  We propose a new intermediate band GaAs solar cell comprising an AlxGa1-xAs
absorber with built-in GaSb type-II quantum dots (QDs) [a gradual AlxGa1-xAs
absorber with built-in AlyGa1-ySb QDs (0<x=y<0.40) as a variant] separated from
the depletion region. We study the modification of the band alignment at
type-II interface by two-photon absorption of concentrated sunlight. Our
calculation shows that photogenerated carriers produce localized exciton-like
electron-hole pairs spatially separated at QDs. Local field of such pairs may
essentially modify potential barrier surrounding QDs, increase recombination
lifetime of mobile carriers and additional photocurrent generated by twophoton
absorption. Concentration of about 300-sun pushes by 15% up the conversion
efficiency as compared to the efficiency of the reference single junction GaAs
solar cell without QDs.
