Characteristics Of GaAs Solar Cells Research Articles

Systematic Investigation of the Optical Characteristics of GaAs Solar Cells with Antireflection Coatings and Metallic Nanoparticles Using Finite Element Analysis

Systematic Investigation of the Optical Characteristics of GaAs Solar Cells with Antireflection Coatings and Metallic Nanoparticles Using Finite Element Analysis

Investigation of the Photoelectric Characteristics of GaAs Solar Cells with Different InGaAs Quantum Dot Array Positioning in the i-Region

Investigation of the Photoelectric Characteristics of GaAs Solar Cells with Different InGaAs Quantum Dot Array Positioning in the i-Region

Application of TiO2/Ag/TiO2 as an Ohmic Contact to an AlGaAs Layer in a GaAs Solar Cell

This paper investigates the possibility of using a nanolaminate TiO2/Ag/TiO2 structure as a transparent conductive coating on GaAs solar cells. A novel result is that this structure forms an Ohmic contact to Al-rich AlGaAs, which is used as a “window” layer in GaAs-based solar cells. The TiO2/Ag/TiO2 structure is deposited by RF magnetron sputtering at room temperature. This nanolaminate coating has good optical and electrical properties: a high transmittance of 94% at 550 nm, a sheet resistance of 7 Ω/sq, and a figure of merit (FOM) of 105 × 10−3 Ω−1. These properties are the result of the presence of a discontinuous layer of Ag between two thin layers of TiO2. The morphology of a discontinuous layer of Ag nanogranules is confirmed by the observation of a cross-section of a sample with high-resolution transmission electron microscopy (HRTEM) and EDX analyses. Current–voltage diode characteristics of GaAs solar cells measured under standard test illumination at 1000 W/m2 are analyzed. The formation of an Ohmic contact is explained by the Fermi-level pinning effect caused by nanosized Ag particles in the nanolaminate TiO2/Ag/TiO2 structure. The obtained results demonstrate a new application of oxide−metal−oxide (OMO) coatings as Ohmic contacts to III-V compound semiconductors.

Investigation of the photoelectric characteristics of GaAs solar cells with different InGaAs quantum dot array positioning in the i-region.

The effect of positioning of the In0.8Ga0.2As quantum dots (QDs) array in the i-region of the solar cell (SC) on its photogenerated current and dark saturation currents, which determine the device operating voltage, have been investigated. It was found out that the indicated photoelectric characteristics depend on the location of the QD array relative to the electric field of the p-n junction. The displacement of the QD array to the boundary of the weakly doped base leads to a decrease in the photogenerated current. But at the same time, the voltage drop effect, which is well-known for nanoheterostructural SC, is minimal. Keywords: solar cells, quantum dots, dark saturation current

Numerical Simulation of GaAs Solar Cell Aging Under Electron and Proton Irradiation

Though gallium arsenide (GaAs) solar cells are proven to be relatively stable in space working conditions, they are prone to the effects of aging, which deteriorate their characteristics. The lifetime of solar cells is restricted by the degree of radiation damage that they receive. This important factor affects the performance of solar cells in practical applications. The aim of this article is to investigate by numerical simulation on the influence of aging on the main characteristics of GaAs solar cells in the space. Degradations of the electrical characteristics are simulated for over a period of 15 years. The atmosphere (AM0) conversion efficiency decreases with time from 19.08% for the unirradiated cells to 10.38% in 15 years of the mission in space. Even with low doses of particle irradiation, the performance is significantly reduced subsequent to usage over the period of 15 years of the mission in space. Numerical simulation results also reveal that the short-circuit current, the open-circuit voltage, and the conversion efficiency decline gradually with time. Moreover, the calculated evolutions are in good agreement with the measured behaviors of GaAs-based solar cells embedded in geostationary satellites during the Navigation Technology Satellite 2 (NTS-2), the Engineering Test Satellite V (ETS-V), and the NAVigation Satellite Timing And Ranging (NAVSTAR) missions, which substantiate the introduced aging law accounting for both the cumulated doses of particles and the different electron and hole traps in the structure.

