CIGS Device Stability: A Comparison of Two Different Process Batches

In this work, we compare the light soaking behavior and potential induced degradation in devices from two different process batches (A and C). The two batches of CIGS devices have been prepared by ZSW with different co-evaporation tools and Ga/(Ga+In) depth profiles. Two different Na barriers (SiO2 or AlOx-AlN) have been used for low Na devices, and two buffers namely CdS and Zn(O,S) have been used in both batches. Initial device performance before stress indicates an improvement in efficiency and open-circuit voltage (V-OC) in the incorporation of Na in the absorber. Replacement of CdS buffer with Zn(O,S) results in a decrease in efficiency due to drop in V-OC albeit a slight increase in short-circuit current density (J(SC)). CdS buffer devices from batch A show more degradation under heat-light soaking (HLS) with short-circuit junction bias compared to batch C. Zn(O,S) devices show similar HLS behavior for both sample batches. Potential induced degradation (PID) tests with 1000 V bias show higher degradation in low Na devices with SiO2 barrier (batch C) compared to AlOx-AlN barrier (batch A).