title: Direct Observation of Two-Step Photon Absorption in an InAs/GaAs Single Quantum Dot for the Operation of Intermediate-Band Solar Cells.
abstract: We present the first direct observation of two-step photon absorption in an InAs/GaAs single quantum dot (QD) using photocurrent spectroscopy with two lasers. The sharp peaks of the photocurrent are shifted due to the quantum confined Stark effect, indicating that the photocurrent from a single QD is obtained. In addition, the intensity of the peaks depends on the power of the secondary laser. These results reveal the direct demonstration of the two-step photon absorption in a single QD. This is an essential result for both the fundamental operation and the realization of ultrahigh solar-electricity energy conversion in quantum dot intermediate-band solar cells.
authors.affiliation: †Institute for Nano Quantum Information Electronics and ‡Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan.|§Advanced Technology Research Laboratories, SHARP Corporation, 2613-1 Ichinomoto-cho, Tenri, Nara 632-8567, Japan.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Nozawa
authors.affiliation: †Institute for Nano Quantum Information Electronics and ‡Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Takagi
authors.affiliation: †Institute for Nano Quantum Information Electronics and ‡Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan.
authors.forename: Katsuyuki
authors.initials: K
authors.lastname: Watanabe
authors.affiliation: †Institute for Nano Quantum Information Electronics and ‡Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan.
authors.forename: Yasuhiko
authors.initials: Y
authors.lastname: Arakawa
keywords: Single quantum dot; intermediate-band solar cell; two-color photoexcitation spectroscopy; two-step photon absorption