Shuyang Lin

End-of-life photovoltaic modules represent a complex waste stream in which polyolefin elastomer (POE) encapsulants are increasingly important but insufficiently characterized after recovery. This study evaluates the structural, morphological and thermal state of POE-rich encapsulant residues obtained from laser-treated fragments of a crystalline-silicon photovoltaic module after approximately five years of field operation, focusing on material quality rather than process optimization. Reference POE and representative polymer-rich residues were examined by FTIR-ATR, TGA/DTG under nitrogen and SEM/EDS. FTIR-ATR showed characteristic polyolefin bands at approximately 2915–2847, 1463 and 718–719 cm⁻¹ in both reference POE and treated residues, indicating retention of the hydrocarbon backbone. Treated residues exhibited additional features in the 1800–1500 and 1100–1000 cm⁻¹ regions, attributed to oxygen-containing surface species and interfacial glass/silicon contributions. TGA/DTG revealed a similar main decomposition range for the POE-rich residues, with DTG peaks mainly between 471.5 and 474.3 °C, while residual mass varied from 1.94 to 23.03%, compared with 0.04% for reference POE. SEM/EDS confirmed heterogeneous surfaces and local silicon/oxygen-rich particles attached to or embedded in the polymer-rich residues. The results show that POE-rich waste fractions can preserve the main polyolefin structure, but their valorization requires control of inorganic contamination, especially for cut, cracked or mechanically damaged modules.

Laser surface microtexturing has emerged as an effective approach for improving the performance of adhesive joints between dissimilar materials. In this study, the influence of laser-generated micrometric surface features on the mechanical behavior of hybrid adhesive joints was investigated for two material systems: structural steel bonded to polyamide (PA66) and structural steel bonded to technical ceramic (Al₂O₃). Single-lap joints were manufactured using a two-component epoxy adhesive with two nominal bond-line thicknesses (0.1 mm and 1.0 mm). Prior to bonding, selected surfaces were modified by ultrashort-pulse laser microtexturing, producing well-defined circular features with characteristic depths on the order of tens of micrometers. The resulting microstructures were characterized using optical and scanning electron microscopy, and their geometric parameters were quantified through profilometric measurements. Mechanical performance was evaluated under shear and bending loading conditions. The results demonstrate a substantial increase in joint strength for laser-microtextured surfaces compared with non-textured references for both material combinations. The effect of surface microtexturing was more pronounced than the influence of adhesive layer thickness within the investigated range. These findings confirm that laser-induced surface microtexturing is a versatile and application-oriented surface preparation method capable of enhancing the reliability of adhesive bonding in hybrid metal–polymer and metal–ceramic assemblies.