Process damage free thin-film GaAs solar cells by epitaxial liftoff with GaInP window layer

We report on process damage free thin-film GaAs cells detached from the GaAs substrates. GaAs cells grown by gas-source MBE were thinned by the epitaxial liftoff (ELO) technique. Photoluminescence spectroscopy showed a peak splitting in the band emission, indicating that a strain was induced in the thin-film cell fixed on the quartz glass substrate. The strain, however, was found not to affect the quality of the thin-film cells, based on the fact that the peak intensity was almost twice that before ELO. The thin-film GaAs cells showed no evidence of degradation in diode characteristics and spectral responses. The keys to avoiding damage on the active region of the solar cell during the thinning process are the introducing a GaInP window layer and improving the thin film process including metallization on thin film cells. These results demonstrates that the thinning and transfer processes dol-not affect the quality of the active region of the cells.