Incorporation of lanthanide-doped UCNPs to improve light harvesting and device stability in perovskite solar cells

• Nd³⁺-doped UCNPs shift NIR absorption from 980 to 808 nm, reducing water vapor losses in the solar spectrum. • Enhanced energy transfer improves light harvesting in PSCs. • PCE rises from 18% to 22.5% (25% improvement) with higher Jsc, Voc, and FF. • Devices retain >85% PCE under humidity vs. 45% for controls. • Simulations confirm improved absorption and reduced recombination. In this work, we present an interfacial engineering strategy based on lanthanide-doped upconversion nanoparticles (UCNPs) incorporated into the mesoporous layer of perovskite solar cells (PSCs) to simultaneously enhance light harvesting and device stability. Core–shell UCNPs were synthesized with neodymium ions (Nd³⁺) in the outer shell to shift near-infrared (NIR) absorption from 980 nm to 808 nm, thereby reducing water-vapor–induced optical losses and improving energy transfer to the perovskite absorber. Embedding UCNPs into the mesoporous scaffold enabled efficient spectral conversion and interfacial modification, as confirmed by experimental characterization and SCAPS-1D device simulations. Experimentally, the Nd³⁺-doped UCNPs increased the short-circuit current density (Jsc) from 24.2 to 25.8 mA cm⁻², the open-circuit voltage (Voc) from 1.05 to 1.10 V, and the fill factor (FF) from 72% to 79%, leading to a 25% relative enhancement in power conversion efficiency (PCE), from 18% to 22.5%. Stability tests under ambient humidity revealed that treated devices retained over 85% of their initial PCE after extended exposure, compared to only ∼45% for untreated controls. SCAPS simulations confirmed enhanced photon absorption, suppressed interfacial recombination, and excellent agreement with the measured J–V curves. These findings highlight the dual function of Nd³⁺-doped UCNPs as spectral converters and interfacial modifiers, providing a scalable pathway toward efficient and stable PSCs.