Lacunary polyoxometalate nanoclusters as versatile interface modifiers for perovskite solar cells

We report the first incorporation of diverse lacunary polyoxometalate (POM) nanocluster materials as efficient interface modifiers in perovskite solar cells (PSCs). Devices utilizing POM-modified SnO₂ electron transport layers demonstrated marked improvements in open-circuit voltage (V_OC), short-circuit current density (J_SC), and fill factor (FF), achieving power conversion efficiencies exceeding 21.6%. Transient photovoltage and photocurrent analyses revealed that the B1-type based device exhibited the longest carrier lifetime and most rapid charge extraction rate, indicating optimized charge transport and suppressed recombination losses. Stability assessments under ambient conditions confirmed that B1-type POM-modified devices retained higher efficiency over time with reduced hysteresis compared to control devices. Work function measurements indicated POM-induced energy level alignment shifts, facilitating efficient charge transport. Morphological and structural analyses via scanning electron microscopy and X-ray diffraction confirmed that POMs using tungsten (W) addenda (i.e., B1-W and B2-W) promoted superior perovskite crystallization, yielding larger grain sizes and enhanced crystallinity. These findings establish the potential for lacunary POMs to serve as effective interface modifiers for advancing the efficiency and durability of perovskite-based optoelectronic devices.