Metallic single-walled carbon nanotube (SWNT) films on space qualified solar cell coverglass were irradiated with 100 keV protons at doses of 1 × 10 13 and 1 × 10 14 protons/cm 2 . 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.
It is well known that solar cell coverglass materials are subject to darkening, or transmission degradation, due to interaction with protons. Our recent laboratory test results have shown that the transmission of coverglasses, once contaminated with organic molecular films, can be further degraded upon space proton irradiation (20-400 keV). The coverglass transmission loss occurs in the short wavelength region, thus multi-junction solar cells are expected to be particularly susceptible to such synergistic effects of contamination and proton irradiation when the top junction is the current limiting junction. In the previous work, AR/ITO coverglass materials, commonly used for space solar arrays, were photo-deposited with the model contaminant DC704. The contaminated coverglass samples were subsequently irradiated with a simulated 15-year geosynchronous orbit low energy proton radiation environment at 5-year increments. The progression of coverglass transmission change was characterized before and after each process. The measured coverglass transmission data were then convolved with the solar cell quantum efficiency and solar spectrum to determine the coverglass darkening effects on solar cell performance. Taking into account space proton radiation effects and the time dependent contaminant film accumulation process, our preliminary analysis indicates that, over a 15-year mission life, approximately 3.7 % solar cell current loss could be attributed to a beginning-of-life (BOL) contaminant film of 100 Å, with no additional on-orbit film growth. For a BOL film of 100 Å and additional film growth while on orbit, the end-of-life (EOL) solar cell current loss due to contamination is approximated at 5.5% for EOL 200 Å, and 7.3% for EOL 300 Å.
Calibration of individual zones in a multi-source solar simulator using isotype reference cells presents unique challenges. Higher bandgap materials are used as filter layers to match the spectral response of an active isotype cell to its corresponding response in a full multijunction cell. Experimental results suggest that luminescence from these filter layers could occur during calibration of isotype references, thereby artificially increasing the current output. We show that proton irradiation of the filter layers can quench radiative recombination within these layers thereby reducing the luminescent coupling. We also take a look at transient responses from some isotype cells.
We combined light current-voltage, dark current-voltage, quantum efficiency, and electroluminescence at varying low temperatures to identify and quantify defects, current mismatch effects, saturation currents, and diode quality of each subcell. We attempt to provide a method for spectral mismatch correction for fill factor for each subcell as well as identify how defects, current mismatch, and radiation will affect performance of multijunction solar cells at LILT, AM 0, and AM 1.5.
AeroCube-10 is a two-CubeSat mission built and operated by The Aerospace Corporation. Among several payloads is a space solar cell experiment designed to measure solar cell radiation damage as well as the space radiation environment believed to cause it. This paper describes first on-orbit results of the space solar cell experiment on AeroCube-10.
We demonstrate the controlled desorption of adventitious dopants on networks of single-walled carbon nanotubes (SWNTs) with 100 keV proton irradiation. Networks of sorted metallic, semiconducting SWNTs, and unsorted SWNTs were investigated. The removal of dopants was indicated by an increase in sheet resistances along with an increase in the absorption of the low energy absorption band of semiconducting SWNTs. Semiconducting and unsorted SWNT networks exhibited the largest change in their sheet resistance, which indicates the conductivity of unsorted SWNT networks is dominated by the tube-tube junctions of semiconducting SWNTs.
We demonstrate the reproducibility and variability of 8 high altitude, near space solar cell characterization flights using the Selenium Ecosystem to be equal to prior JPL solar cell calibration flights. The Selenium Ecosystem consists of hardware and software that can measure and process high altitude solar cell characterization data. The modular nature of Selenium enables it to piggyback on larger balloon platforms as a secondary payload and light enough to be flown as primary payload on small weather balloons (< 2kg). The Selenium software is free to download.
GaInP/(In)GaAs/Ge multijunction solar cells have been state-of-practice for power generation on spacecraft for over a decade but there are still potential improvements for end-of-life (EOL) efficiency. Radiative coupling between GaInP and (In)GaAs subcells is not typically considered in the EOL design of space solar cells because radiative recombination in the GaInP is effectively quenched by radiation-induced damage. This paper shows that quantum well structures incorporated into a GaInP subcell may be less sensitive to radiation damage, thereby enabling radiative coupling between subcells at EOL and providing a current boost in the (In)GaAs subcell to improve EOL efficiency.