Intrinsic radiation tolerance of ultra-thin GaAs solar cells

Radiation tolerance is a critical performance criterion of photovoltaic devices for space power applications. In this paper we demonstrate the intrinsic radiation tolerance of an ultra-thin solar cell geometry. Device characteristics of GaAs solar cells with absorber layer thicknesses 80 nm and 800 nm were compared before and after 3 MeV proton irradiation. Both cells showed a similar degradation in Voc with increasing fluence; however, the 80 nm cell showed no degradation in Isc for fluences up to 1014 p+ cm−2. For the same exposure, the Isc of the 800 nm cell had severely degraded leaving a remaining factor of 0.26.

Space-charge limited current in the series resistance of GaAs solar cells

We report the observation of space-charge limited current in the current–voltage characteristics of GaAs solar cells as evidenced by an abrupt decrease in the series resistance, a concurrent steep increase in the dark current at a threshold voltage and the observation of a quadratic dependence of the dark current on the voltage across the series resistance above threshold. The abrupt decrease in the series resistance at threshold, results in the observation of negative differential resistance and a subsequent hysteresis in the current–voltage characteristics. Auger electron spectroscopy analysis shows that the space-charge limited current can be attributed to a thin insulating CrAs layer at the contact/semiconductor interface.

Influences of InGaP Conical Frustum Nanostructures on the Characteristics of GaAs Solar Cells

Conical frustums with quasihexagonal nanostructures are fabricated on an InGaP window layer of single junction GaAs solar cells using a polystyrene nanosphere lithography technique followed by anisotropic etching processes. The optical and photovoltaic characteristics of the conical frustum nanostructured solar cells are investigated. Reflectance of the conical frustum nanostructured solar cells is significantly reduced in a wide range of wavelengths compared to that of the planar sample. The measured reflectance reduction is attributed to the gradual change in the refractive index of the InGaP conical frustum window layer. An increase of 15.2% in the power conversion efficiency has been achieved in the fabricated cell with an optimized conical frustum nanostructure compared to that of the planar cell.

Spectral characteristics of GaAs solar cells grown by LPE

This paper describes the spectral characteristics of GaAs solar cells grown by low-temperature liquid phase epitaxy (LPE). It demonstrates improvements in blue response and peak internal quantum efficiencies of 100 percent for an optimized cell structure with isovalent In doped base and ultrathin (<100A) heavily doped cap p+-GaAs layer on the photosensitive surface. The conversion efficiency obtained from the optimized cells under one-sun AM 1.5 conditions is 23.4 percent. Our results indicate that the low-cost LPE-grown films are suitable for high-efficiency solar cells.

98/01396 Characteristics of GaAs solar cells on Ge substrate with a preliminary grown thin layer of AlGaAs: Takahashi, K. et al. Solar Energy Materials and Solar Cells, 1998, 50, (1–4), 169–176

98/01396 Characteristics of GaAs solar cells on Ge substrate with a preliminary grown thin layer of AlGaAs: Takahashi, K. et al. Solar Energy Materials and Solar Cells, 1998, 50, (1–4), 169–176

Characteristics of GaAs solar cells on Ge substrate with a preliminary grown thin layer of AlGaAs

Characteristics of GaAs solar cell on Ge substrate with a new buffer layer structure is reported. The buffer layer structure, which consisted of a preliminarily grown thin layer of A1 x Ga 1− x As and a 1 μm thick GaAs layer, was designed to obtain a high quality GaAs layer on Ge substrate by metalorganic chemical vapor deposition (MOCVD). Performance of a GaAs solar cell fabricated on Ge substrate with the buffer layer structure was compared with that fabricated on Ge substrate with a conventional GaAs buffer layer and also that fabricated on GaAs substrate. A conversion efficiency of 23.18% (AM1.5G) was successfully obtained for the cell fabricated on Ge substrate with the new buffer layer structure, while it was 20.92% for the cell fabricated on Ge substrate with the conventional GaAs buffer layer. Values of V oc and J sc, for the cell fabricated on Ge substrate with the new buffer layer structure were approximately comparable to those of a 25.39% efficiency GaAs solar cell fabricated on GaAs substrate.