Spontaneous Direct Band Gap, High Hole Mobility, and Huge Exciton Energy in Atomic-Thin TiO2 Nanosheet
Spontaneous Direct Band Gap, High Hole Mobility, and Huge Exciton Energy in Atomic-Thin TiO2 Nanosheet
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DOI：
10.1021/acs.chemmater.8b02792
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发表时间：
2018-08
影响因子：
8.6
通讯作者：
Wei Zhou;N. Umezawa;R. Ma;Nobuyuki Sakai;Y. Ebina;Kôkiti Sano;Mingjie Liu;Y. Ishida;T. Aida-T.
中科院分区：
文献类型：
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作者：
Wei Zhou;N. Umezawa;R. Ma;Nobuyuki Sakai;Y. Ebina;Kôkiti Sano;Mingjie Liu;Y. Ishida;T. Aida-T.
用G0W0+BSE计算的多体微扰理论精确地预测了原子-薄二氧化钛纳米片的准粒子能带结构、载流子迁移率和光学响应。与锐钛矿型二氧化钛的间接禁带特性不同，纤钛矿型二氧化钛的直接禁带宽度为5.3 eV。由于O-2p轨道强重叠产生的价带色散极大值，提出了锂镁石型纳米片的空穴迁移率为1069cm2·V~(-1)·S~(-1)。包括激子效应的电子-空穴交换效应，我们的模拟很好地再现了实验的吸收光谱，这意味着一个巨大的激子结合能。强各向异性激子来源于锂镁石型二氧化钛纳米片中由于不对称轨道重叠而产生的与晶体相关的有效质量。强束缚激子仍然使水溶液产生氢气的潜力足够高，尽管…
The quasi-particle band structure, carrier mobility, and optical response of atomic-thin TiO2 nanosheets were accurately predicted with the many-body perturbation theory of G0W0+BSE calculations. The lepidocrocite-type TiO2 exhibits an unexpected direct band gap of 5.3 eV, different from the retaining indirect band gap character in anatase-type TiO2 nanosheet. Because of the dispersive valence band maxima from the strong overlap between O-2p orbitals, an extremely high hole mobility of 1069 cm2 V–1 s–1 was proposed for the lepidocrocite-type TiO2 nanosheet. Including the electron–hole exchange of excitonic effect, our simulations well reproduce the experimental absorption spectra implying a huge exciton binding energy. The strong anisotropic exciton originates from the crystal dependent effective mass in the lepidocrocite-type TiO2 nanosheet due to the asymmetric orbital overlaps. The strongly bound exciton still renders a sufficiently high potential for hydrogen production from aqueous solution, although...