TY - JOUR

T1 - Delta doping and positioning effects of type II GaSb quantum dots in GaAs solar cell

AU - James Asirvatham, Juanita Saroj

AU - Fujita, Hiromi

AU - Fernández-Delgado, N.

AU - Herrera, M.

AU - Molina, S. I.

AU - Marshall, Andrew Robert Julian

AU - Krier, Anthony

N1 - This is an Accepted Manuscript of an article published by Taylor & Francis in Materials Research Innovations on 21/01/2016, available online: http://www.tandfonline.com/10.1080/14328917.2015.1115807

PY - 2015

Y1 - 2015

N2 - GaSb quantum dot (QD) solar cell structures were grown by molecular beam epitaxy on GaAs substrates. We investigate the reduction in open-circuit voltage and study the influence of the location of QD layers and their delta doping within the solar cell. Devices with 5 layers of delta-doped QDs placed in the intrinsic, n- and p-regions of a GaAs solar cell are experimentally investigated, and the deduced values of Jsc, Voc, fill factor, efficiency (η) are compared. A trade-off is needed to minimize the Voc degradation while maximizing the short circuit current density (Jsc) enhancement due to sub-bandgap absorption. The voltage recovery is attributed to the removal of the QDs from the high-field region which reduces SRH recombination. The devices with p- or n-doped QDs placed in the flat band potential (p- or n-region) show a recovery in Jsc and Voc compared to devices with delta-doped QDs placed in the depletion region. However, there is less photocurrent arising from the absorption of sub-band gap photons. Furthermore, the long wavelength photoresponse of the n-doped QDs placed in the n-region shows a slight improvement compared to the control cell. The approach of placing QDs in the n-region of the solar cell instead of the depletion region is a possible route towards increasing the conversion efficiency of QD solar cells.

AB - GaSb quantum dot (QD) solar cell structures were grown by molecular beam epitaxy on GaAs substrates. We investigate the reduction in open-circuit voltage and study the influence of the location of QD layers and their delta doping within the solar cell. Devices with 5 layers of delta-doped QDs placed in the intrinsic, n- and p-regions of a GaAs solar cell are experimentally investigated, and the deduced values of Jsc, Voc, fill factor, efficiency (η) are compared. A trade-off is needed to minimize the Voc degradation while maximizing the short circuit current density (Jsc) enhancement due to sub-bandgap absorption. The voltage recovery is attributed to the removal of the QDs from the high-field region which reduces SRH recombination. The devices with p- or n-doped QDs placed in the flat band potential (p- or n-region) show a recovery in Jsc and Voc compared to devices with delta-doped QDs placed in the depletion region. However, there is less photocurrent arising from the absorption of sub-band gap photons. Furthermore, the long wavelength photoresponse of the n-doped QDs placed in the n-region shows a slight improvement compared to the control cell. The approach of placing QDs in the n-region of the solar cell instead of the depletion region is a possible route towards increasing the conversion efficiency of QD solar cells.

KW - Solar cells

KW - Quantum dots

KW - Molecular beam epitaxy

KW - Gallium antimonide

KW - Open-circuit voltage (Voc)

KW - Photocurrent

KW - Delta doping

KW - Photoresponse

U2 - 10.1080/14328917.2015.1115807

DO - 10.1080/14328917.2015.1115807

M3 - Journal article

VL - 19

SP - 512

EP - 516

JO - Materials Research Innovations

JF - Materials Research Innovations

SN - 1432-8917

IS - 7

ER -