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Research Papers

Photovoltaic Cells Based on GaSb and Ge for Solar and Thermophotovoltaic Applications

[+] Author and Article Information
V. P. Khvostikov

 Ioffe Physico-Technical Institute, 26 Polytechnicheskaya, St. Petersburg 194021, Russiavlkhv@scell.ioffe.rssi.ru

O. A. Khvostikova, P. Y. Gazaryan, S. V. Sorokina, N. S. Potapovich, A. V. Malevskaya, N. A. Kaluzhniy, M. Z. Shvarts, V. M. Andreev

 Ioffe Physico-Technical Institute, 26 Polytechnicheskaya, St. Petersburg 194021, Russia

J. Sol. Energy Eng 129(3), 291-297 (May 12, 2006) (7 pages) doi:10.1115/1.2734572 History: Received December 05, 2005; Revised May 12, 2006

In the present work, high efficient photovoltaic (PV) cells based on gallium antimonide have been developed and fabricated with the use of the liquid phase epitaxy (LPE) and diffusion from the gas phase techniques. They are intended for conversion of the infrared (IR) part of the solar spectrum into electricity by tandems of mechanically stacked cells and for conversion of the thermal radiation of emitters heated by the sunlight. On the ground of investigation of the LPE temperature regimes and the tellurium doping effect, GaSb PV cells have been fabricated with the efficiency of 6% at the concentration of 300 suns behind the single-junction GaAs top cell and of 5.6% at the same sunlight concentration of the cells behind the dual-junction GaInPGaAs structure, the substrate thickness being 100μm (the efficiency of PV cells was calculated for AM1.5D Low AOD spectrum, 1000Wm2). The rated efficiency of conversion of solar powered tungsten emitter radiation by PV cells based on gallium antimonide in a thermophotovoltaic (TPV) module appeared to be about 19%. Photovoltaic cells based on germanium with a wide-gap GaAs window grown by LPE or metalorganic chemical vapor deposition and with a p-n junction formed by means of the zinc diffusion from the gas phase have been fabricated. Ge based PV cells without a wide-gap GaAs window had the efficiency of up to 8.6% at a concentration of 150 suns. The efficiency of Ge based cells with a wide-gap GaAs window was 10.9% at the concentration of 150 suns. 4.3% efficiency Ge cells behind a single-junction GaAs top cell at the concentration of 400 suns have been also obtained. The maximum rated conversion efficiency of Ge PV cells appeared to be about 12% in the case of conversion of the tungsten emitter thermal radiation. These efficiency values for Ge based cells are among the highest.

Copyright © 2007 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Photoluminescence spectra of n-GaSb (Te) epitaxial layers obtained in different conditions of LPE: (1) substrate material; (2) epitaxy from the melt enriched with Ga; (3) epitaxy from the melt enriched with Pb; and (4) epitaxy from the melt enriched with Sb

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Figure 2

Dependence of the charge carrier concentration in n-GaSb epitaxial layers on the Te atom content in the liquid phase: (1) at 300K; and (2) at 77K

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Figure 3

Segregation coefficient of Te in GaSb as a function of the temperature: theoretical and experimental data

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Figure 4

Dependence of the charge carrier mobility on their concentration in the n-GaSb epitaxial layers at 300K and 77K at the epitaxy temperatures of 520°C (curves 1, 3) and of 400°C (curves 2, 4)

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Figure 5

Dependence of the theoretical (curves 1) and experimental (curve 2) charge carrier mobility on their concentration in the epitaxial (LPE) n-GaSb layers at the different compensation coefficient values from a=0 to a=0.9

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Figure 6

Dependence of FF on the photocurrent density: (curve 1) the first type cell (GaSb substrate with the doping level n=(2–6)∙1017cm−3, the rear n+ layer); (curve 2) the second type cell (GaSb epitaxial layer on a heavily doped n+-GaSb substrate); and (curve 3) the third type cell (GaSb substrate with the doping level n=(2–6)∙1017cm−3)

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Figure 7

Dependence of the efficiency for a PV cell based on GaSb behind the top cell based on GaAs on the sunlight illumination density: (curve 1) the first type cell (GaSb substrate with the doping level n=(2–6)∙1017cm−3, the rear n+ layer); curve 2- the second type cell (epitaxial GaSb layer on a heavily doped n+-GaSb substrate); and (curve 3) the third type cell (GaSb substrate with the doping level n=(2–6)∙1017cm−3)

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Figure 8

Spectral responses of GaSb solar cells based on “bulk” (curve 1) and LPE grown (curve 2, 3, 4) photoactive layer as it is (curve 1, 2) and under the top IR transparent GaInP∕GaAs cells with GaAs substrate thickness: 100μm (curve 3) and 310μm (curve 4)

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Figure 9

Efficiency versus sunlight concentration for a GaSb bottom cell illuminated through: (1) GaAs cell based on substrate of 450μm thick; (2) GaInP∕GaAs dual-junction cell based on GaAs substrate of 100μm thick; (3, 4) GaInP∕GaInAs dual-junction cells based on GaAs substrate 250μm and 410μm thick, correspondingly. Efficiencies of 6.05% (curve 1) and of 5.6% (curve 2) at 300 suns were achieved

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Figure 10

Internal quantum yield of germanium n-p2 and p-n (1, 3) photocells obtained with the use of different diffusants: zinc (1), antimony (2), and boron (3)

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Figure 11

Dependence of the efficiency of the PV cells based on Ge fabricated by different techniques on the sunlight concentration ratio (AM1.5D spectrum cut off at 1820nm) and on the short circuit photocurrent density: (1, 2) PV cells based on the p-Ge∕n-Ge structure; (3) PV cells based on the p-GaAs∕p-Ge∕n-Ge structure with a GaAs window grown by LPE; and (4) PV cells based on the p-GaAs∕p-Ge∕n-Ge structure with a GaAs window grown by MOCVD

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Figure 12

Dependence of the efficiency of the PV cells based on Ge behind a IR transparent cell based on GaAs (the GaAs substrate thickness was 450μm) on the sunlight concentration ratio: (1) cells based on Ge (n∼1017cm−3); (2) cells based on Ge with a LPE grown GaAs window; and (3) cells based on Ge with a MOCVD grown GaAs window

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Figure 13

Dependence of FF (curves 1, 2, 3) and Voc (curves 4, 5, 6) on the photocurrent density for the PV cells based on p-n-Ge with (curves 1, 3) and without a GaAs window (curves 2, 6)

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Figure 14

Dependence of the efficiency of the TPV cells: (1) based on GaSb; (2, 3) p-GaAs-p-n-Ge structures with a wide-band window grown by LPE (curve 3) and MOCVD (curve 2); and (4, 5) based on p-n-Ge (bulk diffused), as a function of the tungsten emitter temperature

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Figure 15

The efficiency of GaSb (curve 1) and MOCVD GaAs∕Ge (curve 2) based TPV cells assumed the 50% and 90% sub-bandgap photon reflection as a function of the tungsten emitter temperature

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