# Progress in Improving Photovoltaics Longevity
## 4 Results
### PV Degradation Mechanisms
#### 4.1.3 Specific Degradation (Mechanical/Other)
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Degradation Cause** & **Description** & **Effects on PV Modules** & **References** \\ \hline Backsheet cracking & Cracking can occur in either outer or inner layers, affecting electrical insulation & – & Weakens insulation leading to current leakage and risks of ground faults Facilitates moisture entry, risking internal components & [52, 53] \\ \hline Potential-Induced Degradation (PID) & Occurs due to high voltage levels between solar cells and grounded frames & – & Causes leakage currents and can significantly decrease efficiency – Associated with shunting and surface polarization mechanisms & [54, 57, 58, 99] \\ \hline Light-Induced Degradation (LID) & Degradation from exposure to solar light during initial stabilization phase & – & Reduces module performance by up to 5\% due to metastabilities in semiconductor layers – Affected by manufacturing processes like Czochralski and iron-boron pair dissociation & [59, 60, 62, 100, 101, 102] \\ \hline Bypass diode failure & Bypass diodes prevent losses during reverse-bias operation; prone to various failure modes and affected by extreme wearheating and overheating & – Can lead to overheating and potential fire hazards – Failure modes include thermal leakage and open/short circuit failures & [40, 64, 103, 104, 105] \\ \hline Encapsulant failure & Encapsulants (often EVA) degrade due to UV exposure and aging & – & Leads to discoloration and delamination impacts the performance of solar cells and overall module integrity & [44, 65, 66, 106, 107] \\ \hline \hline \end{tabular}
\end{table} 
Table 3: _Cont._of the degradation depends on different parameters, such as environmental conditions, the module's construction features, and the selection of materials used. Over time, the circuit is subjected to fatigue from cyclic thermal stress and wind loading, resulting in progressive PV module degradation. * **Module glass breakage**. Low-iron glass has been established as the first choice for substrate material in PV modules due to its multiple advantages: low cost, high transparency index, low permeation rate, good electrical insulation, and enhanced mechanical resilience. Glass breakage is a common failure and can occur in several stages: during transportation, installation, or operation. The latter case is especially attributed to thermal or mechanical stresses and loads. Weather conditions, such as wind or hail, can also cause glass breakage. Regardless of the cause of the breakage, broken glass in a PV module can have an immediate impact on the solar cell or on its circuit. It may also affect the electrical insulation of the glass or its impermeability to moisture and gases [74]. In all cases, glass breakage can act as an auxiliary on the degradation of the encapsulant or other components of the module and is more likely to occur on an unbreathable module (glass/glass), as glass edges are unshielded [73]. In Figure 3, images retrieved via Red-Green-Blue (RGB), infrared (IR), and ultraviolet fluorescence (UVF) methods from a PV module susceptible to cracks (horizontal and diagonal), delamination, and discoloration are depicted. The different techniques showcase, in a unique way, the effect of each degradation mechanism.