Implications of Redesigned, High-Radiative-Efficiency GaInP Junctions on III-V Multijunction Concentrator Solar Cells

Geisz, John F.; Steiner, Myles A.; García, Iván; Friedman, Daniel; Kurtz, Sarah

doi:10.1109/jphotov.2014.2361014

Cited by 21 publications

(21 citation statements)

References 30 publications

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“…Fig. 2 shows the emission spectra along with the EQE of a twojunction GalnP/GaAs tandem solar cell in which both junctions are rear-heterojunction devices which have been shown to have high radiative emission [19,20]. In the bottom-junction limited case (top cell over-illuminated), the bottom junction is reverse biased and gives no EL emission, but there is still measurable luminescence around the bandgap wavelength which is hence identified as the short-circuit PL contribution.…”

Section: Introductionmentioning

confidence: 99%

Improved modeling of photoluminescent and electroluminescent coupling in multijunction solar cells

Lan

Geisz

Steiner

et al. 2015

Solar Energy Materials and Solar Cells

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The performance of tandem stacks of Group III-V multijunction solar cells continues to improve rapidly, both through improved performance of the individual cells in the stack and through increase in the number of stacked cells. As the radiative efficiency of these individual cells increases, radiative coupling between the stacked cells becomes an increasingly important factor not only in cell design, but also in accurate efficiency measurement and in determining performance of cells and systems under varying spectral conditions in the field. Past modeling has concentrated on electroluminescent coupling between the cells, although photoluminescent coupling is shown to be important for cells operating near their maximum power point voltage or below or when junction defect recombination is significant. Extension of earlier models is proposed to allow this non-negligible component of luminescent coupling to be included. The refined model is validated by measurement of the closely related external emission from both single and double junction cells.

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Section: Introductionmentioning

confidence: 99%

Improved modeling of photoluminescent and electroluminescent coupling in multijunction solar cells

Lan

Geisz

Steiner

et al. 2015

Solar Energy Materials and Solar Cells

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“…This indicates that V oc can approach the value predicted in the internal radiative limit. However, the

\overset{η_{italicint}}{true}

at the maximum power point (MPP), where J rec is smaller than J sc , is generally lower than that at the OC condition . These results evidence that there is room for reduction of non‐radiative recombination losses at the MPP.…”

Section: Introductionmentioning

confidence: 93%

“…Since it is difficult to completely eliminate the optical losses, which depend on the device geometry, η int is usually used for solar cell analyses. The average η int of the total junction volume (

\overset{η_{italicint}}{true}

) depends on the recombination current density ( J rec ), and

\overset{η_{italicint}}{true}

generally increases with J rec . Previous studies have shown that a

\overset{η_{italicint}}{true}

close to 100% can be realized in the case that J rec equals the short‐circuit current density ( J sc ), i.e., it can be realized at the open‐circuit (OC) condition with output voltage V oc .…”

Section: Introductionmentioning

confidence: 99%

“…The average η int of the total junction volume ( η int ) depends on the recombination current density (J rec ), and η int generally increases with J rec . 17,23 Previous studies have shown that a η int close to 100% can be realized in the case that J rec equals the short-circuit current density (J sc ), 17,23 i.e., it can be realized at the open-circuit (OC) condition with output voltage V oc . This indicates that V oc can approach the value predicted in the internal radiative limit.…”

Section: Introductionmentioning

confidence: 99%

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Practical target values of Shockley–Read–Hall recombination rates in state‐of‐the‐art triple‐junction solar cells for realizing conversion efficiencies within 1% of the internal radiative limit

Nakamura

Imaizumi

Akiyama

et al. 2020

Progress in Photovoltaics

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In order to identify the cause of the difference between actual efficiency and the theoretical limit in state‐of‐the‐art triple‐junction solar cells, we investigate the internal luminescence efficiency in the depletion region ( ηintdep). The average internal luminescence efficiency of the whole subcell volume ( trueηitalicint¯) is obtained experimentally, and the ηintdep is deduced by numerical calculations using rate equations. We find that trueηitalicint¯ and ηintdep agree well in the low‐recombination current regime including the maximum power point. This indicates that the non‐radiative recombination loss at the maximum power point strongly depends on the recombination in the depletion region. Furthermore, we determine the actual Shockley–Read–Hall recombination coefficient in the depletion region, Adep, which is proportional to the effective density of recombination centers. Our analysis reveals the target values of Adep required for realizing conversion efficiencies that are within 1% of the internal radiative limit. The analysis also clarifies the extent of reduction of the effective density of recombination centers (in the depletion region) that is required to realize a given target efficiency.

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“…Both the frontcontact resistance and top cell sheet resistance limit the performance, as determined from transmission-line measurements. However, the sheet resistance of the top cell has been reduced from 400 to 100 Q/D by using a rear-heterojunction design with a thick emitter layer rather than a traditional front-homojunction design [8], [20]. The rear-heterojunction structure allows the full thickness of the top cell to transport carriers laterally.…”

Section: A Concentration Performancementioning

confidence: 99%

Quadruple-Junction Inverted Metamorphic Concentrator Devices

Geisz

García

Steiner

et al. 2015

IEEE J. Photovoltaics

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110

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Abstract-We present results for quadruple-junction inverted metamorphic (4J-IMM) devices under the concentrated direct spectrum and analyze the present limitations to performance. The devices integrate lattice-matched subcells with rear heterojunctions, as well as lattice-mismatched subcells with low threading dislocation density. To interconnect the subcells, thermally stable lattice-matched tunnel junctions are used, as well as a metamorphic GaAsSb/GalnAs tunnel junction between the lattice-mismatched subcells. A broadband antireflection coating is used, as well as a front metal grid designed for high concentration operation. The best device has a peak efficiency of (43.8 ± 2.2)% at 327-sun concentration, as measured with a spectrally adjustable flash simulator, and maintains an efficiency of (42.9 ± 2.1)% at 869 suns, which is the highest concentration measured. The V oc increases from 3.445 V at 1-sun to 4.10 V at 327-sun concentration, which indicates high material quality in all of the subcells. The subcell voltages are analyzed using optical modeling, and the present device limitations and pathways to improvement are discussed. Although further improvements are possible, the 4 J-IMM structure is clearly capable of very high efficiency at concentration, despite the complications arising from utilizing lattice-mismatched subcells.

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Implications of Redesigned, High-Radiative-Efficiency GaInP Junctions on III-V Multijunction Concentrator Solar Cells

Cited by 21 publications

References 30 publications

Improved modeling of photoluminescent and electroluminescent coupling in multijunction solar cells

Improved modeling of photoluminescent and electroluminescent coupling in multijunction solar cells

Practical target values of Shockley–Read–Hall recombination rates in state‐of‐the‐art triple‐junction solar cells for realizing conversion efficiencies within 1% of the internal radiative limit

Quadruple-Junction Inverted Metamorphic Concentrator Devices

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