The global photovoltaic industry is accelerating the upgrade of large-size, high-efficiency and low-cost silicon wafers. 182mm and 210mm large-size monocrystalline silicon wafers have completely replaced small-size wafers and become the mainstream of the market. The upgrade of silicon wafer size and the popularization of long-cycle uninterrupted crystal pulling technology have completely subverted the performance requirements of traditional PV graphite thermal field components. The graphite thermal field system composed of graphite heaters, insulation barrels, crucible supports, diversion cylinders and heat preservation cover plates is the core thermal carrier of the crystal pulling furnace. It builds a stable and uniform high-temperature thermal field environment of 1420–1450°C for molten silicon crystallization, and its stability directly determines the yield and production efficiency of monocrystalline silicon ingots.
In the traditional small-size wafer production era, medium-grain ordinary graphite can meet basic production needs. However, large-size silicon wafer crystal pulling has higher requirements on thermal field uniformity, material purity and structural stability. The temperature difference of the thermal field will directly lead to crystal dislocation, lattice defects and uneven resistivity of silicon wafers, reducing the photoelectric conversion efficiency of photovoltaic modules. Long-cycle crystal pulling (more than 200 hours per furnace) makes graphite components work continuously in high-temperature silicon vapor erosion environment, and ordinary graphite is prone to surface peeling, powder falling and local oxidation failure, resulting in frequent furnace shutdown and replacement, seriously restricting production capacity and increasing production costs.
High-purity fine-grain isostatic graphite has become the standard material for new-generation PV thermal fields due to its uniform isotropy, ultra-low porosity and excellent anti-erosion performance. High-density graphite after vacuum impregnation treatment can effectively resist the corrosion of silicon monoxide vapor generated by molten silicon volatilization, reduce the loss rate of thermal field components, and extend the continuous service cycle of the thermal field. In terms of structural design, the integrated large-size graphite thermal field component replaces the traditional spliced structure, eliminates the temperature difference and heat loss caused by assembly gaps, realizes ultra-uniform temperature field distribution, and greatly improves the yield of large-size monocrystalline silicon ingots.
Common failure problems of PV graphite thermal fields in industrial production include four major categories: thermal deformation caused by inconsistent material density, particle contamination caused by insufficient purity, local ablation caused by unreasonable thermal field structure, and crack failure caused by unoptimized thermal stress. Most PV manufacturers only pay attention to the purchase cost of graphite components and ignore the matching degree of material grade and production process, resulting in low service life of thermal field components, frequent equipment shutdown and high comprehensive operating costs. Professional customized thermal field optimization can effectively extend the service life of graphite components by 30%–50% and improve the overall yield of silicon wafers by more than 2%.
With the popularization of N-type high-efficiency solar cells, the purity requirements of photovoltaic silicon wafers have reached a new height. Trace metal impurities in graphite thermal field components will volatilize at high temperature and penetrate into silicon ingots, forming minority carrier recombination centers, reducing the minority carrier lifetime of silicon wafers, and ultimately affecting the conversion efficiency and attenuation performance of photovoltaic modules. Therefore, modern PV thermal field graphite must adopt ultra-high-temperature halogen purification technology to control ash content below 10ppm and strictly limit trace metal impurities such as iron, nickel and copper.
Huixian Jincheng Abrasive & Graphite Mold Factory has long been deeply engaged in the research and development and customized production of photovoltaic full-series graphite thermal field components, with 42 years of graphite processing experience to serve the iterative upgrade of the global photovoltaic industry. The company selects high-quality fine-grain isostatic graphite raw materials for PV thermal field special use, and carries out secondary high-temperature purification and multi-cycle vacuum impregnation treatment to ensure that the components have ultra-high purity, high density and strong anti-silicon vapor erosion ability. Relying on more than 50 precision CNC machining equipment, Jincheng Graphite can customize integrated large-size graphite heaters, integral insulation barrels, high-precision crucible supports and diversion cylinders for 210mm large-size silicon wafer furnaces, abandoning the traditional spliced structure to realize overall thermal field optimization.
Different from standardized universal graphite parts, Jincheng Graphite provides personalized thermal field matching solutions according to the furnace type, crystal pulling process parameters and production cycle of different PV manufacturers. The technical team optimizes the wall thickness, aperture and structural radian of thermal field components to balance thermal insulation performance and thermal conductivity, eliminate local hot and cold spots in the thermal field, and maximize the yield of high-efficiency N-type silicon wafers. In addition, the company provides professional thermal field maintenance, surface repair and re-impregnation regeneration services for used graphite components, helping PV enterprises reduce consumable procurement costs and improve equipment operation efficiency.
At present, the global photovoltaic industry is moving towards ultra-large furnace type, long-cycle production and high-purity high-efficiency wafers. The technical competition of PV graphite thermal fields has shifted from basic dimensional accuracy to material purity, thermal field uniformity and long-life stability. As a professional customized manufacturer of photovoltaic graphite thermal field components, Jincheng Graphite continues to upgrade material purification and precision processing technology, and provides high-cost-performance and high-stability graphite thermal field solutions for global photovoltaic manufacturers, helping the industry reduce costs and increase efficiency.
