Further development of the photovoltaic industry is restricted by the productivity of mono-crystalline silicon technology due to its requirements of low cost and high efficient photocells. The heat shield is not only ...Further development of the photovoltaic industry is restricted by the productivity of mono-crystalline silicon technology due to its requirements of low cost and high efficient photocells. The heat shield is not only the important part of the thermal field in Czochralski（Cz） mono-crystalline silicon furnace, but also one of the most important factors influencing the silicon crystal growth. Large-diameter Cz-Si crystal growth process is taken as the study object, Based on FEM numerical simulation, different heat shield structures are analyzed to investigate the heater power, the melt-crystal interface shape, the argon flow field, and the oxygen concentration at the melt-crystal interface in the process of large Cz-Si crystal growth. The impact of these factors on the growth efficiency and crystal quality are analyzed. The results show that the oxygen concentration on the melt-crystal interface and the power consumption of the heater stay high due to the lack of a heat shield in the crystal growth system. Argon circumfluence is generated on the external side of the right angle heat shield. By the right-angle heat shield, the speed of gas flow is lowered on the melt free surface, and the temperature gradient of the free surface is increased around the melt-crystal interface. It is not conducive for the stable growth of crystal. The shape of the melt-crystal interface and the argon circulation above the melt free surface are improved by the inclined heat shield. Compared with the others, the system pulling rate is increased and the lowest oxygen concentration is achieved at the melt-crystal interface with the composite heat shield. By the adoption of the optimized composite heat shield in experiment, the real melt-crystal interface shapes and its deformation laws obtained by Quick Pull Separation Method at different pulling rates agree with the simulation results. The results show that the method of simulation is feasible. The proposed research provides the theoretical foundation for the thermal field design of the large diameter Cz-Si monocrystalline growth.展开更多
Mono-crystalline silicon solar cells with a passivated emitter rear contact(PERC)configuration have attracted extensive attention from both industry and scientific communities.A record efficiency of 24.06%on p-type si...Mono-crystalline silicon solar cells with a passivated emitter rear contact(PERC)configuration have attracted extensive attention from both industry and scientific communities.A record efficiency of 24.06%on p-type silicon wafer and mass production efficiency around 22%have been demonstrated,mainly due to its superior rear side passivation.In this work,the PERC solar cells with a p-type silicon wafer were numerically studied in terms of the surface passivation,quality of silicon wafer and metal electrodes.A rational way to achieve a 24%mass-production efficiency was proposed.Free energy loss analyses were adopted to address the loss sources with respect to the limit efficiency of 29%,which provides a guideline for the design and manufacture of a high-efficiency PERC solar cell.展开更多
The temperature and velocity distribution of melting pool fields is very important effect to the silicon purification in vacuum induction furnace.A numerical model for the electromagnetic-thermal-hydrodynamic coupling...The temperature and velocity distribution of melting pool fields is very important effect to the silicon purification in vacuum induction furnace.A numerical model for the electromagnetic-thermal-hydrodynamic coupling fields have been developed by using the finite element method(FEM)and a 2D numerical simulation for electromagnetic、 temperature and velocity fields of metallurgical-grade silicon melting in vacuum induction furnace were performed with a software Multi-physics Comsol 3.5a in this paper.The results showed that the temperature field was dependent observably on input power of coils and induction heating times and the maximum temperature gradient in melting pool was 215K in holding time.With the silicon molted gradually a clockwise vortex was come into being for electromagnetic stirring in the smelting poor.The variation of velocity field in melting silicon is mainly influenced with the change of the current intensity and power frequency.The numerical predications of temperature distribution are in good agreement with experiments.展开更多
