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. •Robust photogalvanic effect (PGE) is obtained in the two-dimensional bilayer ZrI2.•The PGE photoresponse is enhanced by interlayer sliding from the bilayer s-ZrI2 (paraelectric phase) to β-ZrI2 (ferroelectric phase).•The mechanism responsible for the enhancement of the photoresponse is revealed.