Enhanced photogalvanic effect in a 2D ferroelectric ZrI2 by interlayer sliding

Two-dimensional ferroelectrics with moderate band gap enable unprecedented applications in optoelectronics. Here, we report that the photogalvanic effect (PGE) of narrow-band-gap semiconductor bilayer ZrI2 is significantly enhanced by the interlayer sliding which turns out to be ferroelectric with both in-plane and out-of-plane polarizations. The intrinsic ferroelectric field promotes the separation efficiency of photogenerated carriers and reduces the recombination rate of electron–hole pairs, thus improving the photoelectric conversion efficiency and resulting in a larger photoresponse. The magnitude of the maximum photoresponse in the bilayer β-ZrI2 (ferroelectric) is enhanced by about 5 times than in the bilayer s-ZrI2 (paraelectric). A robust broadband photoresponse from mid-infrared to visible can be found from its photodetector. Our results provide great insights to engineering novel optoelectronic applications by ferroelectric slidetronics.