Fund Project:Project supported by the National Natural Science Foundation of China (Grant Nos. 51872251, 11875229) and the Opening Project of Science and Technology on Reliability Physics and Application Technology of Electronic Component Laboratory, China (Grant No. ZHD201803)
Received Date:07 August 2020
Accepted Date:07 September 2020
Available Online:24 January 2021
Published Online:05 February 2021
Abstract:The h-LuFeO3 is a kind of narrow band gap hexagonal ferrite material, with a good application prospect in the field of ferroelectric photovoltaic. However, the low polarization intensity of h-LuFeO3 makes the recombination rate of photogenerated electrons and holes large, which is not conducive to the improvement of the efficiency of h-LuFeO3-based ferroelectric photovoltaic cells. In order to improve the ferroelectricity and optical absorption properties of h-LuFeO3, the first principles method is used to calculate the doping formation energy values of In atom at different positions of h-LuFeO3, and the most stable doping position is determined. The comparisons of band gap, optical absorption performance and polarization intensity among h-Lu1-xInxFeO3 (x = 0, 0.167, 0.333, 0.667) are made. With the increase of In doping, the cells of h-Lu1–xInxFeO3 stretch along the c-axis. The ratio of the lattice constant c/a increases from 1.94 at x = 0 to 2.04 at x = 0.667 when all the positions of In replace P1 position. Using the qualitative calculation of Berne effective charge, the results show that the ferroelectric polarization intensity of h-LuFeO3, h-Lu0.833In0.167FeO3, h-Lu0.667In0.333FeO3 and h-Lu0.333In0.667FeO3 along the c-axis are 3.93, 5.91, 7.92, and 11.02 μC·cm–2, respectively. Therefore, with the increase of the number of In atoms replacing Lu atoms, the lattice constant c/a ratio of h-Lu1–xInxFeO3 increases, which can improve the ferroelectric polarization strength of the material. By analyzing the density of states of h-LuFeO3 and h-Lu0.333In0.667FeO3, we can see that In doping enhances the Fe-O orbital hybridization in h-Lu0.333In0.667FeO3, and makes the optical absorption coefficient of h-Lu0.333In0.667FeO3 in the solar light range larger. In summary, In doped h-LuFeO3 is an effective method to improve its polarization intensity and optical absorption coefficient, which is of great significance for improving the performance of ferroelectric photovoltaic. Keywords:h-LuFeO3/ doping/ optical property/ polarization intensity/ first principles
图4为光沿c轴入射h-Lu1–xInxFeO3的光吸收系数变化情况, 发现在1.64—2.4 eV范围内, 掺杂后的光吸收系数比未掺杂的h-LuFeO3略微减小. 但在能量大于2.4 eV区域, 材料光吸收系数随着In/Lu比值的增大而增大, 表明In掺杂能够有效提高h-LuFeO3在太阳光能量范围内的光吸收效率. 图 4 In掺杂前后h-LuFeO3光学吸收系数随入射光子能量的变化 Figure4. Change of optical absorption coefficient of h-LuFeO3 with incident photon energy before and after In doping.