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Transient Absorption for Characterization of Quantum Dot Intermediate Band Solar Cells

Published online by Cambridge University Press:  16 September 2011

Praveen Kolla
Affiliation:
South Dakota School of Mines and Technology, Rapid City, South Dakota.
Andrew Norman
Affiliation:
NREL, Golden, Colorado.
Steve Smith*
Affiliation:
South Dakota School of Mines and Technology, Rapid City, South Dakota.
*
*Corresponding Author: [email protected]
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Abstract

We use transient absorption methods to characterize the sequential two-photon absorption in a quantum-dot super-lattice based intermediate band solar cell (QD-IBSC). Using collinear, orthogonally polarized beams generated from an Optical Parametric Oscillator (OPO) at varying time delay, tuned stepwise from 1050nm to 1250nm, we use the solar cell photocurrent as a direct measure of the transient absorption by measuring the differential photo-current as a function of time delay between two energetically degenerate, 100fs pulses. For comparison, we measure the pulse autocorrelation in the same geometry using a GaAsP photodiode, where all observed photocurrent is derived from instantaneous two-photon absorption. Our measurements show that at high intensity, the measurement is dominated by instantaneous two photon absorption, with a simultaneous sequential two-photon photocurrent which persists beyond the pulse overlap. Our measurements demonstrate the method can reveal carrier dynamics in a working QD-IBSC, and their dependence on energy. The method could potentially give details of the band structure formed in the QD-IBSC. Such knowledge may benefit device development and future designs of IBSCs based on QD superlattices or alternative intermediate band materials or device structures.

Type
Research Article
Copyright
Copyright © Materials Research Society 2011

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References

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