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The angle dependent transmission of light trapping transparent electrodes is investigated. The electrodes consist of triangular metallic wire arrays embedded in a dielectric cover layer. Normal incidence illumination of the structure produces light trapping via total internal reflection, virtually eliminating all shadowing losses. It is found that varying the external angle of incidence can affect the light trapping efficiency ηLTdue to partial loss of internal reflection and increased interaction with neighboring wires. Despite these effects, a judicious selection of geometry and materials can reduce shadowing losses by more than 85% over a surprisingly large angular range of 120°. It is demonstrated that the angle-averaged shadowing losses in an encapsulated silicon solar cell under illumination with unpolarized light can be reduced by more than a factor of two for incident angles between −60° and +60° off-normal across the entire AM1.5 solar spectrum.
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Scale dependent performance of metallic light-trapping transparent electrodes
The optical and electrical performance of light trapping metallic electrodes is investigated. Reflection losses from metallic contacts are shown to be dramatically reduced compared to standard metallic contacts by leveraging total internal reflection at the surface of an added dielectric cover layer. Triangular wire arrays are shown to exhibit increased performance with increasing size, whereas cylindrical wires continue to exhibit diffractive losses as their size is increased. These trends are successfully correlated with radiation patterns from individual metallic wires. Triangular metallic electrodes with a metal areal coverage of 25% are shown to enable a polarization-averaged transmittance of >90% across the wavelength range 0.46-1.1 µm for an electrode width of 2 µm, with a peak transmission of 97%, a degree of polarization of <0.2%, and a sheet resistance of 0.35 Ω/sq. A new figure of merit is introduced to evaluate the light trapping potential of surface-shaped electrodes.
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- Award ID(s):
- 1650002
- PAR ID:
- 10158401
- Publisher / Repository:
- Optical Society of America
- Date Published:
- Journal Name:
- Optics Express
- Volume:
- 28
- Issue:
- 12
- ISSN:
- 1094-4087; OPEXFF
- Format(s):
- Medium: X Size: Article No. 18112
- Size(s):
- Article No. 18112
- Sponsoring Org:
- National Science Foundation
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