Heat- and light-soaking behavior of RbF-treated Cu(In,Ga)Se2 solar cells with two different buffer layers

Degradation in RbF post-deposition-treated (PDT) CIGS solar cells under heat/light/bias stress is evaluated for two different buffers, CdS and Zn(O,S). Initial efficiency of baseline CdS buffer devices is about 17.7% with and without RbF PDT. However, Zn(O,S) buffer devices show considerable improvement in net carrier concentration (N-CV), V-OC, and efficiency from 16.3 to 17.9% with RbF PDT. Under accelerated stress tests, CdS buffer devices show an increase in V-OC under open circuit (OC) light soaking irrespective of the alkali treatments, and the devices are relatively stable under short circuit (SC) stress. Zn(O,S) buffer devices, however, show a decrease in V-OC under all stress conditions irrespective of the alkali treatments. All performance metrics for Zn(O,S) buffer devices typically decreased with stress, resulting in significant efficiency loss. Device models show that an increase in recombination at the CIGS/Zn(O,S) interface and near interface doping can explain the degradation in these devices.

Automated summary

The degradation of RbF post-deposition-treated (PDT) CIGS solar cells under heat/light/bias stress is evaluated for two different buffers, CdS and Zn(O,S). It was found that CdS buffer devices are relatively stable while Zn(O,S) buffer devices show significant efficiency loss. Device models suggest that increased recombination at the CIGS/Zn(O,S) interface and near interface doping contribute to the degradation in Zn(O,S) buffer devices.