Light-management is critical to thin film solar cells due to their usually limited optical absorption in the active layer. Conventional approaches involve employing separate techniques for anti-reflection and light trapping. Here, we demonstrate an embedded biomimetic nanostructure (EBN) that achieves both effects for hydrogenated amorphous silicon (a-Si:H) solar cells. The fabrication of EBNs is accomplished by patterning an index-matching silicon-nitride layer deposited on a glass substrate using polystyrene nanospheres lithography, followed by reactive ion etching. The profile of EBN is then reproduced layer by layer during the deposition of a-Si:H cells. We show that a solar cell with an optimized EBN exhibits a broadband enhanced external quantum efficiency due to both anti-reflection and light-trapping, with respect to an industrial standard cell using an Asahi U glass substrate which is mostly optimized for light trapping. Overall, the cell with an optimized EBN achieves a large short-circuit current density of 17.74 mA/cm², corresponding to a 37.63% enhancement over a flat control cell. The power conversion efficiency is also increased from 5.36% to 8.32%. Moreover, the light management enabled by the EBN remains efficient over a wide range of incident angles up to 60°, which is particularly desirable for real environments with diffused sun light. The novel patterning method is not restricted to a-Si:H solar cells, but is also widely applicable to other thin film materials.

© 2011 OSA

1. R. E. I. Schropp, and M. Zeman, Amorphous and Microcrystalline Silicon Solar Cells: Modeling, Materials, and Device Technology (Kluwer Academic Publishers, 1998).
2. D. E. Carlson and C. R. Wronski, “Amorphous silicon solar cell,” Appl. Phys. Lett. 28(11), 671–673 (1976). [CrossRef]
3. R. C. Chittick, J. H. Alexander, and H. F. Sterling, “The preparation and properties of amorphous silicon,” J. Electrochem. Soc. 116(1), 77–81 (1969). [CrossRef]
4. A. V. Shah, H. Schade, M. Vanecek, J. Meier, E. Vallat-Sauvain, N. Wyrsch, U. Kroll, C. Droz, and J. Bailat, “Thin-film Silicon Solar Cell Technology,” Prog. Photovolt. Res. Appl. 12(23), 113–142 (2004). [CrossRef]
5. R. E. I. Schropp, and M. Zeman, “Amorphous and Microcrystalline Silicon Solar Cells: Modeling, Materials, and Device Technology (Kluwer Academic Publishers, 1998).
6. J. Zhu, Z. Yu, G. F. Burkhard, C. M. Hsu, S. T. Connor, Y. Xu, Q. Wang, M. McGehee, S. Fan, and Y. Cui, “Optical absorption enhancement in amorphous silicon nanowire and nanocone arrays,” Nano Lett. 9(1), 279–282 (2009). [CrossRef]
7. J. G. Mutitu, S. Shi, C. Chen, T. Creazzo, A. Barnett, C. Honsberg, and D. W. Prather, “Thin film solar cell design based on photonic crystal and diffractive grating structures,” Opt. Express 16(19), 15238–15248 (2008). [CrossRef] [PubMed]
8. Ü. Dagkaldiran, A. Gordijn, F. Finger, H. M. Yates, P. Evans, D. W. Sheel, Z. Remes, and M. Vanecek, “Amorphous silicon solar cells made with SnO2:F TCO films deposited by atmospheric pressure CVD,” Mater. Sci. Eng. B 6, 159 (2009).
9. S. Fahr, C. Rockstuhl, and F. Lederer, “Engineering the randomness for enhanced absorption in solar cells,” Appl. Phys. Lett. 92(17), 171114 (2008). [CrossRef]
10. J. Zhu, C. M. Hsu, Z. Yu, S. Fan, and Y. Cui, “Nanodome solar cells with efficient light management and self-cleaning,” Nano Lett. 10(6), 1979–1984 (2010). [CrossRef]
11. D. G. Stavenga, S. Foletti, G. Palasantzas, and K. Arikawa, “Light on the moth-eye corneal nipple array of butterflies,” Proc. Biol. Sci. 273(1587), 661–667 (2006). [CrossRef] [PubMed]
12. A. R. Parker and H. E. Townley, “Biomimetics of photonic nanostructures,” Nat. Nanotechnol. 2(6), 347–353 (2007). [CrossRef]
