Study on the optical and electrochromic properties of polycrystalline WO3 thin films prepared by CVD

doi:10.1016/0165-1633(88)90020-2

Solar Energy Materials

Volume 17, Issue 5, August 1988, Pages 379-390

https://doi.org/10.1016/0165-1633(88)90020-2 Get rights and content

Abstract

Polycrystalline WO₃ thin films were prepared by annealing, under various conditions, of black or reflective tungsten layers produced by CVD on fused quartz or SnO₂ coated substrates. The optical gap was investigated and found to depend on film thickness. It varies ∼2.5 eV for the thicker films to 3.1 eV for the thinner films. The values of the electrochromic efficiency, using protons as inserted ions, varies between 30 and 40 cm²/C for all kinds of films and depends on the film preparation and the coloring-bleaching cycle. Coloring and bleaching times and response of the films are also found to be enhanced with cycling and influenced by the preparation conditions.

References (38)

W.C. Dautremont-Smith
Displays
(1982)
A. Deneuville et al.
Thin Solid Films
(1980)
O. Bohnké et al.
Solid State Ionics
(1982)
C.M. Lampert
Solar Energy Mater.
(1984)
A.P. Schuster et al.
Solar Energy Mater.
(1986)
R.B. Goldner et al.
Solar Energy Mater.
(1986)
C.M. Lampert et al.
Solar Energy Mater.
(1986)
D. Davazoglou et al.
Thin Solid Films
(1987)
D. Davazoglou et al.
Solar Energy Mater.
(1987)
F. Di Quarto et al.
Solar Energy Mater.
(1985)

M.A. Butler et al.

Solid State Commun.

(1976)

F.P. Koffyberg et al.

Solid State Commun.

(1979)

M. Sharon et al.

Solar Energy Mater.

(1984)

O. Bohnké et al.

Solid State Ionics

(1982)

S.F. Cogan et al.

Solar Energy Mater.

(1986)

T. Yoshimura et al.

Thin Solid Films

(1983)

S.K. Deb

Phil. Mag.

(1973)

B.W. Faughnan et al.

RCA Rev.

(1975)

