Potential-induced degradation of Cu(In, Ga)Se2 can occur by shunting the front i-ZnO and by damaging the p-n junction. (15th January 2022)

• Record Type: Journal Article
• Authors: Muzzillo, Christopher P.; Terwilliger, Kent; Hacke, Peter; Moutinho, Helio R.; Young, Matthew R.; Glynn, Stephen; Stevens, Bart; Repins, Ingrid L.; Mansfield, Lorelle M.
• Is Part Of: Solar energy. Volume 232(2022)
• Page Start: 298
• Page End: 303
• Publication Date: 2022-01-15
• Subjects: Photovoltaics -- Reliability -- Thin-film -- Potential-induced degradation -- Chalcopyrite -- Cu(In -- Ga)Se2; Solar energy -- Periodicals; Solar engines -- Periodicals; 621.47
• DOI: 10.1016/j.solener.2021.12.074
• Languages: English
• ISSNs: 0038-092X

Abstract

Highlights: We encapsulate laboratory CIGS cells to study field-relevant PID. K-rich borosilicate glass reduces PID, relative to Na-rich soda-lime glass. Stressing cells at short-circuit leads to faster PID than open-circuit. Front-glass stress shunts the i-ZnO buffer, slowly reducing the FF. Back-glass stress drives Na + into the p-n junction to rapidly degrade VOC and FF. Abstract: In this work we test field-relevant potential-induced degradation (PID) behavior by encapsulating laboratory Cu(In, Ga)Se2 (CIGS) solar cells and applying +1000 V uniformly on the face of the front glass. In this configuration, we find that K-rich borosilicate glass reduces the extent of PID relative to Na-rich soda-lime glass. We also find that the standard testing protocol of stressing cells at short-circuit leads to faster PID than stressing cells at open-circuit. We characterize two types of CIGS PID: The first, front shunting PID, is driven by front-glass stress and occurs when alkali metal cations accumulate in the i-ZnO buffer, where they increase shunt conductance to reduce fill factor. The second, p-n junction PID, results from back-glass stress as alkali metal cations pile up near the CIGS surface/CdS buffer, where they reduce charge carrier concentration, open-circuit voltage, and fill factor to degrade efficiency ∼160 times faster than front shunting PID.