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Design of integrated III-nitride/non-III-nitride tandem photovoltaic devices
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10.1063/1.3690907
/content/aip/journal/jap/111/5/10.1063/1.3690907
http://aip.metastore.ingenta.com/content/aip/journal/jap/111/5/10.1063/1.3690907
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Figures

Image of FIG. 1.
FIG. 1.

(Color online) EQE characteristics of a triple-junction solar cell, wherein (a) all junctions are optically thick, resulting in efficiency, η = 34.86%; (b) the thickness of the top and mid-junctions are optimized for current matching, resulting in η = 42.37%; (c) a III-N top cell is bonded to a current-matched triple-junction cell, resulting in η = 50.64%. Data columns indicate relative current values generated in each junction.

Image of FIG. 2.
FIG. 2.

(Color online) Cross-sectional schematic of a four-terminal, wafer-bonded, stacked, tandem, multi-junction photovoltaic cell. The superstrate configuration (a) retains the III-N substrate for structural support, and light is incident on the III-N substrate. The standard configuration (b) retains the non-III-N substrate for structural support, and light is incident on the III-N device layer.

Image of FIG. 3.
FIG. 3.

(Color online) Power conversion efficiency contribution of an InGaN top cell for various EQE characteristics. The minimum efficiency that the nitride top cell should contribute is the efficiency loss of the triple-junction subcell due to spectral filtering.

Image of FIG. 4.
FIG. 4.

(Color online) Maximum power conversion efficiency contribution of the InGaN top cell and the non-III-N triple junction subcell for varying InGaN absorption edge wavelength, λ N, for AM1.5 G, 1 sun illumination. The maximum efficiency of the stand-alone non-III-N triple junction device is  = 47.97%. Total efficiency saturates at λ N > 520 nm. The bandgap combination for maximum efficiency is also plotted.

Image of FIG. 5.
FIG. 5.

(Color online) Maximum power conversion efficiency contribution of the InGaN top cell and the non-III-N triple junction subcell for varying InGaN absorption edge wavelength, λ N, for AM1.5 D, 1000 suns. The maximum efficiency of the stand-alone non-III-N triple junction device is  = 57.43%. Maximum total efficiency, = 60.88%, occurs at λ N ∼ 564 nm for AM1.5 D, 1000 suns. However, is already = 60.60% at λ N ∼ 517 nm.

Image of FIG. 6.
FIG. 6.

(Color online) Maximum power conversion efficiency contribution of the InGaN top cell and the non-III-N triple junction subcell for varying InGaN absorption edge wavelength, λ N, for AM0, 1 sun. The maximum efficiency of the stand-alone non-III-N triple junction device is = 44.42%. Maximum total efficiency, = 46.32%, occurs at λ N ∼ 564 nm. At λ N ∼ 517 nm, however, is already at 46.03%.

Image of FIG. 7.
FIG. 7.

(Color online) Isoefficiency plots for an integrated III-N/non-III-N triple-junction solar cell for (a) AM1.5 G, 1 sun, (b) AM1.5 D, 1000 suns, and (c) AM0, 1 sun. The bandgaps of the mid- and bottom junctions and the thicknesses of the mid- and top junctions used for the multi-junction subcell efficiencies plotted herein are those resulting in the highest efficiencies for the given non-III-N top junction and III-N top cell bandgap combinations.

Image of FIG. 8.
FIG. 8.

(Color online) External quantum efficiency (EQE) characteristics of different InGaN solar cells. The wideband EQE characteristic of ∼70% for III-N top cell applications is also superimposed. InGaN solar cell EQE data are taken from Refs. 1, 26, and 27.

Image of FIG. 9.
FIG. 9.

(Color online) Reflection at various interfaces with and without AR coating. The AR coating used is a SiO2/Ta2O5 multilayer stack. Simulation data is generated using TFCalc (Ref. 28).

Image of FIG. 10.
FIG. 10.

(Color online) Reflection at the GaN-BCB-InGaP bonding interface with and without AR coating. The AR coatings used are 15-layer and 13-layer SiO2/Ta2O5 stacks for the GaN-BCB and BCB-InGaP interfaces, respectively. Simulation data is generated using TFCalc (Ref. 28).

Image of FIG. 11.
FIG. 11.

(Color online) Performance degradation of the maximum power conversion efficiency of the integrated InGaN/non-III-N triple junction subcell due to reflection. The efficiency of the stand-alone non-III-N triple junction device with no reflection is  = 47.97%. As the reflectance values increase, the required absorption edge wavelength, λ N, for the InGaN to compensate for the loss in the non-III-N subcell due to spectral filtering increases. At RSUB and RBOND > 2.5%, the performance of the integrated cell becomes worse than that of the stand-alone non-III-N cell.

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/content/aip/journal/jap/111/5/10.1063/1.3690907
2012-03-02
2014-04-24
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Design of integrated III-nitride/non-III-nitride tandem photovoltaic devices
http://aip.metastore.ingenta.com/content/aip/journal/jap/111/5/10.1063/1.3690907
10.1063/1.3690907
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