The grown lead iodide (PbI2) is usually a two-dimensional sheet with a finite size which necessitates
sophisticated device metallization and the growth of quasi one-dimensional materials is still challenging.
In this work, large-size (length 4 100 mm), single-crystalline and high-density PbI2 nanobelts are
successfully synthesized by manipulating the microenvironment in a two-step vapor deposition process
at a slow heating rate of B18 1C min1. Firstly, PbI2 nanosheet seeds are grown by physical vapor
deposition, and then PbI2 nanobelts are synthesized by a self-catalyzed vapor–liquid–solid growth
mechanism, which is verified by the Pb nanoparticles on the nanobelt tips. Photoluminescence and
ultraviolet-visible spectra show the uniform high-quality crystallinity of the as-prepared large-size PbI2
nanobelts with a bandgap of 2.36 eV. When configured into photodetectors with a shadow mask, the
fabricated device exhibits a low dark current of 4 pA, an impressive ON/OFF current ratio of 103–104,
a photoresponsivity of 13 mA W1, and a fast response with the rise and decay time constants of
425 and 41 ms, respectively. All these performances are comparable to those of state-of-the-art layered
PbI2 nanostructure photodetectors, but the ease of synthesizing large-size PbI2 nanobelts may have a
useful impact on next-generation easily-fabricated high-performance optoelectronics.