Optical properties of post-annealed ZnO:Al thin films studied by spectroscopic ellipsometry

Hwang, Younghun; Kim, H.M.; Um, Youngho; Park, H.Y.

doi:10.1016/j.materresbull.2012.04.111

Cited by 11 publications

(7 citation statements)

References 27 publications

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“…This may be because of an increase in the carrier concentration, which subsequently reduces and enhances the optical absorption, in wavelength. 98,99 Each sample has two zones for refractive index: anomalous dispersion (low wavelength zone) and normal dispersion. In the low wavelength zone, refractive index increases when wavelength increases, whereas during normal dispersion, refractive index decreases with increasing wavelength.…”

Section: Refractive Indexmentioning

confidence: 99%

Structural and optical properties of Ti and Cu co‐doped ZnO thin films for photovoltaic applications of dye sensitized solar cells

et al. 2020

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Summary ZnO, 1% Ti doped ZnO and 1% Ti and (0.5%, 1%, and 1.5%) Cu co‐doped ZnO thin films are deposited on fluorine doped tin oxide glass substrates using sol‐gel technique. The impact of Ti and Cu co‐doping on optical, structural, and photovoltaic properties of ZnO thin films have been analyzed. X‐ray diffraction also confirms the hexagonal wurtzite crystal structure of the film. The 1% Ti and 1% Cu co‐doping percentage has an astonishing impact on the structural properties of the doped film, such as large grain size (19 nm), d‐spacing (2.48 Å), small dislocation line density (2.96 × 1015 m−2), lattice parameters (a = b = 3.2 Å, c = 5.2 Å), bond length (1.9 Å) and positional parameter (3.7 × 10−1) of the ZnO thin film. Optical parameters like reflectance, absorbance, transmittance, refractive index, and dielectric constants are calculated in the range of spectral from (250‐750) nm by using an ultraviolet ‐ visible spectrophotometer. In the visible region, all the films have approximately 85% transmittance, which is excellent for solar cells. The ZnO film prepared at the co‐doping percentage of 1% Ti and 1% Cu has high absorbance, high refractive index (2.09) and small band gap energy (3.37 eV) as compared to other doped films. The dye‐sensitized solar cells of these films as a Photoanode have been fabricated and studied the efficiency variation of films. It is found that the performance of the dye‐sensitized solar cell (DSSC) using a Ti‐Cu co‐doped film is much better than a pure ZnO film. The highest efficiency of DSSC 2.38% is achieved in the dye‐sensitized solar cell by using a 1% Ti and 1% Cu co‐doped ZnO thin film. When Ti is doped in ZnO then the surface area and pore size of the ZnO increased, which increase the dye loading ability. Cu reduces the recombination rate and enhances the electron injection efficiency rate from the dye to the conduction band of ZnO. Therefore, it is suggested that the thin films prepared by co‐doping of Cu and Ti into ZnO will upgrade the efficiency of cell.

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Section: Refractive Indexmentioning

confidence: 99%

Structural and optical properties of Ti and Cu co‐doped ZnO thin films for photovoltaic applications of dye sensitized solar cells

et al. 2020

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“…Near the band edge, the absorption coefficient shows an exponential dependence on photon energy. The optical bandgap energy was determined by applying the Tauc relation as given below [26, 27]:

α E = A {(E - E_{g})}^{n}

where α is the absorption coefficient, hv is the photon energy, A is a constant and n is 1/2, 2, 3/2 and 3 for allowed direct, allowed indirect, forbidden direct and forbidden indirect bandgap semiconductors, respectively. Due to the direct

E_{g}

for ZnO thin films, n = 1/2 is more suitable.…”

Section: Resultsmentioning

confidence: 99%

“…Due to the direct

E_{g}

for ZnO thin films, n = 1/2 is more suitable. An extrapolation of the linear region of a plot of ( αE ) 2 on the Y‐axis versus photon energy ( E ) on the X‐axis gives the value of the optical bandgap (

