Solution-Processed Lead Iodide for Ultrafast All-Optical Switching of Terahertz Photonic Devices

Solution-processed lead iodide (PbI₂) governs the charge transport characteristics in the hybrid metal halide perovskites. Besides being a precursor in enhancing the performance of perovskite solar cells, PbI₂ alone offers remarkable optical and ultrasensitive photoresponsive properties that remain largely unexplored. Here, the photophysics and the ultrafast carrier dynamics of the solution processed PbI₂ thin film is probed experimentally. A PbI₂ integrated metamaterial photonic device with switchable picosecond time response at extremely low photoexcitation fluences is demonstrated. Further, findings show strongly confined terahertz field induced tailoring of sensitivity and switching time of the metamaterial resonances for different thicknesses of PbI₂ thin film. The approach has two far reaching consequences: the first lead-iodide-based ultrafast photonic device and resonantly confined electromagnetic field tailored transient nonequilibrium dynamics of PbI₂ which could also be applied to a broad range of semiconductors for designing on-chip, ultrafast, all-optical switchable photonic devices.