{"id":391260,"date":"2010-03-05T01:43:23","date_gmt":"2010-03-05T06:43:23","guid":{"rendered":"http:\/\/davidkirkpatrick.wordpress.com\/?p=6951"},"modified":"2010-03-05T01:43:23","modified_gmt":"2010-03-05T06:43:23","slug":"silicon-nanowires-may-improve-solar-costs","status":"publish","type":"post","link":"https:\/\/mereja.media\/index\/391260","title":{"rendered":"Silicon nanowires may improve solar costs"},"content":{"rendered":"

Silicon photovoltaics offer incredible solar cell efficiency and now it looks like nanotechnology may offer a way to add low production cos<\/a>t to that mix. This type of headway and improvement is what will make solar a market-viable power option.<\/p>\n

The release:<\/p>\n

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Trapping Sunlight with Silicon Nanowires<\/a><\/h2>\n

MARCH 03, 2010<\/p>\n

Lynn Yarris<\/p>\n<\/blockquote>\n

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\"This<\/a><\/p>\n<\/blockquote>\n

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This photovoltaic cell is comprised of 36 individual arrays of silicon nanowires featuring radial p-n junctions. The color dispersion demonstrates the excellent periodicity over the entire substrate. (Photo from Peidong Yang)<\/p>\n<\/blockquote>\n<\/blockquote>\n

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Solar cells<\/strong> made from silicon are projected to be a prominent factor in future renewable green energy equations, but so far the promise has far exceeded the reality. While there are now silicon photovoltaics that can convert sunlight into electricity at impressive 20 percent efficiencies, the cost of this solar power is prohibitive for large-scale use. Researchers with the Lawrence Berkeley National Laboratory (Berkeley Lab), however, are developing a new approach that could substantially reduce these costs. The key to their success is a better way of trapping sunlight.<\/p>\n

\u201cThrough the fabrication of thin films from ordered arrays of vertical silicon nanowires we\u2019ve been able to increase the light-trapping in our solar cells by a factor of 73,\u201d says chemist Peidong Yang, who led this research. \u201cSince the fabrication technique behind this extraordinary light-trapping enhancement is a relatively simple and scalable aqueous chemistry process, we believe our approach represents an economically viable path toward high-efficiency, low-cost thin-film solar cells.\u201d<\/p>\n

Yang holds joint appointments with Berkeley Lab\u2019s Materials Sciences Division, and the University of California \u00a0Berkeley\u2019s Chemistry Department. He is a leading authority on semiconductor nanowires \u2013 one-dimensional strips of materials whose width measures only one-thousandth that of a human hair but whose length may stretch several microns.<\/p>\n

\u201cTypical solar cells are made from very expensive ultrapure single crystal silicon wafers that require about 100 micrometers of thickness to absorb most of the solar light, whereas our radial geometry enables us to effectively trap light with nanowire arrays fabricated from silicon films that are only about eight micrometers thick,\u201d he says. \u201cFurthermore, our approach should in principle allow us to use metallurgical grade or \u201cdirty\u201d silicon rather than the ultrapure silicon crystals now required, which should cut costs even further.\u201d<\/p>\n

Yang has described this research in a paper published in the journal\u00a0NANO Letters<\/em>, which he co-authored with Erik Garnett, a chemist who was then a member of Yang\u2019s research group. The paper is titled \u201cLight Trapping in Silicon Nanowire Solar Cells.\u201d<\/p>\n

\"A<\/a><\/p>\n

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A radial p-n junction consists of a layer of n-type silicon forming a shell around a p-type silicon nanowire core. This geometry turns each individual nanowire into a photovoltaic cell.<\/p>\n<\/blockquote>\n<\/blockquote>\n

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Generating Electricity from Sunlight<\/strong><\/p>\n

At the heart of all solar cells are two separate layers of material, one with an abundance of electrons that functions as a negative pole, and one with an abundance of electron holes (positively-charged energy spaces) that functions as a positive pole. When photons from the sun are absorbed, their energy is used to create electron-hole pairs, which are then separated at the interface between the two layers and collected as electricity.<\/p>\n

