Density Functional Study of the Interfacial Electron Transfer Pathway for Monolayer-Adsorbed InN on the TiO2 Anatase (101) Surface

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• 作者：Jyh Shing Lin ; Wen-Chi Chou ; Shao-Yu Lu ; Geng-Jya Jang ; Bo-Rong Tseng ; Yung-Ting Li
• 刊名：Journal of Physical Chemistry B
• 出版年：2006
• 出版时间：November 23, 2006
• 年：2006
• 卷：110
• 期：46
• 页码：23460 - 23466
• 全文大小：501K
• 年卷期：v.110,no.46(November 23, 2006)
• ISSN：1520-5207

文摘

Density functional theory (DFT) in connection with ultrasoft pseudopotential (USP) and generalized gradientspin-polarized approximations (GGSA) is applied to calculate the adsorption energies and structures ofmonolayer-adsorbed InN on the TiO₂ anatase (101) surface and the corresponding electronic properties, thatis, partial density of states (PDOS) for surface and bulk layers of the TiO₂ anatase (101) surface and monolayer-adsorbed InN, to shed light on the possible structural modes for initial photoexcitation within the UV/visadsorption region followed by fast electron injection through the InN/TiO₂ interface for an InN/TiO₂-basedsolar cell design. Our calculated adsorption energies found that the two most probable stable structural modesof monolayer-adsorbed InN on the TiO₂ anatase (101) surface are (1) an end-on structure with an adsorptionenergy of 2.52 eV through N binding to surface 2-fold coordinated O (O_cn2), that is, InN-O_cn2, and (2) aside-on structure with an adsorption energy of 3.05 eV through both N binding to surface 5-fold coordinatedTi (Ti_cn5) and In bridging two surface O_cn2, that is, (O_cn2)₂-InN-Ti_cn5. Our calculated band gaps for bothInN-O_cn2 and (O_cn2)₂-InN-Ti_cn5 (including a 1.0-eV correction using a scissor operator) of monolayer-adsorbed InN on the TiO₂ anatase (101) surface are red-shifted to 1.7 eV (730 nm) and 2.3 eV (540 nm),respectively, which are within the UV/vis adsorption region similar to Gratzel's black dye solar cell. Ouranalyses of calculated PDOS for both surface and bulk layers of the TiO₂ anatase (101) surface and monolayer-adsorbed InN on the TiO₂ anatase (101) surface suggest that the (O_cn2)₂-InN-Ti_cn5 configuration of monolayer-adsorbed InN on the TiO₂ anatase (101) surface would provide a more feasible structural mode for the electroninjection through the InN/TiO₂ interface. This is due to the presence of both occupied and unoccupied electronicstates for monolayer-adsorbed InN within the band gap TiO₂ anatase (101) surface, which will allow thephotoexcitation within the UV/vis adsorption region to take place effectively, and subsequently the photoexcitedelectronic states will overlap with the unoccupied electronic states around the lowest conduction band of theTiO₂ anatase (101) surface, which will ensure the electron injection through the InN/TiO₂ interface. Finally,another thing worth our attention is our preliminary study of double-layer-adsorbed InN on the TiO₂ anatase(101) surface, that is, (O_cn2)₂-(InN)₂-Ti_cn5, with a calculated band gap red-shifted to 2.6 eV (477 nm) anda different overlap of electronic states between double-layer-adsorbed InN and the TiO₂ anatase (101) surfacequalitatively indicated that there is an effect of the thickness of adsorbed InN on the TiO₂ anatase (101)surface on both photoexcitation and electron injection processes involved in the photoinduced interfacialelectron transfer through InN/TiO₂. A more thorough and comprehensive study of different layers of InNadsorbed in all possible different orientations on the TiO₂ anatase (101) surface is presently in progress.