NIR‐Harvesting Upconversion CsPbI ₃ Perovskite Solar Cells with Dye‐Hybridized Nanoparticles

Abstract To transcend the spectral limitations of conventional lead halide perovskite solar cells, a novel upconversion (UC)‐based system is introduced that enables efficient harvesting of near‐infrared (NIR) photons in solar light. In this approach, inherently low absorption and emission efficiencies in conventional lanthanide‐doped UC nanoparticles (UCNPs) are significantly enhanced through sensitization with organic dyes (indocyanine green, ICG). By anchoring ICG onto the UCNP surface, efficient NIR absorption and subsequent energy transfer to the lanthanide ion (Ln 3+ ) centers are facilitated. Encapsulating these dye‐coordinated UCNPs with a CsPbBr 3 perovskite shell not only suppresses non‐radiative losses but also ensures compatibility and charge transfer alignment with the bulk CsPbI 3 perovskite film as a photovoltaic absorber. Integration of the dye‐coordinated UCNPs into CsPbI 3 perovskite solar cells led to a marked enhancement in photocurrent density, demonstrating effective NIR‐to‐visible photon conversion and enhanced sunlight harvesting. This hybrid architecture offers a compelling route to exceed the single‐junction Shockley–Queisser limit and opens new pathways for broadband light management in next‐generation photovoltaic systems.