College of Physics and Electronic Engineering, Center for Computational Sciences, Sichuan Normal University, Chengdu, 610068, China.
Nanoscale. 2019 Oct 10;11(39):18436-18443. doi: 10.1039/c9nr05282h.
Based on first principles calculations, we propose a new 2D ferroelectric material, triple-layer (TL) LaOBiS2, with an ultrahigh carrier mobility over 40 000 cm2 V-1 s-1 and large sunlight absorption. TL-LaOBiS2 is composed of a middle LaO layer and top-and-bottom BiS2 layers that can be possibly exfoliated from its bulk counterpart. We reveal that each BiS2 layer can hold spontaneous in-plane ferroelectric polarization that can be further enhanced by imposing extensive strain. Furthermore, we discover that TL-LaOBiS2 possesses unconventional inner-TL ferroelectric (FE), antiferroelectric (AFE) and orthogonal polarizations. The ground inner-TL AFE state can be flexibly driven into a nearly degenerate FE state. Moreover, the direct band gaps, optical absorption and the carrier mobilities of TL-LaOBiS2 can be effectively regulated by different ferroelectric polarization configurations. This finding of various ferroelectric states with ultrahigh mobility and excellent optical absorption in TL-LaOBiS2 provides a promising platform for future realization of two-dimensional ferroelectric photovoltaic devices.
基于第一性原理计算，我们提出了一种新的二维铁电材料，即三层（TL）LaOBiS2，其载流子迁移率超过 40000 cm2 V-1 s-1，且对阳光具有较大的吸收率。TL-LaOBiS2 由中间的 LaO 层和上下两层 BiS2 层组成，这两层有可能从其体相对应物中剥离出来。我们揭示出，每个 BiS2 层都可以保持自发的面内铁电极化，通过施加广泛的应变可以进一步增强这种极化。此外，我们发现 TL-LaOBiS2 具有非常规的内 TL 铁电（FE）、反铁电（AFE）和正交极化。基态内 TL AFE 状态可以灵活地被驱动到几乎简并的 FE 状态。此外，不同铁电极化构型可以有效地调节 TL-LaOBiS2 的直接带隙、光吸收和载流子迁移率。TL-LaOBiS2 中具有超高迁移率和优异光吸收的各种铁电态的发现为未来实现二维铁电光伏器件提供了一个有前途的平台。
