The influence of various front contact materials on the performance of CdTe solar cells

The use of a resistive, or buffer, layer in the front contact structure of CdTe solar cells has been known to improve solar cell performance, in particular when the CdS thickness is relatively small. This paper reviews the performance of CdTe solar cells fabricated on various front contact bi-layer combinations. Conductive (low-ρ) transparent oxides utilized for this work include SnO₂:F, Cd₂SnO₄ and ITO; resistive (high-ρ) transparent oxides include SnO₂, In₂O₃, and Zn₂SnO₄. All high-ρ layers were found to be effective within a range of processing conditions and process/device characteristics. Buffer layers of Zn-Sn-O appear to be the most promising high-ρ films for the fabrication of CdTe cells with small CdS thickness without compromising the V_OC and FF.