Investigating the reliability of electrically conductive adhesives for shingled photovoltaic Si modules

Abstract

This paper discusses the environmental stability of an electrically conductive adhesive (ECA) applied to shingled photovoltaic (PV) modules. This study aims to verify the degradation behavior of ECA joints when shingled PV modules are exposed to an accelerated aging test under hot and humid environmental conditions. To achieve this, we prepared shingled PV modules through an assembly process wherein five pre-cut crystalline silicon solar cells were bonded with a ECA paste cured by an infrared lamp, and then stored under damp heat (85 degrees C/85% RH) and high temperature (65 and 85 degrees C) conditions. To confirm the aging of the ECA, we determined the changes in the electrical resistance of the ECA and in the efficiencies of the shingled PV modules. Results suggest that the electrical properties of the ECA did not deteriorate under heat and moisture conditions, while the performance of the shingled modules degraded under the same conditions. It was confirmed that the degradation in performance was mainly due to a drop in the fill factor (FF) caused by current leakage. Physicochemical analyses of the samples revealed that Ag atoms, which diffused from the ECA joint to the Si wafer, acted as the shunt path for the solar cell. The bonding properties of the ECA joint to moisture were evaluated as well.