Xia F F, Yang F L, Hu J, Zheng C Z, Yi H B, Sun J H
School of Chemical and Environmental Engineering, Jiangsu University of Technology Changzhou 213001 Jiangsu P. R. China
State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University Changsha 410082 Hunan P. R. China
RSC Adv. 2018 Dec 4;8(70):40464-40470. doi: 10.1039/c8ra08834a. eCollection 2018 Nov 28.
The layered two-dimensional (2D) SnS and SnSe have received intensive attention due to their sizable band gaps and potential properties. However, it has been shown that the visible light absorption of SnS and SnSe are restricted as photocatalysts and light-harvesting material absorbers for water splitting and high-performance optoelectronic devices. Herein, to enhance the visible light absorption performance of SnS and SnSe, we performed a systematic investigation on tuning the electronic and optical properties of monolayers SnS and SnSe surface charge transfer doping (SCTD) with the adsorption of molybdenum trioxide (MoO) and potassium (K) as surface dopants based on density functional theory. Our calculations reveal that MoO molecules and K atoms can draw/donate electrons from/to SnS and SnSe as acceptors and donors, respectively. The adsorption of MoO molecules introduces a new flat impurity state in the gap of the monolayers SnS/SnSe, and the Fermi level moves correspondingly to the top of valence band, resulting in a p-type doping of the monolayer SnS/SnSe. With the adsorption of K atoms, the electrons can transfer from K atoms to the monolayer of SnS and SnSe, making K an effective electron-donating dopant. Meanwhile, the bandgaps of monolayers SnS and SnSe decrease after the MoO and K doping, which leads to the appearance of appreciable new absorption peaks at around ∼650/480 and ∼600/680 nm, respectively, and yielding an enhanced visible light absorption of SnS and SnSe. Our results unveil that SCTD is an effective way to improve the photocatalytic and light-harvesting performance of SnS and SnSe, broadening their applications in splitting water and degrading environmental pollutants under sunlight irradiation.
层状二维（2D）硫化锡（SnS）和硒化锡（SnSe）因其可观的带隙和潜在特性而受到广泛关注。然而，已有研究表明，作为用于水分解的光催化剂和光捕获材料吸收剂以及高性能光电器件，SnS和SnSe的可见光吸收受到限制。在此，为了提高SnS和SnSe的可见光吸收性能，我们基于密度泛函理论，对以三氧化钼（MoO）和钾（K）作为表面掺杂剂吸附在单层SnS和SnSe表面进行电荷转移掺杂（SCTD）来调节其电子和光学性质进行了系统研究。我们的计算表明，MoO分子和K原子可分别作为受体和供体从SnS和SnSe获取/给予电子。MoO分子的吸附在单层SnS/SnSe的带隙中引入了一个新的平坦杂质态，费米能级相应地移动到价带顶部，导致单层SnS/SnSe发生p型掺杂。随着K原子的吸附，电子可从K原子转移到SnS和SnSe单层，使K成为有效的电子供体掺杂剂。同时，MoO和K掺杂后，单层SnS和SnSe的带隙减小，分别导致在约650/480和约600/680 nm处出现明显的新吸收峰，从而增强了SnS和SnSe的可见光吸收。我们的结果表明，表面电荷转移掺杂是提高SnS和SnSe光催化和光捕获性能的有效方法，拓宽了它们在阳光照射下分解水和降解环境污染物方面的应用。
