Suppression of SAM desorption by engineering polyoxometalate interface for inverted perovskite solar cells

Self-assembled monolayers (SAMs) have markedly enhanced the power conversion efficiency (PCE) of inverted perovskite solar cells (PSCs); however, 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. By leveraging vanadium to establish V(V)/V(IV) redox couples, the electron cloud density of the V–O–W bridging oxygens was significantly enhanced, promoting tridentate anchoring between the SAMs and indium tin oxide via proton-coupled electron transfer (PCET). This increased 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 the crystallization of high-quality perovskites and effectively suppress interfacial defects, significantly improving the hole-extraction efficiency and increasing the PCE from 23.68% to 25.15% under continuous AM 1.5 G illumination. Moreover, the device stability was markedly enhanced, with the target retaining 90.7% of its initial efficiency after 1200 h of continuous maximum power point tracking (compared to 53.8% for the control). This study demonstrates that POMs can effectively suppress the desorption of SAMs and reduce interfacial losses, offering new insights for fabricating highly efficient and stable PSCs.