Effects of Back-Reflectors on a-Si: H Solar Cells

AbstractPhase diagrams have been established to describe very high frequency (vhf) plasma-enhanced chemical vapor deposition (PECVD) processes for intrinsic hydrogenated silicon (Si:H) and silicon-germanium alloy (Si1-xGex:H) thin films using crystalline Si substrates that have been over-deposited with n-type amorphous Si:H (a-Si:H). The Si:H and Si1-xGex:H processes are applied for the top and middle i-layers of triple-junction a-Si:H-based n-i-p solar cells fabricated at University of Toledo. Identical n/i cell structures were co-deposited on textured Ag/ZnO back-reflectors in order to correlate the phase diagram and the performance of single-junction solar cells, the latter completed through over-deposition of the p-layer and top contact. This study has reaffirmed that the highest efficiencies for a-Si:H and a-Si1-xGex:H solar cells are obtained when the i-layers are prepared under maximal H2 dilution conditions.

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Light trapping in hydrogenated amorphous and nano-crystalline silicon thin film solar cells

MRS Proceedings ◽

10.1557/proc-1153-a13-02 ◽

2009 ◽

Vol 1153 ◽

Cited By ~ 11

Author(s):

Jeffrey Yang ◽

Baojie Yan ◽

Guozhen Yue ◽

Subhendu Guha

Keyword(s):

Stainless Steel ◽

Solar Cells ◽

Triple Junction ◽

Crystalline Silicon ◽

Light Trapping ◽

Nano Crystalline ◽

Back Reflectors ◽

Back Reflector ◽

Junction Structure ◽

Hydrogenated Amorphous

AbstractLight trapping effect in hydrogenated amorphous silicon-germanium alloy (a-SiGe:H) and nano-crystalline silicon (nc-Si:H) thin film solar cells deposited on stainless steel substrates with various back reflectors is reviewed. Structural and optical properties of the Ag/ZnO back reflectors are systematically characterized and correlated to solar cell performance, especially the enhancement in photocurrent. The light trapping method used in our current production lines employing an a-Si:H/a-SiGe:H/a-SiGe:H triple-junction structure consists of a bi-layer of Al/ZnO back reflector with relatively thin Al and ZnO layers. Such Al/ZnO back reflectors enhance the short-circuit current density, Jsc, by ˜20% compared to bare stainless steel. In the laboratory, we use Ag/ZnO back reflector for higher Jsc and efficiency. The gain in Jsc is about ˜30% for an a-SiGe:H single-junction cell used in the bottom cell of a multi-junction structure. In recent years, we have also worked on the optimization of Ag/ZnO back reflectors for nano-crystalline silicon (nc-Si:H) solar cells. We have carried out a systematic study on the effect of texture for Ag and ZnO. We found that for a thin ZnO layer, a textured Ag layer is necessary to increase Jsc, even though the parasitic loss is higher at the Ag and ZnO interface due to the textured Ag. However, a flat Ag can be used for a thick ZnO to reduce the parasitic loss, while the light scattering is provided by the textured ZnO. The gain in Jsc for nc-Si:H solar cells on Ag/ZnO back reflectors is in the range of ˜60-75% compared to cells deposited on bare stainless steel, which is much larger than the enhancement observed for a-SiGe:H cells. The highest total current density achieved in an a-Si:H/a-SiGe:H/nc-Si:H triple-junction structure on Ag/ZnO back reflector is 28.6 mA/cm2, while it is 26.9 mA/cm2 for a high efficiency a-Si:H/a-SiGe:H/a-SiGe:H triple-junction cell.

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Improvement of a-Si:H and nc-Si:H multi-junction solar cells by optimization of textured back reflectors

2009 34th IEEE Photovoltaic Specialists Conference (PVSC) ◽

10.1109/pvsc.2009.5411668 ◽

2009 ◽

Cited By ~ 2

Author(s):

Guozhen Yue ◽

Baojie Yan ◽

Laura Sivec ◽

Jessica M. Owens ◽

Sherry Hu ◽

...

Keyword(s):

Solar Cells ◽

Back Reflectors

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Plasmonic and Mie scattering in nanopatterned back reflectors for III–V-on-silicon solar cells (Conference Presentation)

Photonics for Solar Energy Systems VIII ◽

10.1117/12.2556088 ◽

2020 ◽

Author(s):

Concetto Eugenio Andrea Cordaro ◽

Nico Tucher ◽

Stefan Tabernig ◽

Hubert Hauser ◽

Oliver Höhn ◽

...

Keyword(s):

Solar Cells ◽

Mie Scattering ◽

Silicon Solar Cells ◽

Back Reflectors

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Effect of self-orderly textured back reflectors on light trapping in thin-film microcrystalline silicon solar cells

Journal of Applied Physics ◽

10.1063/1.3108689 ◽

2009 ◽

Vol 105 (9) ◽

pp. 094511 ◽

Cited By ~ 73

Keyword(s):

Thin Film ◽

Solar Cells ◽

Light Trapping ◽

Silicon Solar Cells ◽

Microcrystalline Silicon ◽

Back Reflectors

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Fabrication of Photonic Crystal based Back Reflectors for Light Management and Enhanced Absorption in Amorphous Silicon Solar Cells

MRS Proceedings ◽

10.1557/proc-1153-a07-15 ◽

2009 ◽

Vol 1153 ◽

Cited By ~ 2

Author(s):

Benjamin Curtin ◽

Rana Biswas ◽

Vikram Dalal

Keyword(s):

Solar Cells ◽

Photonic Crystal ◽

Steel Substrate ◽

Back Surface ◽

Enhanced Absorption ◽

Reference Device ◽

Back Reflectors ◽

Light Management ◽

Back Reflector ◽

Microscopy Images

AbstractPhotonic crystal based back-reflectors are an attractive solution for light management and enhancing optical absorption in thin film solar cells, without undesirable losses. We have fabricated prototype photonic crystal back-reflectors using photolithographic methods and reactive-ion etching. The photonic crystal back-reflector has a triangular lattice symmetry, a thickness of 250 nm, and a pitch of 765 nm. Scanning electron microscopy images demonstrate high quality long range periodicity. An a-Si:H solar cell device was grown on this back-reflector using standard PECVD techniques. Measurements demonstrate strong diffraction of light and high diffuse reflectance by the photonic crystal back-reflector. The photonic crystal back-reflector increases the average photon collection by ˜9% in terms of normalized external quantum efficiency, relative to a reference device on a stainless steel substrate with an Ag coated back surface.

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