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

Abstract

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 MoNx back contact barrier layer, which effectively acts as a diffusion barrier against selenium (Se). The resulting Mo/MoNx/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.