Showing papers on "Polymer solar cell published in 1998"

19.8% efficient “honeycomb” textured multicrystalline and 24.4% monocrystalline silicon solar cells

Abstract: Multicrystalline silicon wafers, widely used in commercial photovoltaic cell production, traditionally give much poorer cell performance than monocrystalline wafers (the previously highest performance laboratory devices have solar energy conversion efficiencies of 186% and 240%, respectively) A substantially improved efficiency for a multicrystalline silicon solar cell of 198% is reported together with an incremental improvement in monocrystalline cell efficiency to 244% The improved multicrystalline cell performance results from enshrouding cell surfaces in thermally grown oxide to reduce their detrimental electronic activity and from isotropic etching to form an hexagonally symmetric “honeycomb” surface texture This texture reduces reflection loss as well as substantially increasing the cell’s effective optical thickness by causing light to be trapped within the cell by total internal reflection

Crystalline Silicon Solar Cells

Abstract: Photovoltaics. Solar Power. The Principles of Photovoltaics. The P-N Junction. The Physics of Solar Cells. High Efficiency Solar Cells. Si Solar Cell Technology. Selected Solar Cell Types. Analysis and Measuring Techniques. Appendices. Index.

Amorphous and Microcrystalline Silicon Solar Cells: Modeling, Materials and Device Technology

Abstract: Part I: Technology of Amorphous and Microcrystalline Silicon Solar Cells. 1. Introduction. 2. Deposition of Amorphous and Microcrystalline Silicon. 3. Optical, Electronic and Structural Properties. 4. Technology of Solar Cells. 5. Metastability. Part II: Modeling of Amorphous Silicon Solar Cells. 6. Electrical Device Modeling. 7. Optical Device Modeling. 8. Integrated Optical and Electrical Modeling. Index.

High-efficiency solar cell and method for fabrication

Abstract: A high-efficiency 3- or 4-junction solar cell (10) is disclosed with a theoretical AMO energy conversion efficiency of about 40 % The solar cell (10) includes p-n junctions (14, 16, 18), formed from indium gallium arsenide nitride (InGaAsN), gallium arsenide (GaAs) and indium gallium aluminum phosphide (InGaAlP) separated by n-p tunnel junctions (22, 24, 26) An optimal germanium (Ge) p-n junction (20) can be formed in the substrate (12) upon which the other p-n junctions are grown The bandgap energies for each p-n junction are tailored to provide substantially equal short-circuit currents for each p-n junction, thereby eliminating current bottlenecks and improving the overall energy conversion efficiency of the solar cell (10) Additionally, the use of an InGaAsN p-n junction overcomes super-bandgap energy losses that are present in conventional multi-junction solar cells A method is also disclosed for fabricating the high-efficiency 3- or 4-junction solar cell (10) by metal-organic chemical vapor deposition (MOCVD)

Cadmium-telluride—Material for thin film solar cells

Abstract: Due to its basic optical, electronic, and chemical properties, CdTe can become the base material for high-efficiency, low-cost thin film solar cells using robust, high-throughput manufacturing techniques. CdTe films suited for photovoltaic energy conversion have been produced by nine different processes. Using n-type CdS as a window-partner, solar cells of up to 16% efficiency have been made in the laboratory. Presently five industrial enterprises are striving to master low cost production processes and integrated modules have been delivered in sizes up to 60 × 120 cm2, showing efficiencies up to 9%. Stability, health, and environmental issues will not limit the commercial potential of the final product. The technology shows high promise for achieving cost levels of $0.5/Wp at 15% efficiency. In order to achieve this goal, scientists will have to develop a more detailed understanding of defect chemistry and device operation of cells, and engineers will have to develop methods for high-throughput manufacturing.

