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Light-trapping enhanced thin-film III-V quantum dot solar cells fabricated by epitaxial lift-off

Cappelluti, F; Kim, D; van Eerden, M; Cédola, AP; Aho, T; Bissels, G; Elsehrawy, F; ... Guina, M; + view all (2018) Light-trapping enhanced thin-film III-V quantum dot solar cells fabricated by epitaxial lift-off. Solar Energy Materials and Solar Cells , 181 pp. 83-92. 10.1016/j.solmat.2017.12.014. Green open access

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Abstract

We report thin-film InAs/GaAs quantum dot (QD) solar cells with n−i−p+deep junction structure and planar back reflector fabricated by epitaxial lift-off (ELO) of full 3-in wafers. External quantum efficiency measurements demonstrate twofold enhancement of the QD photocurrent in the ELO QD cell compared to the wafer-based QD cell. In the GaAs wavelength range, the ELO QD cell perfectly preserves the current collection efficiency of the baseline single-junction ELO cell. We demonstrate by full-wave optical simulations that integrating a micro-patterned diffraction grating in the ELO cell rearside provides more than tenfold enhancement of the near-infrared light harvesting by QDs. Experimental results are thoroughly discussed with the help of physics-based simulations to single out the impact of QD dynamics and defects on the cell photovoltaic behavior. It is demonstrated that non radiative recombination in the QD stack is the bottleneck for the open circuit voltage (Voc) of the reported devices. More important, our theoretical calculations demonstrate that the Vocoffset of 0.3 V from the QD ground state identified by Tanabe et al., 2012, from a collection of experimental data of high quality III-V QD solar cells is a reliable – albeit conservative – metric to gauge the attainable Vocand to quantify the scope for improvement by reducing non radiative recombination. Provided that material quality issues are solved, we demonstrate – by transport and rigorous electromagnetic simulations – that light-trapping enhanced thin-film cells with twenty InAs/GaAs QD layers reach efficiency higher than 28% under unconcentrated light, ambient temperature. If photon recycling can be fully exploited, 30% efficiency is deemed to be feasible.

Type: Article
Title: Light-trapping enhanced thin-film III-V quantum dot solar cells fabricated by epitaxial lift-off
Open access status: An open access version is available from UCL Discovery
DOI: 10.1016/j.solmat.2017.12.014
Publisher version: https://doi.org/10.1016/j.solmat.2017.12.014
Language: English
Additional information: This version is the author accepted manuscript. For information on re-use, please refer to the publisher’s terms and conditions.
Keywords: Solar cell, Thin-film, Epitaxial lift-off, Quantum dot, Light-trapping
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Electronic and Electrical Eng
URI: http://discovery.ucl.ac.uk/id/eprint/10051686
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