Fig. 4: Multispectral narrowband NIR photodetection and underwater information transmission of NaYS₂:Er³⁺ phosphor.

a Schematic illustration of structure and working mechanism in the NaYS₂:Er³⁺/MAPbI₃ PDs. b Photocurrent response of NaYS₂:Er³⁺/MAPbI₃ PDs under 808, 980, and 1532 nm excitation at power density of 5 mW cm⁻², respectively (inset: the responsivity and detectivity of NaYS₂:Er³⁺/MAPbI₃ device under separately 808, 980, and 1532 nm excitation). c On-off switching currents at lowest detectable excitation power density of NaYS₂:Er³⁺/MAPbI₃ device under 808, 980, and 1532 nm, respectively. d Schematic illustration of the NaYS₂:Er³⁺ underwater information transmission in seawater. e Input and output signal information of transmitter and receiver at different frequencies (Hz) with the seawater depth of 0.6 m. f Received signal strength of NaYS₂:Er³⁺ in air and water at different distance between transmitter and receiver. Source data is provided in this paper.