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(a) Schematic band diagram of a cascaded interband/ISB TPV active material under short-circuit conditions. (b) Cross-sectional view of a possible device geometry based on this material.
-valley conduction-band lineup of two adjacent stages based on the QC2 design in Table I and squared envelope functions of the relevant bound states. The processes of photon absorption and photocarrier collection are illustrated by the vertical and diagonal arrows, respectively. Inset: normalized ISB absorption spectra of the four QC structures in Table I. The dashed curve is the radiated intensity spectrum (per unit photon energy) of a blackbody source at 1300 K. The gray line near the horizontal axis indicates the absorption band of the junction.
(a) Total current density vs voltage for the junction and for the four QC structures in Table I in the presence of 1300–K blackbody radiation. (b) Total current density vs combined voltage for the cascaded interband/ISB device comprising the individual junctions of (a) (dashed line) and corresponding output power density vs (solid line).
Layer thicknesses of the QC structures designed in this work in units of Å, starting from the coupled-QW absorption region and moving in the direction of the photocurrent. The bold numbers correspond to the barriers and the underlined numbers indicate the -doped layers, with the doping density specified in multiples of by the subsequent number in parentheses.
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