New method solves degradation in copper-plated solar cells

Background

To make solar panels cheaper, scientists are trying to replace expensive silver with copper in silicon heterojunction (HJT) solar cells. However, applying the necessary photoresist layer through screen printing causes a gradual efficiency decline over thousands of printing cycles, dropping conversion efficiency in commercial production.

Details and Discovery

According to the researchers, traditional silver paste uses screens with small openings and thick emulsion coverage, so the mesh rarely touches the wafer directly. In contrast, photoresist application uses an open mesh that slams directly against the wafer surface. Using confocal microscopy, the team discovered that progressive wear of the screen mesh knuckles increases mechanical stress, damaging the delicate passivation layers underneath.

Solution and Impact

To fix this, the team tested an emulsion buffer layer on the screen. An optimal coverage ratio of 4.7% successfully prevented direct contact between the mesh and the wafer. This reduced minority carrier lifetime degradation to just 0.41% after 10,000 cycles, offering a practical way to improve manufacturing reliability for copper-plated solar cells.