Behavior of Na and RbF-Treated CdS/Cu(In,Ga)Se2 Solar Cells with Stress Testing under Heat, Light, and Junction Bias

The effects of Na and RbF alkali treatment on the metastability behavior of CdS/Cu(In,Ga)Se-2 solar cells are investigated with stress factors of heat, junction bias, and illumination. Four device types with and without Na or RbF treatments are subjected to heat- and light-soaking under open- and short-circuit (OC, SC) junction bias. Low-Na devices show a higher bandgap due to increased minimum Ga content, higher recombination current, and lower open-circuit voltage ( VOC). Devices with RbF post-deposition treatment (PDT) show an improvement in net doping density approximate to 10(16) cm(-3), VOC, and efficiency. Heat- and light-soaking under OC junction bias provokes an increase in net carrier concentration and VOC irrespective of the alkali treatments. After SC stress, a decrease in VOC and net carrier concentration is observed, which can be stabilized by RbF-PDT. An increase in Na and oxygen concentration in CIGS is observed for baseline and low-Na devices, respectively, after OC stress. The oxygen concentration in CdS decreases after heat- and light-soaking for devices without RbF-PDT, whereas it remains unchanged for devices with RbF-PDT. The atomic concentration profiles in CIGS significantly stabilize as a function of stress with the addition of RbF-PDT.

Automated summary

The study demonstrates significant effects of Na and RbF alkali treatment on the performance of CdS/Cu(In,Ga)Se-2 solar cells, with low-Na devices exhibiting higher bandgaps and steady-state carrier densities, and devices with RbF post-deposition treatment showing improvements in net doping density and efficiency. Both heat- and light-soaking processes result in changes in Na and oxygen concentrations in CIGS, while the atomic concentration profiles in CIGS stabilize significantly with the addition of RbF-PDT.