Band Gap Values Of Samples Research Articles

Bi-doped SnO2 transparent conducting thin films deposited by spray pyrolysis: structural, electrical, optical, and photo-thermoelectric properties

In this research, light and heavy Bi-doped SnO2 thin films were prepared on glass substrates by spray pyrolysis technique. The effect of heavy doped-Bi on the structural, morphological, electrical, photo-thermo-electrical, optical properties of SnO2 thin films has been investigated. The Bi/Sn atomic ratios (x = [Bi/Sn]) were varied from 0 to 0.30 in the spray solution. X-ray diffraction analysis showed the formation of SnO2 tetragonal rutile structure in low doped deposited thin films and amorphous structure for heavy Bi-doped SnO2. Also, the SnO2–Bi2O3 binary thin films were formed for x = [Bi/Sn] = 0.05. Scanning electron microscopy images indicated that the nanostructure of the condensed thin films has a rectangular-particle growth toward particle-spherical growth. The Hall effect measurements have shown n-type conductivity in all deposited thin films. The lowest sheet resistance of 39.3 MΩ/□ and highest carrier concentration of n = 4.53 × 1018 cm−3 was obtained for the thin film deposited with x = 0.10. The maximum of the Seebeck coefficient (S) = 325 μVK−1 and figure of merit (ZT) = 1.85 was obtained for the thin film deposited with x = 0.20. The average transmittance of thin films varied over the range of T = 72–84%. The bandgap values of samples were obtained in the range of Eg = 3.52–3.88 eV for the direct band gap. From the photoconductivity studies, the sample prepared with x = 0.20 exhibited the highest photoconductivity among the SnO2: Bi thin films.

Albumin assisted sol-gel synthesized SrSnO3: Pr3+ red persistent phosphors for temperature sensing

SrSnO3: Pr3+ phosphors with red long afterglow (LAG)and temperature sensing were prepared by albumin assisted sol-gel method. The typical sample had cubic structure. The mean particle size was about 2.02 μm. The band gap values of samples were in the range of about 4.06–4.09 eV. The luminescent properties and LAG behaviors of SrSnO3: Pr3+ phosphors were investigated and the luminescence mechanism of red LAG was discussed. Albumin assisted SrSnO3: Pr3+ phosphor with a red long afterglow had an average decay time of 74.25 s. Pr3+ ions not only act as an activator, emitting red long afterglow, but also act as a trap provider. Moreover, the temperature sensing property was studied based on the non-thermal coupling FIR of TE and 3P0→3H4 transition emission. The relative sensitivity was as high as 3580.89/T2. The absolute sensitivity (Sa) and relative sensitivity (Sr) of SrSnO3: 0.5%Pr3+ were 0.0374 K-1 and 4.03% K−1, respectively. Its optical thermometry performance is better than that of most phosphors. It has the potential to be applied in the field of temperature sensing.

Hydrothermal synthesis and characterization of CuO–CoO/TiO2 for photocatalytic degradation of methylene blue under visible light and catalytic reduction of P-nitrophenol

CuO–CoO/TiO2 has been prepared using TiO2-P-25, Cu(acac)2/Co(acac)3 (sample 1) and Cu(NO3)2/Co (NO3)2 (sample 2) by hydrothermal method. DRS, CV, EDX, XRD, XPS, Raman, FE-SEM, and TEM have been used for structural, optical, and morphological analyses of the samples. The anatase phase formation of the samples has been identified by powder X-ray diffraction and Raman spectroscopy. Cu and Co metals were present as CuO and CoO in both samples, according to XPS and Raman spectroscopy data. UV–Vis–NIR reflectance and cyclic voltammetry analysis were used to determine the absorption nature of the samples. Through these techniques, the band gap values of samples 1 and 2 were determined as 2.0 and 2.5 eV, respectively. Nanotube/nanosheet and nanoparticle morphologies were shown by samples 1 and 2, respectively, based on transmission electron microscopy (TEM) results. The synthesized nanomaterials were applied in the degradation of methylene blue (MB) under visible light. The photocatalytic activity of the samples was studied in the presence and absence of H2O2. Degradation time was 4–40 min in the presence of 2 mg of the catalyst. In addition, the samples were used as catalysts in the reduction of P-nitrophenol (PNP) by NaBH4. UV–Vis spectroscopy was used to monitor the progress of the catalytic and photocatalytic degradation reactions. Furthermore, the catalyst samples were removed and recycled several times. The photocatalytic degradation reaction was carried out in the presence of various free radical scavengers and hydroxyl radical and hole were determined as the main active species for samples 1 and 2, respectively.

Synthesis and characterization of Cu2FeSnS4 thin films prepared by electrochemical deposition

Quaternary compound Cu2FeSnS4 (CFTS) thin films, a potential absorber layer candidate in thin film solar cells, were successfully synthesized for the first time by electrochemical deposition method with a post-sulfurization treatment at 500°C and 550°C. The samples were analyzed by X-ray diffraction (XRD), Raman spectroscopy (Raman), X-ray photoelectron spectroscopy (XPS) and ultraviolet–visible-near-infrared spectrophotometer (UV–vis-NIR spectrophotometer). XRD data and Raman spectra revealed that the CFTS thin films possess a stannite structure and the crystallinity of the samples was improved with the increasing sulfurization temperature. X-ray photoemission spectroscopy analysis of the four constituent elements indicated Cu(I), Fe(II), Sn(IV) and sulfide ions. The direct band gap values of samples with post-sulfurization treatment at 500°C and 550°C were evaluated to be 1.35eV and 1.40eV by UV–vis-NIR absorption spectra respectively, which show that CFTS is promising for photovoltaic applications.

