Air-Stable In-Plane Anisotropic GeSe₂ for Highly Polarization-Sensitive Photodetection in Short Wave Region

Abstract

In-plane anisotropic layered materials such as black phosphorus (BP) have emerged as an important class of two-dimensional (2D) materials that bring a new dimension to the properties of 2D materials, hence providing a wide range of opportunities for developing conceptually new device applications. However, all of recently reported anisotropic 2D materials are relatively narrow-bandgap semiconductors (<2 eV), and there has been no report about this type of materials with wide bandgap, restricting the relevant applications such as polarization-sensitive photodetection in short wave region. Here we present a new member of the family, germanium diselenide (GeSe) with a wide bandgap of 2.74 eV, and systematically investigate the in-plane anisotropic structural, vibrational, electrical, and optical properties from theory to experiment. Photodetectors based on GeSe exhibit a highly polarization-sensitive photoresponse in short wave region due to the optical absorption anisotropy induced by in-plane anisotropy in crystal structure. Furthermore, exfoliated GeSe flakes show an outstanding stability in ambient air which originates from the high activation energy of oxygen chemisorption on GeSe (2.12 eV) through our theoretical calculations, about three times higher than that of BP (0.71 eV). Such unique in-plane anisotropy and wide bandgap, together with high air stability, make GeSe a promising candidate for future 2D optoelectronic applications in short wave region.

Multilayered 2D Cesium‐Based Hybrid Perovskite with Strong Polarization Sensitivity: Dimensional Reduction of CsPbBr3

“…Particularly, the dimensional reduction from 3D hybrid perovskite lattice to 2D‐layered derivates enables unique quantum‐confinement effects, as demonstrated by the lead–iodide perovskite system. The derivative 2D subclass not only preserves high photoelectric properties of the 3D prototype but also exhibits anisotropic architecture that further leads to electrical and optical anisotropy . For instance, intrinsic linear dichroism of the multilayered 2D hybrid perovskite (isobutylammonium) 2 (MA)Pb 2 I 7 enables remarkable polarized‐light photoelectric detection behaviors .…”

“…Therefore, the anisotropic structure can result in the anisotropy of the dielectric function. Anisotropic dielectric function induces the imaginary as well as real parts of the complex index of refractive to transform as a function of crystalline direction, resulting in absorption anisotropy . As shown in Figure f, the optical absorption spectra under polarized light were obtained by calculating the dielectric function and display significant absorption anisotropy from 350 to 500 nm.…”

“…[14][15] Particularly,t he dimensional reduction from 3D hybrid perovskite lattice to 2D-layered derivates enables unique quantum-confinement effects, [16][17] as demonstrated by the lead-iodide perovskite system.T he derivative2 Ds ubclass not only preserves high photoelectric properties of the 3D prototype but also exhibits anisotropic architecture that furtherl eads to electrical and optical anisotropy. [18][19][20][21][22][23][24][25][26] For instance, intrinsic linear dichroism of the multilayered 2D hybrid perovskite (isobutylammonium) 2 (MA)Pb 2 I 7 enables remarkable polarized-light photoelectric detection behaviors. [27] This design strategy was recently extended to the cesium-based perovskites, and af ew 2D Cscontaining hybrid perovskites were fabricated by alloying organic moieties into the prototypic CsPbBr 3 such as (isobutylammonium) 2 CsPb 2 Br 7 [28] and (n-butylammonium) 2 CsPb 2 Br 7 .…”

“…Anisotropic dielectric function induces the imaginary as well as real parts of the complex index of refractivet ot ransform as af unctiono fc rystalline direction, resulting in absorption anisotropy. [24] As shown in Figure 2f,t he optical absorption spectrau nder polarized light were obtained by calculating the dielectric function and display significant absorptiona nisotropy from 350 to 500 nm. Concretely,a bsorption coefficients exhibit the evident decreasing trend as the increaseo ft he wavelength of incident light and are much greater along the b-a nd c-axis directions at 405 nm.…”

In-Plane Anisotropic Faceting of Ultralarge and Thin Single-Crystalline Colloidal SnS Nanosheets

“…This is consistent with the SAED suggesting that the surface is oriented along Recently, in-plane electronic anisotropy of 2D materials has gained great attentions and it has been widely investigated for potential electronic devices. 5,[17][18] Therefore, insolution tuning of edge faceting plays an important role in the application of electronic anisotropy for 2D colloidal nanomaterials. Generally, after adjusting reaction parameters, we achieved two different types of SnS NSs in respect to edge faceting: 1.…”