Abstract
Silicon nanowires (NWs) could enable low-cost and efficient photovoltaics, though their performance has been limited by nonideal electrical characteristics and an inability to tune absorption properties. We overcome these limitations through controlled synthesis of a series of polymorphic core/multishell NWs with highly crystalline, hexagonally-faceted shells, and well-defined coaxial p-type/n-type (p/n) and p/intrinsic/n (p/i/n) diode junctions. Designed 200-300 nm diameter p/i/n NW diodes exhibit ultralow leakage currents of approximately 1 fA, and open-circuit voltages and fill-factors up to 0.5 V and 73%, respectively, under one-sun illumination. Single-NW wavelength-dependent photocurrent measurements reveal size-tunable optical resonances, external quantum efficiencies greater than unity, and current densities double those for silicon films of comparable thickness. In addition, finite-difference- time-domain simulations for the measured NW structures agree quantitatively with the photocurrent measurements, and demonstrate that the optical resonances are due to Fabry-Perot and whispering-gallery cavity modes supported in the high-quality faceted nanostructures. Synthetically optimized NWdevices achieve current densities of 17 mA/cm 2 and power-conversion efficiencies of 6%. Horizontal integration of multiple NWs demonstrates linear scaling of the absolute photocurrentwith number ofNWs, as well as retention of the high open-circuit voltages and short-circuit current densities measured for single NW devices. Notably, assembly of 2 NW elements into vertical stacks yields short-circuit current densities of 25 mA/cm 2 with a backside reflector, and simulations further show that such stacking represents an attractive approach for further enhancing performance with projected efficiencies of >15% for 1.2 μm thick 5 NW stacks.
| Original language | English |
|---|---|
| Pages (from-to) | 1407-1412 |
| Number of pages | 6 |
| Journal | Proceedings of the National Academy of Sciences of the United States of America |
| Volume | 109 |
| Issue number | 5 |
| DOIs | |
| Publication status | Published - 2012 Jan 31 |
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Keywords
- Nanodevices
- Nanomaterials
- Nanophotonics
- Optical nanocavities
- Solar cells
ASJC Scopus subject areas
- General
Cite this
Coaxial multishell nanowires with high-quality electronic interfaces and tunable optical cavities for ultrathin photovoltaics. / Kempa, Thomas J.; Cahoon, James F.; Kim, Sun Kyung; Day, Robert W.; Bell, David C.; Park, Hong Kyu; Lieber, Charles M.
In: Proceedings of the National Academy of Sciences of the United States of America, Vol. 109, No. 5, 31.01.2012, p. 1407-1412.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Coaxial multishell nanowires with high-quality electronic interfaces and tunable optical cavities for ultrathin photovoltaics
AU - Kempa, Thomas J.
AU - Cahoon, James F.
AU - Kim, Sun Kyung
AU - Day, Robert W.
AU - Bell, David C.
AU - Park, Hong Kyu
AU - Lieber, Charles M.
PY - 2012/1/31
Y1 - 2012/1/31
N2 - Silicon nanowires (NWs) could enable low-cost and efficient photovoltaics, though their performance has been limited by nonideal electrical characteristics and an inability to tune absorption properties. We overcome these limitations through controlled synthesis of a series of polymorphic core/multishell NWs with highly crystalline, hexagonally-faceted shells, and well-defined coaxial p-type/n-type (p/n) and p/intrinsic/n (p/i/n) diode junctions. Designed 200-300 nm diameter p/i/n NW diodes exhibit ultralow leakage currents of approximately 1 fA, and open-circuit voltages and fill-factors up to 0.5 V and 73%, respectively, under one-sun illumination. Single-NW wavelength-dependent photocurrent measurements reveal size-tunable optical resonances, external quantum efficiencies greater than unity, and current densities double those for silicon films of comparable thickness. In addition, finite-difference- time-domain simulations for the measured NW structures agree quantitatively with the photocurrent measurements, and demonstrate that the optical resonances are due to Fabry-Perot and whispering-gallery cavity modes supported in the high-quality faceted nanostructures. Synthetically optimized NWdevices achieve current densities of 17 mA/cm 2 and power-conversion efficiencies of 6%. Horizontal integration of multiple NWs demonstrates linear scaling of the absolute photocurrentwith number ofNWs, as well as retention of the high open-circuit voltages and short-circuit current densities measured for single NW devices. Notably, assembly of 2 NW elements into vertical stacks yields short-circuit current densities of 25 mA/cm 2 with a backside reflector, and simulations further show that such stacking represents an attractive approach for further enhancing performance with projected efficiencies of >15% for 1.2 μm thick 5 NW stacks.
AB - Silicon nanowires (NWs) could enable low-cost and efficient photovoltaics, though their performance has been limited by nonideal electrical characteristics and an inability to tune absorption properties. We overcome these limitations through controlled synthesis of a series of polymorphic core/multishell NWs with highly crystalline, hexagonally-faceted shells, and well-defined coaxial p-type/n-type (p/n) and p/intrinsic/n (p/i/n) diode junctions. Designed 200-300 nm diameter p/i/n NW diodes exhibit ultralow leakage currents of approximately 1 fA, and open-circuit voltages and fill-factors up to 0.5 V and 73%, respectively, under one-sun illumination. Single-NW wavelength-dependent photocurrent measurements reveal size-tunable optical resonances, external quantum efficiencies greater than unity, and current densities double those for silicon films of comparable thickness. In addition, finite-difference- time-domain simulations for the measured NW structures agree quantitatively with the photocurrent measurements, and demonstrate that the optical resonances are due to Fabry-Perot and whispering-gallery cavity modes supported in the high-quality faceted nanostructures. Synthetically optimized NWdevices achieve current densities of 17 mA/cm 2 and power-conversion efficiencies of 6%. Horizontal integration of multiple NWs demonstrates linear scaling of the absolute photocurrentwith number ofNWs, as well as retention of the high open-circuit voltages and short-circuit current densities measured for single NW devices. Notably, assembly of 2 NW elements into vertical stacks yields short-circuit current densities of 25 mA/cm 2 with a backside reflector, and simulations further show that such stacking represents an attractive approach for further enhancing performance with projected efficiencies of >15% for 1.2 μm thick 5 NW stacks.
KW - Nanodevices
KW - Nanomaterials
KW - Nanophotonics
KW - Optical nanocavities
KW - Solar cells
UR - http://www.scopus.com/inward/record.url?scp=84863115681&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84863115681&partnerID=8YFLogxK
U2 - 10.1073/pnas.1120415109
DO - 10.1073/pnas.1120415109
M3 - Article
C2 - 22307592
AN - SCOPUS:84863115681
VL - 109
SP - 1407
EP - 1412
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
SN - 0027-8424
IS - 5
ER -