Abstract
Strain-free GaAs/Al0.33Ga0.67As quantum rings are fabricated by droplet epitaxy. Both photoresponse and photoluminescence spectra confirm optical transitions in quantum rings, suggesting that droplet epitaxial nanomaterials are applicable to intermediate band solar cells. The effects of post-growth annealing on the quantum ring solar cells are investigated, and the optical properties of the solar cells with and without thermal treatment are characterized by photoluminescence technique. Rapid thermal annealing treatment has resulted in the significant improvement of material quality, which can be served as a standard process for quantum structure solar cells grown by droplet epitaxy.
Highlights
Since the proposal of intermediate band concept for high-efficiency solar cell, great efforts have been devoted to intermediate band solar cells (IBSCs)
Strain-free quantum ring solar cell is evidenced by the reciprocal space mapping (RSM) patterns
The IBSC is intended to increase the voltage at the expense of some of the sub-bandgap current because some of the intermediate band states are filled with electrons preventing transitions from the valence band to these filled intermediate band states [14]
Summary
Since the proposal of intermediate band concept for high-efficiency solar cell, great efforts have been devoted to intermediate band solar cells (IBSCs). Several approaches have been taken to achieve IBSCs, such as quantum dots (QDs) and impurity bands [2]. Among these approaches, most of the current studies on IBSCs have been focused on QDs, and prototype QDIBSCs have been demonstrated [3,4]. The intermediate band impact on the cell performance is still marginal, mainly due to the high recombination rate in strongly confined QDs and low absorption volume of QDs
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