Japan Quality Assurance Organization Research Articles

Characterization of CdS Thin-Film in High Efficient CdS/CdTe Solar Cells

Cadmium sulfide (CdS) thin films are the most commonly used window materials for high efficient cadmium telluride (CdTe) and chalcopyrite polycrystalline thin-film photovoltaic devices. High efficient CdS/CdTe solar cells with thin CdS films have been developed using ultrathin CdS films with a thickness of less than 0.1 µm. CdS films were deposited on transparent conductive oxide (TCO)/glass substrates by the metal organic chemical vapor deposition (MOCVD) technique. CdTe films were subsequently deposited by the close-spaced sublimation (CSS) technique. The screen printing and sintering method fabricated carbon and silver electrodes. Cell performance depends primarily on the electrical and optical properties of CdS films. Therefore we started to develop higher-quality CdS films and found clear differences between high- and low-quality CdS films from the analyses of scanning electron microscope (SEM), atomic force microscope (AFM), secondary ion mass spectroscopy (SIMS), thermal desorption spectrometry (TDS) and Fourier transforms-infrared spectrometry (FT-IR) measurements. As a result of controlling the quality of CdS films, a photovoltaic conversion efficiency of 10.5% has been achieved for size of 1376 cm2 of the solar cells under the Air Mass (AM) 1.5 conditions of the Japan Quality Assurance Organization.

Characterization of CdS thin film in high efficient CdS/CdTe solar cells

Cadmium sulfide (CdS) thin film is the most commonly used window material for high-efficient cadmium telluride (CdTe) thin-film photovoltaic devices. High-efficient CdS/CdTe solar cells have been developed using ultra-thin CdS films having a thickness of below 0.1 μm. CdS film is deposited on transparent conductive oxide (TCO) film coated glass substrates by the metal organic chemical vapor deposition (MOCVD) technique, CdTe film is subsequently deposited by the close-spaced sublimation (CSS) technique. Finally, carbon and Ag–In electrodes are fabricated by the screen printing and sintering method. Cell performance depends primarily on the electrical and optical properties of CdS film, and hence we started to develop higher quality CdS film and found out clear differences between high- and low-quality CdS films from various analyses: SEM, AFM, SIMS, TDS and FT–IR. As a result of controlling qualities of CdS films, photovoltaic conversion efficiency of 10.5% has been achieved for a size of 1376 cm 2 of the solar module under air mass (AM) 1.5 conditions by the Japan Quality Assurance Organization (JQA).

Bifacial silicon solar cells with 21�3% front efficiency and 19�8% rear efficiency

We introduced a triode structure with p–n junctions on both sides into single-crystalline bifacial silicon solar cells in order to improve solar cell performance. These fabricated bifacial silicon solar cells have an energy conversion efficiency of 21·3% under front 1 sun illumination (the standard 1 kW/m2 AM 1·5 global spectrum at 25°C) and 19·8% under rear 1 sun illumination tested at the Japan Quality Assurance Organization. The total of the front and rear conversion efficiencies is the highest ever reported for bifacial silicon solar cells. Copyright © 2000 John Wiley & Sons, Ltd.

Effects of very high hydrogen dilution at low temperature on hydrogenated amorphous silicon germanium

The effects of hydrogen dilution of up to 54:1 (=H2: SiH4) on hydrogenated amorphous silicon germanium (a-SiGe:H) were investigated at substrate temperatures <200°C. The photoconductivity (>10−5 Ω−1 cm−1 and silicon dihydride content (<2 at.%) of a-SiGe:H can be maintained with a high hydrogen dilution ratio of 54:1, although these properties deteriorate with our conventional low hydrogen dilution conditions at a substrate temperature range <200°C. And this high-quality a-SiGe:H film was applied to the bottom photovoltaic layer of a glass superstrate type a-Si/a-SiGe tandem solar cell submodule (30 cm×40 cm), and a stabilized efficiency of 9.5% (light-soaked and measured at Japan Quality Assurance organization (JQA)) was achieved.

積算皮膚線量計（ＳＤＭ‐モデル１０４‐１０１）のエネルギー特性

The purpose of this study is to estimate the energy response of a SKIN DOSE MONITOR (SDM model 104-101), which was developed to measure and assess medical exposure conveniently. The energy responses of pre-calibrated sensors were estimated by comparative measurements in the same calibration fields with sensors calibrated by Japan Quality Assurance Organization. The relative energy responses obtained for the precalibrated sensors agreed approximately with those of the calibrated sensors. The differences of the calibration factors in different calibration fields for the pre-calibrated sensors were 5 percent at the most in the range from 30keVto 40keVof effective energies. The sensor and coupling optical fiber of the SDM are faintly visible on a radiograph taken under ordinary operating conditions. The influence on diagnosis of this phenomenon is to be considered hereafter.

