Improved Mechanical and Physical Properties of Epoxy Acrylate Oligomers by Chemical Modification for the Effective Encapsulation of the Triple-Cation Perovskite Solar Cells

This study modifies epoxy acrylate to enhance its mechanical, thermal, and barrier properties, such as hardness, flexibility, gloss, adhesion, and water/oxygen resistance. Adipic acid (AdAc) and 3-aminotriethoxysilane (ATES) were incorporated into the epoxy acrylate structure, and the resulting oligomers were characterized by Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy. Thermal analysis showed that AdAc-modified epoxy acrylate oligomer-3 (AdAc-MO3) (1.70% AdAc) had a lower glass transition temperature (<i>T</i> _g) of 48.2 °C, improving flexibility, while ATES-modified epoxy acrylate oligomer-5 (ATES-MO5) (1.70% ATES) exhibited a higher <i>T</i> _g of 56 °C, enhancing thermal stability. AdAc-MO3 achieved excellent mechanical and barrier performance, with a water vapor transmission rate (WVTR) of 7.46 g/m²day and an oxygen transmission rate (OTR) of 5.10 g/m²day. Mechanical tests confirmed that AdAc-MO3 balanced hardness and flexibility, passing adhesion and conical mandrel tests without deformation. The encapsulants were tested on perovskite solar cells (PSCs) with an FTO/Li-TiO₂/perovskite/Spiro-OMeTAD/Au configuration. After 48 h of stability testing under 60% humidity, 25 °C, and a light intensity of 100 mW/cm², AdAc-MO3 retained 26.8% of its initial power conversion efficiency (PCE), compared to 20.5% for the control device. ATES-MO3 retained 56.1% of its initial PCE, outperforming both the control and AdAc-MO3, but its higher cross-linking density reduced adhesion and flexibility, limiting its use in certain encapsulation applications. Visible light curing further improved stability, reducing efficiency loss to 8% compared to 16% with UV curing. These results demonstrate that AdAc-MO3 is a promising encapsulant for PSCs, combining enhanced properties and stability under realistic conditions.