DELAMINATION AND FATIGUE ANALYSIS OF SILICON SOLAR CELLS USING FINITE ELEMENT METHOD

Fracture of silicon solar cells in photovoltaic (PV) modules are widely reported and a wellknown issue in the PV industry, since it is exposed to adverse climatic conditions and varying temperature loads. A commercial silicon solar cell is mainly composed of four different layers. This thesis investigates delamination failure and thermal fatigue failure due to alternating temperature loads using finite element method (FEM) simulation.

The delamination of the encapsulant (EVA) layer and the cell interface was simulated using

finite element (FE) simulations in the COMSOL Multiphysics software. The adhesion between the

layers were modeled using the cohesive zone model (CZM). The CZM parameters such as normal

strength and penalty stiffness were used for the bilinear traction-separation law for the cohesive

model in a 90-degree configuration. The critical energy release rate (𝐺𝐺𝑐𝑐) was experimentally calculated as one of the CZM parameters. A uniaxial tensile test of the upper layer of the cell was conducted to determine the material properties of the solar cell layers, and that information was

later used for FE simulations. To validate the simulation, we compared the peeling force graph

from the experiment and FE simulation, and it was found both graphs showed a maximum peeling

force of 120 N.

Finite element simulations were also conducted to predict the stress variations in the silicon

solar cell layer due to alternating temperatures. An alternating temperature function was developed

using triangular waveform equations in the COMSOL Multiphysics software. For this simulation,

a 3D model of the cell with a 90-degree peel arm was used, like in the peeling simulation. A

maximum stress of 7.31 x 10−3 𝑁/𝑚𝑚2 was observed on the encapsulant (EVA)/cell layer, but no

delamination was observed for the given temperature range. In future work, we plan to explore the

calculation of fatigue life using thermal simulation to predict the reliability of a solar cell.