Co-doped ZnO Transparent Conductive Films Research Articles

Fabrication of Fluorine, Chlorine, and Gallium Co-Doped ZnO Transparent Conductive Films by Sol–Gel Spin Coating

Fabrication of Fluorine, Chlorine, and Gallium Co-Doped ZnO Transparent Conductive Films by Sol–Gel Spin Coating

Insight of the doping mechanism of F and Al co-doped ZnO transparent conductive films

Transparent conductive oxide (TCO) films, as transparent electrodes, are widely used in thin-film solar cells. The performance of TCO film has a significant influence on the conversion efficiency of the film solar cell fabricated byusing it. Although the conductivity can be improved by increasing the carrier concentration, the transmittance in the long wave will be sacrificed. Therefore, the only feasible method is to increase the carrier mobility within a certain carrier concentration range, rather than increase the mobility by reducing carrier concentration. In this paper, the F and Al co-doped ZnO (FAZO) films are deposited on glass substrates (Corning XG) by an RF magnetron sputtering technique with using a small amount of ZnF<sub>2</sub> (1 wt.%) and Al<sub>2</sub>O<sub>3</sub> (1 wt.%) dopant. The influences of sputtering pressure on the structure, morphology and photoelectric characteristics of the films are respectively investigated by X-ray diffraction analysis, scanning electron microscope, Hall effect measurement, and ultraviolet–visible–near infrared spectrophotometry. All the thin films show typical wurtzite structure with the <i>c</i> axis preferentially oriented perpendicular to the substrate. With the increase of sputtering pressure, the deposition rate of FAZO film decreases, the crystallization quality is deteriorated, surface topography changes gradually from “crater-like” to co-existent “crater-like” and “granular-like”, and the surface roughness increases. The FAZO film deposited at 0.5 Pa presents the optimal performance with a mobility of 40.03 cm<sup>2</sup>/V·s, carrier concentration of 3.92 × 10<sup>20</sup> cm<sup>–3</sup>, resistivity of 3.98 × 10<sup>–4</sup> Ω·cm, and about 90% average transmittance in a range of 380－1200 nm. The theoretical result shows that the co-doping of F and Al takes the advantages of single F and Al doped ZnO films, and overcomes the shortcoming of metal elements doping, which donates the carriers just from doped metal elements. Furthermore, the co-doping of F and Al not only increases the carriers but also reduces the scatterings caused by the inter-orbital interaction of doped atoms. The doped F 2p electron orbitals repel the O 2p and Zn 4s electron orbitals, making them move down and donate electrons. At the same time, the orbitals of Al 3s and Al 3p also make a contribution to the conductivity. After co-doping of F and Al, both the carrier concentration and conductivity increase significantly.

Preparation and characterization of Mg, Al and Ga co-doped ZnO transparent conductive films deposited by magnetron sputtering

Mg, Al and Ga co-doped ZnO (AGMZO) thin films were deposited on flexible substrates by rf magnetron sputtering using ceramic targets at room temperature. The effect of Mg content on structural, morphological, electrical and optical properties of the films was investigated in detail. X-ray photoelectron spectroscopy measurements indicated that the Mg content in the films was substantially consistent with that of corresponding targets. X-ray diffraction (XRD) results revealed that the films had the hexagonal wurtzite structure. The (0 0 2) preferred orientation of the crystallites detected by XRD suggested that the grains grew perpendicular to the surface of the film, which was confirmed by the cross-section image. The average transmittance in the visible range was above 82% for all the films. The lowest resistivity of 2.8 × 10−3 Ω cm with carrier concentration of 1.54 × 1020 cm−3 and Hall mobility of 14.6 cm2/Vs can be obtained. The optical transmission spectra revealed that when the Mg concentration increased, the UV absorption edge moved toward the shorter wavelength direction and the optical band gap increased from 3.4 to 3.5 eV.

Fabrication of high-performance F and Al co-doped ZnO transparent conductive films for use in perovskite solar cells

Fluorine and aluminum co-doped ZnO (FAZO) films were deposited on glass substrates by RF magnetron sputtering. The effects of the substrate temperature (Tsub) on the structural, morphological, electrical, and optical properties of the films were investigated by X-ray diffraction analysis, atomic force microscopy, photoluminescence spectroscopy, Hall effect measurement, and ultraviolet–visible–near infrared spectrophotometry. All the thin films showed typical wurtzite structure with the c axis preferentially oriented perpendicular to the substrate. With increasing Tsub, the grain size shows a parabolic-like enhancement; the film surface became relatively smooth and dense, and the crystallinity was also improved. At Tsub = 320 °C, the films showed the best electrical properties, with a resistivity of 3.53 × 10−4 Ω cm, Hall mobility of 39.33 cm2/V s, and carrier concentration of 4.50 × 1020 cm−3. An optical transmittance of more than 80% in a wide wavelength range from 400 to 1200 nm was also achieved. Perovskite solar cells employing the FAZO film had a higher power conversion efficiency than reference cells using F-doped SnO2 and Sn-doped In2O3, demonstrating its suitability for application in high-efficiency solar cells.

