  Recombination through quantum dots (QDs) is a major factor that limits
efficiency of QD intermediate-band (IB) solar cells. Our proposal for a new IB
solar cell based on type-II GaSb QDs located outside the depletion region of a
GaAs p-n-junction aims to solve this problem. The important advantage of
proposed heterostructure appears due to the outside location of IB. Such IB
does not assist generation of additional leakage current flow through the
depletion region. Carriers cannot escape from outside QDs through the buffer
layer and the depletion region into GaAs substrate by tunneling because QDs are
far from the depletion layer. Only solar photon or thermal assistance may
enable electron escape from QDs. Such type-II QD IB solar cell concept promises
an efficiency enhancement relative to that of GaAs solar cells.
