Ag2BiI5 Perovskite Quantum Dots Passivated with Oleylamine Sulfide for Solar Cells and Detection of Cu(II) Ions

Improving charge transport properties between the quantum dots (QDs) and reducing the non-radiative recombination have been attempted on silver bismuth iodide (Ag2BiI5) perovskite QDs using oleylamine–sulfide passivation. Herein, we have prepared Ag2BiI5 silver bismuth iodide QDs via a simple ligand-assisted reprecipitation method, and the samples were passivated with the oleylamine–sulfide complex. The absorption and emission profiles were red-shifted, which implies that the overall size of the QDs has increased after the passivation. An increase in the emission intensity confirmed the reduction of non-radiative recombination and an increase in excited-state carrier lifetime, as observed from the time-correlated single-photon counting-lifetime measurements. Further, the photocurrent devices were fabricated and generated high-magnitude photocurrent values in the ranges of ∼1.1 to 1.8 μA (bare Ag2BiI5) and ∼0.27 to 0.54 μA (oleylamine–sulfide-passivated Ag2BiI5) for the biasing voltages of 0.1 and 0.2 V, respectively. Surprisingly, the oleylamine–sulfide-passivated Ag2BiI5 sample exhibited a sharp rise in the photocurrent value with a high on/off ratio. In addition, the bare and oleylamine–sulfide-passivated QDs were further applied for the fluorescence detection of copper Cu(II) ions in drinking water samples for the first time.