PID is module degradation driven by high voltage between the cells and the grounded frame. The voltage grows with the number of modules in a string and drives leakage currents. Heat, humidity, wet surfaces and soiling speed it up. Cells near the frame and modules at one end of the string are hit hardest. You usually cannot see it by eye. What you see is a power loss that keeps growing, and string losses can reach 20 to 80 percent. Infrared imaging in sunlight often shows warmer cells along the bottom frame or a patchwork pattern. EL imaging at low current shows dark cells near the frame and catches PID early. Confirm it and measure the loss with IV curve tracing or Voc checks. Look for a lower fill factor and lower Voc, and for lower Isc in the polarization type. To prevent it, keep modules clean, use grounding or offset boxes that apply reverse voltage at night, and choose PID-resistant modules. If you catch it early, reversing the bias polarity can regenerate affected modules. Corrosion damage at later stages cannot be reversed.
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caused_byc1 verified · fact High voltage to ground
Stress grows with the number of modules in series; p-type cells degrade in negative-polarity strings, n-type in positive-polarity strings.
sec=h4 h=21df64fc133esec=h63 h=8878a24975cbsec=front h=4921d46d666fverified by: joshuahamsaverified on: 2026-10-16
c2 drafted · lead Leakage current
PID-s is driven by leakage current through the front glass and encapsulant.
sec=h63 h=8878a24975cbsec=front h=4921d46d666ftbl=1.r2 h=9a1182df900cc3 drafted · lead Sodium ion migration
Na+ ions moving mainly from the glass into the cell create shunts.
sec=h63 h=8878a24975cbc4 drafted · lead Moisture exposure
Humidity, rain wetting and condensation speed up degradation; the electrochemical form is corrosion from moisture ingress.
sec=h63 h=8878a24975cbtbl=1.r3 h=777f6ba7af3ereview note: support check: partial - Humidity, rain wetting and condensation accelerate PID and electrochemical corrosion from moisture infiltration is listed, but moisture as a cause of PID itself is only acceleration.
c5 drafted · lead High operating temperature
sec=h63 h=8878a24975cbreview note: support check: partial - Temperature is said to accelerate PID, but not that high operating temperature is a cause.
c6 drafted · lead Surface soiling
Dust carrying positive charges increases PID risk.
sec=h63 h=8878a24975cbsec=h9 h=1a8ef7f958edaffectsc7 verified · fact Solar cell
sec=h63 h=8878a24975cbtbl=1.r1 h=f5b8d9f781ffverified by: joshuahamsaverified on: 2026-10-16
c8 drafted · lead Module front glass
Leakage path and sodium source.
sec=h63 h=8878a24975cbpresents_asc9 drafted · lead Gradual performance decline
tbl=15.r1 h=6e2cec50e730sec=h63 h=8878a24975cbc10 verified · fact Warm cells near frame
IR pattern of warmer cells near the bottom frame or a patchwork pattern, strongest in modules near one string pole.
tbl=15.r1 h=6e2cec50e730sec=h63 h=8878a24975cbverified by: joshuahamsaverified on: 2026-10-16
c11 drafted · lead Hotspot in IR image
sec=h7 h=4ba0228f747ctbl=15.r1 h=6e2cec50e730sec=h63 h=8878a24975cbreview note: support check: partial - Hot spots are mentioned and IR thermography reveals hotspots, but the primary IR pattern is warmer cells; hotspots are secondary/late.
c12 drafted · lead Reduced fill factor
Typical of PID-s, along with lower shunt resistance; more visible under low light.
tbl=15.r1 h=6e2cec50e730sec=h63 h=8878a24975cbc13 drafted · lead Low module open-circuit voltage
tbl=15.r1 h=6e2cec50e730sec=h63 h=8878a24975cbc14 verified · fact Reduced short-circuit current
Mainly PID-p; for PID-s Isc only drops in a very advanced stage.
