of n-CdS films onto single crystal p-CdTe. In addition, a number of other II-VI p-n heterojunctions have been prepared by the close-spaced vapor transport technique. The highest solar efficiency to date has been obtained with a cell prepared by vacuum evaporation of n-CdS film onto p-CdTe crystal, in which the CdS is covered with an indium-tin-oxide coating and then with an antireflection coating; the photovoltaic parameters of this cell are an open-circuit voltage of 0.63 V, a quantum efficiency of 0.82, a fill factor of 0.66, and a solar efficiency of 7.9 percent. II-VI heterojunction cells with efficiency greater than 10 percent are expected in the near future.
TL;DR: In this article, the physical constraints on CdS thin films and the economic constraints on thin-film fabrication, imposed by the 10% conversion efficieny requirement and the low-cost production scale-up requirement, are discussed.
TL;DR: In this article, single crystal InP-CdS solar cells with AM2 efficiencies of 15 percent and polycrystalline thin-film cells having AM2 efficiency of 5.7 percent were reported.
Abstract: We report single crystal InP-CdS solar cells having AM2 efficiencies of 15 percent and polycrystalline thin-film cells having AM2 efficiencies of 5.7 percent. Basic studies of the interface reveal that the thin-film efficiency is presently limited at least in part by the quality of the InP within the grains, and not exclusively by interface phenomena intrinsic to a polycrystalline cell. Preliminary accelerated life tests indicate a remarkable insensitivity of these unencapsulated cells to the ambient.
TL;DR: In this article, a continuous tuning of the oscillation frequency of a continuous-wave Raman fiber-optic laser has been demonstrated over a 3 nm band in the visible range and exhibits low threshold and high conversion efficiency.
Abstract: Continuous tuning of the oscillation frequency of a continuous-wave Raman fibre-optic laser has been demonstrated. The device operates over a 3 nm band in the visible range and exhibits low threshold and high conversion efficiency.
TL;DR: In this article, an improved technique for making large area high efficiency (AlGa)As-GaAs solar cells is described, which includes a modified infinite melt liquid phase epitaxial process, for growing the desired (Alga)AsGaAs and GaAs layers.
Abstract: An improved technique for making large-area high-efficiency (AlGa)As-GaAs solar cells is described. This includes a modified infinite melt liquid phase epitaxial process, for growing the desired (AlGa)As-GaAs and GaAs layers. Representative solar cells fabricated in this manner are described. Performance with an air mass zero efficiency in excess of 16 percent is shown, for cells of a 4-cm 2 area. Means are also shown for increasing this efficiency to about 18 percent.
TL;DR: In this paper, a single-crystal antireflection-coated GaAs solar cells fabricated without the use of Ga1−xAlxAs layers are presented.
Abstract: Conversion efficiencies as high 15.3% (17% when corrected for contact area) have been obtained for single‐crystal antireflection‐coated GaAs solar cells fabricated without the use of Ga1−xAlxAs layers. These devices employ a thin n+/p/p+ structure prepared by chemical vapor deposition, in which surface recombination losses are reduced because the n+ layer is so thin (1300 A) that most of the carriers are generated in the p layer below the junction.
TL;DR: The optical constants below the fundamental absorption edge of silicon single crystals and sputtered amorphous silicon films at high temperatures have been determined and the photothermal efficiencies of silicon-metal selective absorbers for thermal solar energy conversion calculated.
Abstract: The optical constants below the fundamental absorption edge (up to 5 μm) of silicon single crystals and sputtered amorphous silicon films at high temperatures (up to 800°C) have been determined and the photothermal efficiencies of silicon–metal selective absorbers for thermal solar energy conversion calculated.
TL;DR: In this paper, an experimental 95% TE-TM mode conversion efficiency for an uniform longitudinal magnetization was presented for an integrated optics integrated optics system with magnetic birefringence dependence.
Abstract: TE-TM mode conversion, in magneto-optic guides for integrated optics, requires TE-TM mode overlap and phasematching. This two properties are analyzed with circular and linear magnetic birefringence dependence. In application an experimental 95% TE-TM mode conversion efficiency is presented for an uniform longitudinal magnetization.
Patent•
05 Dec 1977TL;DR: In this article, the laser wavelength was adjusted to compensate for the phase mismatching and improve the conversion efficiency of harmonic generation in a nonlinear crystal, arising from high power optical energy produced by a neodymium-doped glass laser operating at 1.06 micrometers wavelength.
Abstract: Harmonic generation in a nonlinear crystal, arising out of high power optical energy produced by a neodymium-doped glass laser operating at 1.06 micrometers wavelength, is normally limited by crystal self-heating due to thermal-optical effects that cause phase-mismatch and reduce conversion efficiency. This limitation is overcome by tuning the laser wavelength to compensate for the phase-mismatch and thereby permit improved conversion efficiency for harmonic generation. The tuning is varied in accordance with sensed crystal temperature.