UV Degradation Analysis of Material for Solar Cell Modules Using GC/MS and FTIR

Importance of the Topic

Ensuring the long-term stability of polymers used in solar cell modules is critical for module performance and reliability. Ultraviolet radiation can induce polymer degradation, leading to mechanical failure, discoloration, and loss of encapsulation integrity. Rapid and detailed analysis of these degradation processes supports material design and quality control.

Objectives and Overview of the Study

This work presents a comparative evaluation of three analytical approaches to characterize UV-induced changes in ethylene-vinyl acetate (EVA) copolymer films. The study aims to accelerate degradation using a UV-Py/GC-MS system, assess evolved gases via EGA-MS, and probe surface chemistry modifications by ATR-FTIR.

Methodology and Used Instrumentation

• UV-Py/GC-MS: Frontier micro-UV irradiator (UV-1047Xe) coupled with PY-3030D pyrolyzer and Shimadzu GCMS-QP2020 mass spectrometer for rapid UV aging and volatile product analysis.
• EGA-MS: PY-3030D pyrolyzer linked to GC-MS via an inert transfer tube, monitoring evolved species during a controlled temperature ramp from 40 to 750 °C.
• ATR-FTIR: Shimadzu IRAffinity-1S FTIR equipped with DuraSamplIR II single-reflection ATR accessory for surface functional group analysis.

Each EVA sample (~2 mg) underwent UV irradiation (0–5 h) in air at 60 °C, followed by helium purging and GC-MS analysis. EGA-MS used ~0.5 mg samples with a 20 °C/min ramp. ATR-FTIR measurements examined the film surface after irradiation.

Main Results and Discussion

• UV-Py/GC-MS revealed increasing formation of CO₂, acetone, acetaldehyde, acetic acid, and α,ω-dienes with longer UV exposure, indicating breakdown of both side chains and the polymer backbone.
• EGA-MS profiles showed two main thermal events: low-temperature side-chain detachment and high-temperature main-chain scission. The onset of main-chain decomposition decreased by ~3.6 °C after 5 h of UV, suggesting surface chain cleavage.
• ATR-FTIR spectra displayed a progressive decrease in the ester C=O band at ~1735 cm⁻¹ and increases in ketone/aldehyde C=O (~1716 cm⁻¹) and O–H (~3300 cm⁻¹) bands, confirming oxidative and hydrolytic modifications at the film surface.

Benefits and Practical Applications

• The combined UV-Py/GC-MS approach offers rapid acceleration of UV aging and direct detection of volatile degradation markers under controlled conditions not achievable with standard weathering tests.
• EGA-MS quantifies polymer degradation kinetics, while ATR-FTIR provides sensitive detection of surface chemical changes, together enabling a more complete degradation assessment.
• This analytical suite supports formulation optimization of encapsulant materials and enhances quality assurance protocols for photovoltaic module manufacturing.

Future Trends and Potential Uses

• Correlating accelerated aging data with long-term outdoor performance using in situ field monitoring of volatile emissions.
• Applying these analytical techniques to other module components, such as backsheets and adhesives, to predict and extend solar module lifetimes.
• Leveraging advanced chemometric and machine learning models to predict degradation pathways and service life based on analytical fingerprints.

Conclusion

By integrating UV-Py/GC-MS, EGA-MS, and ATR-FTIR, this study provides a comprehensive methodology for characterizing UV-induced degradation of EVA films. These complementary techniques deliver rapid, quantitative, and mechanistic insights, facilitating improved material design and reliability assessment in photovoltaic applications.