The rapid growth and steady expansion of PV industry in China encourage the development of solar cells that offer extra high efficiency, such as N-type bifacial, HJT and half-cut cells. Meanwhile, cost reduction and efficiency improvement have become the primary goals of the entire industry. However, an increase of mere 0.01% in solar cell efficiency requires tremendous efforts. According to the forecast of CPIA, the market share of TOPcon+HJT cells will rise to 35% in 2025, and theoretically, N-type cells featuring low oxygen content and high conversion efficiency are likely to achieve higher efficiency than P-type cells.

The new stage of solar cell efficiency improvement requires superior N-type mono-Si cells that promise lower oxygen content, less resistivity and longer minority carrier lifetime. A better engineered and proven crystal growth furnace is prerequisite to producing such quality mono-Si cells.

The bigger the furnace body and the crystal size are, the longer the time to stabilize the silicon melt temperature, and this will adversely affect the stability of oxygen content in single crystals. To address this technical difficulty and satisfy the need of market, Songci Electromechanical carried out a lot of technical development, verification and test, and finally obtained the solution for lowering the oxygen content of mono-Si cells, namely the low oxygen content type crystal growth furnace: SC-1600-LO₂.

The R&D team of Songci Electromechanical conducted extensive research and test into the mechanism of concentric circle defect occurred in N-type single crystals as well as the corresponding oxygen control technology. The numerical simulation of Czochralski process and the basic study of concentric circle defect helped the team to discover the correlation between the probability of concentric circle defect and the oxygen content of single crystals. Leveraging the low oxygen content crystal growth technology and the optimization of furnace's software and hardware, the team managed to reduce the proportion of concentric circle defect significantly. Under the same conditions, the concentric circle defect can be reduced by 50%.

Compared to the oxygen content level of popular silicon cells, the low oxygen content type crystal growth furnace can reduce the oxygen content by more than 24% under the same conditions and the efficiency of cell is improved by 0.1% according to the data from test line.

Design of Songci Electromechanical oxygen content reduction scheme:

●    Simulate the hot zone process and take the fluid flow path into account so as to make sure the opening location and the fluid pipe routing are carefully designed to fit the pipes in the furnace perfectly and impurities like oxygen will be removed as more as possible.

●    Add the functional module for oxygen control to the software control algorithms and turn on the oxygen removal function from time to time without affecting the crystal growth; other impurity removal modules will be incorporated later in the same manner.

●    Adjust some part of the process package to enhance the matching between process and hardware.

The low oxygen content type crystal growth furnace of Songci Electromechanical can not only ensure efficiency improvement but also bring benefits to customers and help customers to recoup the cost of equipment quickly. At present, several top PV companies are testing low oxygen content crystal growth using the laboratory furnaces of Songci Electromechanical.

About us

Songci Electromechanical(Wuxi Songci Electromechanical Co., Ltd.), a subsidiary controlled by Wuxi Autowell Technology Co., Ltd. (stock code: 688516), is mainly engaged in the R&D, manufacturing and sales of crystal growth equipment for PV and semiconductor industries as well as the provision of comprehensive solutions. With over a decade of manufacturing expertise and excellent performance of SC-1600 furnace, Songci Electromechanical has accumulated impressive achievements up to 2022: over 2000 units of equipment sold annually and a six-fold increase in annual order value. Their esteemed clientele includes industry leaders like Trina Solar, Qinghai Jinko Solar, JA Solar, Yuze Semiconductor, Hoshine, Zhongchengyu Energy, and notably, a landmark contract with Adani Solar in India, marking the delivery of the nation's first monocrystalline silicon rod.

For now, Songci Electromechanical is working on the development of intelligent crystal growth system on the basis of big data. In the future, Songci Electromechanical will make effort to clear technical bottlenecks of process and equipment, integrate crystal growing with AI and big data so as to realize the scientific production mode with functions of fully sensing, dynamic prediction and collaborative control. In order to meet the new requirements of bigger, thinner and higher-quality solar cells, Songci Electromechanical will be committed to provide outstanding solutions, create more value for customers and drive global intelligent manufacturing in PV industry.