title: Control of hot-carrier relaxation for realizing ideal quantum-dot intermediate-band solar cells.
abstract: For intermediate-band solar cells, the broad absorption spectrum of quantum dots (QDs) offers a favorable conversion efficiency, and photocurrent generation via efficient two-step two-photon-absorption (TS-TPA) in QDs is essential for realizing high-performance solar cells. In the last decade, many works were dedicated to improve the TS-TPA efficiency by modifying the QD itself, however, the obtained results are far from the requirements for practical applications. To reveal the mechanisms behind the low TS-TPA efficiency in QDs, we report here on two- and three-beam photocurrent measurements of InAs quantum structures embedded in AlGaAs. Comparison of two- and three-beam photocurrent spectra obtained by subbandgap excitation reveals that the QD TS-TPA efficiency is improved significantly by suppressing the relaxation of hot TS-TPA carriers to unoccupied shallow InAs quantum structure states.
authors.affiliation: 1] Institute for Chemical Research, Kyoto University, Uji, Kyoto, 611-0011 Japan [2] Japan Science and Technology Agency, CREST, Uji, Kyoto, 611-0011 Japan.
authors.forename: David M
authors.initials: DM
authors.lastname: Tex
authors.affiliation: Toyota Technological Institute, Nagoya, Aichi, 468-8511 Japan.
authors.forename: Itaru
authors.initials: I
authors.lastname: Kamiya
authors.affiliation: 1] Institute for Chemical Research, Kyoto University, Uji, Kyoto, 611-0011 Japan [2] Japan Science and Technology Agency, CREST, Uji, Kyoto, 611-0011 Japan.
authors.forename: Yoshihiko
authors.initials: Y
authors.lastname: Kanemitsu