How does stress affect the reliability of solar cells?

Stress in solar cells plays a crucial role in the reliability of photovoltaic (PV) modules. Influences on stress are as diverse as the number of different materials in a PV module and become more and more complex with growing variety of PV modules for different applications.

How does the size of a solar cell affect its properties?

The material properties are determined by its function as a semiconductor and are predominately the ones of silicon. However, the size has three different influences. Firstly, the height. It influences the specific thermal expansion stiffness and hereby the solar cells resistance to external strain.

How to reduce bending stress in solar cells?

Minimal bending stress by placing the solar cells in the neutral axis, for example, by a symmetrical module design. Rule 6 is in symmetric module designs more important than for asymmetric designs (glass-foil). In fact, the possibilities to reduce stress within solar cells by modifying themselves are limited to the size.

Why do asymmetric glass-foil PV modules deflection in mechanical load?

In the asymmetric glass-foil module design, the glass sheet is the dominating mechanical layer, with by far the highest specific thermal expansion stiffness (52 ). Therefore, its properties determine the PV modules deflection in mechanical load. At least one stiff layer is needed.

Does glass height affect thermal stress in solar cells?

At least one stiff layer is needed. The large difference of the specific thermal expansion stiffness to the solar cells value of 1.5 is also the reason why the glass' height has almost no influence on thermal stress in the solar cells. Differently, the front- and backsheet CTE strongly influences the thermal stress.

Why do solar cells have a low stress level after soldering?

This arises from the different contraction of ribbon and solar cell, which mainly comes from the cooling process after soldering and lamination. At lamination temperature, there is just a low stress level remaining from the soldering process.