Takao Oda

Comparison of High Energy Proton Radiation Damages on AlGaAs/GaAs and Si Solar Cells

We have developed high performance AlGaAs/GaAs solar cells with a conversion efficiency in excess of 18% and high resistance to radiation damage by high energy protons. Results on radiation hardness of AlGaAs/GaAs solar cells for 5, 10, 15, and 52 MeV proton with fluences up to 5×1012 p/cm2 are presented. The AlGaAs/GaAs solar cells are superior to Si solar cells for radiation damage of high energy proton capable of penetrating a coverglass.

An AlGaAs/GaAs Concentrator Solar Cell Operating at High Concentration Ratios without Forced Cooling

A 1×1 cm2 p-AlGaAs/p-GaAs/n-GaAs concentrator solar cell operating at high concentration ratios without forced cooling is described. The cell has a fairly large junction depth (the thickness of the p-GaAs layer) of 3 µm which reduces the sheet resistance of the surface layer and permits the use of a relatively crude contact grid pattern which is easily fabricated. The cell has its highest fill factor of 0.889 at 50–100 suns and its highest efficiency of 22.7% at 50–200 suns, and also maintains a practical efficiency of 17.6% even at 1025 suns without forced cooling.

High Efficiency Large Area AlGaAs/GaAs Concentrator Solar Cells

A 1-kWp ( peak at 100 mw/cm2 incident power dencity ) concentrating photovoltaic array with 180 square Presnel plastic lenses and AlGaAs/GaAs concentrator solar cells has been constructed. The AlGaAs/GaAs concetrator solar cells consist of p-AlGaAs/p-GaAs/ n-GaAs with an area of 2 × 2 cm2. The 2 × 2 cm2 concentrator cells are obtained by a new liquid phase epitaxial growth technique, which treats a large quantity of large area (∼24 cm2 ) wafers at one batch. The p-GaAs layer thickness is set at 3–5 μn so as to keep the spreading resistance low. The concentrator cells are passively cooled by natural convection. The maximum output power from the best concentrator cell is 9.1 W. The array output power of 977 W ( Isc= 8.4 A, Voc=184 V, FF=0.632 ) has been obtained at about 125 suns.

Performance of 1 kWp AIGaAs/GaAs Terrestrial Concentrator Solar Cell Array

A 1 kWp (electrical output power at 100 mw/cm2 incident power density) concentrating photovoltaic array with 180 square Fresnel lenses and AIGaAs/GaAs concentrator solar cells has been constructed. The AIGaAs/GaAs concentrator solar cells consist of p-AlGaAs/p-GaAs/n-GaAs with an area of 2×2cm2. The p-GaAs layer thickness is set at 3–5 µm so as to keep the spreading resistance low. The concentrator cells are passively cooled by natural convection. The maximum output power from the best concentrator cell is 9.1 W with the efficiency of 22.6% at about 125 suns. The array output power of 977 W (Isc=8.4 A, Voc= 184 V, FF=0.632) has been obtained at 125 suns.

A New Structure for High Efficiency and Humidity Resistant AlGaAs/GaAs Solar Cells

For p-AlGaAs/p-GaAs/n-GaAs heteroface solar cells, the results of humidity resistance test under the condition of 65°C and ≥90% relative humidity are described. Humidity resistant cells with high efficiency over 20% have been attained by (1) covering the side walls of the p-AlGaAs layer as well as the top surface with CVD Si3N4 antireflective coating, (2) covering CVD Si3N4 with relatively thick CVD SiO2, and (3) forming p-contact on p-GaAs.