I.F. Chang

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Influence of substrate temperature on growth and Electrochromic properties of WO<inf>3</inf> thin films
2018, Optik
Citation Excerpt :
Several research and review articles show the immense popularity of the material owing to its electrochromic properties. Numerous synthesis techniques were used for the production of thin films include thermal deposition [26], flash evaporation [27], electron beam evaporation (EBE) [28], DC and RF sputtering [29], pulsed laser ablation [30] Matrix Assisted Pulsed Laser Evaporation (MAPLE) [31], Molecular Beam Epitaxy [32], spray pyrolysis [33], Sol-Gel [34], electrodeposition [35] and hydrothermal technique [36], Atomic Layer Deposition (ALD) [37], Chemical vapor deposition [38] and Glancing angle deposition technique [39]. However, there are very less reports available for the study of electrochromic properties of electron beam evaporated WO3 thin films.
WO₃ thin films are prepared by electron beam evaporation (EBE) technique under the base pressure of 2 × 10^-5 mbar at various substrate temperature (T_s) ranging from room temperature (RT) to 450 °C. The deposited films were characterized systematically to analyse the influence of substrate temperature on structural, morphological, compositional, vibrational, electrical, optical and electrochromic properties. The EDS data of deposited films confirm the presence of tungsten (W) and Oxygen (O) elements. XRD spectra reveal that films deposited at T_s < 250 °C are found to be amorphous and turns to crystalline as the substrate temperature raised to 450 °C. The morphological studies reveal that, beyond 250 °C of substrate temperature the material structure slowly changes to well crystallined structure with grain size about 70-80 nm. W = O and O-W-O bonds were present in the films which were confirmed by Raman spectra. The optical data represents the indirect allowed transitions and the band gap values are observed to be decreased from 3.24 to 2.93 eV with rise of substrate temperature from RT to 450 °C. It is also found that the RT electrical conductivity is increased with increase of T_s. Finally it is found that the coloration efficiency (CE) of the films deposited at RT is 30.63 cm²/C at the wavelength of 550 nm.
Influence of substrate temperature on structural, morphological, optical and electrical properties of Bi-doped MnInS<inf>4</inf> thin films prepared by nebuliser spray pyrolysis technique
2017, Journal of Physics and Chemistry of Solids
Bismuth (Bi)-doped manganese indium sulphide (MnInS₄) thin films were deposited on heated glass substrates using an aqueous solution of MnCl₂, InCl₃, (NH₂)₂CS and BiCl₃ by the common nebuliser spray pyrolysis technique. The thin films were grown at various substrate temperatures ranging from 250 to 400 °C with a constant spray time (5 min). The present work aims to study the effect of substrate temperature on the structural, optical, photoluminescence and electrical properties of the grown thin films using various techniques like X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive spectrum (EDS), UV–Vis absorption spectroscopy, photoluminescence spectra (PL) and four probe methods. The XRD pattern reveals that the Bi-doped MnInS₄ thin films were polycrystalline in nature with a cubic spinel structure whose particle size varies between 8.2 and 23.5 nm. From the FE-SEM micrographs, due to the change in the substrate temperature, shapes such as spherical, needle-shaped and T-shaped grains were observed throughout the surface of the films. The energy dispersive analysis spectrum (EDS) shows the presence of Mn, In, S and Bi in the film grown at 250 °C. It is interesting to note that the structural homogeneity and crystallinity of the film is improved due to the decrease in the absorption coefficient (α) and extinction coefficient (K) with an increase in substrate temperature. Also, with an increase in the substrate temperature, the calculated band gap energy was found to decrease from 1.87 to 1.59 eV. From the PL spectra, several intense peaks corresponding to blue, green, yellow, orange and red band emissions were observed in the wavelength region of 350–650 nm. Moreover as the intensity of the peak increases with increase in the substrate temperature, the crystallinity of the material of the film greatly improves concomitant with minimum strain and defect states. From the electrical studies, the electrical conductivity increases with increase in substrate temperature and a maximum electrical conductivity of 3.73 × 10⁻³ Ω⁻¹m⁻¹ were obtained for the film prepared at 400 °C. The thickness of the films was also measured and the values ranged between 743 nm (250 °C) to 629 nm (400 °C). The high absorption coefficient (1.85 × 10⁴ cm⁻¹) and high transmittance of the films make them an efficient window layer for solar cell applications. Incorporation of Bismuth (Bi) into MnInS₄ matrix leads to improve the optical transmittance (85%) and electrical conductivity (3.11 × 10⁻³ Ω⁻¹ m⁻¹) of the film grown at 400 °C. Other important parameters like dislocation density (δ), strain (ε), the number of crystallites per unit area (N) and lattice distortion (LD), which are commonly used to describe the structural analysis were also presented. Bi-doped MnInS₄ thin films were grown by a variety of deposition methods. Among them, spray pyrolysis is an eco-friendly method because of its low cost, mass production capacity, large area coatings and minimum wastage of the source materials.
Optimization and characterization of CuO thin films for P–N junction diode application by JNSP technique
2017, Optik
The present work illustrates the optimization of substrate temperature, mole concentration and volume of the solution of copper oxide (CuO) thin films prepared by jet nebulizer spray pyrolysis (JNSP) technique. Such prepared CuO films were optimized and characterized by XRD, SEM, EDX, UV–vis and I–V. From XRD analysis the mole concentration, volume level and substrate temperature of the prepared CuO films were fixed as 0.20 M, 5 ml and 450 °C respectively and optimized for P–N diode application. The XRD pattern of the optimized CuO film reveals monoclinic structure. The surface morphological variations and elemental present were confirmed by SEM and EDX analysis. The optical properties were recorded by UV–vis spectrum and the minimum band gap value is observed as 1.63 eV for 450 °C substrate temperature. The maximum conductivity value of the prepared CuO is recorded as 7.4 × 10⁻⁹ S/cm from I–V characterization. Using J–V, the diode parameters of p-CuO/n-Si prepared at 450 °C with 0.2 M and 5 ml were measured in dark and under illumination. The ideality factor (n) and barrier height (Φ_b) values of p-CuO/n-Si diode are 6.2 and 0.80 eV in dark and 4.6 and 0.81 eV under illumination.