13. Y. F. Huang, S. Chattopadhyay, Y. J. Jen, C. Y. Peng, T. A. Liu, Y. K. Hsu, C. L. Pan, H. C. Lo, C. H. Hsu, Y. H. Chang, C. S. Lee, K. H. Chen, and L. C. Chen, “Improved broadband and quasi-omnidirectional anti-reflection properties with biomimetic silicon nanostructures,” Nat. Nanotechnol. 2(12), 770–774 (2007). [CrossRef]
14. H. Sai, Y. Kanamori, K. Arafune, Y. Ohshita, and M. Yamaguchi, “Light trapping effect of submicron surface textures in crystalline Si solar cells,” Prog. Photovolt. Res. Appl. 15(5), 415–423 (2007). [CrossRef]
15. C. H. Chiu, P. Yu, H. C. Kuo, C. C. Chen, T. C. Lu, S. C. Wang, S. H. Hsu, Y. J. Cheng, and Y. C. Chang, “Broadband and omnidirectional antireflection employing disordered GaN nanopillars,” Opt. Express 16(12), 8748–8754 (2008). [CrossRef] [PubMed]
16. Y. Kanamori, M. Sasaki, and K. Hane, “Broadband antireflection gratings fabricated upon silicon substrates,” Opt. Lett. 24(20), 1422–1424 (1999). [CrossRef]
17. Y.-J. Lee, D. S. Ruby, D. W. Peters, B. B. McKenzie, and J. W. P. Hsu, “ZnO nanostructures as efficient antireflection layers in solar cells,” Nano Lett. 8(5), 1501–1505 (2008). [CrossRef] [PubMed]
18. M.-Y. Chiu, C.-H. Chang, M.-A. Tsai, F.-Y. Chang, and P. Yu, “Improved optical transmission and current matching of a triple-junction solar cell utilizing sub-wavelength structures,” Opt. Express 18(Suppl 3), A308–A313 (2010). [CrossRef] [PubMed]
19. M. A. Tsai, P. Yu, C. H. Chiu, H. C. Kuo, T. C. Lu, and S. H. Lin, “Self-assembled two-dimensional surface structures for beam shaping of GaN-based vertical-injection light-emitting diodes,” IEEE Photon. Technol. Lett. 22(1), 12–14 (2010). [CrossRef]
20. C. H. Chiu, P. Yu, H. C. Kuo, C. C. Chen, T. C. Lu, S. C. Wang, S. H. Hsu, Y. J. Cheng, and Y. C. Chang, “Broadband and omnidirectional antireflection employing disordered GaN nanopillars,” Opt. Express 16(12), 8748–8754 (2008). [CrossRef] [PubMed]
21. M. A. Tsai, P. C. Tseng, H. C. Chen, H. C. Kuo, and P. Yu, “Enhanced conversion efficiency of a crystalline silicon solar cell with frustum nanorod arrays,” Opt. Express 19(Suppl 1), A28–A34 (2011). [CrossRef] [PubMed]
22. Y. K. Ee, R. A. Arif, N. Tansu, P. Kumnorkaew, and J. F. Gilchrist, Enhancement of light extraction efficiency of InGaN quantum wells light emitting diodes using SiO2/polystyrene microlens arrays,” Appl. Phys. Lett. 91(22), 221107 (2007). [CrossRef]
23. Y. K. Ee, R. A. Arif, H. Tong, H. P. Zhao, J. F. Gilchrist, and N. Tansu, “Optimization of light extraction efficiency of III-nitride LEDs with self-assembled colloidal-based microlenses,” IEEE J. Sel. Top. Quantum Electron. 15(4), 1218–1225 (2009). [CrossRef]
24. Y. K. Ee, P. Kumnorkaew, R. A. Arif, H. Tong, J. F. Gilchrist, and N. Tansu, “Light extraction efficiency enhancement of InGaN quantum wells light-emitting diodes with polydimethylsiloxane concave microstructures,” Opt. Express 17(16), 13747–13757 (2009). [CrossRef] [PubMed]
25. W. Ley, E. Plescher, A. Freiburg, N. Nikolaizig, and A. Popvitch, “SUN Simulator Calibration Procedure,” in Proceedings of the Third International Symposium: Environmental Testing for Space Programmes (1997) , pp. 339–344.
26. L. Raniero, I. Ferreira, A. Pimentel, A. Goncalves, P. Canhola, E. Fortunato, and R. Martins, “Role of hydrogen plasma on electrical and optical properties of ZGO, ITO and IZO transparent and conductive coatings,” Thin Solid Films 511–512, 295–298 (2006). [CrossRef]
27. P. C. Tseng, H. C. Chen, M. A. Tsai, C.-H. Chang, H. C. Kuo, and P. Yu, “Angle-resolved characteristics of silicon photovoltaics with passivated conical-frustum nanostructures,” Sol. Energy Mater. Sol. Cells (to be published).

