在应变异质结价带偏移从头算赝势法的理论计算中,建议一种以平均键能为参考能级的△E_v 值理论计算方法,该方法在以 Si 为衬底、以 Ge 为衬底和自由共度生长等3种不同应变情况的 Si/Ge 异质结价带偏移△E_v 值计算中,分别得到0.731eV、0...在应变异质结价带偏移从头算赝势法的理论计算中,建议一种以平均键能为参考能级的△E_v 值理论计算方法,该方法在以 Si 为衬底、以 Ge 为衬底和自由共度生长等3种不同应变情况的 Si/Ge 异质结价带偏移△E_v 值计算中,分别得到0.731eV、0.243eV 和0.521eV 的计算结果。展开更多
Band offset is a dominant factor affecting the photocatalytic performance of heterostructure photocatalysts. Therefore, controlling the band gap structure of semiconductors is a key challenge in the development of eff...Band offset is a dominant factor affecting the photocatalytic performance of heterostructure photocatalysts. Therefore, controlling the band gap structure of semiconductors is a key challenge in the development of efficient photocatalysts. We used a typical in situ-method to prepare diverse graphite-phase carbon nitride(g-C_3N_4)samples from melamine, thiourea, and a mixture thereof,and found that they exhibited band gaps between2.3–2.8 e V. From UV–Vis spectra and X-ray photoelectron spectroscopy measurements, we determined that the g-C_3N_4 samples exhibited different band gap values and valence band positions. On this basis, we constructed g-C_3N_4/m-La VO_4 heterojunctions with different band offsets. UV–Vis spectra and X-ray photoelectron spectroscopy measurements revealed that the valence band offsets(VBOs) of the different heterojunctions were similar, but their conduction band offsets(CBOs) were significantly different. Photocatalytic experiments revealed that the reaction rate was enhanced with an increase in the CBO value. Furthermore, the three-phase g-C_3N_4/g-C_3N_4/mLa VO_4 heterojunction composed of m-La VO_4 and mixed g-C_3N_4 showed the highest photocatalytic activity, which was mainly due to the construction of a multilevel structure. This work investigates the influence of the band offset on heterojunction photoelectrochemical properties and provides a new strategy to improve the photocatalytic activity by constructing multilevel structures.展开更多
文摘利用第一性原理模拟计算铜铟硒(CIS)太阳能电池CIS吸收层,及CIS中普遍存在的有序缺陷化合物(ordered defect compound,ODC)CuIn_5Se_8的性质.依据CuIn_5Se_8形成的方式,结合对称性越高、能量越低的原则,建立CuInS_2中的ODC-CuIn_5S_8结构,并从态密度角度讨论CuInS2与CuIn_5S_8的差异.分别选用ZnSe和CuI半导体作为CIS和CuInS_2电池的缓冲层,利用第一性原理计算得到价带偏移(valence band offset,VBO).在ZnSe/CIS界面处,CIS的价带顶(valence band maximum,VBM)比ZnSe高0.52 eV;在CuI/CuInS_2界面处,CuI的价带顶比CuInS_2低0.37 eV,表明CuI非常适合应用于CuInS_2电池缓冲层.ODC中由于Cu的缺失,其d轨道电子和阴离子p轨道电子的p-d排斥力减小,使ODC材料的价带顶相对于自身本征材料有所下降.
基金supported by the National Natural Science Foundation of China(21173131)the Taishan Scholar Project of Shandong Province
文摘Band offset is a dominant factor affecting the photocatalytic performance of heterostructure photocatalysts. Therefore, controlling the band gap structure of semiconductors is a key challenge in the development of efficient photocatalysts. We used a typical in situ-method to prepare diverse graphite-phase carbon nitride(g-C_3N_4)samples from melamine, thiourea, and a mixture thereof,and found that they exhibited band gaps between2.3–2.8 e V. From UV–Vis spectra and X-ray photoelectron spectroscopy measurements, we determined that the g-C_3N_4 samples exhibited different band gap values and valence band positions. On this basis, we constructed g-C_3N_4/m-La VO_4 heterojunctions with different band offsets. UV–Vis spectra and X-ray photoelectron spectroscopy measurements revealed that the valence band offsets(VBOs) of the different heterojunctions were similar, but their conduction band offsets(CBOs) were significantly different. Photocatalytic experiments revealed that the reaction rate was enhanced with an increase in the CBO value. Furthermore, the three-phase g-C_3N_4/g-C_3N_4/mLa VO_4 heterojunction composed of m-La VO_4 and mixed g-C_3N_4 showed the highest photocatalytic activity, which was mainly due to the construction of a multilevel structure. This work investigates the influence of the band offset on heterojunction photoelectrochemical properties and provides a new strategy to improve the photocatalytic activity by constructing multilevel structures.
