Department of Materials Science and Engineering and Research Institute of Advanced Materials, Seoul National University, Seoul 151-755, South Korea.
Phys Chem Chem Phys. 2013 Nov 21;15(43):18906-14. doi: 10.1039/c3cp53311e.
The native point defects in Fe2O3 are theoretically investigated using ab initio methods based on the GGA + U formalism. We consider vacancies and interstitials of Fe and O atoms as well as the electron polaron as Fe(II) defects at the host Fe(III) site. The formation energies and charge transition levels are computed for each defect type with careful elimination of size effects of the supercell. It is found that the Fe interstitial and vacancy form donor and acceptor levels close to band edges, respectively, thereby allowing for charge carriers at room temperature. We determine the oxygen deficiency under high-temperature equilibrium conditions and find an excellent agreement with experiment. In the quenched condition, it is found that the Fermi level is pinned at ~0.5 eV below the conduction band minimum, which may limit the performance of Fe2O3 as a photoanode in solar water-splitting cells. Furthermore, the oxygen vacancy is mostly neutral and the Fe interstitial is responsible for electron carriers.
采用基于 GGA + U 形式的第一性原理方法，对 Fe2O3 中的本征点缺陷进行了理论研究。我们考虑了 Fe 和 O 原子的空位和间隙以及作为 Fe(III)位中 Fe(II)缺陷的电子极化子。通过仔细消除超晶胞的尺寸效应，计算了每种缺陷类型的形成能和电荷跃迁能级。结果发现，Fe 间隙和空位分别形成接近能带边缘的施主和受主能级，从而允许室温下存在电荷载流子。我们确定了高温平衡条件下的氧空位，并与实验结果非常吻合。在淬火条件下，发现费米能级被钉扎在导带最小值以下约 0.5 eV，这可能限制了 Fe2O3 在太阳能水分解电池中作为光阳极的性能。此外，氧空位大多呈电中性，Fe 间隙则负责载流子。
