The impacts of dopants on the small polaron mobility and conductivity in hematite – the role of disorder
The impacts of dopants on the small polaron mobility and conductivity in hematite – the role of disorder
复制标题
掺杂剂对赤铁矿中小极化子迁移率和电导率的影响——无序的作用
DOI：
10.1039/d2nr04807h
复制
发表时间：
2023
期刊：
影响因子：
6.7
通讯作者：
Ping, Yuan
中科院分区：
文献类型：
--
作者：
Chen, Mingpeng;Grieder, Andrew C.;Smart, Tyler J.;Mayford, Kiley;McNair, Samuel;Pinongcos, Anica;Eisenberg, Samuel;Bridges, Frank;Li, Yat;Ping, Yuan
赤铁矿（α-Fe 2 O3）具有成本低、丰度高、化学稳定性好等优点，是一种具有广泛应用前景的过渡金属氧化物。然而，其低的载流子迁移率和电导率阻碍了赤铁矿基器件的广泛应用。从根本上说，这主要是由小极化子的形成引起的，小极化子通过热激活跳跃显示传导。原子掺杂是提高赤铁矿电导率的最有前途的方法之一。然而，它对赤铁矿的载流子迁移率和电导率在原子水平上的影响仍然是虚幻的。在这项工作中，通过动力学蒙特-卡罗采样的扩散系数结合电荷中性条件下计算的载流子浓度的方法，我们得到了掺杂的赤铁矿的电导率。考虑到面内载流子输运占主导地位，我们考虑了单个Fe-O层的贡献。然后，我们研究了不同的掺杂剂如何影响载流子迁移率在赤铁矿使用锡，钛，铌作为原型的例子。我们发现载流子迁移率的变化与Fe-Fe对的局部变形密切相关，即Fe-Fe对与原始系统相比拉伸得越多，载流子迁移率就越低。因此，对于赤铁矿中更高的载流子迁移率，更需要限制Fe-Fe对距离从原始的畸变的元素。掺杂体系的局域结构和对分布函数的计算结果与实验测量结果吻合得很好，进一步验证了我们的第一性原理预测.我们的工作揭示了掺杂剂如何影响赤铁矿的载流子迁移率和电导率，并为实验人员选择掺杂剂以实现赤铁矿的最佳电导率和基于赤铁矿的器件的性能提供了实用指南。
Hematite (α-Fe2O3) is a promising transition metal oxide for various energy conversion and storage applications due to its advantages of low cost, high abundance, and good chemical stability. However, its low carrier mobility and electrical conductivity have hindered the wide application of hematite-based devices. Fundamentally, this is mainly caused by the formation of small polarons, which show conduction through thermally activated hopping. Atomic doping is one of the most promising approaches for improving the electrical conductivity in hematite. However, its impact on the carrier mobility and electrical conductivity of hematite at the atomic level remains to be illusive. In this work, through a kinetic Monte-Carlo sampling approach for diffusion coefficients combined with carrier concentrations computed under charge neutrality conditions, we obtained the electrical conductivity of the doped hematite. We considered the contributions from individual Fe–O layers, given that the in-plane carrier transport dominates. We then studied how different dopants impact the carrier mobility in hematite using Sn, Ti, and Nb as prototypical examples. We found that the carrier mobility change is closely correlated with the local distortion of Fe–Fe pairs, i.e. the more stretched the Fe–Fe pairs are compared to the pristine systems, the lower the carrier mobility will be. Therefore, elements which limit the distortion of Fe–Fe pair distances from pristine are more desired for higher carrier mobility in hematite. The calculated local structure and pair distribution functions of the doped systems have remarkable agreement with the experimental EXAFS measurements on hematite nanowires, which further validates our first-principles predictions. Our work revealed how dopants impact the carrier mobility and electrical conductivity of hematite and provided practical guidelines to experimentalists on the choice of dopants for the optimal electrical conductivity of hematite and the performance of hematite-based devices.