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Discrete-contact nanowire photovoltaics
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10.1063/1.4826361
/content/aip/journal/jap/114/17/10.1063/1.4826361
http://aip.metastore.ingenta.com/content/aip/journal/jap/114/17/10.1063/1.4826361

Figures

Image of FIG. 1.
FIG. 1.

Cross-sectional view of select semiconductor photovoltaic designs under illumination. (a) A nanowire solar cell featuring a conformal and uniform contact. The terms and denote the nanowire height and radius, respectively. (b) A planar point-contact solar cell featuring discrete, ohmic-selective contacts on the backside. The term denotes the wafer thickness. (c) A nanowire solar cell featuring a series of discrete, ohmic-selective contacts. The terms and are as in (a) and Δ is the contact width. Blue and red coloring denote regions where electrons and holes are collected, respectively. Gray coloring indicates regions where the semiconductor has no added dopants. Not drawn to scale.

Image of FIG. 2.
FIG. 2.

Energy band diagram illustrating either (top) doped or (bottom) undoped ohmic-selective contacts. In doped ohmic-selective contacts, a thin, degenerately doped contact region results in an electric field that imparts carrier selectivity. In undoped ohmic-selective contacts, the relative magnitudes of the electron or hole transmission velocities ( or , respectively) dictate the contact carrier selectivity.

Image of FIG. 3.
FIG. 3.

Simulation results for a nanowire solar cell featuring a series of discrete, doped, and ohmic-selective contacts as a function of contact width. (a) Internal quantum yield-potential (Ф–) responses for a nanowire featuring ten dopant-diffused alternating hole- and electron-selective contacts with widths ranging from 20 nm to 4500 nm. (b) Photovoltage at open circuit ( ) values as a function of ohmic-selective contact width. (c) Internal energy conversion efficiency (η) as a function of ohmic-selective contact width. The dashed horizontal line indicates the thermodynamic limit for η. Major simulation parameters are  = 50 m,  = 100 nm,  = 1012 cm−3,  = 5 × 10−4 s,  = 10−4 cm s−1,  = 100× AM 1.5. Additional simulation parameters were set to default values given in Table S2 in the supporting information.

Image of FIG. 4.
FIG. 4.

Cross sectional view of the recombination processes within a nanowire solar cell (a)–(c) with Δ  = 20 nm and (d)–(f) with Δ  = 2000 nm operating at . (a) and (d) Auger recombination, . (b) and (e) Shockley-Read-Hall recombination, . (c) and (f) Radiative recombination, . Major simulation parameters are  = 50 m,  = 100 nm,  = 1012 cm−3,  = 5 × 10−4 s,  = 10−4 cm s−1,  = 100× AM 1.5. Additional simulation parameters were set to default values given in Table S2 in the supporting information.

Image of FIG. 5.
FIG. 5.

Simulation results for a nanowire solar cell featuring a series of discrete, doped, and ohmic-selective contacts as a function of nanowire radius. (a) Internal quantum yield-potential (Ф–) responses for a nanowire doped at  = 1012 cm−3 featuring ten dopant-diffused alternating hole- and electron-selective contacts with radii ranging from 20 nm to 5000 nm. (b) Photovoltage ( ) values as a function of nanowire radius. (c) Internal energy conversion efficiency (η) as a function of nanowire radius. The dashed horizontal line indicates the thermodynamic limit for η. Major simulation parameters are  = 50 m,  = 100 nm, Δ = 20 nm,  = 1012 cm−3,  = 5 × 10−4 s,  = 10−4 cm s−1,  = 100× AM 1.5. Additional simulation parameters were set to default values given in Table S2 in the supporting information.

Image of FIG. 6.
FIG. 6.

Comparison of the modeled responses for a (a)–(c) planar and a (d)–(f) nanowire solar cell with discrete, doped, and ohmic–selective contacts as a function of the surface recombination velocity, . (a) Internal quantum yield-potential (Ф–) response for a planar solar cell with discrete (point) ohmic-selective contacts,  = 50 m and ranging between 104 and 10−1 cm s−1. (b) The photovoltage ( ) values from (a) as a function of . (c) The internal energy conversion efficiency (η) as a function of . The dashed horizontal line indicates the thermodynamic limit for η. (d)Internal quantum yield-potential (Ф–) response for a nanowire solar cell with discrete, ring ohmic-selective contacts,  = 50 m and ranging between 104 and 10−1 cm s−1. (e) The photovoltage ( ) values from (d) as a function of . (f) The internal energy conversion efficiency (η) as a function of . The dashed horizontal line indicates the thermodynamic limit for η. Major simulation parameters are  = 50 m,  = 100 nm, Δ = 20 nm, τ = 5 × 10−4 s,  = 100× AM 1.5. Additional simulation parameters were set to default values given in Tables S2 and S5 in the supporting information.

