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.