Type-II Quantum Dots for Application to Photon Ratchet Intermediate Band Solar Cells

In intermediate band solar cells (IBSCs), long photo-carrier lifetime in IB is indispensable to obtain appropriate carrier filling ratio in IB and achieve efficient twostep photon absorption. In this paper, type-II quantum dot (QD) heterostructures, electron-confinement InGaAs/GaAsSb QDSC and hole-confinement GaSb/GaAs QDSC, have been investigated as candidates for photon ratchet IBSCs. Fourier transform infrared (FTIR) photocurrent spectroscopy with absolute calibration revealed that the quantum efficiency was ~10
^-5
for IR photon absorption in QDSCs at 9 K. Furthermore, higher operation temperature was determined in type-II QDSCs, which is a more desirable feature as photon ratchet IBSCs.