Role of Metal Oxide Interlayers in Preventing Gold Migration in Perovskite Solar Cells

Thermal stress significantly impacts the durability of perovskite solar cells (PSCs), as evidenced by severe degradation observed at 85 °C in this study. This degradation is attributed to gold migration through the soft 2,2′,7,7′-tetrakis(N,N-di-4-methoxyphenylamino)-9,9′-spirobifluorene (spiro-MeOTAD) hole transport layer (HTL) into the perovskite layer, driven by gold's low formation energy and diffusion barrier. To mitigate this issue, several vacuum-evaporable hard transition metal oxides as charge extraction interlayers between the gold electrode and the HTL to suppress gold migration are investigated. PSCs incorporating MoO₃, V₂O₅, MoO₂, and ReO₃ interlayers achieve a power conversion efficiency of ≈20%, comparable to PSCs without interlayers. Notably, these interlayer-equipped PSCs exhibit enhanced thermal durability at 85 °C by effectively suppressing gold migration into the perovskite layer under elevated temperatures, with the MoO₂ interlayer also improving durability at 25 °C. These findings offer a promising strategy for fabricating thermally durable PSCs, contributing to the future commercialization of photovoltaic technology.