Enhanced light harvesting in lead-free Cs2AgBiBr6 double perovskite solar cells with plasmonic Ag nanoparticles

Abstract

Lead-free Cs₂AgBiBr₆ double perovskite solar cells (PSCs) possess unique environmental-friendly and stable attributes. However, the wide bandgap of Cs₂AgBiBr₆ weakens the light capture capability, thus limiting the improvement in power conversion efficiency (PCE) for PSC devices. Herein, a convenient and efficient method is presented by incorporating plasmonic Ag nanoparticles (NPs) onto perovskite surface. Owing to the synergistic effect of far-field light scattering and near-field enhancement of Ag NPs, the short-circuit current density of the modified PSC device has been enhanced by approximately 30%. In addition, the introduction of Ag NPs makes a larger Fermi energy level difference between TiO₂/perovskite interface, resulting a higher open-circuit voltage. The optimized device with structure of fluorine-doped tin oxide/compact TiO₂/mesoporous TiO₂/Cs₂AgBiBr₆/carbon delivers a PCE of 2.69% as compared to the control device with a PCE of 2.04%, which represents one of the highest efficiencies of hole transport layer-free, carbon-based PSCs. Furthermore, the unencapsulated device retains nearly 98% of its initial PCE even after being stored for 32 days at 25℃ and relative humidity of 40 ± 5%. This work provides a new insight in constructing high-efficient and environmental-friendly PSCs.