A hidden symmetry-broken phase of MoS2 revealed as a superior photovoltaic material
A hidden symmetry-broken phase of MoS2 revealed as a superior photovoltaic material
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MoS2 隐藏的对称破缺相被揭示为一种优异的光伏材料
DOI：
10.1039/c8ta05459b
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发表时间：
2018
影响因子：
11.9
通讯作者：
Ma Yanming
中科院分区：
文献类型：
--
作者：
Xu Meiling;Chen Yue;Xiong Fen;Wang Jianyun;Liu Yanhui;Lv Jian;Li Yinwei;Wang Yanchao;Chen Zhongfang;Ma Yanming
单层MoS 2一直被认为是可穿戴光伏器件的最有前途的候选者。然而，其光伏效率受到其大的带隙（2.0 eV）的限制。虽然可以通过增加层数来减小带隙，但是所得多层MoS 2的间接带隙性质是不利的。在这里，我们报告了一个迄今为止未知的单分子层MoS 2的破磁相（表示为1 Td）通过群结构搜索的理论发现。1 Td相具有Mo的扭曲八面体配位图案，并且其1.27 eV的直接带隙接近给出光伏效率的肖克利-奎塞尔极限的1.34 eV的最佳值。重要的是，直接带隙的性质仍然存在于薄膜与多层由于相邻的1 Td层之间的非常弱的VDW力。在30 nm厚度下的理论光伏效率达到1033.3%，这是迄今为止已知的所有薄膜太阳能电池吸收体中最高的转换效率。在此基础上，提出了几种可行的合成方法，包括适当的电子注入和退火方法。一旦合成，1 Td相的上级光伏性能可能会导致过渡金属二硫属化物太阳能电池的研究的一个全新的路线的发展。
Monolayer MoS2 has long been considered as the most promising candidate for wearable photovoltaic devices. However, its photovoltaic efficiency is restricted by its large band gap (2.0 eV). Though the band gap can be reduced by increasing the number of layers, the indirect band gap nature of the resulting multilayer MoS2 is unfavorable. Herein, we report a theoretical discovery of the hitherto unknown symmetry-broken phase (denoted as 1Td) of monolayer MoS2 through a swarm structure search. The 1Td phase has a distorted octahedral coordinated pattern of Mo, and its direct band gap of 1.27 eV approaches the optimal value of 1.34 eV that gives the Shockley–Queisser limit for photovoltaic efficiency. Importantly, the direct band gap nature persists in thin films with multilayers owing to extremely weak vdW forces between adjacent 1Td layers. The theoretical photovoltaic efficiency at 30 nm thickness reaches ∼33.3%, which is the highest conversion efficiency among all the thin-film solar cell absorbers known thus far. Furthermore, several feasible strategies including appropriate electron injection and annealing methods were proposed to synthesize the 1Td phase. Once synthesized, the superior photovoltaic properties of the 1Td phase may lead to the development of an entirely new line of research for transition metal dichalcogenide solar cells.