Intermediate band solar cell (IBSC) is a promising concept to achieve next generation high-efficiency solar cells by producing the gain in photocurrent via two-step photon absorption while preserving the output voltage as of the host materials. Quantum dot (QD) superlattice is a widely studied candidate to implement the IB in real devices. In this paper, a missing transition from the IB to the conduction band (CB) has been investigated by applying extreme broadband photocurrent spectroscopy extended to mid-infrared (IR) region. In both direct and delta Si-doped InAs QDSCs, photocurrent signals were observed at the short-circuit condition at low temperature solely with sub-bandgap mid-IR photo-irradiation. On the other hand, in an undoped QDSC, no significant signal was obtained. Furthermore, the mid-IR signal was reduced by decreasing the modulation frequency and turned to be zero at DC detection. We ascribe this to the displacement photocurrent by the inter-subband transition of thermal equilibrium carriers in QDs.

Date Published: 16 March 2015
PDF: 6 pages
Proc. SPIE 9358, Physics, Simulation, and Photonic Engineering of Photovoltaic Devices IV, 93580V (16 March 2015); doi: 10.1117/12.2081084

Published in SPIE Proceedings Vol. 9358:
Physics, Simulation, and Photonic Engineering of Photovoltaic Devices IV
Alexandre Freundlich; Jean-François Guillemoles; Masakazu Sugiyama, Editor(s)