Absorption Enhancement in inGaAsP/InGaP Quantum Well Solar Cells

InGaAsP/lnGaP quantum well (QW) structure is a potential candidate for subcells in next-generation multijunction solar cells because of its tunable bandgap (1.5-1.8 eV). However, the insufficient light absorption in the QWs has previously limited the sub-bandgap quantum efficiency (QE) to less than 25%. We report on the development of InGaAsP/InGaP superlattice solar cell with improved sub-bandgap QE exceeding 75% and bandgap-voltage offset of 0.40 V. The enhancements were accomplished by reducing the background doping in the QW region, monitoring the stress evolution during growth, modifying the QW design to grow thicker wells and processing the devices with optical reflector to enhance light absorption.