Solar Lattice

Symptom

Reduced short-circuit current

ID
symptom:isc-reduction
IRI
https://solarlattice.org/kb/symptom/isc-reduction
Status
active
Also known as
Isc

Reduced short-circuit current shows up when a string's Isc is measured with a short-circuit test. Compare it with the expected value and with identical strings under stable irradiance. On an IV trace, look at the other parameters too. Metallization corrosion lowers Isc and fill factor because series resistance rises, while LID lowers Isc, fill factor and Voc together. PID-p causes a significant drop in Isc, Voc and power. PID-s mainly reduces fill factor and affects Isc only when it is far advanced. Cell cracks reduce current because isolated cell areas stop contributing. EL imaging shows microcracks that cannot be seen by eye. Most cracks do not isolate cell parts and cause little power loss. A large inactive area can reverse-bias the cell or switch on the bypass diode. Soiling also lowers Isc. Soiling stations measure it by comparing a regularly cleaned reference device with a soiled one, using temperature-corrected Isc. Uneven soiling can cost more power than the change in Isc suggests, so record power as well as Isc. First check whether the module surface is soiled or the cells are visibly corroded. Then use IV tracing, EL and thermography to tell cracks, corrosion, LID and PID apart.

<!-- review notes

Claims

observed_as

c1 drafted · lead Low string short-circuit current

In a string short-circuit test, measured string Isc is compared with the expected value and with identical strings under stable irradiance; the standard expects identical strings to agree typically within 5 % of the average. The test is meant to detect faults, not to rate performance.

c2 verified · fact Lowered Isc on IV curve

Shown in IV traces for metallization corrosion, LID, PID-p and cracks that isolate part of a cell.

verified by: joshuahamsaverified on: 2026-10-20review note: support check: partial - Corrosion, LID and PID-p lowering Isc are stated, but cracks lowering Isc is not stated in the IV context here (only EL-based mention elsewhere); the IV-trace attribution for cracks is missing.

c3 verified · fact Reduced fill factor

Occurs together with lower Isc in metallization corrosion (higher series resistance) and in LID.

verified by: joshuahamsaverified on: 2026-10-20

c4 verified · fact Low open-circuit voltage

LID and PID-p lower Voc along with Isc, while cracks and soiling mainly lower current.

verified by: joshuahamsaverified on: 2026-10-20review note: support check: partial - LID and PID-p lowering Voc with Isc is stated, but the claim that cracks and soiling mainly lower current is not supported for Voc comparison in these passages.

c5 drafted · lead Soiled vs clean Isc ratio

Soiling stations take the soiling ratio from the temperature-compensated Isc of a regularly cleaned device and a soiled one. Data are usually filtered to clear-sky midday hours.

c6 verified · fact Crack pattern in EL image

Microcracks that cannot be seen by eye show up in EL images and can isolate cell regions, which lowers Isc.

verified by: joshuahamsaverified on: 2026-10-20

c7 drafted · lead Patchwork EL pattern

Growing non-uniformity in EL can point to ongoing LID. PID also shows patchwork patterns.

review note: support check: partial - Patchwork EL non-uniformity for LID is stated, but PID patchwork is mentioned only for IRT patterns, not EL.

typical_power_loss

c8 verified · fact ≤ 30 PERCENT

Conditions: Light induced degradation (light soaking effect), module power

verified by: joshuahamsaverified on: 2026-10-20review note: support check: partial - Passage says LID could entail losses up to 30% in module power performance, but not specifically as Isc reduction or typical value; 'up to' is a bound.; reviewer: the compiler-flagged conflict is a different scenario or technology, not disagreement

c9 disputed 1–3 PERCENT

Conditions: LID (boron-oxygen) in c-Si modules, first days of sun exposure

conflicts with: Reduced short-circuit current (c11)conflicts with: Reduced short-circuit current (c12)conflicts with: Reduced short-circuit current (c13)

c10 disputed ≤ 10 PERCENT

Conditions: LeTID, mainly PERC modules, over years at elevated temperature; adds to the LID loss

conflicts with: Reduced short-circuit current (c11)conflicts with: Reduced short-circuit current (c12)

c11 verified · fact ≥ 20 PERCENT

Conditions: PID yield losses observed within 1 year

verified by: joshuahamsaverified on: 2026-10-20review note: reviewer: the compiler-flagged conflict is a different scenario or technology, not disagreement

c12 verified · fact nominal 35 PERCENT

Conditions: Simulated module with one cracked cell at 45 % inactive area, which activates the substring bypass diode

verified by: joshuahamsaverified on: 2026-10-20review note: possible conflict with c13 (same source; check the conditions); reviewer: the compiler-flagged conflict is a different scenario or technology, not disagreement

c13 verified · fact nominal 5 PERCENT

Conditions: Simulated module with one cracked cell at 15 % inactive area

verified by: joshuahamsaverified on: 2026-10-20review note: possible conflict with c12 (same source; check the conditions); reviewer: the compiler-flagged conflict is a different scenario or technology, not disagreement

degradation_rate

c14 drafted · lead ≤ 3 PERCENT-PER-YR

Conditions: Cell cracks, global rate in all climate zones except cold and snowy ones

review note: possible conflict with c15 (same source; check the conditions)

c15 verified · fact nominal 8 PERCENT-PER-YR

Conditions: Cell cracks, affected part, cold and snowy climate zones

verified by: joshuahamsaverified on: 2026-10-20review note: possible conflict with c14 (same source; check the conditions)

Referenced by

Data