Porous silicon in crystalline silicon solar cells: a review and the effect on the internal quantum efficiency

Abstract: Crystalline silicon (c-Si) is the dominant semiconductor material in use for terrestrial photovoltaic cells and a clear tendency towards thinner, active cell structures and simplified processing schemes is observable within contemporary c-Si photovoltaic research. The potential applications of porous silicon and related benefits are reviewed. Specific attention is given to the different porous silicon formation processes, the use of this porous material as anti-reflection coating in simplified processing schemes and for simple selective emitter processes and its light trapping and surface passivating capabilities, which are required for advantageous use in thin active cell structures. Our analysis of internal quantum efficiency data obtained on both conventional and thin-film c-Si solar cells has been performed with the aim of describing the light diffusing behaviour of porous Si as well as investigating the surface passivating capabilities. An effective entrance angle of 60° is derived, which corresponds to totally diffuse isotropic light, and the importance of a correction for absorption losses in the porous layer is illustrated. Furthermore, photoconductivity decay measurements of freshly etched porous Si on float-zone p-type Si indicate a strong bias-light dependency and a fast degradation of the surface recombination velocity. © 1998 John Wiley & Sons, Ltd.

Solar cell and fabrication method thereof

Abstract: In a solar cell, a crystal defect layer by ion implantation or an amorphous layer by ion implantation is formed between p type diffusion layers provided in an island-like manner at a side opposite to a light receiving surface of a low concentration p type semiconductor single crystalline substrate. The element of the ion implantation may be at least one selected from the group consisting of hydrogen, silicon, germanium, fluorine, oxygen and carbon. The constituent substance of the semiconductor substrate, such as Si is preferably used for the ion implantation. In such a solar cell structure having the crystal defect or amorphous layer, relatively long wavelength light that could not effectively be utilized in the prior art solar cell may be utilized so that the photoelectric conversion efficiency may be improved.

High efficiency Cu(In,Ga)Se{sub 2} thin film solar cells without intermediate buffer layers

Abstract: The nature of the interface between CuInGaSe2 (CIGS) and the chemical bath deposited CdS layer has been investigated. We show that heat-treating the absorbers in Cdor Zncontaining solutions in the presence of ammonium hydroxide sets up an interfacial reaction with the possibility of an ion exchange occurring between Cd and Cu. The characteristics of devices made in this manner suggest that the reaction generates a thin, n-doped region in the absorber. We suggest that this aspect might be more important than the CdS layer in the formation of the junction. It is quite possible that the CdS/CuInSe2 device is a buried, shallow junction with a CdS window layer, rather than a heterojunction between CdS and CIGS. We use these ideas to develop methods for fabricating diodes without CdS or Cd.

Barrier lowering in dye-sensitized porous- TiO2 solar cells

Abstract: The current–voltage characteristics of dye-sensitized porous-TiO2(por-TiO2) solar cells are investigated in the dark and under illumination at light intensities up to 1500 W/m2 and temperatures between −5 and 80 °C. In the dark, the barrier height and the ideality factor of the por-TiO2/electrolyte contact are 0.67 eV and 1.05, respectively. The very low effective Richardson constant indicates the importance of diffusion for transport. A current-dependent effective barrier height has been established under illumination of dye-sensitized por-TiO2 solar cells. The barrier lowering effect should be caused by the low neutralization rate of the positively charged dye radicals in the electrolyte.

Evidence for proton motion in the recovery of light-induced degradation in amorphous silicon solar cells

Abstract: The light-induced degradation of amorphous silicon solar cells can be reversed by the application of a strong electric field in the dark, and the rate of reversal increases with field strength, temperature, and light intensity. The activation energy for annealing the degradation in the dark is reduced from about 1.34 eV under open circuit conditions to 1.16 eV by applying a strong reverse bias. When the degraded cells are exposed to intense illumination in addition to a strong reverse bias, the activation energy for the recovery of the performance decreases to about 0.77 eV. Both the light-induced degradation and the reversal of the degradation can be explained by a model based on proton motion within a metastable defect complex.

Investigation of Hydrogenated Amorphous Silicon Germanium Fabricated under High Hydrogen Dilution and Low Deposition Temperature Conditions for Stable Solar Cells

