Suppressing Electrode Diffusion With a PMMA Metal‐Capture Mesh Enables Stable Conventional Organic Photovoltaics

ABSTRACT

Conventional organic photovoltaics (OPVs) often suffer from premature failure because top‐electrode metals diffuse into the organic stack under thermal stress, generating interfacial traps and leakage pathways. Here, we identify severe aging‐driven Ag diffusion as a critical failure pathway in high‐efficiency conventional architectures. To suppress this without compromising charge extraction, we introduce polymethyl methacrylate (PMMA) that self‐assembles into a discontinuous, mesh‐like network on the PDINN layer, functioning as both a physical diffusion barrier and a chemical metal‐capture mesh. Spectroscopic analyses reveal that PMMA carbonyl groups coordinate with Ag through Ag‐O interactions, providing chemical immobilization that complements the physical barrier in blocking thermally activated, concentration‐gradient‐driven migration. Therefore, PMMA‐modified devices deliver a power conversion efficiency (PCE) of 20.2% with markedly enhanced stability: they retain >80% of the initial PCE after 3,574 h under ISOS‐D‐1I shelf storage, show a T ₈₀ of 105 h under ISOS‐D‐2I thermal aging at 85°C, compared with only 10 h for control devices, and retain 70.1% after 94 h under ISOS‐L‐3 conditions (1 sun, 65°C, 50% relative humidity), versus 51.4% for controls. This strategy also improves the thermal stability of Cu‐ and Au‐based devices, establishing a broadly applicable interfacial concept for mitigating electrode‐diffusion‐induced failure in high‐efficiency conventional OPVs.