Influence of cell packaging and design parameters on thermo-mechanical reliability of fingers in crystalline silicon photovoltaic modules

Abstract

The performance of front grid fingers in a crystalline silicon photovoltaic (PV) cell is crucial in maintaining the overall reliability of a PV module. The reliability of fingers is often discussed in the premise of solder layer degradation due to their close proximity, and vulnerability under transient high-temperature variations. This paper presents the damage accumulation focused at the finger-solder interface under accelerated thermal cycling (TC) conditions via a 3-D finite element model (FEM) of a PV module packaged assembly. The study further investigates the effect of different packaging layers (encapsulant and back-sheet) and variable cell geometrical design parameters (solder layer thickness, copper ribbon thickness, and silicon wafer thickness) on the thermo-mechanical damage accumulation at the finger-solder interface. An increase in thermo-mechanical stability of the fingers was demonstrated by comparing damage accumulation with the addition of different levels of packaging layers. Further, it was found that the solder layer and copper ribbon thickness are crucial parameters affecting thermo-mechanical degradation at the finger-solder interface.