Kechiantz A., Afanasev A., Lazzari J.-L.
The George Washington University, US
Keywords: GaAs/GaSb, intermediate band, quantum dot, solar cell
Experiments have shown that extrinsic intermediate band (IB) states, for instance, formed by artificial quantum dots (QDs), located in the depletion region participate in electron-hole recombination. This facilitates dramatically the dark current and reduces the open circuit voltage of IB solar cells. On the other hand, spatial separation of IB-states from the depletion region adds more flexibility for the cell design, eliminates dark current leakage through IB-states, and limits recombination through IB-states. The later enables generation of additional photocurrent by two-photon resonant absorption of concentrated sunlight in such QDs. In this report we present a model of a new GaAs IB solar cell with strained GaSb type-II QDs spatially separated from the depletion region into the p-doped part of the cell. We use continuity equations enforced by the detailed balance principle and non-radiative recombination through IB-states to calculate both photocurrents and efficiency of the cell. Our calculation shows that the newly proposed design may increase efficiency of GaAs solar cells from 30% to 50% in response to concentration of sunlight from 1-sun to 500-sun. Noteworthy, though non-radiative recombination in QDs degrades the efficiency, it is still above the Shockley-Queisser limit by 5% to 10%.
Journal: TechConnect Briefs
Volume: Technical Proceedings of the 2013 Clean Technology Conference and Trade Show
Published: May 12, 2013
Pages: 88 - 91
Industry sector: Energy & Sustainability
Topic: Solar Technologies
ISBN: 978-1-4822-0594-7