John C. Nocerino

Evaluation of multijunction solar cell performance in radiation environments

This report contains the results of the first systematic radiation study of five types of production multijunction solar cells. Cells optimized for beginning of life (BOL) efficiency were developed and obtained under the Air Force Manufacturing Technology (ManTech) program. These included GaInP/sub 2//GaAs two junction cells from Spectrolab, and GaInP/sub 2//GaAs/Ge three junction cells from both Spectrolab and TECSTAR. Additional two junction cells optimized for end of life (EOL) efficiency were obtained from Spectrolab. Radiation test data on EOL-optimized three junction cells were provided by Spectrolab. For all cell types I-V characteristics were obtained as a function of radiation fluence using electrons (0.6, 1.0, and 1.6 MeV) and protons (0.05, 0.1, 0.2, 0.4, 1.0, 5.0, and 10 MeV). From these data, omnidirectional damage coefficients were calculated, assuming infinite backshielding and eight different coverglass thicknesses.

Radiation Effects and Annealing Studies on Amorphous Silicon Solar Cells

Results of radiation effects and annealing studies are presented for amorphous silicon solar cells from three manufacturers. Data scale well with ionizing dose in many cases for proton, x-ray, and electron irradiation. Significant long-term annealing occurs at room temperature. Results for small-area diodes are in reasonable agreement with findings for monolithic modules. Damage mechanisms in irradiated and illuminated devices are compared.

Results from an International Measurement round Robin of III-V Triple-Junction Solar Cells Under Air Mass Zero

This paper reports the results of an international measurement round robin of monolithic, triple-junction, GaInP/GaAs/Ge space solar cells. Eight laboratories representing national labs, solar cell vendors and space solar cell consumers, measured cells using in-house reference cells and compared those results to measurements made where each lab used the same set of reference cells. The results show that most of the discrepancy between laboratories is likely due to the quality of the standard cells rather than the measurement system or solar simulator used

Proton Irradiation and Annealing of a -Si Thin -Film Solar Cells for Space Applications: Results at 160 keV

†, ‡ § ** , Thin -film solar cells are of interest for satellite power generation because of the potential advantages in terms of having hig her specific power (lightweight), lower specific volume (flexible), and higher end -of -life power (superior radiation resistance), as compared to the crystalline solar cells. The space radiation environment causes gradual solar cells performance degradatio n, thus limiting the lifetime of the solar array. Due to the self annealing effect, the radiation damage on thin -film solar cells can be partially reversed. This paper presents proton irradiation and annealing of amphorous silicon (a -Si) solar cell test results.

Thin-Film Photovoltaic Radiation Testing for Space Applications

Although thin-film photovoltaic technology on lightweight flexible substrates has lower beginning-of-life efficiency compared to traditional single crystalline solar cells, it can offer advantages in high-specific power and low-stowed volume for power generation in space. To date, radiation testing on thin-film solar cells has demonstrated superior radiation hardness compared to traditional crystalline solar cells. In addition, radiation induced damage in thin-film solar cells can be removed by annealing at temperatures readily achievable in space. Prior to deployment of this new technology for any mission, a more thorough understanding of its performance in the space environment will be required. The Aerospace Corporation has initiated a comprehensive study of thin-film solar cell performance in a simulated space radiation environment. A new testbed has been constructed to study the combined space environmental effect of proton irradiation and air mass zero light spectrum light soaking on a thin-film photovoltaic

Dark current characterization of irradiated solar cells

A decrease in ideality factor of GaAs solar cells due to irradiation with 1MeV electron radiation resulted in decreased open circuit voltage and maximum power. Dark current-voltage measurements suggest that 1 MeV electron radiation primarily affects dark current produced at voltages greater than 0.5 V. The dark saturation current of irradiated solar cells increased but a simultaneous decrease in ideality factor caused a reduction of the open circuit voltage. The reduced ideality factor further indicates a change in the primary recombination mechanism.

Proton irradiation of metallic single-walled carbon nanotubes

Metallic single-walled carbon nanotube (SWNT) films on space qualified solar cell coverglass were irradiated with 100 keV protons at doses of 1 × 10¹³ and 1 × 10¹⁴ protons/cm². The samples were analyzed using UV-vis-NIR spectroscopy, Raman spectroscopy, and four-point probe measurements. The results indicate that defects are not introduced into the metallic carbon nanotubes after irradiation.

Solar simulator air mass zero calibration method

A method of AM0 solar simulator calibration is demonstrated that does not rely on balloon or similar solar cell reference standards [5]. This work presents the development of a new tool for calibrating a solar simulator and measuring solar cell performance using a real-time diode array spectroradiometer calibrated with an absolute irradiance standard, the ASTM-E-490 solar spectrum, and spectral response curves. An in-house developed software application acquires data, convolves the measured simulator spectrum with the spectral response curves in two wavelength bands, and reports measurement and calculation results allowing solar simulator irradiance adjustment for AM0 matching. Various calibration scenarios will be reported, with comparisons between primary and secondary calibration standards, and the spectroradiometric calibration.

On-orbit characterization of space solar cells on nano-satellites

The Aerospace Corporation has been building, testing, and flying miniature satellites in the pico-and nano-satellite class for over a decade. Significant advances have been made to the bus avionics unit and other satellite subsystems during this time. The advances have enabled various on-orbit tests and experiments, one of which has been to host space solar cell experiment payloads. Recent solar cell flight experiments on Aerospaces CubeSats (AeroCubes) demonstrated several subsystems can simultaneously operate to obtain precise measurements of space solar cell performance. Low cost, rapid return CubeSat missions can be valuable development tools for advancing the readiness level of space technologies.