[轉錄][情報] 光電轉換率最高可達100% 新型太똠…

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※ [本文轉錄自 Tech_Job 看板] 作者: domimgo (..) 看板: Tech_Job 標題: [情報] 光電轉換率最高可達100% 新型太陽能電池研發成功時間: Tue Mar 2 23:58:44 2010 光電轉換率最高可達100% 新型太陽能電池研發成功 2010-03-02 15:36 cnBeta 科学探索 http://www.cnbeta.com/articles/105346.htm http://img.cnbeta.com/newsimg/100302/15364801915357861.jpg

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加州理工學院近日研發出了一種新的太陽能電池，其基本原理是將細長的矽線陣列嵌入聚合物基板中。除了纖薄可彎曲外，它對太陽光的吸收和光電轉換效率方面都取得了極大地突破。此外，和傳統太陽能電池所需要的昂貴的半導體材料量相比，這種新型太陽能電池僅需要一小部分。應用物理學及材料學教授Harry Atwater和Howard Hughes表示： “這些太陽能電池首次突破了傳統的吸光材料的光捕獲極限。” 新型太陽能電池所採用的矽線陣列對單一波長的入射光的吸收率高達96%，對全波長陽光的捕獲率可達85%。光电轉換率最高可達100% 新型可捲曲太陽能電池研發成功 Atwater指出：“許多材料對光線的捕獲能力很好，但是卻無法轉換成電能，比如黑塗料。對於太陽能電池來說，吸收的光子能否轉換為電荷載子（charge carrier）也非常重要。 ”而他們研發的矽線陣列太陽能電池則可以將所吸收光子的90%至100%轉換為電子。從技術上講，這種陣列擁有幾近完美的內部量子效率（internal quantum efficiency）。 Atwater總結說：“對光的高吸收率和較好的轉換能力成就了這種太陽能電池的高質量。” 矽線陣列中的矽線長度在30至100微米（micron）之間，直徑僅為1微米。整個陣列的厚度相當於矽線的長度，但是從面積或體積角落來看，這種材料中只有2%才是矽，其它98%都是聚合物。由於矽是傳統太陽能電池中一種很昂貴的成分，所以這種只需要傳統所需量1/50的太陽能電池投產的成本將低很多。 ----------------------------------------------------------------------------- 原文出處來自加州理工學院網頁所揭露 http://media.caltech.edu/press_releases/13325 02/17/10 Caltech Researchers Create Highly Absorbing, Flexible Solar Cells with Silicon Wire Arrays PASADENA, Calif.—Using arrays of long, thin silicon wires embedded in a polymer substrate, a team of scientists from the California Institute of Technology (Caltech) has created a new type of flexible solar cell that enhances the absorption of sunlight and efficiently converts its photons into electrons. The solar cell does all this using only a fraction of the expensive semiconductor materials required by conventional solar cells. "These solar cells have, for the first time, surpassed the conventional light-trapping limit for absorbing materials," says Harry Atwater, Howard Hughes Professor, professor of applied physics and materials science, and director of Caltech's Resnick Institute, which focuses on sustainability research. This is a photomicrograph of a silicon wire array embedded within a transparent, flexible polymer film. [Credit: Caltech/Michael Kelzenberg] The light-trapping limit of a material refers to how much sunlight it is able to absorb. The silicon-wire arrays absorb up to 96 percent of incident sunlight at a single wavelength and 85 percent of total collectible sunlight. "We've surpassed previous optical microstructures developed to trap light," he says. Atwater and his colleagues—including Nathan Lewis, the George L. Argyros Professor and professor of chemistry at Caltech, and graduate student Michael Kelzenberg—assessed the performance of these arrays in a paper appearing in the February 14 advance online edition of the journal Nature Materials. Atwater notes that the solar cells' enhanced absorption is "useful absorption." "Many materials can absorb light quite well but not generate electricity— like, for instance, black paint," he explains. "What's most important in a solar cell is whether that absorption leads to the creation of charge carriers." The silicon wire arrays created by Atwater and his colleagues are able to convert between 90 and 100 percent of the photons they absorb into electrons— in technical terms, the wires have a near-perfect internal quantum efficiency. "High absorption plus good conversion makes for a high-quality solar cell," says Atwater. "It's an important advance." The key to the success of these solar cells is their silicon wires, each of which, says Atwater, "is independently a high-efficiency, high-quality solar cell." When brought together in an array, however, they're even more effective, because they interact to increase the cell's ability to absorb light. "Light comes into each wire, and a portion is absorbed and another portion scatters. The collective scattering interactions between the wires make the array very absorbing," he says. This is a schematic diagram of the light-trapping elements used to optimize absorption within a polymer-embedded silicon wire array. [Credit: Caltech/Michael Kelzenberg] This effect occurs despite the sparseness of the wires in the array—they cover only between 2 and 10 percent of the cell's surface area. "When we first considered silicon wire-array solar cells, we assumed that sunlight would be wasted on the space between wires," explains Kelzenberg. "So our initial plan was to grow the wires as close together as possible. But when we started quantifying their absorption, we realized that more light could be absorbed than predicted by the wire-packing fraction alone. By developing light-trapping techniques for relatively sparse wire arrays, not only did we achieve suitable absorption, we also demonstrated effective optical concentration—an exciting prospect for further enhancing the efficiency of silicon-wire-array solar cells." Each wire measures between 30 and 100 microns in length and only 1 micron in diameter. “The entire thickness of the array is the length of the wire,” notes Atwater. “But in terms of area or volume, just 2 percent of it is silicon, and 98 percent is polymer.” In other words, while these arrays have the thickness of a conventional crystalline solar cell, their volume is equivalent to that of a two-micron-thick film. Since the silicon material is an expensive component of a conventional solar cell, a cell that requires just one-fiftieth of the amount of this semiconductor will be much cheaper to produce. The composite nature of these solar cells, Atwater adds, means that they are also flexible. "Having these be complete flexible sheets of material ends up being important," he says, "because flexible thin films can be manufactured in a roll-to-roll process, an inherently lower-cost process than one that involves brittle wafers, like those used to make conventional solar cells." Atwater, Lewis, and their colleagues had earlier demonstrated that it was possible to create these innovative solar cells. "They were visually striking," says Atwater. "But it wasn't until now that we could show that they are both highly efficient at carrier collection and highly absorbing." The next steps, Atwater says, are to increase the operating voltage and the overall size of the solar cell. "The structures we've made are square centimeters in size," he explains. "We're now scaling up to make cells that will be hundreds of square centimeters—the size of a normal cell." Atwater says that the team is already "on its way" to showing that large-area cells work just as well as these smaller versions. In addition to Atwater, Lewis, and Kelzenberg, the all-Caltech coauthors on the Nature Materials paper, "Enhanced absorption and carrier collection in Si wire arrays for photovoltaic applications," are postdoctoral scholars Shannon Boettcher and Joshua Spurgeon; undergraduate student Jan Petykiewicz; and graduate students Daniel Turner-Evans, Morgan Putnam, Emily Warren, and Ryan Briggs. Their research was supported by BP and the Energy Frontier Research Center program of the Department of Energy, and made use of facilities supported by the Center for Science and Engineering of Materials, a National Science Foundation Materials Research Science and Engineering Center at Caltech. In addition, Boettcher received fellowship support from the Kavli Nanoscience Institute at Caltech. # # # Contact: Lori Oliwenstein (626) 395-3631 lorio@caltech.edu -- ※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 220.134.137.115

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