A photodetector fabricated from 2H-PbI₂ micro-crystals recycled from waste lead acid batteries

Recycling Pb from lead acid batteries is rather important in environmental protection, but current strategies need a high temperature or produce secondary pollution. Herein, we present a green reactant recycling method to synthesize PbI₂ micro-crystals by extracting the Pb from waste lead acid batteries. Systematical characterizations indicate that the as-prepared PbI₂ micro-crystals show high purity, high crystal quality with a 2H-hexagonal crystal structure, and excellent optical properties with a bandgap of 2.3 eV. Based on the recycled 2H-PbI₂ micro-crystals, a symmetrically structured ITO/PbI₂/ITO photodetector is fabricated. Under 10 V bias voltage, the device reveals a distinct photo-response to UV-visible light and superior performance, with a dark current of 1.06 nA, an on-off ratio of 103, a responsivity of 15.5 mA/W, and a detectivity of 4.7 × 10¹⁰ Hz^1/2 W^-1. In addition, the photodetector also exhibits relatively rapid response speeds of 69 ms (rise time) and 64 ms (decay time). Our study provides an innovative and green strategy for producing a UV-visible photodetector based on recycled lead acid batteries, which is significant in environmental protection and the recycling economy.