Control of Mose2 formation in hydrazine-free solution-processed CIS/CIGS thin film solar cells

This study investigated an approach to control the MoSe₂ layer formation at the Mo/CIGS interface of hydrazine-free solution-processed CIGS solar cells. The MoSe₂ layer thickness reduction was achieved by deposition of a MoN_x back contact barrier layer, which effectively acts as a diffusion barrier against selenium (Se). The resulting Mo/MoN_x/Mo multilayer was applied in a CIGS device as the back contact. The electrical performance of this device was compared to our baseline approach with bare Mo as the back contact. The MoSe₂ layer formed after selenization was dramatically reduced when the barrier layer was present and the corresponding device exhibited a power conversion efficiency (PCE) of 8.2%. More importantly, the application of the barrier layer as an intermediate layer within the Mo back contact allows for longer, or even multiple selenization steps. A longer or a multiple selenization was shown to improve the absorber grain growth and consequently result in higher PCEs.