Silver incorporated bilayer Kesterite solar cell for enhanced device performance: A numerical study

Abstract

In this work, the analytical results pertaining to modeling of silver substituted Kesterite absorber (Cu1-xAgx)2ZnSnSe4 (ACZTSe) and (Cu1-xAgx)2ZnSnS4 (ACZTS) materials are demonstrated. The basic approach adopted here is the tailoring of bandgap and electron affinity of the modified Kesterite structure so as to enhance the performance. The promising Ag incorporated materials exhibit improvement in open circuit voltage which is one of the bottlenecks in the Kesterite structure. The pure Cu2ZnSnS4 (CZTS) and Cu2ZnSnSe4 (CZTSe) are considered and modeled as the baseline structures for simulation in SCAPS. To improve the performance parameters, the analysis was carried out for tandem structures with silver substituted in place of copper in the Kesterite material. As Ag has got favorable atomic properties which makes it an ideal candidate to substitute against copper. The equations of bandgap and electron affinity for Ag doped CZTS and CZTSe with a tuning factor of [Ag]Ag+[Cu] is modeled for optimizing the tandem structures. The front linear grading with reverse linear bandgap profile is used for the improvement of the overall performance of the device with variation in absorber layer thickness, acceptor doping density. The modeled Ag substituted tandem devices ACZTSe/CZTSe and CZTS/ACZTS results in efficiency of 19.37% and 23.50% respectively. Finally, the impact of temperature variation on Capacitance-Frequency calculation along with the influence of series and shunt on the device performance is investigated and discussed.