【摘要】：太陽能是一種清潔的可再生能源,是解決未來能源危機(jī)的理想選擇。目前,多晶硅太陽電池具有生產(chǎn)工藝簡單,成本低廉等優(yōu)點(diǎn)而被廣泛使用。然而,多晶硅的定向凝固是多物理場耦合作用下一個復(fù)雜的晶體生長過程。在實(shí)際生產(chǎn)過程中,難以精確的掌握硅熔體中各個物理場的變化規(guī)律。隨著計算機(jī)數(shù)值模擬技術(shù)的發(fā)展,模擬仿真方法成為了一種直觀了解晶體生長的有效手段。本工作借助Comsol Multiphysics 4.3 a多物理場仿真軟件對多晶硅晶體生長的過程進(jìn)行了數(shù)值模擬,并獲得了硅熔體的熱場、流場、磁場、應(yīng)力場的分布規(guī)律,為探索多晶硅定向生長提供了一種新的途徑。本文采用熱場和流場或應(yīng)力場耦合研究了多晶硅定向凝固爐內(nèi)的坩堝和冷卻平臺組合結(jié)構(gòu)以及加熱器分布對硅熔體熱場和流場的影響,并分析了坩堝形狀、坩堝倒角半徑和晶體內(nèi)溫度梯度對硅晶體內(nèi)熱場和應(yīng)力場的影響規(guī)律。采用倒錐形坩堝有利于減小多晶硅鑄錠中的熱應(yīng)力。隨著坩堝倒角半徑的增加,晶體中的熱應(yīng)力值下降幅度逐漸減小。當(dāng)硅晶體中溫度梯度增加時,晶體中的熱應(yīng)力平均值增加幅度逐漸降低。運(yùn)用熱場、流場和磁場耦合研究了多晶硅晶體定向生長的過程,重點(diǎn)分析了不同磁場結(jié)構(gòu)、不同磁場分布和不同磁場強(qiáng)度作用下多晶硅定向凝固工藝參數(shù)的變化情況。當(dāng)磁場線圈與硅熔體中心面的距離由60mm減小到-60mm時,硅熔體的最大流速由70μm/s減小到了41μm/s,相比減小了41.43%。當(dāng)磁場線圈保持在硅熔體中心面下方60mm處,磁場強(qiáng)度逐漸由0T逐漸增加到0.8T時,硅熔體的軸向溫度梯度最大降幅為15K/cm。另外,通過建立二維軸對稱瞬態(tài)模型,揭示了多物理場作用下多晶硅結(jié)晶階段三個時期(初期、中期、后期)的流場變化規(guī)律。在多晶硅結(jié)晶階段施加0T到1T的變化磁場時,硅熔體的流速峰值由結(jié)晶初期的51.644μm/s減小到了后期的21.074μm/s,而且其三個時期的平均流速在多場耦合作用下分別減小了42.11%、58.59%、45.16%。以上模擬結(jié)果表明,數(shù)值模擬技術(shù)對多晶硅實(shí)際生產(chǎn)具有重要的理論指導(dǎo)意義。
[Abstract]:Solar energy is a kind of clean renewable energy, which is the ideal choice to solve the future energy crisis. At present, polysilicon solar cells are widely used because of their simple production process and low cost. However, the directional solidification of polysilicon is a complex crystal growth process under the coupling of multiple physical fields. In the actual production process, it is difficult to accurately grasp the changes of each physical field in silicon melt. With the development of computer numerical simulation technology, simulation method has become an effective method to directly understand crystal growth. In this work, the growth process of polycrystalline silicon crystal is numerically simulated with the help of Comsol Multiphysics 4.3a multi-physical field simulation software, and the distribution of thermal field, flow field, magnetic field and stress field of silicon melt is obtained. It provides a new way to explore the directional growth of polysilicon. In this paper, the combined structure of crucible and cooling platform in polysilicon directional solidification furnace and the influence of heater distribution on the thermal field and flow field of silicon melt are studied by means of the coupling of heat field and flow field or stress field, and the shape of the crucible is analyzed. The influence of crucible chamfer radius and temperature gradient in crystal on thermal field and stress field in silicon crystal. The use of inverted conical crucible can reduce the thermal stress in polysilicon ingot. With the increase of the corner radius of the crucible, the decrease of thermal stress in the crystal decreases gradually. When the temperature gradient in silicon crystal increases, the average value of thermal stress in silicon crystal decreases gradually. The process of oriented growth of polysilicon crystal was studied by means of thermal field, flow field and magnetic field coupling. The variation of technological parameters of polysilicon directional solidification under different magnetic field structure, different magnetic field distribution and different magnetic field intensity was analyzed. When the distance between the magnetic coil and the central surface of the silicon melt decreases from 60mm to-60mm, the maximum flow velocity of the melt decreases from 70 渭 m / s to 41 渭 m / s, which is 41.43%. When the magnetic field coil is kept at 60mm below the central surface of the silicon melt and the magnetic field intensity gradually increases from 0 T to 0.8 T, the maximum decrease of the axial temperature gradient of the silicon melt is 15 K / cm ~ (-1). In addition, by establishing a two-dimensional axisymmetric transient model, the variation of flow field in three phases (initial, middle and late) of polycrystalline silicon crystallization phase under the action of multi-physical field is revealed. When the magnetic field from 0T to 1T is applied in the crystallization phase of polysilicon, the peak velocity of the melt velocity decreases from 51.644 渭 m / s in the early stage of crystallization to 21.074 渭 m / s in the later stage of crystallization. Moreover, the mean velocity in three periods decreased by 42.1158.59 and 45.1659 respectively under the action of multi-field coupling. The above simulation results show that the numerical simulation technology has important theoretical significance for the practical production of polysilicon.
【學(xué)位授予單位】：南昌大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TN304.12

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