LID and LeTID

Also called: Light Induced Degradation · Light and elevated Temperature Induced Degradation

In one line

Two distinct degradation mechanisms: LID causes a rapid 1–3% power loss in the first hours of sun exposure, while LeTID develops slowly over months at elevated temperature and can reach 6%.

LID loss

1–3%

LID onset

First hours of sun

LeTID loss

Up to ~6%

LeTID onset

Weeks to months

What it means

Light Induced Degradation is the fast one. In boron-doped p-type silicon, boron-oxygen complexes form within the first hours to days of illumination, costing 1–3% of power. It is well understood, largely stabilised before delivery on modern products, and already priced into datasheet first-year degradation figures. LeTID — light and elevated temperature induced degradation — is the more troublesome relative: it develops over weeks to months in hot operation, can reach 6% in susceptible p-type PERC products, and then partially recovers over years. N-type architectures such as TOPCon and HJT are largely immune to both mechanisms because they are not boron-doped in the same way, which is one of the underappreciated arguments for n-type in hot climates.

Worth knowing

LID is fast (hours-days) and small; LeTID is slow (weeks-months) and larger.
Both are p-type problems; n-type cells are largely unaffected.
LeTID is temperature-driven, making it a hot-climate risk in particular.
First-year degradation allowances on warranties exist largely because of LID.

At a glance

LID versus LeTID at a glance

Aspect	LID	LeTID
Trigger	First light exposure	Light + elevated temperature
Timescale	Hours to days	Weeks to months
Magnitude	1–3%	Up to 6%
Recovery	Stabilises	Partial, over years
Affected cells	Boron-doped p-type	Mainly p-type PERC

Field notes

1Baseline plant performance after the first few weeks of operation, not on day one, or LID will contaminate your reference.
2In hot climates specifying p-type, ask explicitly for LeTID test data — it is not on standard datasheets.

Common mistakes

Reading normal first-year LID as a warranty claim.
Assuming n-type immunity extends to every degradation mechanism — PID and soiling still apply.

Frequently asked

What is the difference between LID and LeTID?

LID occurs within the first hours of light exposure and costs 1–3% of power. LeTID develops over weeks to months of operation at elevated temperature, can reach around 6%, and then partially recovers over subsequent years.

Do n-type solar panels suffer from LID?

Largely no. Both LID and LeTID are associated with boron-doped p-type silicon, so n-type architectures such as TOPCon and HJT are substantially less affected — a meaningful advantage in hot climates.

Sources

[1]Degradation mechanisms in crystalline silicon PV — NREL
[2]LeTID research and characterisation — Fraunhofer ISE

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