Abstract: The effects of hydrogen dilution of up to 54:1 (=H2:SiH4) on hydrogenated amorphous silicon germanium (a-SiGe:H) were investigated while keeping the optical gap (Eopt) constant. It was found that deterioration of the film properties of a-SiGe:H due to a decrease in substrate temperature (Ts) can be compensated by the high hydrogen dilution method. As Ts decreases from 230°C to 180°C, the high photoconductivity [~1×10-5 (Ωcm)-1] and low silicon dihydride content (~1 at.%) of a-SiGe:H can be maintained with a high hydrogen dilution ratio of 54:1, although these properties deteriorate with the conventional low hydrogen dilution ratio of 2.5:1. Probably, hydrogen radicals supply the energy required for the surface reaction during a-SiGe:H deposition which is lost when Ts is decreased. This tendency is useful for solar cell fabrication, especially for superstrate-type a-Si/a-SiGe tandem solar cells, because the decrease in the deposition temperature of a-SiGe:H for the bottom photovoltaic layer can reduce damage to the underlying layers caused by a high deposition temperature. As a result of applying this technique to the fabrication process of an a-Si/a-SiGe stacked solar cell submodule (area: 1200 cm2), the world's highest stabilized efficiency of 9.5% (light-soaked and measured at JQA) was achieved.

Explanation for carrier removal and type conversion in irradiated silicon solar cells

Abstract: Heavy doses of radiation in space can cause the failure of n+/p/p+ silicon solar cells due to the gradual introduction of compensating defects into the base layer of the diode. In this letter, we show that the radiation-induced defects, which play the most important role in this process, referred to as “carrier removal,” are probably minority-carrier traps at an energy level approximately 0.18 eV below the conduction band. We conclude that these defects must be positively charged before electron capture, and therefore, act as donor centers which compensate the p-type base layer.

Sol-Gel Derived TiO2/Lead Phthalocyanine Photovoltaic Cells

Abstract: Transparent TiO2 films were deposited onto a base electrode comprising an InSnO2 glass substrate using the (alkoxide) sol-gel technique. Lead phthalocyanine was subsequently vacuum sublimed onto the TiO2 surface. The resulting InSnO2/TiO2/PbPc/Au heterojunction cell was investigated for its illuminated current density/voltage, and spectral characteristics. The ideality factor (m) and saturation current (Jo) were determined from current density/voltage J(V) measurements. Photoelectrical measurements were conducted under both simulated solar radiation and within a wavelength range of 300–900 nm. This allowed calculation of open circuit voltage Voc, short circuit current Jsc, fill factor FF, quantum efficiency Z and the overall conversion efficiency. Typical photovoltaic characteristics were obtained indicating the potential of the device for solar cell applications. The power conversion efficiency η was ∼0.001%; improvements are therefore required.

Effect of Excitation Frequency on the Performance of Amorphous Silicon Alloy Solar Cells

Abstract: We have studied amorphous silicon alloy solar cells made by using a modified-very-highfrequency glow discharge at 75 MHz with a deposition rate of ∼6 A/s. The solar cell performance is compared with those made from conventional glow discharge at 13.56 MHz with lower deposition rates. Cells made at ∼6 A/s with 75 MHz showed comparable stabilized efficiency to those made at ∼3 A/s with 13.56 MHz. The best performance, however, was obtained with ∼1 A/s, including a stabilized 9.3% a-Si alloy single-junction cell employing conventional glow discharge technique. Using 75 MHz, we have achieved 11.1% and 10.0% initial active-area efficiencies for a-Si alloy and a-SiGe alloy n i p cells, respectively. An initial efficiency of 11.0% has also been obtained in a dual bandgap double-junction structure.

Hydrogenated amorphous silicon transverse junction solar cell

Abstract: In this letter, we introduce a new thin film solar cell design on amorphous silicon, called the transverse junction solar cell. In this concept, the p-i-n junction is formed perpendicular to the surface. With conventional deposition and silicon device processing techniques test cells have been made with a conversion efficiency up to 5.2%±1.4% under standard AM1.5 illumination.

Silicon solar cell or semiconductor device production

Abstract: In the production of a silicon solar cell with a p-n junction formed by a functional silicon layer covered with a thin film of opposite conductivity type on its front face, its front and back face or all its faces, the p-n junction is electrically separated by provision of a glass-based material which has the property of melting silicon and which is subsequently fired. Also claimed are: (i) a solar cell having the above structure; (ii) a method of producing a semiconductor device having a junction-containing semiconductor substrate with an insulating layer on its front face and optionally its back face. The novelty is that: (a) an electrode penetrates the insulating layer for electrically contacting the substrate; (b) the insulating layer is coated with a glass-containing metal paste material which has the property of melting the insulating layer; and (c) the material is subsequently fired. Preferably, the glass contains Pb, B, Si and O as main components and the metal paste is a silver and/or aluminium paste.