Structural, optical and electrical characterization of Ga-Mg co-doped ZnO transparent conductive films

The transparent conducting Ga-Mg co-doped ZnO films were prepared on glass substrates by radio-frequency (rf) magnetron sputtering. The effect of growth temperature on structural, morphological and optoelectronic properties of the films was investigated by XRD, XPS, SEM, UV-visible spectrophotometer and four-point probe. The results show that all the films are polycrystalline and (0 0 2) oriented. The growth temperature significantly affects the structure and optoelectronic properties of the films. The film deposited at the growth temperature of 270 °C has the largest grain size of 52.38 nm, the minimum tensile stress of 0.037GPa, the highest average visible transmittance of 89.39%, the lowest resistivity of 1.52 × 10−3 Ω⋅cm and the maximum figure of merit of 5.87 × 103 Ω-1⋅cm-1. Furthermore, the optical bandgaps were determined by extrapolation method and observed to be in the range of 3.36–3.59 eV.

Experimental and theoretical analysis of H and Ti co-doped ZnO transparent conductive films

Ti-doped ZnO (TZO) films were grown by radio frequency (RF) magnetron sputtering using a Ti-doped ZnO ceramic target in an Ar+H2 atmosphere at room temperature. Both the experimental and theoretical methods were employed to investigate the effect of H in TZO films. As the H2 flow rate increased, the surface morphology changed from pyramid-like features to a crater-like topography and the root-mean-square (RMS) roughness increased. The crystal quality was found to deteriorate at first but subsequently improved at an optimum doping ratio. A resistivity of 7.97×10−4Ωcm and an average transmittance of more than 83% in the 400–1100nm range were obtained with an optimal H2 flow rate of 1.2 sccm. Results of theoretical calculations show that the H dopant behaves as a shallow donor in the TZO films. The doping position of H is located in a BC ⊥ configuration at the center of the Zn-O bond, in which the O atom bonded to a substituted Ti atom parallel to the c axis. The charge carrier bands shifted from Ti 3d and O 2p orbitals in the TZO film to Ti 3d and H 1s orbitals in H and Ti co-doped ZnO films.

The Effect of Sputtering Power on the Properties of Zr-Ga Co-Doped ZnO Films by DC Magnetron Sputtering

Zr-Ga co-doped ZnO transparent conductive films were prepared on glass substrates by DC magnetron sputtering at room temperature. The influence of sputtering power on the structural, electrical and optical properties of Zr-Ga co-doped ZnO films was investgated by X-ray diffraction, scanning electron microscopy (SEM), digital four-point probe and optical transmission spectroscopy. The lowest resistivity of the Zr-Ga co-doped ZnO films is 3.02×10-4Ω﹒cm and the average transmittance of the films is over 90% in the visible range. The obtained optical band gap of these films is much larger than of pure ZnO (3.34 eV).

Co-Doped ZnO Transparent Conductive Films for LCD and UV Detectors

Zr,Ga co-doped ZnO transparent conductive films were deposited on glass substrates by DC magnetron sputtering at room temperature.The influence of sputtering pressure on the structural,electrical,and optical properties of Zr,Ga co-doped ZnO films was investigated by X-ray diffraction,scanning electron microscopy (SEM),digital four-point probe,and optical transmission spectroscopy.The lowest resistivity of the Zr,Ga co-doped ZnO film is 3.01×10-4Ω﹒cm.All the films present a high transmittance of above 91% in the visible range.These results make the possibility for liquid crystal display (LCD) and UV photoconductive detectors.

Co-Doped ZnO Transparent Conductive Films for LCD and UV Detectors

Zr,Ga co-doped ZnO transparent conductive films were deposited on glass substrates by DC magnetron sputtering at room temperature.The influence of sputtering pressure on the structural,electrical,and optical properties of Zr,Ga co-doped ZnO films was investigated by X-ray diffraction,scanning electron microscopy (SEM),digital four-point probe,and optical transmission spectroscopy.The lowest resistivity of the Zr,Ga co-doped ZnO film is 3.01×10-4Ω﹒cm.All the films present a high transmittance of above 91% in the visible range.These results make the possibility for liquid crystal display (LCD) and UV photoconductive detectors.