發(fā)布時(shí)間：2017-12-27 22:33

  本文關(guān)鍵詞：低缺陷密度大單晶比例太陽能級類單晶硅錠制備及其表面制絨研究　出處：《蘇州大學(xué)》2016年博士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 定向凝鑄法 多晶硅 類單晶 黑硅 太陽能電池

【摘要】：類單晶籽晶輔助定向凝鑄法是近年來在多晶硅籽晶輔助定向凝鑄法基礎(chǔ)上發(fā)展起來的一種全新的低成本、高效率類單晶硅錠制備技術(shù)。該技術(shù)具有單爐生產(chǎn)量大,單位質(zhì)量能耗低,硅錠質(zhì)量好等優(yōu)點(diǎn),其對應(yīng)的太陽能電池片相對于多晶片轉(zhuǎn)換效率更高。但是,現(xiàn)有制備技術(shù)存在單錠單晶比例低,缺陷密度高,無法進(jìn)入產(chǎn)業(yè)化階段的問題;同時(shí),由于其表面單晶與多晶晶粒共存,一般的酸、堿腐蝕法對其制絨都存在困難。為了制備可產(chǎn)業(yè)化的低缺陷密度大單晶比例類單晶硅錠及提升對應(yīng)太陽能電池的效率,本文使用適合產(chǎn)業(yè)化的定向凝鑄爐,進(jìn)行了多晶硅錠和類單晶硅錠的制備技術(shù)優(yōu)化和生長機(jī)理分析,并對制備的類單晶太陽能電池片表面制絨技術(shù)進(jìn)行了研究。采用的美國GT公司G6-850定向凝鑄爐具有目前世界最先進(jìn)的雙電源雙加熱器結(jié)構(gòu),熱場比較均勻,適合G6(即單爐生產(chǎn)硅錠可切割出36個(gè)156×156mm2的硅晶柱)及更大尺寸硅錠產(chǎn)業(yè)化生產(chǎn)。本文首先進(jìn)行了多晶硅籽晶輔助定向凝鑄技術(shù)優(yōu)化研究。實(shí)驗(yàn)表明:籽晶輔助定向凝鑄工藝制備的多晶硅錠從底部到頂部的缺陷密度分布狀態(tài)可以分為準(zhǔn)直線平坦區(qū)和準(zhǔn)線性增加區(qū)。在直線區(qū)中,硅錠缺陷密度基本保持不變或微弱增加;準(zhǔn)線性區(qū)中,硅錠缺陷密度隨著高度的增加而準(zhǔn)線性增加。隨著結(jié)晶降溫速率減小,硅錠的缺陷密度整體降低,直線區(qū)變長,準(zhǔn)線性區(qū)變短,對應(yīng)太陽能電池轉(zhuǎn)換效率高于18%的比例增加。為了克服籽晶層局部過熔現(xiàn)象,本論文創(chuàng)新地設(shè)計(jì)了一種緩沖式籽晶熔化控制技術(shù)。緩沖層位于籽晶層上,由小顆粒的原生多晶硅料層和其上的晶磚層構(gòu)成。采用緩沖式籽晶熔化控制技術(shù)制備多晶硅鑄錠的實(shí)驗(yàn)表明:該技術(shù)可以有效避免因硅熔液從硅料間隙滲下造成的籽晶層局部過熔現(xiàn)象,提高了籽晶層的熔化均勻性,延長了硅錠中低缺陷密度直線區(qū)的長度,降低硅錠底部紅區(qū)(即少子壽命低于2μs的區(qū)域)的高度,提高了硅錠質(zhì)量,為超薄籽晶層定向凝鑄工藝產(chǎn)業(yè)化奠定了基礎(chǔ)。采用單晶硅籽晶輔助,我們研究了定向凝鑄工藝制備類單晶硅錠的制備工藝。G6類單晶鑄錠實(shí)驗(yàn)結(jié)果與多晶硅實(shí)驗(yàn)基本一致,即結(jié)晶降溫速率下降,硅錠缺陷密度整體降低,直線區(qū)變長,準(zhǔn)線性區(qū)變短。通過類單晶鑄錠實(shí)驗(yàn)發(fā)現(xiàn),當(dāng)降溫速率較大,即降低溫度/結(jié)晶時(shí)間的比例為0.467時(shí),類單晶硅錠中單晶比例約為61%;當(dāng)降溫速率較小,即降低溫度/結(jié)晶時(shí)間的比例為0.154時(shí),類單晶硅錠中單晶的比例可以達(dá)到75%以上,這一比例對產(chǎn)業(yè)化來說,已具有應(yīng)用價(jià)值。在類單晶緩沖式籽晶熔化控制技術(shù)裝料鑄錠的基礎(chǔ)上,發(fā)展了緩沖層中心低四周高凹陷式類單晶緩沖籽晶熔化控制技術(shù)。實(shí)驗(yàn)結(jié)果表明:該裝料方式克服了坩堝中心熔化過程中溫度較低,坩堝四周熔化過快的問題,硅熔液通過緩沖層后,形成了更為平直的固液面,與籽晶層實(shí)現(xiàn)了良好的接觸。該技術(shù)克服了類單晶硅片中十字紋的形成。最終實(shí)驗(yàn)制備出單晶比例高達(dá)87.5%的產(chǎn)業(yè)化類單晶硅錠,具有較高的應(yīng)用價(jià)值。定向凝鑄硅錠頂部和底部的紅區(qū)降低了硅錠的硅片有效切片數(shù)。本文通過類單晶和多晶硅的定向凝鑄工藝實(shí)驗(yàn),研究了硅錠中紅區(qū)的形成機(jī)理。通過不同結(jié)晶工藝溫度實(shí)驗(yàn)發(fā)現(xiàn),硅錠底部紅區(qū)的高度受到硅熔液溫度的影響,硅溶液溫度越高,紅區(qū)的高度越低。通過對鑄錠結(jié)晶工藝降溫速率的實(shí)驗(yàn)研究表明,隨著降溫速率的降低,紅區(qū)高度降低�；趯�(shí)驗(yàn)結(jié)果我們提出:硅錠底部紅區(qū)受到硅熔液中溫度梯度的影響。溫度梯度越大,在鑄錠初期越易生長小晶粒,從而形成了大量的位錯(cuò)和晶粒間界,成為了雜質(zhì)的吸附中心,降低了硅錠底部晶體的載流子的壽命,形成硅錠底部紅區(qū)。緩沖式籽晶熔化控制技術(shù)實(shí)驗(yàn)表明硅料熔化時(shí)較為平直的固液面避免了籽晶層局部過熔,提高了硅熔液溫度,從而降低了紅區(qū)高度。類單晶硅片因其制絨效果差,限制了其在太陽電池中的應(yīng)用。本文創(chuàng)新地采用了兩步腐蝕法制備納米絨面結(jié)構(gòu)的類單晶太陽電池,有效提高了電池的光吸收率和載流子壽命。實(shí)驗(yàn)結(jié)果表明:從硅晶柱底部到頂部的類單晶電池轉(zhuǎn)換效率均獲得了提高。兩步腐蝕法制備的類單晶太陽電池的轉(zhuǎn)換效率從酸腐蝕的18.4%提高到了18.9%,并且減少了電池上的色差。通過亞電池并聯(lián)模型很好的解釋了類單晶電池的性能取決于最差亞電池的性能。本文制備的類單晶電池的轉(zhuǎn)換效率遠(yuǎn)超過了傳統(tǒng)高效多晶電池18.0%左右。
[Abstract]:The class of single crystal seed assisted directional solidification method is a new low cost, in recent years in the polysilicon seed assisted directional tracing method based on the development of efficient class of single crystal silicon ingot preparation technology. The technology has the advantages of large volume of single furnace production, low unit mass energy consumption and good quality of silicon ingot, and its corresponding solar cell chip has higher conversion efficiency than multi chip. However, the existing preparation technology has low single crystal single crystal ratio and high defect density, and can not enter the industrialization stage. At the same time, because of the coexistence of single crystal and polycrystalline grain on the