IMM3J ELO solar cells from “generation I” were also tested for mechanical stability as “de-risking” test of this new cell technology. After irradiation, a conversion efficiency of 25.4% was measured for “generation II” devices under AM0 illumination, which corresponds to a power-to-mass ratio of 2.6 W/g. The resulting power-to-mass ratio of 3.0 W/g for the bare solar cell is one of the highest published ratios. The newest solar cells (generation III) with a mass density of only 13.2 mg/cm 2 reach conversion efficiencies of 30.2% at 25☌. Several IMM3J ELO solar cells with an area of approximately 20 cm 2 from different development stages were tested under AM0 illumination. Assuming realistic charge carrier lifetime in the materials, we predict a near-term efficiency potential for the IMM3J ELO of 30.9% under AM0 illumination before and 26.7% after irradiation. The solar cell structure is optimized for maximum EOL efficiency, that is, after 1-MeV electron irradiation with a fluence of 1 × 10 15 cm −2, by means of simulations that include the irradiation induced defects in the various semiconductor alloys. The nondestructive nature of the ELO process makes multiple reuses of the GaAs substrate possible. After epitaxial growth, the inverted layer stack is metallized, with the metal serving as back-contact, back reflector and support layer for the ultra-thin solar cells before the GaAs substrate is separated by an epitaxial lift-off (ELO) process. The inverted metamorphic triple junction (IMM3J) solar cells with Ga 0.51In 0.49P/GaAs/Ga 0.73In 0.27As subcells are grown on GaAs substrates and have a total epitaxy thickness of about 10 μm. A thin, lightweight, flexible solar cell is developed that maximizes the power-to-mass ratio under AM0 illumination and has a competitive efficiency after typical high energy electron irradiation.
0 kommentar(er)