Development of Stable a-Si/a-SiGe Tandem Solar Cell Submodules Deposited by a Very High Hydrogen Dilution at Low Temperature

ABSTRACTThe world's highest stabilized efficiency of 9.5% (light-soaked and measured by the Japan Quality Assurance Organization (JQA)) for an a-Si/a-SiGe superstrate-type solar cell submodule (area: 1200 cm2) has been achieved. This value was obtained by investigating the effects of very-high hydrogen dilution of up to 54:1 (= H2: SiH4) on hydrogenated amorphous silicon germanium (a-SiGe:H) deposition at a low substrate temperature (Ts). It was found that deterioration of the film properties of a-SiGe:H when Ts decreases under low hydrogen dilution conditions can be suppressed by the high hydrogen dilution. This finding probably indicates that the energy provided by hydrogen radicals substitutes for the lost energy caused by the decrease in Ts and that sufficient surface reactions can occur. In addition, results from an estimation of the hydrogen and germanium contents of a-SiGe:H suggest the occurrence of some kinds of structural variations by the high hydrogen dilution. A guideline for optimization of a-SiGe:H films for solar cells can be presented on the basis of the experimental results. The possibility of a-SiGe:H as a narrow gap material for a-Si stacked solar cells in contrast with microcrystalline silicon (μ c-Si:H) will also be discussed from various standpoints. At present, a-SiGe:H is considered to have an advantage over μ1 c-Si:H.

16.0% Efficient Thin-Film CdS/CdTe Solar Cells

High efficiency cadmium sulfide (CdS)/cadmium telluride (CdTe) solar cells have been developed using ultrathin CdS films having a thickness of 50 nm. CdS films deposited on indium tin oxide (ITO)/#1737 glass substrates by the metal organic chemical vapor deposition technique, and CdTe films subsequently deposited by the close-spaced sublimation technique were used for the fabrication of CdS/CdTe solar cells. A photovoltaic conversion efficiency of 16.0% under Air Mass (AM) 1.5 conditions has been measured by the Japan Quality Assurance Organization.

A new traceability system in Japan

In 1993, the measurement law was revised and enacted in Japan. The old law had provided only the use of legal metrology units and the approval and verification systems for measuring equipment. The new one has added the provision of a traceability system to match the needs for a high accuracy measurement technique and international mutual recognition. In the Electrotechnical Laboratory (ETL), the national standard of sound-pressure level has been established and maintained in an audible frequency range. The type approval test and verification of sound level meters have been carried out in the Japan Quality Assurance Organization (JQA). Now, in conformity with the law, ETL has started to construct the new traceability system for the acoustical standards in cooperation with JQA. An outline, is made of the traceability system in Japan and of the newly constructed pressure calibration systems for laboratory standard microphones.

Research and development of evaluation technology of photovoltaic power systems

Abstract A sizing method of photovoltaic power systems is presented by using the measured quantitative efficiency and parameters in order to determine the optimum capacity of the units. A number of experimental units (total capacity 112 kW) including 5 stand-alone, 2 water pumping, and 8 grid-connected systems were constructed at the Hamamatsu Solar Energy Laboratory of the Japan Quality Assurance Organization (JQA), to simulate several types of systems. Here the parameters can be analyzed and evaluated on the basis of the data gathered from these systems. An evaluation technology of photovoltaic power systems is being developed, through the construction and data acquisition of PV power systems of various patterns, and through identification and formulation of design parameters, as well as establishment of database and simulation techniques.

Polycrystalline silicon solar cells with V-grooved surface

Mechanical grooving techniques are effective to uniform reduction of surface reflectance over all polycrystalline silicon solar cells. Furthermore, to reduce the surface reflectance, a V-shaped grooving technique was newly examined. To improve the short-circuit current (Isc) and the open-circuit voltage (Voc), a shallow n+/p junction was also examined for the grooved surface. By forming the shallower junction, both Isc and Voc remarkably increased. Consequently, a record high conversion efficiency of 17.2% has been confirmed at Japan Quality Assurance Organization (JQA) for a 10 × 10 cm2 area polycrystalline silicon solar cell.