InGaP/GaAs/Ge triple-junction solar cell with a thinned germanium substrate

The creating problems of lightweight flexible InGaP/GaAs/Ge solar cells with a thinned germanium substrate and approaches for their solution are discussed. Design of a lightweight flexible solar cell with a Ge substrate thinned to 40 $\times$ 80 mm has been implemented, based on 40 mm by 80 mm standard photovoltaic cell with anti-radiation glass 120 $\mu$m thick. Specific weight and ultimate bending radius of the experimental sample was $\sim$0.6 kg/m$^2$ and – $\sim$54 mm respectively. It efficiency for AM0 spectrum at the temperature of 28$^\circ$C is 27.6% with a fill factor of $\sim$83.8%. It has been shown that germanium surface passivity by means several silicon atom layers deposited from an atomic flux at temperatures below 80$^\circ$C reduces the back surface recombination.