16 March 2015 Extreme broadband photocurrent spectroscopy on InAs quantum dot solar cells
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Abstract
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.
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R. Tamaki, R. Tamaki, Y. Shoji, Y. Shoji, S. Naitoh, S. Naitoh, Y. Okada, Y. Okada, K. Miyano, K. Miyano, } "Extreme broadband photocurrent spectroscopy on InAs quantum dot solar cells", Proc. SPIE 9358, Physics, Simulation, and Photonic Engineering of Photovoltaic Devices IV, 93580V (16 March 2015); doi: 10.1117/12.2081084; https://doi.org/10.1117/12.2081084
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