Xiao Pin, Fan Xiao-Li, Liu Li-Min, Lau Woon-Ming
School of Material Science and Engineering, State Key Laboratory of Solidification Processing, Northwestern Polytechnic University, 127 YouYi Western Road, Xi'an, Shaanxi 710072, China.
Phys Chem Chem Phys. 2014 Nov 28;16(44):24466-72. doi: 10.1039/c4cp03453h.
The promising photovoltaic activity of pyrite (FeS2) is attributed to its excellent optical absorptivity and earth abundance, but its band gap, 0.95 eV, is slightly lower than the optimum value of 1.3 eV. Here we report the first investigation of strained FeS2, whose band gap can be increased by ∼0.3 eV. The influence of uniaxial and biaxial strains on the atomic structure as well as the electronic and optical properties of bulk FeS2 is systematically examined by the first principles calculations. We found that the biaxial strain can effectively increase the band gap with respect to uniaxial strain. Our results indicate that the band gap increases with increasing tensile strain to its maximum value at 6% strain, but under the increasing compressive strain, the band gap decreases almost linearly. Moreover, the low intensity states at the bottom of the conduction band disappear and a sharp increase in the intensity appears at the lower energy level under the tensile strain, which causes the red shift of the absorption edge and enhances the overall optical absorption. With the increase of the band gap and enhanced optical absorption, FeS2 will make a better photovoltaic material.
黄铁矿（FeS₂）具有良好的光伏活性，这归因于其出色的光吸收能力和在地壳中的丰富储量，但其带隙为0.95电子伏特，略低于1.3电子伏特的最佳值。在此，我们报告了对应变FeS₂的首次研究，其带隙可增加约0.3电子伏特。通过第一性原理计算系统地研究了单轴和双轴应变对块状FeS₂的原子结构以及电子和光学性质的影响。我们发现，相对于单轴应变，双轴应变能有效增加带隙。我们的结果表明，带隙随着拉伸应变的增加而增大，在6%应变时达到最大值，但在压缩应变增加时，带隙几乎呈线性减小。此外，在拉伸应变下，导带底部的低强度态消失，在较低能级处强度急剧增加，这导致吸收边缘红移并增强了整体光吸收。随着带隙的增加和光吸收的增强，FeS₂将成为一种更好的光伏材料。
