Ferroelectric Polarization Enhanced Photodetector Based on Layered NbOCl2

NbOCl2 is an emerging ferroelectric layered material with unique optoelectronic properties, in which the built‐in electric field caused by spontaneous polarization can independently drive the separation and transport of photoexcited electrons and holes. However, the optoelectronic performance of NbOCl2 and its device application have remained elusive. Here, few‐layer NbOCl2 is prepared by the liquid exfoliation method and used to construct photoelectrochemical (PEC)‐type photodetectors. The photodetectors are self‐powered with broadband photoresponse and long‐term cycle stability. Due to the built‐in electric field generated by the spontaneous polarization, the whole system exhibits an open circuit potential of approximately 0.205 V. Interestingly, the open circuit potential can be significantly increased to 0.446 V after poling treatment. The responsivity without external bias is increased by about 2.5 times after 1 V poling and by about 4 times after a poling time of 500 s. Moreover, the tunable ferroelectric polarization shows memory effect and retains about 25% enhancement in photocurrent density even after 60 min. The tuneability of the built‐in electric field in PEC systems based on NbOCl2 offers numerous possibilities for the development of photodetectors and nonvolatile memory devices.