LeTID

Key Takeaways

• LeTID = slower-onset PERC cell degradation at elevated temperatures.
• Total loss 2–4% over module life.
• Absent in n-type TOPCon and HJT cells.
• Mitigated in modern PERC via “anti-LeTID” treatment.
• Hot climates worsen LeTID.

How LeTID Differs From Standard LID

LID shows up in the first few weeks a module sees sunlight and then stabilizes — it’s a fast, front-loaded effect that manufacturers bake into first-year power ratings. LeTID behaves differently: instead of settling out in weeks, it develops gradually over months of combined light exposure and elevated cell temperature, and in some cases partially recovers before the module’s output re-stabilizes at a lower baseline. That slower, temperature-driven timeline is exactly why hot-climate installations — rooftop and ground-mount sites running consistently warm cell temperatures — see more pronounced LeTID than modules operating in cooler climates. Because the mechanism is tied to boron-hydrogen defects that form in boron-doped PERC cells, it does not appear in n-type TOPCon or HJT modules, which use a different cell chemistry.

Why It Matters for Module Selection and Yield Modeling

A 2–4% lifetime loss sounds small next to the broader degradation rate budget for a 25-year plant, but it still needs to be accounted for rather than assumed away, especially on projects in consistently hot regions where cell temperatures run high for much of the year. Most current-generation PERC production uses an anti-LeTID regeneration step specifically to suppress this loss, so the practical question for a design team is less “does this module have LeTID” and more “how much has the manufacturer’s process reduced it, and is that reflected in the module’s warranty curve and the site’s yield simulation.” That distinction is the kind of detail that gets checked during module technology selection in a PV module’s datasheet review, and it’s one more variable that feeds into the degradation assumptions carried through a full energy yield run.

Related Reading

LeTID is one of several module-level effects a yield simulation has to get right before a lender will sign off on a project’s numbers — the kind of modeling covered in PV Yield Simulation Software: The Bankable Yield 5. Because LeTID losses widen the uncertainty band around long-term output, they feed into the P50 and P90 figures that lenders use to size debt on a project. Teams comparing simulation platforms for this kind of degradation-aware forecasting may also find Solar Simulation Software 2026: Lender-Grade Yield Picks useful for seeing how different tools handle module-level loss assumptions.