Polyoxometalates interface engineering via suppressing SAMs desorption for inverted perovskite solar cells

Self-assembled monolayers (SAMs) have markedly enhanced the power conversion efficiency (PCE) of inverted perovskite solar cells (PSCs), but the desorption of SAMs limits the long-term stability of the devices. Herein, Lindqvist-type polyoxometalates (POMs) [V_nW_6-nO₁₉] ^(n+2)- (n=1~3) were incorporated into SAMs. Leveraging vanadium(V) to establish V(V)/V(IV) redox couples significantly enhances the electron cloud density of V-O-W bridging oxygens, which subsequently promotes tridentate anchoring between SAMs and ITO via proton-coupled electron transfer (PCET), increasing the anchoring ratio from 29.93% to 53.98% while reducing the desorption rate from 30.7% to 5.6%. The robustly anchored SAMs facilitate high-quality perovskite crystallization and effectively suppress interfacial defects, markedly improving hole extraction efficiency and elevating the PCE from 23.68% to 25.15% under continuous AM 1.5 G illumination. Meanwhile, device stability was markedly enhanced, with the target retaining 90.7% of its initial efficiency after 1200 hours of continuous maximum power point tracking (compared to 53.8% for the control). This study demonstrates that POMs can effectively suppress SAMs desorption and reduce interfacial losses, offering new insights for fabricating highly efficient and stable PSCs.