Self-healing catechol–metal PDMS networks with ultra-low WVTR for flexible photovoltaic roof encapsulation in solar electric vehicles

Flexible photovoltaic modules integrated into vehicle roofs require encapsulants that combine optical transparency, low moisture permeability, mechanical compliance, and self-repairing capability. Conventional EVA and POE systems exhibit limited barrier performance and lack dynamic bonding, restricting their durability under damp heat and cyclic loading. The research gap lies in the absence of a transparent, self-healing elastomer that simultaneously delivers ultralow water vapor transmission and long-term device stability across multiple metal coordination chemistries. This study aims to develop and systematically evaluate catechol-grafted PDMS networks coordinatively cross-linked by Fe³ ⁺, Al³ ⁺, Zr⁴⁺, or Ti⁴⁺ for flexible solar roof encapsulation. films were synthesised via hydrosilylation grafting, followed by controlled metal coordination, cast to ∼150 µm thickness, and characterised using FT-IR, XPS, DMTA, DSC, WVTR/OTR testing, peel adhesion, healing assays, and mini-module reliability under 85 °C/85% RH, UV, thermal cycling, and bending. Zr⁴⁺ and Ti⁴⁺ networks achieved WVTR values of ∼0.07–0.15 g m⁻² d⁻¹ with T₅₅₀ ≈ 96–97% and haze ≤ 0.8%, and modules retained ∼97% and ∼96% power after 1000 h at 85/85. A WVTR threshold near ∼0.10 g m⁻² d⁻¹ was identified, below which ≥ 95% power retention was sustained. Fe³ ⁺ networks exhibited rapid healing with barrier recovery of ∼95% and tensile recovery of ∼80% within 24 h at 50 °C. Metal–catechol coordination provides an adjustable platform for high-barrier, self-healing photovoltaic encapsulation compatible with curved vehicle modules. Future research should focus on mixed-metal architectures and full-scale automotive validation.