Structural, morphological and optical properties of electron beam evaporated WO<inf>3</inf> thin films
2017, Journal of Taibah University for Science
Citation Excerpt :
The reported band gap for the films deposited at 250 °C is approximately the same as the value reported by Nakamura [30] with the same pattern of diminishing bandgap values. These values are also in agreement with the thinner films deposited using CVD by Davazoglou [31]. The structural, morphological and optical properties of the WO3 thin films deposited by electron beam evaporation were strongly dependent on the substrate temperature.
Tungsten trioxide (WO₃) is one of the best transparent metal oxides for advanced technological applications. WO₃ exhibits a wide variety of novel properties, particularly in thin film form. This investigation focuses on the morphological and optical properties of WO₃ thin films prepared by electron beam deposition in an oxygen partial pressure of 2 × 10⁻⁴ mbar and at various substrate temperatures. The deposited films at room temperature (RT) are amorphous, but the crystallinity is enhanced by increasing the substrate temperature with noticeable x-ray diffraction peaks at (320), (210) and (402). The peaks represent the predominantly orthorhombic phase, with a portion of the hexagonal phase being included, of the WO₃ films. The surface roughness and the grain size also increased as the substrate temperature increased. The optical transmittance and energy band gaps decreased with increasing substrate temperature. The band gap energy values were from 3.302 to 3.084 eV for the films deposited at substrate temperatures ranging from RT to 450 °C.
Study of the influence of substrate temperature on structural, optical, and electrical properties of Zn-doped MnIn<inf>2</inf>S<inf>4</inf> thin films prepared by chemical spray pyrolysis
2016, Physics Letters, Section A: General, Atomic and Solid State Physics
The Zn-doped MnIn₂S₄ thin films were deposited by chemical spray pyrolysis technique on a heated glass substrate using the aqueous solution of MnCl₂, InCl₃, (NH₂)₂CS and ZnCl₂. The thin films were grown at different substrate temperatures ranging from 250–400 °C. The synthesized films were characterized by X-ray diffraction (XRD), energy dispersive analysis spectrum (EDS), field emission scanning electron microscope (FESEM), UV–Vis absorption spectroscopy and four probe method. The XRD analysis indicates Zn-doped MnIn₂S₄ thin films were polycrystalline in nature with a cubic spinel structure having (101) plane as the preferred orientation. The structural parameters like crystalline size (D), dislocation density (δ), strain (ε) and lattice distortion (LD) have been evaluated from XRD results. The energy dispersive analysis spectrum (EDS) predicts the presence of Mn, In, S and Zn in the film grown at 250 °C. The formation of the needle and spherical shaped grains was clearly observed from FE-SEM analysis. From the optical studies, it is analyzed that about (88%) of light transmission occurs in the Vis–IR regions. It is interesting to note that the structural homogeneity and crystallinity of the films has improved due to the decrease in the absorption coefficient (α) and extinction coefficient (K) with an increase in substrate temperature. The calculated optical band gap energies increase (1.51–1.74 eV) with an increase of substrate temperatures. The photoluminescence (PL) spectrum reveals the presence of well-defined band edge (<400 nm) and defect emissions in the wavelength region around 400–650 nm. Moreover, from electrical studies, the electrical resistivity decreases with increase in substrate temperature and a minimum electrical resistivity of $1.20 \times 10^{3} Ω m$ was obtained for the film coated at 400 °C. The high absorption coefficient (α) in the order of $10^{4} {cm}^{- 1}$ and high transmittance (88%) of the films makes them an efficient absorber and a good window layer in photovoltaic applications.
Characterization of jet nebulizer sprayed CdO thin films for solar cell application
2016, Optik
Citation Excerpt :
Band gap energy values of the films deposited above and below 400 °C substrate temperature are nearly same. This change in optical band gap may be attributed to change in crystallinity of the films, since grain size changes with temperature [29]. Semiconductor films often show a band gap widening and the absorption edge moves towards the shorter wavelength side (blue shift) than that of the bulk semiconductor material.
The highly transparent conducting cadmium oxide (CdO) films were prepared by jet nebulizer spray pyrolysis. Characterization and optimization of CdO films have been scrutinized using various techniques such as X-ray diffraction (XRD) pattern, scanning electron microscope (SEM), energy dispersive analysis by X-ray (EDAX) spectroscopy, Atomic force microscopy (AFM), ultraviolet visible (UV-Vis) spectroscopy, hall Effect and current–voltage (I–V) characteristics. The sample prepared at 400 °C with 4 ml and 0.20 M of volume and concentration of the precursor solution respectively have the transmittance of about 70% with a band gap of 2.37 eV and the resistivity was found to be a minimum of 3.38 × 10⁻³ Ω cm. The XRD, SEM and AFM studies have implied the presence of CdO nanocrystallites with cubic structure and having smooth surface. The short circuit current (I_sc) = 5.90 mA/cm² and open circuit volatge (V_oc) = 429.3 mV values were established to be the maximum for the cell made with CdO films at 400 °C. The fill factor (FF) = 0.32 and conversion efficiency η = 0.8% was also maximum for this solar cell. The low fill factor and efficiency might be due to the formation of excess silicon dioxide (SiO₂) at the CdO/p-Si interface due to reaction between CdO and Si at 400 °C.

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Study on the optical and electrochromic properties of polycrystalline WO3 thin films prepared by CVD

Abstract

Displays

Thin Solid Films

Solid State Ionics

Solar Energy Mater.

Solar Energy Mater.

Solar Energy Mater.

Solar Energy Mater.

Thin Solid Films

Solar Energy Mater.

Solar Energy Mater.

Solid State Commun.

Solid State Commun.

Solar Energy Mater.

Solid State Ionics

Solar Energy Mater.

Thin Solid Films

Phil. Mag.

RCA Rev.

Study on the optical and electrochromic properties of polycrystalline WO₃ thin films prepared by CVD