Enhancing the bulk photovoltaic effect of ZrI2 through regulation of external stimuli

The bulk photovoltaic effect (BPVE) in layered materials has garnered widespread attention due to its large shift current responses and promising potential for efficient photoelectric energy conversion. Here, we systematically investigate the shift current responses of BPVE in layered β-ZrI2 and bilayer ZrI2, demonstrating that large shift current of out-of-plane of 110 μA/V2 and 55 μA/V2 are achieved in β-ZrI2 and bilayer ZrI2 respectively, under ambient conditions. Intriguingly, the shift current of β-ZrI2 and bilayer ZrI2 demonstrates further improvement under the regulation of external stimuli. Especially, the σzxx component of shift current tensor in β-ZrI2 increases from 29 μA/V2 to 51 μA/V2 upon compression up to 3 GPa, while the largest shift current of bilayer ZrI2 reaching 170 μA/V2 under tensile strain. The notable enhancement of shift current responses in β-ZrI2 and bilayer ZrI2 is closely associated with charge delocalization occurred around Zr atoms and strain-enhanced joint density of states (JDOS), respectively. These findings provide the visionary insights for exploring and developing high-performance BPVE materials.