Aqueous-Phase Formation of Two-Dimensional PbI₂ Nanoplates for High-Performance Self-Powered Photodetectors

The process of the aqueous synthesis of nanomaterials has gained considerable interest due to its ability to eliminate the need for complex organic solvents, which aligns with the principles of green chemistry. Fabricating nanostructures in aqueous solutions has gained recognition for its potential to develop ultrasensitive, low-energy, and ultrafast optoelectronic devices. This study focuses on synthesizing lead iodide (PbI₂) nanoplates (NPs) using a water-based solution technique and fabricating a planar photodetector. The planar photodetectors (ITO/PbI₂ NPs/Au) demonstrated a remarkable photosensitivity of 3.9 × 10³ and photoresponsivity of 0.51 mA/W at a wavelength of 405 nm. Further, we have carried-out analytical calculations for key performance parameters including open-circuit voltage (V), short-circuit current (I), on-off ratio, responsivity (R), and specific detectivity (D*) at zero applied bias, while photodetector operating in self-powered mode. These values are as follows: V = 0.103 V, I = 1.93 × 10^-8, on-off ratio = 10³, R = 4.0 mA/W, and D* = 3.3 × 10¹¹ Jones. Particularly, the asymmetrical output properties of ITO/PbI₂ NPs/Au detector provided additional evidence of the effective creation of a Schottky contact. Therefore, the photodetector exhibited a photo-response even at 0 V bias (rise/decay time ~1 s), leading to the realization of self-powered photodetectors. Additionally, the device exhibited a rapid photo-response of 0.23/0.38 s (-5 V) in the visible range. This study expands the scope of aqueous-phase synthesis of PbI₂ nanostructures, enabling the large-area fabrication of high-performance photodetectors.