AM0 power-to-mass ratios vs. efficiencies plot of the IMM4J and IMM3J in comparison to commercial available solar cells. 1 MeV electron irradiation fluences in e^–/cm⁻² are labelled on the symbols to show the degeneration of each cell. For the latest generation of IMM3J are unfortunately no irradiation results available yet. The 4G32C from Azur [5] and the XTE-SF from Spectrolab [6] are based on thinned Germanium substrates whereas the cells from Sharp [10] and MicroLink [22] are IMM3J based solar cells. The IMM based solar cells have a more than three times higher power-to-mass ratio in comparison to the thinned Germanium based devices. The IMM‑α from Solaero [7] is an IMM based solar cell but permanently bonded to a robust substrate and therefore not as lightweight as the other IMM based cells. The ISE/tf2 simulation target assumes an areal mass density of 11.27 mg/cm² (as for the Gen IV IMM3J) and the realistic efficiency potential of 35.9% of the IMM4J design with a bandgap spread from 2.10 eV to 1.00 eV.