Electrostatic Discharge Test on Cu (In, Ga) Se2 Solar Cell Array

The boundary part of dielectric material, conductive material, and space, known as the triple junction, causes electrostatic discharge. Because the triple junction does not exist on the Cu (In, Ga) Se2 solar cell surface, it should be free of electrostatic discharge. Electrostatic discharge tests on Cu (In, Ga) Se2 were performed in a vacuum chamber which simulated the plasma environment in low Earth orbit and the high-energy electron environment in geostationary orbit. Contrary to the theoretical expectations, electrostatic discharge occurred on the surface of Cu (In, Ga) Se2 and Cu (In, Ga) Se2 suffered degradation of electric performance. The arc track was investigated to make clear the degradation mechanism of Cu (In, Ga) Se2. The arc track worked as a leak resistance because the PN junction collapsed and the materials of front and back surfaces electroded adhere along the arc track

Environmental Effects on Solar Array Electrostatic Discharge Current Waveforms and Test Results

A solar array electrostatic discharge ground test is necessary to assure spacecraft reliability in orbit. Laboratory experiments were carried out to characterize an electrostatic discharge current waveform with different background pressures and charging environments to identify the importance of the test setup. The waveform strongly depended on the background pressure. This difference can affect the result of the solar cell degradation test. However, in the case of the secondary arc test, the difference of the primary arc current waveform did not affect the duration of the secondary arc. The current available from a power supply mostly determined the duration of the secondary, irrespective of the test environment. Methods to control the primary arc current supplied by an external capacitance are proposed

Analysis of Flashover Discharge on Large Solar Panels under a Simulated Space Plasma Environment

Electrostatic discharge tests were performed on large solar array panels under the simulated plasma environments of a geostationary orbit and a low Earth orbit to investigate the propagation length and velocity of flashover plasma. To investigate the propagation length, the neutralized current on the strings was also examined. The neutralized charge value due to flashover plasma was found to decrease with distance. Propagation length was limited under both the geostationary orbit environment and the low-Earth-orbit environment. Visual investigation of the velocity of flashover plasma clarified that velocity decreases with time. The initial velocity of flashover plasma measured was several tens of km/s, regardless of orbital environment conditions

Time-resolved photoluminescence measurements for determining voltage-dependent charge-separation efficiencies of subcells in triple-junction solar cells

Conventional external quantum-efficiency measurement of solar cells provides charge-collection efficiency for approximate short-circuit conditions. Because this differs from actual operating voltages, the optimization of high-quality tandem solar cells is especially complicated. Here, we propose a contactless method, which allows for the determination of the voltage dependence of charge-collection efficiency for each subcell independently. By investigating the power dependence of photoluminescence decays, charge-separation and recombination-loss time constants are obtained. The upper limit of the charge-collection efficiencies at the operating points is then obtained by applying the uniform field model. This technique may complement electrical characterization of the voltage dependence of charge collection, since subcells are directly accessible