E_{g}

) [26, 27] (as shown in Fig. 5).…”

Section: Resultsmentioning

confidence: 99%

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Spectroscopic‐ellipsometry measurement of the optical properties of zinc oxide thin films prepared by sol–gel method: coating speed effect

Aghgonbad

Sedghi

2018

Micro & Nano Letters

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In this work, thin films of zinc oxide were prepared by sol-gel spin coating method with different coating speeds of 3600, 4800 and 6000 rpm. Spectroscopic ellipsometry analysis was used to extract the optical constants such as refractive index n, and extinction coefficient k, in the wavelength range of 300-800 nm. The knowledge of both n and k allows the calculation of the important properties such as real and imaginary parts of the dielectric function, the absorption coefficient and the optical bandgap energy. Ellipsometric measurements were collected at an incidence angle of 70°. Also, a computer programming of Kramers-Kronig (KK) relations was used to calculate the optical properties. The ellipsometric results were compared with the parameters obtained by the KK method. It was found that the coating speed in sol-gel method, noticeably affect optical properties of the films. The films were found to exhibit high transmittance and low absorbance in the visible region. The direct optical bandgap of the films was obtained in the range of 3.4-3.7 eV using the ellipsometric method. A decrease in the void fraction of layers with an increment in the coating speed had been seen.

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“…The interference fringes of the transmittance curves revealed that the films surface is smooth and highly reflecting, there is no match scattering or absorption loss in the films. It has observed that the absorption edges of doped ZnO are slightly shifted to the shorter wavelength (blue shift); this is mainly attributed to the Burstein-Moss effect [9]. The variation of (αhν)² as a function of the photon energy hν of the pure and Sn doped ZnO are sketched in Fig.3 the optical band gap for as-grown films is obtained by the intercept of the straight line on the horizontal axis.…”

Section: Fig 2: Transmittance Spectra Of Sn-zno Thin Filmsmentioning

confidence: 98%

Spectroscopic ellipsometry, optical, structural and electrical investigation of sprayed pure and Sn-doped ZnO thin films

Mokhtari

Benhaliliba

Aida

et al. 2013

EPJ Web of Conferences

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in this work, we report the transparent pure and Sn-doped zinc oxide (ZnO). The films were deposited onto microscope glass substrate which was heated at 350±5C° by ultrasonic spray pyrolysis (U S P) deposition technique. The concentrations of Sn were selected within the range of 0-3% by step of 0.5% and the time deposition is kept at 5 min. A (002)-oriented wurtzite crystal structure was confirmed by X-rays patterns; and grain size varied within the range 7.37-14.84nm, and cristanillity is calculated goes from14.4 to 45.9%. Based on UV-VIS-IR analysis, the results revealed the high transparency of the sprayed films which exceeds 90%. The band gap energy was of 3.26-3.30 eV. The film thickness was estimated by spectroscopy ellipsometry and the found values were of 165-270nm. The refractive index is in the range of 2.75.The obtained electrical parameters were around 10 18 cm -3 , 3.6 cm²/Vs, 1.6Ω.cm; 5.8cm 3 /C. finally the Sn-doping has influenced the physical parameters of asground ZnO films

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Optical properties of post-annealed ZnO:Al thin films studied by spectroscopic ellipsometry

Cited by 11 publications

References 27 publications

Structural and optical properties of Ti and Cu co‐doped ZnO thin films for photovoltaic applications of dye sensitized solar cells

Structural and optical properties of Ti and Cu co‐doped ZnO thin films for photovoltaic applications of dye sensitized solar cells

Spectroscopic‐ellipsometry measurement of the optical properties of zinc oxide thin films prepared by sol–gel method: coating speed effect

Spectroscopic ellipsometry, optical, structural and electrical investigation of sprayed pure and Sn-doped ZnO thin films

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