Appl. Phys. Lett.

• D. E. Carlson and C. R. Wronski, “Amorphous silicon solar cell,” Appl. Phys. Lett. 28(11), 671–673 (1976). [CrossRef]
• S. Fahr, C. Rockstuhl, and F. Lederer, “Engineering the randomness for enhanced absorption in solar cells,” Appl. Phys. Lett. 92(17), 171114 (2008). [CrossRef]
• Y. K. Ee, R. A. Arif, N. Tansu, P. Kumnorkaew, and J. F. Gilchrist, Enhancement of light extraction efficiency of InGaN quantum wells light emitting diodes using SiO2/polystyrene microlens arrays,” Appl. Phys. Lett. 91(22), 221107 (2007). [CrossRef]

IEEE J. Sel. Top. Quantum Electron.

• Y. K. Ee, R. A. Arif, H. Tong, H. P. Zhao, J. F. Gilchrist, and N. Tansu, “Optimization of light extraction efficiency of III-nitride LEDs with self-assembled colloidal-based microlenses,” IEEE J. Sel. Top. Quantum Electron. 15(4), 1218–1225 (2009). [CrossRef]

IEEE Photon. Technol. Lett.

• M. A. Tsai, P. Yu, C. H. Chiu, H. C. Kuo, T. C. Lu, and S. H. Lin, “Self-assembled two-dimensional surface structures for beam shaping of GaN-based vertical-injection light-emitting diodes,” IEEE Photon. Technol. Lett. 22(1), 12–14 (2010). [CrossRef]

J. Electrochem. Soc.

• R. C. Chittick, J. H. Alexander, and H. F. Sterling, “The preparation and properties of amorphous silicon,” J. Electrochem. Soc. 116(1), 77–81 (1969). [CrossRef]

Mater. Sci. Eng. B

• Ü. Dagkaldiran, A. Gordijn, F. Finger, H. M. Yates, P. Evans, D. W. Sheel, Z. Remes, and M. Vanecek, “Amorphous silicon solar cells made with SnO2:F TCO films deposited by atmospheric pressure CVD,” Mater. Sci. Eng. B 6, 159 (2009).

Nano Lett.

• J. Zhu, Z. Yu, G. F. Burkhard, C. M. Hsu, S. T. Connor, Y. Xu, Q. Wang, M. McGehee, S. Fan, and Y. Cui, “Optical absorption enhancement in amorphous silicon nanowire and nanocone arrays,” Nano Lett. 9(1), 279–282 (2009). [CrossRef]
• J. Zhu, C. M. Hsu, Z. Yu, S. Fan, and Y. Cui, “Nanodome solar cells with efficient light management and self-cleaning,” Nano Lett. 10(6), 1979–1984 (2010). [CrossRef]
• Y.-J. Lee, D. S. Ruby, D. W. Peters, B. B. McKenzie, and J. W. P. Hsu, “ZnO nanostructures as efficient antireflection layers in solar cells,” Nano Lett. 8(5), 1501–1505 (2008). [CrossRef] [PubMed]

Nat. Nanotechnol.

• A. R. Parker and H. E. Townley, “Biomimetics of photonic nanostructures,” Nat. Nanotechnol. 2(6), 347–353 (2007). [CrossRef]
• Y. F. Huang, S. Chattopadhyay, Y. J. Jen, C. Y. Peng, T. A. Liu, Y. K. Hsu, C. L. Pan, H. C. Lo, C. H. Hsu, Y. H. Chang, C. S. Lee, K. H. Chen, and L. C. Chen, “Improved broadband and quasi-omnidirectional anti-reflection properties with biomimetic silicon nanostructures,” Nat. Nanotechnol. 2(12), 770–774 (2007). [CrossRef]

