Potential Induced Degradation and Recovery Effects in CdS/CIGS Solar Cells with Na and RbF Treatments

In this work, the effect of alkali treatments namely Na and RbF has been investigated on the potential induced degradation (PID) for CdS/CIGS solar cells. Four device types with variations in Na content and RbF post-deposition treatment (PDT) have been studied. Baseline Na devices (Type 1) show an average efficiency of ~18% which does not show an improvement with RbF-PDT (Type 1R) in this sample series. Low Na devices with and without RbF-PDT both show average efficiency of ~16% for this sample series. PID tests were conducted in dark at temperatures between RT- 85 °C under 1000 V applied between back of the soda-lime glass and the Mo contact. All device types show degradation due to increase in shunt conductance, which could be partially recovered by reversing the bias voltage polarity. Recovery of PID degradation is a temperature dependent phenomenon, wherein, higher recovery is observed at higher temperature. Preliminary results show low-Na devices recover to 80%, whereas, baseline Na devices recover to 50% of initial efficiency at 85 °C. RbF-PDT does not change the recovery of baseline Na devices, however, low-Na devices with RbF-PDT show recovery to only 25% of initial device efficiency.