Anisotropic photoresponse in a van der Waals CuInP2S6 crystal

Photoelectronic devices that utilize ferroelectric polarization offer significant advantages in terms of dipole-modulated charge separation and energy band gap. In this paper, we investigate the unusual photoresponse characteristics of a two-dimensional ${\mathrm{CuInP}}_{2}{\mathrm{S}}_{6}$ crystal with cation order-disorder mediated phases, namely, paraelectricity, ferroelectricity, and dipolar glass. Notably, the photocurrent demonstrates a clear anisotropic photoresponse in the ferroelectric state, whereas it becomes isotropic with significantly reduced values in the dipolar glass state. This anisotropy-isotropy change can be attributed to ferroelectric frustration within the dipolar glass phase. In addition, the Cu cation ordering at low temperature results in a larger band gap and suppressed photocurrent compared with the paraelectric and ferroelectric phases. This discovery offers valuable insights into understanding the impact of order-disorder phase transitions on the photodetective performance of ferroelectric materials.