Growth of Ultraflat PbI 2 Nanoflakes by Solvent Evaporation Suppression for High‐Performance UV Photodetectors

2D lead iodide (PbI 2 ) is attracting great interest due to its great potential in the application of UV photodetectors. In this work, a facile solution‐based method is developed to synthesize ultraflat PbI 2 nanoflakes for high‐performance UV photodetectors. By maintaining at proximate room temperature and adding an evaporation suppression solvent for slow‐rate crystal growth, high‐quality PbI 2 nanoflakes with an ultraflat surface are obtained. The UV photodetectors based on 2D PbI 2 nanoflakes exhibit a high photoresponsivity of 0.51 A W −1 , a high detectivity of 4.0 × 10 10 Jones, a high external quantum efficiency (EQE) of 168.9%, and a rapid response speed including a rise time of 14.1 ms and a decay time of 31.0 ms. The balanced and excellent photodetector performance of these devices paves the road for practical UV photodetection based on 2D PbI 2 nanoflakes.