Substituted polyoxometalate-modified SnO2 for enhanced interfacial contact for high-efficiency carbon-based all inorganic perovskite solar cells

Abstract

SnO₂ demonstrates three critical characteristics for photovoltaic applications, low temperature preparation process, high conductivity and high ultraviolet light stability. These superiorities makes it a preferred choice for high-performance perovskite solar cells (PSCs) as a charge transport material. However, PSCs based on SnO₂ still faces great challenges. Poor interface contact and interface defects are important factors for loss of efficiency and long-term stability. This study demonstrates a synergistic interface engineering in all-inorganic CsPbI₂Br solar cells through strategic integration of transition-metal substituted Keggin-type polyoxometalates K₆H₄[SiW₉O₃₇{Ni(H₂O)}₃ ({SiW₉Ni₃}) with SnO₂ quantum dots. The SnO₂@SiW₉Ni₃ composite electron transport layer boosts electrical conductivity through enhanced electron mobility channels. {SiW₉Ni₃} can also passivate interfacial defects via strong chemical bonding between terminal oxygens and undercoordinated Sn⁴⁺ and reduce oxygen vacancy defects, effectively suppressing non-radiative recombination. Additionally, perovskite crystallization can be regulated by metal–oxygen coordination, which result in a pinhole-free and high quality film based on SnO₂@SiW₉Ni₃. The target devices achieve a champion PCE of 13.09 % (vs. 10.75 % control) with a remarkable open-circuit voltage (V_OC) enhancement from 1.256 V to 1.301 V. At the same time, the optimized devices retain over 90 % initial efficiency after 600 h ambient aging, demonstrating prominent operational stability. This work establishes a polyoxometalate-driven interfacial engineering strategy for advancing high-performance all-inorganic perovskite solar cells.