Image of FIG. 7.
FIG. 7.

Comparison of the modeled responses for (a)–(c) a planar and (d)–(f) a nanowire solar cell with discrete, doped, and ohmic-selective contacts as a function of the bulk Shockley-Read-Hall carrier lifetime. (a) Internal quantum yield-potential (Ф–) response for a planar solar cell with discrete (point) ohmic-selective contacts,  = 50 m and ranging between 10−2 and 10−6 cm s−1. (b) The photovoltage ( ) values from (a) as a function of . (c) The internal energy conversion efficiency (η) from the curves in (a) as a function of . The dashed horizontal line indicates the thermodynamic limit for η. (d) Internal quantum yield-potential (Ф-) response for a nanowire solar cell with discrete, ring ohmic-selective contacts,  = 50 m and ranging between 10−2 and 10−12 cm s−1. (e) The photovoltage ( ) values from (d) as a function of and different numbers of ohmic-selective contacts. (f) The internal energy conversion efficiency (η) as a function of and different numbers of ohmic-selective contacts. The dashed horizontal line indicates the thermodynamic limit forη. Major simulation parameters are  = 50 m,  = 100 nm, Δ = 20 nm,  = 10−4 cm s−1,  = 100× AM 1.5. Additional simulation parameters were set to default values given in Tables S2 and S5 in the supporting information.

Image of FIG. 8.
FIG. 8.

Simulation results for nanowire solar cells operating under 100× AM 1.5 illumination. (a) Internal quantum yield-potential responses for nanowire solar cells featuring a conformal and uniform Schottky contact (1.0 eV barrier height) and either ()  = 1012 cm−3 or ()  = 1017 cm−3. (b) Internal quantum yield-potential responses for a nanowire solar cell featuring 10 doped, ohmic-selective contacts with  = 1012 cm−3. (c)–(e) Cross sectional view of the internal electric field within the three nanowire solar cells in (a) and (b). Major simulation parameters: radius = 200 nm, Δ = 20 nm (discrete-contact devices), τ = 5 × 10−4 s,  = 10−4 s. Additional simulation details are given in Tables S2 and S3 in the supporting information.

Image of FIG. 9.
FIG. 9.

Internal quantum yield-potential responses for discrete contact nanowire solar cells operating under (dashed line) 1× AM 1.5 illumination and (solid line) 100 × AM 1.5 illumination and featuring 72 evenly spaced contacts with Δ = 20 nm. Other major simulation parameters:  = 3 × 1013 cm−3,  = 100 nm, τ = 10−8s,  =   = 1 cm2 V−1 s−1, and  = 5 cm s−1.

Image of FIG. 10.
FIG. 10.

Simulation results for a nanowire solar cell featuring a series of discrete, undoped, and ohmic-selective contacts as a function of the relative ratio, γ, of the electron or hole transmission velocities. (a) Internal quantum yield-potential responses for a nanowire featuring 10 dopant-diffused alternating hole- and electron-selective contacts with γ ranging from 102 to 108. (b) Photovoltage ( ) values as a function of γ. (c) Internal energy conversion efficiency (η) as a function of γ. The dashed horizontal line indicates the thermodynamic limit for η. Major simulation parameters:  = 100 nm, Δ = 20 nm,  = 1012 cm−3,  = 5 × 10−4 s,  = 10−4 cm s−1,  = 100× AM 1.5. Additional simulation parameters were set to default values and are given in Table S4 in the supporting information.

Tables

Generic image for table
Table I.

Summary of important terms.

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/content/aip/journal/jap/114/17/10.1063/1.4826361
2013-11-01
2014-04-20
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Discrete-contact nanowire photovoltaics
http://aip.metastore.ingenta.com/content/aip/journal/jap/114/17/10.1063/1.4826361
10.1063/1.4826361
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