Potential-Induced Degradation Depends on Leakage Current and Light/Electrical Bias in Cu(In,Ga)Se2 Devices

Abstract

Potential-induced degradation (PID) of encapsulated Cu(In,Ga)Se2 (CIGS) solar cells was studied for different substrates: soda-lime glass (SLG), SLG with an Al2O3 diffusion barrier, and borosilicate glass (BSG). The Al2O3 and BSG samples increased the time to PID failure by 5x and 30x, respectively. The relationship between PID and coulombs transferred from the substrate to the device through leakage current differed depending on the sample type. When the (unrepresentative) dark PID stress test was interrupted to characterize devices with light/electrical bias, PID was partially reversed. In addition, applying high voltage stress to open-circuit devices was less damaging, relative to forward-biased and short-circuited cells. Light/electrical bias may therefore reduce PID by driving alkali metal cations away from the p-n junction to diminish their degrading effects. These results show that device light/electrical bias should be carefully controlled during CIGS PID testing, as it affects PID in addition to leakage current.