The Beer-Lambert law for electrochromic tungsten oxide thin films

Scarmínio, Jair; Urbano, Alexandre; Gardes, Bernard

doi:10.1016/s0254-0584(99)00132-7

Cited by 30 publications

(12 citation statements)

References 12 publications

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“…The band gap of the thin films was estimated by plotting (-InT) 1/2 against energy (hν) for undoped and Fe-doped WO 3 thin films, assuming the materials are indirect semiconductors. The band gap of the undoped WO 3 is 2.74 eV and it is in agreement with previous studies [22][23][24][25][26]. Meanwhile, the band gap of the doped thin films was decreased to 2.60 eV as the concentration of Fe increased up to 20%.…”

supporting

confidence: 91%

“…In order to reduce the band gap, WO 3 was synthesized via different methods [18][19][20][21]. The narrow band gap of 2.20 -2.80 eV helps in absorption of ultraviolet region and blue region of visible light in solar spectrum [22][23][24][25]. Furthermore, WO 3 has been investigated with the aim of improving catalyst activity and stability in the irradiated aqueous environment [26][27][28][29].…”

Section: Ng Et Al: Fabrication and Characterization Of Fe-doped Tungsmentioning

confidence: 99%

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FABRICATION AND CHARACTERIZATION OF Fe-DOPED TUNGSTEN TRIOXIDE PHOTOELECTRODES IN AQUEOUS MEDIUM USING TUNGSTIC ACID AND FERROCENE AS STARTING MATERIALS

Hang

Jaafar

Minggu³

et al. 2016

MJAS

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Different compositions of Fe-doped tungsten trioxide thin films were synthesized on fluorine-doped tin oxide (FTO) glass substrate by sol-gel method, with ferrocene and tungstic acid as starting materials. The synthesized thin films was characterized with X-ray diffraction (XRD), scanning electron microscope (SEM), UV/Vis spectrophotometer and photoelectrochemical (PEC) analysis. The results show that the surface morphology of the thin films became rough and the grain size increased along with the concentration of Fe. Monoclinic structure of tungsten trioxide was obtained for all doped and undoped WO 3 and red-shift can be observed from UV-vis spectrum. Band gap reduced from 2.74 eV of undoped WO 3 thin films to 2.60 eV of 20 % Fe-doped WO 3 thin films. Photoactivities of all Fe-doped WO 3 are higher than undoped thin films. The highest photoactivities contributed by 5 % Fe-doped WO 3 films with photocurrent densities measured was 0.148 mA/cm 2 , which is 3 times higher compared to undoped WO 3 .Keywords: Fe-doped WO 3 , direct water splitting, photoelectrochemical cell, photoanode Abstrak Filem nipis tungsten trioksida terdop Fe berbagai komposisi telah disediakan di atas kaca substrat FTO (fluorine-doped tin oxide) dengan kaedah sol-gel, dengan menggunakan ferosin dan asid tingstik sebagai bahan pemula. Filem nipis yang terhasil kemudiannya dicirikan dengan pembelauan sinar X (XRD), mikroskopi elektron pengimbasan (SEM), UV/Vis spektrofotometer dan analisis fotoelektrokimia. Keputusan menunjukkan bahawa morfologi permukaan filem nipis menjadi kasar dan saiz butiran bertambah dengan penambahan kepekatan Fe. Tungsten trioksida yang berstruktur monoklinik telah dihasilkan dan anjakan merah telah diperhatikan di dalam spectrum UV-vis. Jurang tenaga telah berkurang dari 2.74 eV (WO 3 tulen) kepada 2.60 eV (20 % Fe-dop WO 3 ). Fotoaktiviti WO 3 terdop Fe adalah lebih tinggi berbanding WO 3 tulen. Fotoaktiviti yang tertinggi dicatatkan oleh filem 5 % WO 3 terdop Fe dengan ketumpatan fotoarus 0.148 mA/cm 2 . Ia adalah 3 kali ganda lebih tinggi berbanding WO 3 tulen.Kata kunci: Fe-dop WO 3 , pembelahan air secara langsung, sel fotoelektrokimia, fotoanod

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supporting

confidence: 91%

Section: Ng Et Al: Fabrication and Characterization Of Fe-doped Tungsmentioning

confidence: 99%

FABRICATION AND CHARACTERIZATION OF Fe-DOPED TUNGSTEN TRIOXIDE PHOTOELECTRODES IN AQUEOUS MEDIUM USING TUNGSTIC ACID AND FERROCENE AS STARTING MATERIALS

Hang

Jaafar

Minggu³

et al. 2016

MJAS

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“…Briefly, ΔOD( t ) d is proportional to the time-dependent concentration of (Li-W 5+ ) color centers, Δ c ( t ), according to ref. 55:ΔOD(t)d=Δc(t)ε940/d,…”

Section: Methodsmentioning

confidence: 99%

Influence of single-nanoparticle electrochromic dynamics on the durability and speed of smart windows

Evans

Ellingworth

Cashen

et al. 2019

Proc. Natl. Acad. Sci. U.S.A.