tbl=15.r1 h=6e2cec50e730sec=h63 h=8878a24975cbverified by: joshuahamsaverified on: 2026-10-16
c15 verified · fact Dark regions in EL image
PID-s cells near the frame show reduced luminescence, especially at low current bias.
tbl=15.r1 h=6e2cec50e730verified by: joshuahamsaverified on: 2026-10-16
detected_byc16 verified · fact Electroluminescence imaging
EL at about one tenth of rated current can find PID early, before power loss is noticed.
sec=h7 h=4ba0228f747ctbl=15.r1 h=6e2cec50e730sec=h63 h=8878a24975cbverified by: joshuahamsaverified on: 2026-10-16
c17 drafted · lead Infrared thermography
sec=h7 h=4ba0228f747ctbl=15.r1 h=6e2cec50e730sec=h63 h=8878a24975cbc18 drafted · lead IV curve tracing
Used to confirm and quantify loss together with IR or EL.
sec=h7 h=4ba0228f747ctbl=15.r1 h=6e2cec50e730sec=h63 h=8878a24975cbc19 drafted · lead Open-circuit voltage measurement
sec=h7 h=4ba0228f747csec=h2 h=ff7ac62c1dc0c20 verified · fact PID susceptibility lab test
IEC 62804 chamber test; a module fails above 5% power degradation.
sec=h7 h=4ba0228f747csec=h63 h=8878a24975cbverified by: joshuahamsaverified on: 2026-10-16
leads_toc21 drafted · lead Discoloration
tbl=15.r1 h=6e2cec50e730sec=h63 h=8878a24975cbc22 drafted · lead Delamination
tbl=3.r17 h=75fbc77dd47etbl=15.r1 h=6e2cec50e730c23 drafted · lead Severe Metallization Corrosion
Corrosion appears as a secondary failure in advanced stages; not reversible.
sec=h63 h=8878a24975cbtbl=1.r3 h=777f6ba7af3emitigated_byc24 verified · fact Regular cleaning
sec=h9 h=1a8ef7f958edsec=h2 h=ff7ac62c1dc0verified by: joshuahamsaverified on: 2026-10-16
c25 drafted · lead System grounding scheme
For example setting the frame to a negative potential.
sec=h9 h=1a8ef7f958edsec=h2 h=ff7ac62c1dc0c26 drafted · lead PV offset box
Applies reverse voltage overnight.
sec=h9 h=1a8ef7f958edc27 drafted · lead PID-resistant modules
sec=h63 h=8878a24975cbsec=h2 h=ff7ac62c1dc0c28 verified · fact Alternative encapsulant material
Such as TPO.
sec=h9 h=1a8ef7f958edverified by: joshuahamsaverified on: 2026-10-16
c29 drafted · lead Low-ion front glass
sec=h9 h=1a8ef7f958edc30 drafted · lead Cell ARC layer optimization
Higher Si/N ratio or an added SiO2 layer under the ARC.
sec=h9 h=1a8ef7f958edc31 verified · fact Polarity reversal regeneration
PID-p can be fully regenerated; PID-s only if caught in time.
sec=h63 h=8878a24975cbsec=h2 h=ff7ac62c1dc0verified by: joshuahamsaverified on: 2026-10-16
typical_power_lossc32 verified · fact nominal 41 PERCENT
Conditions: Average performance loss reported for a 10.7 MW plant in Spain (Libby et al.)
sec=h4 h=21df64fc133everified by: joshuahamsaverified on: 2026-10-16
c33 drafted · lead 20–80 PERCENT
Conditions: Reduction of PV string performance after commissioning, per Libby et al.
sec=h3 h=0587f1d564aereview note: support check: partial - Source says 'up to 20-80%', an upper bound range, not a typical value.
c34 verified · fact ≥ 20 PERCENT
Conditions: Yield losses observed within 1 year in past field cases
sec=h63 h=8878a24975cbverified by: joshuahamsaverified on: 2026-10-16review note: support check: partial - Source says losses of 20 percent and more within 1 year; 20% is a lower bound, not typical.
related_to c4related_to c5related_to c3leads_to c1caused_by c8