Critical role of {002} preferred orientation on electronic band structure of electrodeposited monoclinic WO3 thin films†,Sustainable Energy & Fuels

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Critical role of {002} preferred orientation on electronic band structure of electrodeposited monoclinic WO3 thin films†
Sustainable Energy & Fuels ( IF 5.0 ) Pub Date : 2018-09-04 00:00:00 , DOI: 10.1039/c8se00239h
Wai Ling Kwong _{1,

2,

3,

4,

5} , Pramod Koshy _{1,

2,

3} , Judy N. Hart _{1,

2,

3} , Wanqiang Xu _{1,

2,

3} , Charles C. Sorrell _{1,

2,

3}

Affiliation

Monoclinic WO₃ films with tunable (002) and (200) orientations parallel to fluorine-doped tin oxide substrates were electrodeposited from peroxotungstic acid (PTA) solutions and subjected to annealing (≤500 °C). It is concluded that the crystallographic orientations of the films are dependent on the nucleation density and the thermal-induced recrystallisation kinetics, which can be controlled respectively by the tungsten concentration of the PTA solution and the annealing conditions. This approach allows the fabrication of films with preferred (002), equally mixed (002) and (200), and (200) orientations, which were characterised in terms of the associated mineralogical, nanostructural, optical, chemical, photoelectrochemical, and photocatalytic properties. The present work decouples the concurrent effects of crystallographic orientation and trend in oxygen vacancy concentration on the optical indirect band gap of WO₃ thin films, where the linear correlation between these three variables can be used as a diagnostic tool to engineer the electronic band structure of films for applications requiring photosensitivities in different regions of the solar spectrum. In effect, a low valence band maximum, low oxygen vacancy concentration, and resultant low band gap associated with (002) preferred orientation results in the highest photoelectrochemical performance, which is relevant to applications under solar illumination. In contrast, a high concentration of oxygen vacancies, which act as surface reaction sites associated with (200) preferred orientation, results in the highest efficiency in the photodegradation of methylene blue, which is relevant to applications under UV illumination.

中文翻译：

{002}择优取向对电沉积单斜晶WO ₃薄膜电子带结构的关键作用†

单斜面WO ₃从过氧钨酸（PTA）溶液中电沉积具有平行于掺氟氧化锡衬底的可调（002）和（200）取向的薄膜，并进行退火（≤500°C）。结论是，薄膜的晶体取向取决于成核密度和热诱导的再结晶动力学，这可以分别通过PTA溶液中的钨浓度和退火条件来控制。这种方法允许制造具有优选（002），均等（002）和（200）和（200）取向的薄膜，这些薄膜的特征在于相关的矿物学，纳米结构，光学，化学，光电化学和光催化性能。_3个薄膜，其中这三个变量之间的线性关系可以用作诊断工具，以设计薄膜的电子能带结构，以用于需要在太阳光谱的不同区域进行光敏性的应用。实际上，低价带最大值，低氧空位浓度以及与（002）优选取向相关的所得低带隙导致最高的光电化学性能，这与日光照射下的应用有关。相反，高浓度的氧空位作为与（200）优选取向相关的表面反应位点，导致亚甲基蓝的光降解效率最高，这与在紫外线照射下的应用有关。

更新日期：2018-09-04

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