Dry Heat-Induced Degradation of (Ag,Cu)(In,Ga)Se2 Solar Cells: Experiment and Simulation
Aaron Arehart1, Pran Paul1, Jeff Bailey2, Rouin Farshchi2, Dmitry Poplavskyy2
1The Ohio State University, Columbus, OH, United States
/2MiaSolé Hi-Tech Corp., Santa Clara, CA, United States

Dry heat stressing of CIGS solar cells leads to decreases in fill factor (FF) and open circuit voltage (VOC).  Using quantitative defect spectroscopies, the trap spectra are characterized before and after the dry heat stress.  Using current-voltage-temperature measurements, it is demonstrated that dry heats causes an barrier to form likely at the Mo/CIGS interface.  Simulations with this experimental data and no fitting parameters are in good agreement with the experimental results indicating the traps and back barrier are sufficient to explain the dry heat degradation effects on Voc and FF.  The simulations show the FF reduction is due to the barrier formation while the VOC reduction is mostly due to an increase in the EV+0.98 eV trap concentration.