Solar cells, while designed for long-term operation, are subject to various degradation mechanisms that can reduce their efficiency and lifespan. Understanding these mechanisms is critical for improving reliability and performance. Key degradation processes include potential-induced degradation (PID), light-induced degradation (LID), UV-induced aging, and moisture ingress. Accelerated testing protocols such as IEC 61215 help evaluate these effects, while mitigation strategies like advanced encapsulants enhance durability.

Potential-induced degradation (PID) occurs when high voltage differences between the solar cell and its frame cause ion migration, leading to power loss. PID is particularly prevalent in high-voltage systems and can result in significant efficiency drops, sometimes exceeding 30%. The mechanism involves sodium ions from the glass migrating into the cell, disrupting the p-n junction. Mitigation strategies include using PID-resistant modules, anti-PID coatings, and system designs that minimize voltage stress.

Light-induced degradation (LID) primarily affects crystalline silicon solar cells, where exposure to sunlight causes boron-oxygen defects to form, reducing carrier lifetime. LID can lead to an initial efficiency loss of 1-3%, stabilizing after prolonged exposure. Advanced manufacturing techniques, such as gallium doping instead of boron, reduce LID susceptibility. Additionally, pre-treatment methods like illuminated annealing can stabilize performance before deployment.

UV-induced aging results from prolonged exposure to ultraviolet radiation, which degrades polymer-based materials in solar modules, such as encapsulants and backsheets. Over time, UV exposure causes yellowing, delamination, and loss of optical transparency, reducing light absorption. UV-stabilized encapsulants, such as those incorporating UV absorbers or hindered amine light stabilizers (HALS), improve resistance. IEC 61215 includes UV preconditioning tests to evaluate module durability under simulated sunlight.

Moisture ingress is another critical degradation factor, particularly in humid environments. Water vapor penetrates the module, leading to corrosion of metal contacts, delamination, and increased leakage currents. Encapsulation materials like ethylene-vinyl acetate (EVA) must have low water vapor transmission rates (WVTR) to prevent moisture damage. Advanced solutions include multilayer barriers and edge-sealing technologies that enhance moisture resistance.

Accelerated testing protocols, such as IEC 61215, simulate decades of environmental stress in a condensed timeframe. These tests include thermal cycling, damp heat exposure, mechanical load testing, and UV irradiation. Modules must pass these tests to qualify for commercial use, ensuring a minimum lifespan of 25 years. The damp heat test, for example, subjects modules to 85°C and 85% relative humidity for 1,000 hours to assess moisture resistance.

Mitigation strategies focus on material improvements and design optimizations. Advanced encapsulants, such as polyolefin elastomers (POE), offer better resistance to PID, UV, and moisture compared to traditional EVA. Additionally, robust frame designs with proper grounding reduce PID risks. For LID, manufacturers employ alternative dopants or post-processing treatments to stabilize cell performance.

In summary, solar cell degradation mechanisms like PID, LID, UV aging, and moisture ingress pose significant challenges to long-term reliability. Standardized testing protocols ensure module durability, while material innovations and design improvements enhance resistance. Continued research into encapsulation technologies and system-level protections will further extend the operational lifetime of photovoltaic systems.