surface, the general acid and alkali corrosion method has difficulty in making the pile. For the low efficiency of large single crystal defect density ratio can be prepared in the industrialization of the class of monocrystalline silicon ingots and enhance the corresponding solar cell, this paper combines the use of directional furnace for industrialization, analyzes the polysilicon ingots and silicon ingots class preparation technology optimization and growth mechanism, and the preparation of single crystal like solar cell surface cashmere is studied. Double power is currently the world's most advanced double heater with American GT company G6-850 directional combines furnace, thermal field is relatively uniform, suitable for G6 (i.e., a single furnace production of silicon ingot cutting silicon crystal column 36 156 x 156mm2) and large size silicon ingot production. This paper combines the technology of polysilicon seed assisted directional optimization research. Experimental results show that the seed polysilicon assisted directional preparation combines the ingot from the bottom to the top of the defect density distribution can be divided into quasi linear and quasi linear increase in flat area. In the straight line, the defect density of the silicon ingot remains unchanged or slightly increased; in the quasi linear region, the density of the defects in the silicon ingot increases linearly with the increase of height. With the decrease of crystallization cooling rate, the defect density of silicon ingot decreases, the linear area becomes longer, and the Quasilinear zone becomes shorter, which corresponds to the increase of solar cell conversion efficiency over 18%. In order to overcome the phenomenon of partial melting of the seed layer, a new technique for controlling the melting of seed grain was designed in this paper. The buffer layer is located on the seed layer, consisting of a small particle's primary polysilicon layer and a brick layer on it. The buffer type seed melting control technology of preparation of polycrystalline silicon ingot experiment shows that this technology can effectively avoid molten silicon from silicon material clearance caused by seepage under the seed layer partial melting phenomenon, improve the melting of the seed layer uniformity, low defect density of silicon ingot to extend the length of straight line, reduce at the bottom of the ingot red zone (i.e., the lifetime of less than 2 mu s area) height, improve the quality of the ingot, laid the foundation for the thin seed layer orientation combines the industrialization process. The seed of single crystal silicon, we studied the directional preparation process combines the class preparation process of single crystal silicon ingot. The experimental results of G6 single crystal ingot are basically the same with that of polysilicon experiment, that is, the cooling rate of crystallization decreases, and the density of silicon ingot decreases as a whole, and the linear region becomes longer and the quasi linear region becomes shorter. The monocrystalline ingot is found when the cooling rate is larger, the lower the temperature / crystallization time ratio of 0.467, class of single crystal silicon ingots in the proportion is about 61%; when the cooling rate is smaller, lower temperature crystallization time ratio of 0.154, the proportion of single crystal silicon ingots in class can reach more than 75%, the a proportion of industrialization, has application value. On