Polycrystalline solar panels have become a mainstream choice in the renewable energy market due to their cost-effectiveness and reliable performance. The manufacturing process begins with raw material preparation, where metallurgical-grade silicon (MG-Si) is purified to solar-grade silicon (SoG-Si) through the Siemens process or fluidized bed reactors. This results in 99.9999% pure silicon, critical for minimizing electron recombination in finished panels.
The purified silicon is then melted in quartz crucibles at temperatures exceeding 1,400°C and poured into square molds. Unlike monocrystalline production that uses single-crystal seeds, polycrystalline ingots form through controlled cooling that creates multiple crystal structures. This directional solidification process typically takes 20-40 hours in industrial-scale furnaces, with cooling rates carefully managed to prevent stress fractures. The resulting ingots weigh 250-400 kg and contain 5-9 nine-inch pseudo-square cells when sliced.
Wire saws using diamond-coated cutting edges slice these ingots into 180-200μm thick wafers. Unlike the kerf loss-intensive process for monocrystalline wafers, polycrystalline cutting achieves 150-170μm kerf width through optimized slurry mixtures containing polyethylene glycol and silicon carbide abrasives. Surface texturing follows, where wafers undergo acid etching (usually HF/HNO3 solutions) to create light-trapping microstructures. This “random pyramid” texture reduces reflection from 35% to under 12% across visible light spectra.
Phosphorus diffusion then creates the p-n junction in tube furnaces at 800-900°C. POCl3 gas introduces n-type doping, with junction depth controlled to 0.3-0.5μm. Screen printing applies front and rear electrodes using silver paste for busbars and aluminum paste for back surface fields. Firing in conveyor belt furnaces at 700-800°C sinters these contacts, with peak temperature timing critical for achieving <1Ω/sq contact resistance.Quality control stages include electroluminescence imaging to detect microcracks and potential-induced degradation (PID) testing at 85°C/85% humidity. Finished cells are laminated into panels using ethylene-vinyl acetate (EVA) encapsulant sheets and tempered glass with 92% transparency. The lamination process occurs in vacuum chambers at 140-160°C, creating hermetic seals that withstand 25+ years of UV exposure and thermal cycling.Recent innovations include diamond wire saws reducing silicon waste by 40% compared to slurry-based cutting, and black silicon texturing using plasma etching to boost efficiency to 19.8% in commercial polycrystalline panels. Manufacturers like those at Polycrystalline Solar Panels now integrate reverse busbar designs and half-cell configurations to minimize resistive losses, achieving 380-400W output in standard 72-cell formats.
End-of-line testing includes STC (Standard Test Conditions) verification at 1000W/m² irradiance and 25°C cell temperature, with IEC 61215 and IEC 61730 certifications requiring rigorous hail impact (23m/s ice balls) and mechanical load tests (5400Pa wind/snow loads). These processes ensure polycrystalline modules maintain >80% performance after 25 years, with degradation rates averaging 0.7%/year in field studies.
The entire manufacturing cycle from quartz to completed panel takes 5-7 days in vertically integrated facilities, with energy payback times now under 2 years due to process optimizations. This positions polycrystalline technology as a sustainable solution balancing efficiency (17-20%), durability, and affordability in utility-scale and residential installations.