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

•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.