TOPCon vs HJT vs PERC solar cells: what is the difference?
PERC is the older mainstream silicon cell now being phased down; TOPCon adds a passivated contact layer for higher efficiency; HJT (heterojunction) reaches the highest efficiency and has a flatter temperature coefficient, so it loses less output in heat. For procurement, the cell technology drives the efficiency floor, the degradation curve, and the price.
PERC, TOPCon, and HJT are three crystalline-silicon solar cell architectures. They use the same basic silicon wafer but differ in how the rear and front surfaces are passivated and how the electrical contacts are formed. Those differences change conversion efficiency, behavior in heat, long-term degradation, and cost.
How the three architectures differ
PERC (Passivated Emitter and Rear Cell) adds a rear passivation layer to a standard cell and has been the mass-market baseline for years; its efficiency ceiling is now largely reached and new capacity is shifting away from it. TOPCon (Tunnel Oxide Passivated Contact) adds an ultra-thin oxide plus a doped polysilicon layer that reduces contact losses, lifting efficiency above PERC on similar production lines. HJT (Heterojunction) combines crystalline silicon with thin amorphous-silicon layers, reaching the highest cell efficiency of the three and a lower temperature coefficient, meaning less power loss as the panel heats up.
| Attribute | PERC | TOPCon | HJT |
|---|---|---|---|
| Relative cell efficiency | Baseline (lowest of the three) | Higher than PERC | Highest |
| Temperature coefficient | Higher loss in heat | Better than PERC | Best (flattest) |
| Maturity / capacity trend | Mature, capacity declining | Mainstream, growing | Premium, scaling |
| Typical relative cost | Lowest | Moderate | Highest |
| First-year and long-term degradation | Standard | Generally low | Generally low |
Why a buyer specifies cell technology, efficiency floor, and degradation
Two modules can carry the same wattage label yet behave very differently in the field. A hot rooftop favors a flatter temperature coefficient (HJT), while a cost-sensitive utility array may accept TOPCon or PERC. Energy yield over 25 years depends on the degradation curve, not just nameplate watts. That is why a serious specification states the cell technology, a minimum module efficiency, a first-year and annual degradation cap, and the temperature coefficient, rather than buying on price-per-watt alone.
How MPBxChange handles it
On MPBxChange you shape the requirement as a capability spec: cell technology, efficiency floor, degradation limits, temperature coefficient, and certification. Matching is on that capability rather than on a brand name, the counterparty stays sealed until you accept, and milestone escrow can release against conformity evidence such as flash-test reports and datasheets tied to the agreed spec.
Frequently asked questions
No. HJT typically delivers the highest efficiency and the flattest temperature coefficient, but it usually costs more. For cost-driven utility projects, TOPCon or even PERC can give a better return; the right choice depends on roof temperature, space constraints, and project economics.
Not yet, but it is past its peak. PERC remains widely available and inexpensive, while new manufacturing capacity is shifting toward TOPCon and HJT. Buyers planning long-life assets should weigh long-term availability and degradation, not just todays price.
At minimum: cell technology (PERC, TOPCon, or HJT), minimum module efficiency, first-year and annual degradation caps, temperature coefficient, certification, and the warranty terms. These let you compare modules on energy yield instead of nameplate wattage alone.