the basis of single crystal buffer seed melting control technology, loading and casting ingots, a high concave single crystal buffer seed melting control technology is developed for the center of the buffer layer. The experimental results show that the charging method overcomes the problem of low melting temperature and melting too fast around the crucible, and forms a more straight solid liquid surface after the silicon melt passes through the buffer layer, which achieves good contact with the seed layer. The technique overcomes the formation of the cross pattern in the monocrystalline silicon. In the final experiment, the industrial monocrystalline silicon ingot with a high ratio of 87.5% is prepared, which has high application value. Directional solidification of silicon ingot at the top and bottom of the red zone reduces the effective number of silicon ingot slicing of silicon wafer. This paper combines the technology of directional experiment by single crystals and polycrystalline silicon, the formation mechanism of the red area in the study of silicon ingot. It is found that the height of the red region at the bottom of the silicon ingot is influenced by the temperature of the molten silicon, and the higher the temperature of the silicon solution, the lower the height of the red region. The experimental study on the cooling rate of the ingot crystallization process shows that the height of the red region is reduced with the decrease of the cooling rate. Based on the experimental results, we suggest that the red region at the bottom of the silicon ingot is affected by the temperature gradient in the silicon melt. The greater the temperature gradient, the easier the growth of small grains in the initial stage of the ingot, resulting in a large number of dislocation and grain boundaries, which become the adsorption centers of impurities, and reduce the lifetime of carriers at the bottom of the ingot, forming the red area at the bottom of the ingot. The experiment of buffering seed melting control technology shows that the relatively straight solid liquid surface melts the silicon material and avoids the local overmelting of seed layer, and improves the temperature of silicon melt, thereby reducing the height of red zone. The application of the monocrystalline silicon chip is limited in the solar cell because of its poor cashmere effect. In this paper, the two step corrosion method is used to prepare the single crystal solar cell with nano suede structure, which can effectively improve the light absorption and carrier life of the battery. The experimental results show that the conversion efficiency of the single crystal cell from the bottom to the top of the silicon crystal column has been improved. The conversion efficiency of the single crystal solar cell prepared by the two step corrosion method increased from 18.4% of acid corrosion to 18.9%, and the chromatic aberration on the battery was reduced. Through the sub cell parallel model can well explain the properties of single cell performance depends on the subgrain cell. The conversion efficiency of the single crystal cell prepared in this paper is far more than 18% of the traditional high performance polycrystalline battery.
【學(xué)位授予單位】：蘇州大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2016
【分類號】：TN304.12

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1 王強(qiáng);低缺陷密度大單晶比例太陽能級類單晶硅錠制備及其表面制絨研究[D];蘇州大學(xué);2016年

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