Spectral Selective Coatings Literature Review: Difference between revisions

Fundamentals of Semiconductors/PV

${\displaystyle e=mc^{2}}$

The following equations came from Solar Cells by Martin E. Green

pg 41 Reflection ${\displaystyle R={\frac {({\hat {n}}-1)^{2}+{\hat {k}}^{2}}{({\hat {n}}+1)^{2}+{\hat {k}}^{2}}}}$

Where:

• ${\displaystyle {\hat {n}}}$ is the real part of the index of refraction
• ${\displaystyle {\hat {k}}}$ is the imaginary part of the index of refraction
• Index of Refraction ${\displaystyle {\hat {n_{c}}}={\hat {n}}-i{\hat {k}}}$

Note: Transmission is T = 1 - R

Absorption of Light

Absorbed light at a distance into the semiconductor

Intensity of light = I

${\displaystyle I=I(x_{o})exp(-\alpha (x-x_{o}))}$

• ${\displaystyle \alpha ={\frac {4\pi f{\hat {k}}}{c}}}$

Note:

• ${\displaystyle \lambda ={\frac {c}{f}}}$

Math Equation Help in Wiki

http://en.wikipedia.org/wiki/Help:Displaying_a_formula

Other Wiki Basics

http://www.appropedia.org/Help:Contents

Direct Band Gap Semiconductor

${\displaystyle hf=E_{f}-E_{i}}$

${\displaystyle \alpha (hf)=A(hf-E_{g})^{1/2}}$

Where

• ${\displaystyle E_{f}}$ Final energy state
• ${\displaystyle E_{i}}$ Initial energy state
• ${\displaystyle E_{g}}$ Band Gap Energy
• A is a constant with a value of 2E4 when alpha is expressed in ${\displaystyle cm^{(}-1)}$ and hf and ${\displaystyle E_{g}}$ is in eV.

Indirect Band Gap Semiconductor

${\displaystyle hf=E_{g}-E_{p}}$

${\displaystyle \alpha (hf,T)=\sum _{m=1,2n=1,2}A_{ij}({\frac {(hf-E_{gn}(T)+E_{pm})^{2}}{exp(E_{pm}/kT)-1}}+{\frac {(hf-E_{gn}(T)-E_{pm})^{2}}{1-exp(-E_{pm}/kT)}})+A_{d}(hf-E_{gd}(T))^{1/2}}$

Where

• ${\displaystyle E_{p}}$ is energy of an absorbed phonon with the required momentum

The values can be found in Table 3.1 page 49 for Silicon

Helpful Papers

[1] Limits to the Efficiency of Silicon Multilayer Thin Film Solar CellsS.R. Wenham, M.A. Green, S. Edmiston, P. Campbell, L. Koschier, C.B. Honsberg, A.B. Sproul, D. Thorpe, Z. Shi and G. Heiser. Solar Energy Materials and Solar Cells. Volumes 41-42, June 1996, Pages 3-17

This article is a detailed report on silicon multilayer multijunction thin film (MMTF) solar cells. The article talks about the performance of multilayer solar cells, quantum efficiencies, resistive losses, open circuit voltage, tolerance to grain boundaries, junction recombination and limits to efficiency. By injecting carriers between parallel layers the MMTF are ablilty to minise lateral resistance losses. It was found through testing that the efficiency was about 15%.

[2]Solar Collector Overheating Protection M. Slaman and R. Griessen. Solar Energy. Volume 83, Issue 7, Pages 982-987 The article is about reducing the about of light interacting with the PV panel to reduce the amount of heat generated by the PV panel. They use a primatic structure to reduce the incoming light. Several different experiments were complete; the light was shawn directly at the panel with the primatric cover, the panel was tilted to mimic the earth's rotation and two layers of the primatic structure were used. The conclusion was that it did help reduce the amount of light and therefore some of the temperature. Further publications will use the light reducing properties of pyramids and cones.

[3]Solar@anu

This paper just talks about the resarch being completed at the Australian National University. They are studying the effects of impurities on semiconductors such as iron impurities. They mainly work on multicrystalline silicon cells which usually have thin films applied ot thier surfaces. Furthermore, they are looking at ways to get the maximum benift from thin films such as amorphous silicon and silicon nitride.

Sliver cells are highly efficient thin single crystalline solar cells which have reached an effiency greater than 20%.

They are also looking at Fluorescent Organic Dyes which have several interesting properties such as they emit one wavelength but emit a longer one and the emission is random. If this dye were applied to glaze the effiency of the PV would increase since the glaze would reflect less light and therefore more light would make contact with the PV cells.

They have also looked at PVTs and residential scale thermal systems.

Email at: solar@anu.edu.au

[4]TCO and Light Trapping in Silicon Thin Film Solar CellsJoachim Müller, Bernd Rech, Jiri Springer and Milan Vanecek. Solar Energy. Volume 77, Issue 6, December 2004, Pages 917-930

[5]Fabrication and optimisation of highly efficient cermet-based spectrally selective coatings for high operating temperature S. Esposito, A. Antonaia, M.L. Addonizio, and S. Aprea. Thin Solid Films, 517 (2009) 6000–6006

[6]Photoreflectance study of Si delta-doped low-temerature GaAs grown by molecular beam epitaxy. T.M. Cheng and C.Y. Chang. Journal of Applied Physics. Vol. 77, No. 5

[7]Optical constants and film density of TiNxOy solar selective absorbers. M. Lazarov, P.Raths, H. Metzger, and W.Spirkl. Journal of Applied Physics, Vol. 77, No. 5

[8]Performance improvement of organic solar cells with moth eye anti-reflection coating. K. Forberich, G. Dennler, M. Scharber, K. Hingerl, T. Fromherz, and C. Brabec. Thin Solid Films. Vol. 516. No 20. 30, August 2008. P.7167-7170

[9] Mg-Ti-H thin films for smart solar collectors. D.M Borsa, A Baldi, M. Pasturel, H. Schreuders, B. Dam, and R. Griessen. Applied Physics Letters. Vol. 88 June 14, 2006

[10]On the development, optical properties and thermal performance of cool coloured coatings for the urban environment. A Synnefa, M. Santamouris, and K. Apostolakis. Solar Energy. Vol. 81, No. 4. April 2007, Pages 488-497

[11]Nanostructured black cobalt coatings for solar absorbers. Z. Hamid, A. Aal, and P. Schmuki. Surface and Interface Analysis. October 10, 2008

[12]Structure and optical properties of pulsed sputter deposited Cr_xO_y/Cr/Cr₂O₃ solar selective coatings. H Barshilia, N. Selvakumar, and K. S. Rajam. Journal of Applied Physics. Vol. 103 (2008)

[13]Solar selective absorber coating for high service temperatures, produced by plasma sputtering. M. Lanxner, Z. Elgat. Proc. SPIE Vol. 1272. February 15, 2005

[14]Solar selective coatings based on Nickel Oxide obtained via spray pyrolysis. M. Voinea, E. Ienei, C. Bogatu, A. Duta. Journal of Nanoscience and Nanotechnology. Vol. 9 No. 7, July 2009. Pages 4279-4284

[15]TiAlN/TiAlON/Si₃N₄ tandem absorber for high temperature solar selective applications. D.V. Sridhara Rao and K. Muraleedharan. Applied Physics Letters. Vol 89. November 8 2006.