Abstract
A type II GaSb quantum ring solar cell is fabricated and measured under the concentrated sunlight. The external quantum efficiency confirms the extended absorption from the quantum rings at long wavelength coinciding with the photoluminescence results. The short-circuit current of the quantum ring devices is 5.1% to 9.9% more than the GaAs reference's under various concentrations. While the quantum ring solar cell does not exceed its GaAs counterpart in efficiency under one-sun, the recovery of the open-circuit voltages at higher concentration helps to reverse the situation. A slightly higher efficiency (10.31% vs. 10.29%) is reported for the quantum ring device against the GaAs one.
Highlights
Since last decades, due to the diminishing reserve of fossil fuel and the concerns of global warming, the need to develop alternative energy sources becomes great
The quantum scale structure, such as quantum dots (QDs) or quantum rings (QRs) [3,4], can construct an extra absorptive transition by introducing an intermediate band (IB) within the band gap of the host material. This intermediate band solar cell (IBSC) allows the extra electron-hole pairs generated from the two inter-band transitions [2], and the power conversion efficiency (PCE) of the device can surpass the SQ limit
As can be seen from the figure, the one-sun VOC reduction is still severe and the PCE of the QR device suffers from this fact
Summary
Due to the diminishing reserve of fossil fuel and the concerns of global warming, the need to develop alternative energy sources becomes great. The quantum scale structure, such as quantum dots (QDs) or quantum rings (QRs) [3,4], can construct an extra absorptive transition by introducing an intermediate band (IB) within the band gap of the host material This intermediate band solar cell (IBSC) allows the extra electron-hole pairs generated from the two inter-band transitions [2], and the PCE of the device can surpass the SQ limit. Since its first introduction in 1997, many attempts to realize such designs have been failed due to serious open-circuit voltage (VOC) reduction of the devices This drop of VOC, accompanied with limited increase of short-circuit current (JSC), is the main culprit that makes the PCEs of quantum structure embedded solar cells falling behind their single band gap counterparts [5,6].
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