Enhancement of current collection in epitaxial lift-off InAs/GaAs quantum dot thin film solar cell and concentrated photovoltaic study

We report the fabrication of a thin film InAs/GaAs quantum dot solar cell (QD cell) by applying epitaxial lift-off (ELO) approach to the GaAs substrate. Except the enhanced sub-GaAs bandgap current collection (~0.16mA/cm²) from 900nm and beyond, we confirmed significant current collection enhancement (~0.91mA/cm²) in ELO-InAs QD cell within the wavelength range of 700nm~900nm. We also confirmed the ELO induced resonance cavity effect is able to increase the solar cell efficiency by increasing both the short circuit current and open voltage. The electric field intensity of the resonance cavity formed in the ELO film between the Au back reflector and the GaAs front contact layer was analyzed in detail by finite-differential time-domain (FDTD) simulation. In addition we performed concentrate photovoltaic study and analyzed the effect of intermediates states on the open voltage under varied concentrated light intensity for the ELO-InAs QD cell.