Opt. Express

• M.-Y. Chiu, C.-H. Chang, M.-A. Tsai, F.-Y. Chang, and P. Yu, “Improved optical transmission and current matching of a triple-junction solar cell utilizing sub-wavelength structures,” Opt. Express 18(Suppl 3), A308–A313 (2010). [CrossRef] [PubMed]
• C. H. Chiu, P. Yu, H. C. Kuo, C. C. Chen, T. C. Lu, S. C. Wang, S. H. Hsu, Y. J. Cheng, and Y. C. Chang, “Broadband and omnidirectional antireflection employing disordered GaN nanopillars,” Opt. Express 16(12), 8748–8754 (2008). [CrossRef] [PubMed]
• J. G. Mutitu, S. Shi, C. Chen, T. Creazzo, A. Barnett, C. Honsberg, and D. W. Prather, “Thin film solar cell design based on photonic crystal and diffractive grating structures,” Opt. Express 16(19), 15238–15248 (2008). [CrossRef] [PubMed]
• C. H. Chiu, P. Yu, H. C. Kuo, C. C. Chen, T. C. Lu, S. C. Wang, S. H. Hsu, Y. J. Cheng, and Y. C. Chang, “Broadband and omnidirectional antireflection employing disordered GaN nanopillars,” Opt. Express 16(12), 8748–8754 (2008). [CrossRef] [PubMed]
• M. A. Tsai, P. C. Tseng, H. C. Chen, H. C. Kuo, and P. Yu, “Enhanced conversion efficiency of a crystalline silicon solar cell with frustum nanorod arrays,” Opt. Express 19(Suppl 1), A28–A34 (2011). [CrossRef] [PubMed]
• Y. K. Ee, P. Kumnorkaew, R. A. Arif, H. Tong, J. F. Gilchrist, and N. Tansu, “Light extraction efficiency enhancement of InGaN quantum wells light-emitting diodes with polydimethylsiloxane concave microstructures,” Opt. Express 17(16), 13747–13757 (2009). [CrossRef] [PubMed]

Opt. Lett.

• Y. Kanamori, M. Sasaki, and K. Hane, “Broadband antireflection gratings fabricated upon silicon substrates,” Opt. Lett. 24(20), 1422–1424 (1999). [CrossRef]

Proc. Biol. Sci.

• D. G. Stavenga, S. Foletti, G. Palasantzas, and K. Arikawa, “Light on the moth-eye corneal nipple array of butterflies,” Proc. Biol. Sci. 273(1587), 661–667 (2006). [CrossRef] [PubMed]

Prog. Photovolt. Res. Appl.

• H. Sai, Y. Kanamori, K. Arafune, Y. Ohshita, and M. Yamaguchi, “Light trapping effect of submicron surface textures in crystalline Si solar cells,” Prog. Photovolt. Res. Appl. 15(5), 415–423 (2007). [CrossRef]
• A. V. Shah, H. Schade, M. Vanecek, J. Meier, E. Vallat-Sauvain, N. Wyrsch, U. Kroll, C. Droz, and J. Bailat, “Thin-film Silicon Solar Cell Technology,” Prog. Photovolt. Res. Appl. 12(23), 113–142 (2004). [CrossRef]

Sol. Energy Mater. Sol. Cells

• P. C. Tseng, H. C. Chen, M. A. Tsai, C.-H. Chang, H. C. Kuo, and P. Yu, “Angle-resolved characteristics of silicon photovoltaics with passivated conical-frustum nanostructures,” Sol. Energy Mater. Sol. Cells (to be published).

Thin Solid Films

• L. Raniero, I. Ferreira, A. Pimentel, A. Goncalves, P. Canhola, E. Fortunato, and R. Martins, “Role of hydrogen plasma on electrical and optical properties of ZGO, ITO and IZO transparent and conductive coatings,” Thin Solid Films 511–512, 295–298 (2006). [CrossRef]

Other

• W. Ley, E. Plescher, A. Freiburg, N. Nikolaizig, and A. Popvitch, “SUN Simulator Calibration Procedure,” in Proceedings of the Third International Symposium: Environmental Testing for Space Programmes (1997) , pp. 339–344.
• R. E. I. Schropp, and M. Zeman, “Amorphous and Microcrystalline Silicon Solar Cells: Modeling, Materials, and Device Technology (Kluwer Academic Publishers, 1998).
• R. E. I. Schropp, and M. Zeman, Amorphous and Microcrystalline Silicon Solar Cells: Modeling, Materials, and Device Technology (Kluwer Academic Publishers, 1998).

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