# Progress in Improving Photovoltaics Longevity
## 4 Results
### PV Longevity Improvement
#### 4.4.2 Mitigation Strategies  
PV Modules  
To mitigate these degradation processes and improve the long-term stability and lifetime of PV modules, several strategies have been employed [169]. These include appropriate material selection, updated manufacturing processes, and meticulous testing protocols in both field and laboratory. In Figure 6, a schematic diagram, including several mitigation strategies at both the module and operation-maintenance level, is depicted. * **Encapsulation materials with low permeation rates. ** Choosing encapsulants with a low permeation index is vital, as they can mitigate the ingress of harmful for the module's environmental and atmospheric constituents. The optimization of the encapsulants can, on a long-term scale, prevent delamination, discoloration, corrosion, and other degradation phenomena that pose a threat to the lifespan and performance of PV modules [170]. Despite their satisfactory performance in normal operation service and cost-effectiveness, typical EVA encapsulants show significant drawbacks and easy degradation and, as a consequence, require redesign and reformulation [171]. Seeking other economically beneficial encapsulation materials, polyolefins provide lower oxygen and water permeation rates, good UV resistance, stable chemical properties, and reduced degradation tendencies [172]. Ionomers [173] also have a prominent position in encapsulation manufacturing. While their design has proven costly, their superior characteristics, including high UV resistance, low moisture transmission, and improved adhesion to the adjacent components of the module, promise to ensure longevity, especially for modules based on thin-film technology. Figure 6: Mitigation strategies on both PV module and operation–maintenance level. * **Materials with high glass transition temperature (Tg)**. The glass transition temperature (Tg) is an important feature of backsheets and encapsulants integrated into PV modules. During operation, the temperature of the module rises significantly, and a plethora of temperature-related degradation phenomena begin to appear and escalate. For proper performance, PV module materials must be able to encounter high temperatures and secure their structure's stability under extreme thermal stresses. Encapsulants and backsheet materials with high Tg values above 100 \({}^{\circ}\)C are selected to maintain thermal stability and mechanical incorruptibility at operating temperatures. High-Tg materials remain unaffected under temperature elevations in outdoor conditions and show lower sensitivity to temperature-induced degradation (TID) mechanisms. These properties moderate the impacts of degradation on the PV modules and offer great potential for longevity. Typical examples of materials with high Tg values include polyolefins, polyamides, and polyimides. Polyolefins are more thermally resistant than EVA and are mainly used as encapsulation materials [106]. Polyamides are a well-considered choice for backsheets, providing enhanced properties and long-term reliability under thermal stress regimes [161]. Polyimides, with Tg on the order of 300 \({}^{\circ}\)C, are preferably selected when thermal stresses are extremely high and exceptionally high stability is a first priority [174; 175]. * **Reduction in photo-induced burn-in effects**. Photo-induced burn-in effects refer to degradation signs and drops in the performance of PV modules immediately after their installation and first interaction with solar irradiance. Defects, impurities, and disordered film morphological patterns are recognized as the responsible mechanisms. A widespread mitigation strategy applied to reduce these effects is the use of pure materials with dense and ordered film morphologies [176]. Current research has revealed that perovskite materials are ideal candidates in the attempt to limit photodegradation and improve the longevity of PV modules, provided that during their manufacture process, high-ordered crystal lattices are created [177; 178].