Because of its superior photo-electronic properties, silicon remains the photovoltaic semiconductor of choice but rising demand has inflated the price of the raw material. Furthermore, because of the high-level of crystal purification required, even the fabrication of the simplest silicon-based solar cell is a complex, energy-intensive and costly process.<\/p>\n

Yang and his group are able to reduce both the quantity and the quality requirements for silicon by using vertical arrays of nanostructured radial p-n junctions rather than conventional planar p-n junctions. In a radial p-n junction, a layer of n-type silicon forms a shell around a p-type silicon nanowire core. As a result, photo-excited electrons and holes travel much shorter distances to electrodes, eliminating a charge-carrier bottleneck that often arises in a typical silicon solar cell. The radial geometry array also, as photocurrent and optical transmission measurements by Yang and Garrett revealed, greatly improves light trapping.<\/p>\n

\u201cSince each individual nanowire in the array has a p-n junction, each acts as an individual solar cell,\u201d Yang says. \u201cBy adjusting the length of the nanowires in our arrays, we can increase their light-trapping path length.\u201d<\/p>\n

While the conversion efficiency of these solar nanowires was only about five to six percent, Yang says this efficiency was achieved with little effort put into surface passivation, antireflection, and other efficiency-increasing modifications.<\/p>\n

\u201cWith further improvements, most importantly in surface passivation, we think it is possible to push the efficiency to above 10 percent,\u201d Yang says.<\/p>\n

Combining a 10 percent or better conversion efficiency with the greatly reduced quantities of starting silicon material\u00a0 and the ability to use metallurgical grade silicon, should make the use of silicon nanowires an attractive candidate for large-scale development.<\/p>\n

As an added plus Yang says, \u201cOur technique can be used in existing solar panel manufacturing processes.\u201d<\/p>\n

This research was funded by the National Science Foundation\u2019s Center of Integrated Nanomechanical Systems.<\/p>\n

Berkeley Lab is a U.S. Department of Energy national laboratory located in Berkeley, California. It conducts unclassified scientific research for DOE\u2019s Office of Science and is managed by the University of California. Visit our website at\u00a0http:\/\/www.lbl.gov<\/a>.<\/p>\n


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\"Peidong<\/a><\/p>\n

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Peidong Yang (Photo by Roy Kaltschmidt, Berkeley Lab Public Affairs)<\/p>\n<\/blockquote>\n

Additional Information<\/strong><\/p>\n

For more about the research of Peidong Yang and his group, visit the Website at\u00a0http:\/\/www.cchem.berkeley.edu\/pdygrp\/main.html<\/a><\/p>\n

For more about the Center of Integrated Nanomechanical Systems (COINS) visit the Website at\u00a0http:\/\/mint.physics.berkeley.edu\/coins\/<\/a><\/p>\n<\/blockquote>\n

\"\"<\/a> \"\"<\/a> \"\"<\/a> \"\"<\/a> \"\"<\/a> \"\"<\/p>\n","protected":false},"excerpt":{"rendered":"

Silicon photovoltaics offer incredible solar cell efficiency and now it looks like nanotechnology may offer a way to add low production cost to that mix. This type of headway and improvement is what will make solar a market-viable power option. The release: Trapping Sunlight with Silicon Nanowires MARCH 03, 2010 Lynn Yarris This photovoltaic cell […]<\/p>\n","protected":false},"author":4050,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[],"class_list":["post-391260","post","type-post","status-publish","format-standard","hentry","category-news"],"_links":{"self":[{"href":"https:\/\/mereja.media\/index\/wp-json\/wp\/v2\/posts\/391260","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/mereja.media\/index\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/mereja.media\/index\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/mereja.media\/index\/wp-json\/wp\/v2\/users\/4050"}],"replies":[{"embeddable":true,"href":"https:\/\/mereja.media\/index\/wp-json\/wp\/v2\/comments?post=391260"}],"version-history":[{"count":0,"href":"https:\/\/mereja.media\/index\/wp-json\/wp\/v2\/posts\/391260\/revisions"}],"wp:attachment":[{"href":"https:\/\/mereja.media\/index\/wp-json\/wp\/v2\/media?parent=391260"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/mereja.media\/index\/wp-json\/wp\/v2\/categories?post=391260"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/mereja.media\/index\/wp-json\/wp\/v2\/tags?post=391260"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}