基金Supported by National Natural Science Foundation of China(Grant Nos.61075044,F0304)
文摘Further development of the photovoltaic industry is restricted by the productivity of mono-crystalline silicon technology due to its requirements of low cost and high efficient photocells. The heat shield is not only the important part of the thermal field in Czochralski（Cz） mono-crystalline silicon furnace, but also one of the most important factors influencing the silicon crystal growth. Large-diameter Cz-Si crystal growth process is taken as the study object, Based on FEM numerical simulation, different heat shield structures are analyzed to investigate the heater power, the melt-crystal interface shape, the argon flow field, and the oxygen concentration at the melt-crystal interface in the process of large Cz-Si crystal growth. The impact of these factors on the growth efficiency and crystal quality are analyzed. The results show that the oxygen concentration on the melt-crystal interface and the power consumption of the heater stay high due to the lack of a heat shield in the crystal growth system. Argon circumfluence is generated on the external side of the right angle heat shield. By the right-angle heat shield, the speed of gas flow is lowered on the melt free surface, and the temperature gradient of the free surface is increased around the melt-crystal interface. It is not conducive for the stable growth of crystal. The shape of the melt-crystal interface and the argon circulation above the melt free surface are improved by the inclined heat shield. Compared with the others, the system pulling rate is increased and the lowest oxygen concentration is achieved at the melt-crystal interface with the composite heat shield. By the adoption of the optimized composite heat shield in experiment, the real melt-crystal interface shapes and its deformation laws obtained by Quick Pull Separation Method at different pulling rates agree with the simulation results. The results show that the method of simulation is feasible. The proposed research provides the theoretical foundation for the thermal field design of the large diameter Cz-Si monocrystalline growth.
基金supported by the National Natural Science Foundation of China(No.61504155)。
文摘Mono-crystalline silicon solar cells with a passivated emitter rear contact(PERC)configuration have attracted extensive attention from both industry and scientific communities.A record efficiency of 24.06%on p-type silicon wafer and mass production efficiency around 22%have been demonstrated,mainly due to its superior rear side passivation.In this work,the PERC solar cells with a p-type silicon wafer were numerically studied in terms of the surface passivation,quality of silicon wafer and metal electrodes.A rational way to achieve a 24%mass-production efficiency was proposed.Free energy loss analyses were adopted to address the loss sources with respect to the limit efficiency of 29%,which provides a guideline for the design and manufacture of a high-efficiency PERC solar cell.
基金Item Sponsored by the NSFC project (51066003u1137601) +1 种基金National science & technology support plan project (2011BAE03B01) Scientific Research Foundation Project (2010Y408) of Yunnan Province Education Department
文摘The temperature and velocity distribution of melting pool fields is very important effect to the silicon purification in vacuum induction furnace.A numerical model for the electromagnetic-thermal-hydrodynamic coupling fields have been developed by using the finite element method(FEM)and a 2D numerical simulation for electromagnetic、 temperature and velocity fields of metallurgical-grade silicon melting in vacuum induction furnace were performed with a software Multi-physics Comsol 3.5a in this paper.The results showed that the temperature field was dependent observably on input power of coils and induction heating times and the maximum temperature gradient in melting pool was 215K in holding time.With the silicon molted gradually a clockwise vortex was come into being for electromagnetic stirring in the smelting poor.The variation of velocity field in melting silicon is mainly influenced with the change of the current intensity and power frequency.The numerical predications of temperature distribution are in good agreement with experiments.
文摘根据自动调流式滴头的结构组成和工作原理,利用Auto CAD软件、计算流体动力学CFD技术的Fluent软件,建立由平角齿形消能流道和控制体形成滴头流量组合体的流体模型,并进行网格划分,分别以控制组合体的膜片开度0.5、1.0、1.5和2.0 mm为初始条件,以进口压力30、40和50 k Pa和壁面的粗糙高度、粗糙常数等为边界条件,采用SIMPLE算法的二阶迎风离散格式,对滴头的流量控制组合体进行水流运动通道内部流场的二维数值模拟,分析得出自动调流式滴头的平角齿形消能流道的速度矢量图、内部流场特征,在流道消能齿的单元处会产生独立的水流漩涡,容易引起灌溉水中杂质颗粒的累积、造成堵塞。为自动调流式滴头的结构优化改进、抗堵塞性和适宜工作压力取值范围提供了理论指导。