Effect of very low to high Sb-doping on the structural, electrical, photo-conductive and thermoelectric properties of fluorine-doped SnO2 (FTO) thin films prepared by spray pyrolysis technique

Transparent conducting fluorine and Sb-doped [SnO2: (F, Sb)] thin films have been deposited onto preheated glass substrates using the spray pyrolysis technique by the various dopant quantity of spray solution. The effect of antimony impurities on the structural, morphological, electrical, Thermo-electrical, optical and photoconductive properties of films has been investigated. The [F/Sn] atomic concentration ratio (x) in the spray solution is kept at value of 0.7 and the [Sb/Sn] atomic ratio (y) varied at values of 0, 0.0005, 0.001, 0.002, 0.01, 0.03, 0.05, 0.07 and 0.10. It is found that the films are polycrystalline in nature with a tetragonal crystal structure corresponding to SnO2 phase having orientation along the (110) and (200) planes. SEM images indicated that nanostructure of the films has a particle type growth. The average grain size increases with increasing spraying quantity of Sb-dopant. The compositional analysis of SnO2: (F, Sb) thin films were studied using EDAX. SEM and AFM study reveals the surface of SnO2: (F, Sb) to be made of nanocrystalline particles. The Hall Effect measurements have shown n-type conductivity in all deposited films. The lowest sheet resistance and highest the carrier concentration about 7.7 Ω/□ and 6.6 × 1022, respectively, were obtained for the film deposited with y = [Sb/Sn] = 0.001 and x = [F/Sn] = 0.7. The maximum of the Seebeck coefficient equal to 12.8 μV K−1 was obtained at 400 K for the film deposited with y = [Sb/Sn] = 0.10. The average transmittance of films varied over the range 10–80 % with change of Sb-concentration. The band gap values of samples were obtained in the range of 3.19–3.8 eV. From the photoconductive studies, the Sb-doped films exhibited sensitivity to incident light especially in y = 0.001. The electrical resistivity and carrier concentration vary in range 5.44 × 10−4 to 1.02 × 10−2Ω cm and 2.6 × 1022–6.6 × 1022 cm−3, respectively.

Tin doped β-In2S3 thin films prepared by spray pyrolysis: Correlation between structural, electrical, optical, thermoelectric and photoconductive properties

In this research, Sn-doped In2S3 thin films were prepared on glass substrates by spray pyrolysis technique. The effect of tin impurity on the structural, morphological, electrical, thermo-electrical, optical and photoconductive properties of films has been investigated. The tin to indium atomic ratios (x=[Sn]/[In]) were varied from 0 to 0.15 in the spray solution. X-ray diffraction analysis showed the formation of cubic β-In2S3 phase in all deposited films. Scanning electron microscopy images indicated that nanostructure of the condensed films has a particle-cluster to rock-plate growth type. The Hall effect measurements have shown n-type conductivity in all deposited films. The lowest resistance of 1.3MΩ/□ and the highest the carrier concentration of 3.93×1018cm−3 were obtained for the film deposited with x=0.08. The maximum of the Seebeck coefficient equal to 132μVK−1 was obtained at 400K for the film deposited with x=0.15. The average transmittance of films varied over the range of 40–60%. The band gap values of samples were obtained in the range of 2.89–3.75eV for direct and 2.61–3.37eV for indirect allowed transitions. From the photoconductivity studies, the sample prepared with x=0.05 exhibited the highest photoconductivity among the In2S3:Sn films.

The structural, thermoelectric and photoconductive properties of sulfur doped In2O3 thin films prepared by spray pyrolysis

In this study In2O3 and In2O3:S thin films were prepared on glass substrates using the spray pyrolysis technique. The effect of sulfur impurities on the structural, morphological, electrical, thermo-electrical, optical and photoconductive properties of films has been investigated. The sulfur to indium atomic ratios (x = [S]/[In]) were varied from 0 to 15 in the spray solution. From the x-ray diffraction analysis, a phase transition occurred from the cubic In2O3 to the cubic β-In2S3 phase with increasing S-doping level. SEM images indicated that the nanostructure of the films has a particle-cluster type growth. The Hall effect measurements have shown n-type conductivity in all of the deposited films. The lowest resistance of 19 kΩ sq−1 and the highest carrier concentration of 1.32 × 1019 cm−3 were obtained for the film deposited with an [S]/[In] atomic ratio of 0.6. The maximum of the Seebeck coefficient equal to 141 μV K−1 was obtained at 400 K for the film deposited with an [S]/[In] atomic ratio of 1. The average transmittance of films varied over the range 40–80% with S-concentration. The band gap values of samples were obtained in the range of 3.85–3.96 eV. From the photoconductivity studies, the sample prepared with the [S]/[In] atomic ratio of 0.2 exhibited the highest photoconductivity among the In2O3:S films.