Flexible high-efficiency III-V multijunction solar cells are being developed for use in unmanned Aerial Vehicles ( UAVs) , wearable devices and space applications. The solar cell epitaxial layers are grown on GaAs substrate by metalorganic chemical vapor deposition ( MOCVD) and then are transferred to flexible substrates by coldbonding and epitaxial lift-off process ( ELO) . Through the design of ELO apparatus and a large number of experiments on the optimal parameter, GaAs solar cell structure can be effectively separated from 4-inch GaAs wafer without defects and degradation in performance. Recently, 30 cm2 large area flexible GaInP/GaAs/In GaAs 3-junciton solar cells on 50 μm polyimide film achieved a 1-sun, AM0 conversion efficiency of 31. 5% with an open-circuit-voltage of 3. 01 V, a short-circuit current-density of 16. 8 mA/cm2, and a fill factor of 0. 845. By using the very light PI substrate, the unit weight of the solar cell is only 168. 5 g/m2 and the specific power is up to 2 530 W/kg.