Tungsten Oxide Materials for Optoelectronic Applications

Cong, Shan; Geng, Fengxia; Zhao, Zhigang

doi:10.1002/adma.201601109

Cited by 263 publications

(190 citation statements)

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“…The several possible oxidations states of tungsten make WO 3 particularly active in undergoing redox reactions. For this reason this material is often utilized in electrochemical applications and electrochromic devices [20][21][22]. Also, both crystalline and amorphous WO 3 can host vacancies and interstitial atoms, thus allowing cation accommodation and diffusion, with a tendency to form compounds such as tungsten bronzes [23,24].…”

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confidence: 99%

Insulator-to-Metal Transition at Oxide Interfaces Induced by WO₃ Overlayers

Mattoni

Baek²,

Manca

et al. 2017

ACS Appl. Mater. Interfaces

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Interfaces between complex oxides constitute a unique playground for 2D electron systems (2DES), where superconductivity and magnetism can arise from combinations of bulk insulators. The 2DES at the LaAlO 3 /SrTiO 3 interface is one of the most studied in this regard, and its origin is determined by both the presence of a polar field in LaAlO 3 and the insurgence of point defects, such as oxygen vacancies and intermixed cations. These defects usually reside in the conduction channel and are responsible for a decreased electronic mobility. In this work, we use an amorphous WO 3 overlayer to control the defect formation and obtain an increased electron mobility in WO 3 /LaAlO 3 /SrTiO 3 heterostructures. The studied system shows a sharp insulator-to-metal transition as a function of both LaAlO 3 and WO 3 layer thickness. Low-temperature magnetotransport reveals a strong magnetoresistance reaching 900% at 10 T and 1.5 K, the presence of multiple conduction channels with carrier mobility up to 80 000 cm 2 V −1 s −1 and an unusually high effective mass of 5.6 me. The amorphous character of the WO 3 overlayer makes this a versatile approach for defect control at oxide interfaces, which could be applied to other heterestrostures disregarding the constraints imposed by crystal symmetry.The formation of a two-dimensional electron system (2DES) at the interface between band insulators SrTiO 3 (STO) and LaAlO 3 (LAO) is among the most intriguing effects studied in oxide electronics [1]. Gate tunable superconductivity [2,3], strong spin-orbit coupling [4,5] and magnetism [6,7] are some of the many phenomena observed. The origin of this 2DES is a long standing question in the solid state community and recent results indicate that a consistent picture should take into account both the built-in polar field and the presence of point defects [8][9][10]. Among these, oxygen vacancies and cation off-stoichiometry in STO are capable of inducing a 2DES [11,12]. However, defects residing in the conductive channel are usually responsible for a decreased electronic mobility [13]. In order to promote high electron mobility, it is crucial to confine donor sites away from the conducting plane, without preventing the 2DES formation in the STO top layers. Previous attempts to control the defect concentration profile and thus enhance the mobility involved the use of crystalline insulating overlayers [14,15] [18,19]. A promising material to control defect formation is tungsten oxide WO 3 . The several possible oxidations states of tungsten make WO 3 particularly active in undergoing redox reactions. For this reason this material is often utilized in electrochemical applications and electrochromic devices [20][21][22]. Also, both crystalline and amorphous WO 3 can host vacancies and interstitial atoms, thus allowing cation accommodation and diffusion, with a tendency to form compounds such as tungsten bronzes [23,24]. Recent progress demonstrated the high-quality growth of WO 3 thin films on perovskite materials [25][26][27].In this work we co...

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mentioning

confidence: 99%

Insulator-to-Metal Transition at Oxide Interfaces Induced by WO₃ Overlayers

Mattoni

Baek²,

Manca

et al. 2017

ACS Appl. Mater. Interfaces

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“…In this regard, a wide transmittance window is important as it enables facile modulation upon demands. [2,9,10] Hence, nanostructuring has been proven as an effective strategy for improving the EC performance of WO 3 film. [38] It showed nearly ideal optical modulation, reaching about 97.7% at 633 nm, well above the mostly reported level of over 80%.…”

Section: Tungsten Oxidementioning

confidence: 99%

“…[1][2][3][4][5][6][7][8][9][10] A typical electrochromic device (ECD) has a multilayer structure consisting of a transparent conductor, an electrochromic film, an electrolyte layer, and an ion storage film. In recent years, electrochromic materials have received a great deal of attention in many promising applications, such as smart windows for energy efficient buildings, self-dimming rear mirror for automobiles, information displays, and electrochromic e-skins, energy storage devices including electrochromic supercapacitors and electrochromic batteries, etc.…”

Section: Introductionmentioning

confidence: 99%

“…The ion storage film is the "counter electrode," which can be either a noncoloring redox material or an EC film referring to a "complementary-type" device. 2 :W, and various codoped alternatives. The five films of an ECD are described below in detail.…”

Section: Introductionmentioning

confidence: 99%

“…Finally, an outlook on the future research trends in electrochromism is presented. [2,8,10] ">Electrochromism: Fundamentals, Principles, and Device Structure …”

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Electrochromic Metal Oxides: Recent Progress and Prospect

Wang

et al. 2018

Adv Elect Materials

229

144

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The studied EC materials usually include viologens (as polymeric films), conjugated conducting polymers, transition metal oxides (e.g., WO 3 and NiO), metal coordination complexes (e.g., polymeric, evaporated, sublimed films). [7,11] Bene fitted by the diversity in composition/structure and the superior electrochromic performance, the electrochromism based on the thin-film transition metal oxides has become a hot topic. Recently, there have been some important breakthroughs in the transition metal oxide-based electrochromism, ranging from the development of new materials, [12] the introduction of new nanostructures, [13][14][15] element doping, [16,17] and composites [18][19][20][21] to novel designs and concepts of visible light and near-infrared radiation (NIR) dual-modulated smart windows [8,14,20] and the self-powered electrochromic batteries. [22,23] Therefore, the exploration of electrochromic devices with multifunctionalities and unique features by integrating both energy storage and electrochromism has been attracting great attention.There are several elaborate reviews serving as good references for this field, [1,3,4,6,[8][9][10] however, more comprehensive integration and up-to-date summaries embracing all relevant materials and applications are still lacking. Under such a background, as outlined in Figure 1, we attempt to provide a systematic and recapitulative review on the material developments and application status of electrochromism with a focus on transition metal oxides. Additionally, tailored synthesis and material design toward enhanced optical modulation and fast switching are also illustrated. Finally, an outlook on the future research trends in electrochromism is presented. This review will be very instructive and of special importance for directing other researchers in the future. Electrochromism: Fundamentals, Principles, and Device Structure Fundamentals and PrinciplesElectrochromism refers to the reversible change of colors and transparency under charge insertion/extraction or chemical reduction/oxidation induced by the application of an electrical current or a potential difference. [4][5][6] In the mid-1980s, the acceptance of electrochromism in fenestration technology as an approach to achieve energy efficiency in buildings captured the interest of researchers and the public. [3,24] This concept was coined as "smart window," which was capable of achieving Electrochromism has received increasing attention due to its unique electrochromic feature and the induced applications. This review provides an overview on the recent developments in the synthesis and application of the electrochromic metal oxides in smart windows, display devices, e-skins, and multifunctional energy storage devices. The main cathodic and anodic electrochromic metal oxides are surveyed here, with the discussion of representative examples in details. The current state-of-the-art research activities of the derived multifunctional electrochromic devices are highlighted, i.e., material systems, components, structures, m...

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