EPJ Photovoltaics 13, 25 (2022)
https://doi.org/10.1051/epjpv/2022024

Regular Article

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

¹ Fraunhofer Institute for Solar Energy Conversion ISE, Heidenhofstr. 2, 79110 Freiburg im Breisgau, Germany
² INATECH – University of Freiburg, Emmy-Noether-Straße 2, 79110 Freiburg im Breisgau, Germany
³ tf2 devices, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
⁴ Institute for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 Nijmegen, The Netherlands

^* e-mail: malte.klitzke@ise.fraunhofer.de

Received: 29 July 2022
Received in final form: 26 September 2022
Accepted: 20 October 2022
Published online: 18 November 2022

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 Ga_0.51In_0.49P/GaAs/Ga_0.73In_0.27As subcells, with 30.6% efficiency is also shown. The IMM4J solar cells consist of Al_0.05Ga_0.46In_0.49P/Al_0.14Ga_0.86As/Ga_0.89In_0.11As/Ga_0.73In_0.27As 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.