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Nanomaterials have tremendous potential to increase electrochromic smart window efficiency, speed, and durability. However, nanoparticles vary in size, shape, and surface defects, and it is unknown how nanoparticle heterogeneity contributes to particle-dependent electrochromic properties. Here, we use single-nanoparticle-level electro-optical imaging to measure structure–function relationships in electrochromic tungsten oxide nanorods. Single nanorods exhibit a particle-dependent waiting time for tinting (from 100 ms to 10 s) due to Li-ion insertion at optically inactive surface sites. Longer nanorods tint darker than shorter nanorods and exhibit a Li-ion gradient that increases from the nanorod ends to the middle. The particle-dependent ion-insertion kinetics contribute to variable tinting rates and magnitudes across large-area smart windows. Next, we quantified how particle–particle interactions impact tinting dynamics and reversibility as the nanorod building blocks are assembled into a thin film. Interestingly, single particles tint 4 times faster and cycle 20 times more reversibly than thin films made of the same particles. These findings allow us to propose a nanostructured electrode architecture that optimizes optical modulation rates and reversibility across large-area smart windows.

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“…where ϵ is the molar extinction coefficient (in units of cm 2 /mol) . We assume that ϵ =3.7×10 6 cm 2 /mol and is particle independent .…”

Section: Resultsmentioning

confidence: 99%

“…where ɛ is the molar extinction coefficient (in units of cm 2 / mol). [29] We assume that ɛ = 3.7 × 10 6 cm 2 /mol and is particle independent. [28] By correcting for thickness, we are directly comparing the change in concentration of color centers.…”

Section: Single Nanoparticle Imaging Of Ion Insertion Reactionsmentioning

confidence: 99%

Quantifying Capacitive‐Like and Battery‐Like Charge Storage Contributions Using Single‐Nanoparticle Electro‐optical Imaging

et al. 2020

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Pseudocapacitors promise to combine the high‐rate capability of electrochemical capacitors with the high energy‐density of batteries. A major challenge in the field is to demonstrate that pseudocapacitors behave electrochemically like a capacitor and the charge storage process is faradaic in nature. It is challenging to do so because pseudocapacitive charging has the same electrical signatures as non‐faradaic electrical double‐layer charging. Here we use electro‐optical imaging to measure Li‐ion insertion reactions in single WO3 nanoparticles. On average, these WO3 particles exhibit a hybrid charge storage mechanism: both diffusion‐limited (battery‐like) and pseudocapacitive (capacitor‐like) mechanisms contribute to the total charge stored. Individual particles exhibit different charge storage mechanisms at the same applied potential. Longer nanorods store more pseudocapacitive charge than shorter nanorods, presumably due to 1) a surface step edge gradient that exposes large hexagonal window Li‐ion binding sites along the nanorod length and/or 2) higher structural water content that influences the Li‐ion binding energetics and diffusion behavior. Importantly, we quantified the penetration depth of Li‐ion insertion and concluded that Li ions insert as deep as two‐unit cells below the surface. The methodology presented herein can be applied to a wide range of solid‐state ion‐insertion materials.

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The Beer-Lambert law for electrochromic tungsten oxide thin films

Cited by 30 publications

References 12 publications

FABRICATION AND CHARACTERIZATION OF Fe-DOPED TUNGSTEN TRIOXIDE PHOTOELECTRODES IN AQUEOUS MEDIUM USING TUNGSTIC ACID AND FERROCENE AS STARTING MATERIALS

FABRICATION AND CHARACTERIZATION OF Fe-DOPED TUNGSTEN TRIOXIDE PHOTOELECTRODES IN AQUEOUS MEDIUM USING TUNGSTIC ACID AND FERROCENE AS STARTING MATERIALS

Influence of single-nanoparticle electrochromic dynamics on the durability and speed of smart windows

Quantifying Capacitive‐Like and Battery‐Like Charge Storage Contributions Using Single‐Nanoparticle Electro‐optical Imaging

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