Extending Carrier Diffusion via Interfacial Dielectric Shielding for Operationally Stable Perovskite/TOPCon Tandem Solar Cells

ABSTRACT Perovskite/silicon tandem solar cells have achieved remarkable power conversion efficiencies beyond the Shockley–Queisser limit of single‐junction devices. However, their operational stability remains a key challenge, with the low‐dielectric perovskite/C ₆₀ contact—though often negligible in single‐junction devices—being one of several factors that limit carrier diffusion length and thereby aggravate carrier accumulation and recombination in the thick perovskite layer required for textured silicon in tandems. To address this, a high‐dielectric‐constant niobium oxide (NbO _X ) electron‐selective contact is introduced, which suppresses defect‐mediated carrier trapping by shrinking the capture radius of interfacial defects and chemically passivates undercoordinated Pb ²⁺ and PbI ₂ through Pb–O bond formation. These effects collectively extend the carrier diffusion length and optimize energy‐level alignment at the perovskite/C ₆₀ interface. As a result, single‐junction 1.68 eV perovskite solar cells deliver a PCE of 22.4% with 91% efficiency retention after 650 h of maximum power point (MPP) tracking, while monolithic perovskite/TOPCon tandems reach 32.0% PCE and maintain full initial performance after 200 h of MPP tracking. These results underscore the vital role of extended carrier diffusion in achieving both high efficiency and Carrier accumulation. High dielectric oxide, Perovskite/silicon tandem solar cells, carrier diffusion length, long‐term stability, and long‐term operational stability in perovskite/silicon tandems.