Grain-boundary locking with N-CQDs for efficient and stable dual-light perovskite solar cells

The development of multifunctional perovskite solar cells (PSCs) capable of operating efficiently under both strong sunlight and low indoor lighting conditions is crucial for expanding their applications from outdoor power generation to self-powered Internet of Things (IoT) ecosystems. However, trap-assisted recombination and grain boundary (GB) instability severely limit their dual-light performance and operational lifetime. Herein, we propose a robust dual-light harvesting strategy by introducing nitrogen-doped carbon quantum dots (N-CQDs) as multifunctional nano-additives into the MAPbI₃ active layer. The abundant carbonyl (CO) and amine (-NH) functional groups on the N-CQDs surface act as Lewis bases to coordinate with Pb²⁺ defects while forming strong hydrogen bonds with the iodide lattice, producing a "synergistic effect": regulating crystallization kinetics to increase grain size, comprehensively passivating deep-level traps, and acting as nanoscale "anchors" to stabilize GBs. Consequently, the optimized N-CQD device achieved a power conversion efficiency (PCE) of 21.0% under AM 1.5G illumination and an outstanding efficiency of 32.8% under 1000 lux indoor LED lighting (∼327 μW cm^-2). More importantly, the GB-locking strategy effectively suppresses ion migration and the volatilization of organic components, enabling the unencapsulated device to retain over 86% of its initial efficiency after 1540 hours of thermal aging at 85 °C in a nitrogen atmosphere, while demonstrating excellent resistance to moisture and indoor light-induced degradation. This study establishes the great potential of multifunctional CQDs in defect and interface engineering, providing a simple and efficient method for constructing high-efficiency, durable PSCs adapted to complex lighting environments.