Henry B. Curtis

The effect of different module configurations on the radiation tolerance multijunction solar cells

The effects of different module configurations on the performances of multijunctioning (MJ) solar cells in a radiation environment were investigated. Module configuration refers to the electrical circuit in which the subcells of the multijunction cell are wired. Experimental data for AlGaAs, GaAs, InGaAs, and silicon single-junction concentrator cells subjected to 1 MeV electron irradiation were used to calculate the expected performance of AlGaAs/InGaAs, AlGaAs/silicon, GaAs/InGaAs, and GaAs/silicon MJ concentrator cells. These calculations include independent, series, and voltage-matched configurations. The module configuration is found to have a significant impact on the radiation tolerance characteristics of MJ cells.<<ETX>>

Progress toward technology transition of GaInP/sub 2//GaAs/Ge multijunction solar cells

The objective of the joint WL/PL/NASA Multijunction Solar Cell Manufacturing Technology (ManTech) Program is to scale up high efficiency GaInP/sub 2//GaAs/Ge multijunction solar cells to production size, quantity, and yield while limiting the production cost/Watt (

First results from the Starshine 3 power technology experiment

/W) to 15% over GaAs cells. Progress made by the program contractors, Spectrolab and TECSTAR, include, respectively, best cell efficiencies of 25.76% and 24.7% and establishment of 24.2% and 23.8% lot average efficiency baseline designs. The paper also presents side-by-side testing results collected by Phillips Laboratory and NASA Lewis on Phase I deliverable cells, which shows compliance with program objectives. Cell performance, pre- and post-radiation, and temperature coefficient results on initial production GaInP/sub 2//GaAs/Ge solar cells are presented.

Photovoltaic cell and array technology development for future unique NASA missions

Starshine 3 is principally a passive experiment measuring atmospheric density and does not need electrical power to complete its mission. The requirement for a highly reliable power system is therefore greatly reduced. This creates an excellent opportunity to test new power technologies. The Starshine 3 satellite has a power supply that uses triple-junction, GaInP/GaAs/Ge solar cells and rechargeable lithium-ion batteries. This satellite is the first to use both of these advanced technologies for a primary power system. In addition to the power system, several other PV related experiments are on board Starshine 3. The results from the first 3 months of operation are presented.

One year of flight data from the PASP-Plus experiment

A technology review committee from NASA, the U.S. Department of Energy (DOE), and the Air Force Research Lab (AFRL) was formed to assess solar cell and array technologies required for future NASA science missions. After consulting with mission planning offices, solar cell and array manufacturers, universities, and research laboratories, the committee assessed the state of the art of solar cells and arrays and made a comparison with projected needs. A technology development program was proposed in high-efficiency cells, electrostatically clean arrays, high-temperature solar arrays, high-power arrays for solar electric propulsion, low-intensity/low-temperature array conditions for deep-space mission, high-radiation missions, and Mars arrays that operate in dusty environments.

Radiation and temperature effects in heteroepitaxial and homoepitaxial InP cells

The PASP-Plus (Photovoltaic Array Space Power Plus Diagnostics) program is a photovoltaic experiment which is flying on the Air Force satellite APEX (Advanced Photovoltaic and Electronics Experiments). The satellite was launched on August 3, 1994 with a Pegasus low-cost launch vehicle. There are two other small experiments on APEX, however PASP-Plus is the largest, uses the most power, and accounts for the largest portion of the data requirements. The satellite is in an elliptical orbit with an apogee of 2552 km and a perigee of 363 km. The inclination is 70 degrees. The PASP-Plus experiment consists of twelve photovoltaic panels containing a total of sixteen separate cell modules. Two of the modules are concentrator modules, while the rest are planar. There are several different solar cell types flying on PASP-Plus including silicon, GaAs on germanium substrates, InP, amorphous silicon, and three multi-bandgap cells. The purpose of this paper is to present some of the data from the first year of the PASP-Plus flight. Cell performance and module thermal performance will be discussed as well as other relevant data.

Engineering Development Model Testing of the PowerSphere

Heteroepitaxial (InP/GaAs) and homoepitaxial (InP/InP) solar cells were irradiated by 1 MeV electrons and their performance, temperature dependencies and carrier removal rates determined. The radiation resistances of the InP/GaAs cells were significantly higher than that of the InP/InP cells. This was attributed to the high dislocation density present in the heteroepitaxial cells. In addition, the effects of dislocations in these latter cells were dominant in determining the temperature dependence of the open-circuit voltage.<<ETX>>

Performance of GaAs concentrator cells under electron irradiations from 0.4 to 2.3 MeV

The Aerospace Corporation, NASA Glenn Research Center, Lockheed-Martin, and ILC Dover over the past two years have been engaged in developing a Multifunctional Inflatable Structure for the PowerSphere Concept under contract with NASA (NAS3-01115). The PowerSphere concept consists of a relatively large spherical solar array, which would be deployed from a micro satellite. 1–8 The PowerSphere structure and the deployment method was patented by the Aerospace Corporation (U.S. Patent Numbers 6,284,966 B1 and 6,318,675). The work on this project has resulted in a number of technological innovations in the state of the art for integrating flexible thin-film solar cells with flex circuit harness technology and inflatable ultraviolet-light-rigidizable structures.

Fabrication and Testing of a PowerSphere Engineering Development Unit

Gallium arsenide concentrator cells were irradiated with electrons with energies varying from 0.4 to 2.3 MeV, and their electrical performance was measured. The cells are 5*5 mm square with a 4 mm diameter illuminated area. At each of four different electron energy levels (0.4, 0.7, 1.0, and 2.3 MeV), three n/p and two p/n cells were irradiated. I-V performance measurements were made prior to irradiation and at several intermediate fluence levels. The final fluence level was 3*10/sup 15/ e/cm/sup 2/. It is concluded that the power degradation is independent of the temperature at which it is measured.<<ETX>>

Proton irradiated heteroepitaxial InP solar cells

During the past three years the team of The Aerospace Corporation, Lockheed Martin Space Systems, NASA Glenn Research Center, and ILC Dover LP have been developing a multifunctional inflatable structure for the PowerSphere concept under contract with NASA (NAS3-01115). The PowerSphere attitude insensitive solar power-generating microsatellite, which could be used for many different space and Earth science purposes as discussed elsewhere, is ready for further refinement and flight demonstration. The project culminated during the third year with the manufacturing of the Powersphere Engineering Development Unit (EDU). One hemisphere of the EDU system was tested for packing and deployment and was subsequently rigidized. The other hemisphere was packed and stored for future testing in an uncured state. Both cured and uncured hemisphere components were delivered to NASA Glenn Research Center for thermal cycle testing and long term storage respectively. This paper will discuss the design, manufacturing, and thermal cycle testing of the PowerSphere EDU. The program also had a significant Education Outreach segment that will also be discussed.