Influence of Amorphous Silicon Carbide Intermediate Layer in the Back-Contact Structure of Cu2 ZnSnSe4 Solar Cells

Cu
₂
ZnSn(S
_1-y
Sey )
₄
(CZTS) thin-film solar cells have been qualified as potential competitors of the more established CIGS ones. One of the more important handicaps of CZTS solar cells is the open-circuit voltage deficit. The rear-contact/absorber interface is known to be very sensitive to the formation of secondary phases, which are detrimental for the electrical behavior of photovoltaic devices. The addition of intermediate layers to favor the formation of an adequate interface has been repeatedly tested. In this work, an amorphous silicon carbide (a-SiC) layer is added to explore its influence on the material properties and electrical performance of CZTSe solar cells. According to scanning electron microscopy (SEM) analysis, when the a-SiC layer thickness is increased, bigger grains along the absorber are obtained. Additionally, a lower [V
_Cu
+ Zn
_Cu
] defect cluster density is also deduced from the analysis of Raman measurements. Both results indicate a favorable impact of a-SiC films on the material quality of the absorber. Fabricated solar cells show an enhancement of 0.9% abs. of efficiency compared to identical solar cells without a-SiC layers used as a reference. This increase is mainly related to an improvement of open-circuit voltage and fill factor (FF) when the proposed intermediate layer is included.