Ultra-lightweight and flexible inverted metamorphic four junction solar cells for space applications

Abstract

In this work an inverted metamorphic four junction (IMM4J) solar cell with 30.9% conversion efficiency in beginning of life conditions under the AM0 (1367 W/m2) spectrum is presented. Additionally, our newest improved IMM3J cell, consisting of Ga0.51In0.49P/GaAs/Ga0.73In0.27As subcells, with 30.6% efficiency is also shown. The IMM4J solar cells consist of Al0.05Ga0.46In0.49P/Al0.14Ga0.86As/Ga0.89In0.11As/Ga0.73In0.27As subcells and are epitaxially grown by metal organic vapor phase epitaxy (MOVPE) on a GaAs substrate. These IMM solar cells achieve power-to-mass ratios of 3 W/g or more, which is more than three times higher than standard germanium based triple or four junction space solar cells. The losses in comparison to the simulated near-term potential efficiency of 33.8% for the IMM4J are analyzed in detail. Furthermore, the irradiation behavior for 1 MeV electron fluences of 1 × 1014 e−/cm2 and 2.5 × 1014 e−/cm2 for the IMM4J cells was investigated. A roadmap to further develop this concept towards an IMM5J with a realistic begin of life (BOL) efficiency potential of 35.9% under AM0 is presented.

Sheet Resistance Optimization in (Al)GaInP Solar Cells for Concentrator Quadruple–Junction Solar Cells

“…[ 21 ] The electrical part in this model considers charge carrier transport, band‐to‐band tunnel mechanisms, and recombination processes, while the optical model is based on the transfer–matrix method. [ 22 ] The basic material properties of GaAs, AlGaAs, and lattice matched AlGaInP were sourced from prior research, [ 23 ] while the optical properties of the ternary III–V materials with changing compositions were obtained using a morphing algorithm that ensures Kramers–Kronig consistency of the dielectric function. [ 24 ] The same morphing was applied to create optical absorption data of AlGaInP lattice matched to GaAs with bandgaps not exceeding 2.00 eV, in this case based on absorption data obtained by ellipsometry measurements from three 2 μm thick AlGaInP samples lattice matched to GaAs featuring bandgap energies of 1.90, 1.95, and 2.00 eV.…”