Polysilicon: Characteristics
What nine nines of purity means for a solar cell
What this tab covers The physical and chemical properties that set its grade, price and uses, with the commercial grades and the standards that define them.Polysilicon is sold by purity and form. Solar buyers care about donor and acceptor impurities (boron, phosphorus), metals and carbon at parts-per-billion levels, because they reduce cell efficiency. Semiconductor buyers require 10-11 nines and surface metal levels in the parts-per-trillion range.
Properties that matter commercially
| Property | Value / specification | Why it matters | Source |
|---|---|---|---|
| Purity | solar multicrystalline up to 8 nines, monocrystalline 9 nines, semiconductor 10 or more nines | Higher purity raises cell efficiency and is needed for chips | Conway, Material World (2023) |
| Metallic impurities (granular) | under 1 ppbw for 95% of GCL granular output (2025) | Qualifies granules for n-type cells | China Polysilicon 2026 report |
| Form | dense chunk, coral, granular | Granules flow, suiting continuous ingot pulling | China Polysilicon 2026 report |
| n-type premium | RMB 3,000-5,000/t in 2025 | Rewards higher purity | China Polysilicon 2026 report |
Commercial grades
- N-type dense (solar)
- N-type granular (FBR)
- P-type and mixed (legacy solar)
- Semiconductor grade (electronic grade polysilicon)
- UMG silicon