Single-source Thermal Evaporation Method Research Articles

Inorganic and lead-free CsBi3I10 thin-film solar cell prepared by single-source thermal evaporation

All inorganic lead-free halide perovskites have attracted much attention due to their non-toxic and suitable bandgap. In this paper, we first prepared all inorganic lead-free perovskite CsBi3I10 thin-films by single-source thermal evaporation deposition. The results show that CsBi3I10 thin films prepared by single-source thermal evaporation have layered structure, high purity hexagonal phase and high crystallinity, which are consistent with the theoretical calculation results. The surface of the thin film was compact and uniform, and had high homology with the crystal structure of the evaporation source material. After annealing, the crystallinity of the film was further improved. The photovoltaic conversion efficiency of perovskite solar cells based on the CsBi3I10 thin film is as high as 0.84%. These results indicate that the proposed single-source thermal evaporation method has the potential to prepare high efficiency inorganic lead-free perovskite solar cells.

The influence of Ag doping and annealing on phase, structural and carrier transport characteristics of CIS thin films

Abstracts The un-doped and Ag-CIS thin films were deposited on quartz glass substrates by single source thermal evaporation method. Then, some CIS films were annealed in vacuum or N2 atmosphere from 350 °C to 550 °C. The results of XRD patterns showed the phase compositions of CIS thin films were changed with the increase of annealing temperature. Meanwhile, the results of Raman measurement confirmed a dramatic transition from CA phase to CH phase. Furthermore, the Ag atoms could promote the recrystallization process and the transition from CA phase to CH phase, which might result in the improvement of optical-electrical properties of CIS film. The transient photocurrent of the CIS-3 sample annealed at 450 °C was higher than those of other samples, which might be related to the good crystal quality. The results of I-V curves confirmed the N-type conduction of CIS-3 films, which was consistent with the results of EDS measurement. The C-V results of CIS-2 films also were the same as the results of EDS measurement. Furthermore, for the CIS-2 samples, with increase of annealing temperature, the change of conduction type may be related to the S element volatilization under vacuum situation and the decomposition of the substitutional defects AgIn.

Effects of sulfurization temperature on Cu2ZnSnS4 thin film deposited by single source thermal evaporation method

In this study, the effects of sulfurization temperature on the properties of thermally evaporated Cu2ZnSnS4 (CZTS) thin films were investigated. Molybdenum (Mo) coated soda lime glass (SLG) was used as substrates and stoichiometric CZTS powder (99.95%) was used as the source material. XRD patterns showed that CZTS were formed with preferential orientations of (112) > (220) > (312) for all the investigated films. The intensity of (112) peak is found increasing until a certain temperature indicating that the highest degree of crystallinity is achieved together with secondary phases such as ZnS and SnS. It was confirmed by raman shift at 338 cm−1 from Raman spectroscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM) results showed a trend for surface roughness as well as morphology. From Hall effect measurement, all deposited films exhibited p-type conductivity. From UV–vis spectroscopy measurement, the optical band gap of all the films are found in the range of potential absorbers for CZTS based thin film solar cells.

Effect of intentional Na-incorporation on the structural, optical and electrical properties of CuInS2:Na thin films for solar energy conversion

Na-doped CuInS2 material is obtained by the incorporation of the sodium of an atomic percentage in amounts of 0, 0.1, 0.5, 1, 2 and 3% with a stoechiometric mixture of the elements copper, indium and sulfur taken in the stoechiometric proportions. We have investigated in this work the effect of intentional Na-incorporation on the structural, optical and electrical properties of CuInS2:Na-doped thin films grown by the single source thermal evaporation method. In the resulting Bridgman-grown ingots brittleness were increased with increased Na and measured hot point probe changed sign from p- to n-type in stoechiometric ingots above 0.5at.%. The samples having a low Na atomic percentage exhibit better crystallinity that shows the effect of the sodium for the larger percentage to degrade the crystallinity of layers (atomic percentage greater than 2at.%). The film conductivity was strongly affected by Na-doping, which increased from 10−6 to 10−3S/cm by increasing [Na]/[CuInS2] ratio from 0.1 to 3at.%. Indeed for an atomic percentage Na of 1% we obtained the biggest thickness (1μm) corresponds to the lowest refractive index value (2.08).

Growth, structural and optical properties of copper indium diselenide thin films deposited by thermal evaporation method

Copper indium diselenide (CuInSe 2) compound was synthesized by reacting its constituent’s elements copper, indium and selenium in near stoichiometric proportions (i.e. 1:1:2 with 5% excess selenium) in an evacuated quartz ampoule. Synthesized pulverized compound material was used as an evaporant material to deposit thin films of CuInSe 2 onto organically cleaned sodalime glass substrates, held at different temperatures (300–573 K), by means of single source thermal evaporation method. The phase structure and the composition of chemical constituents present in the synthesized compound and thin films have been investigated using X-ray diffraction and energy dispersive X-ray analysis, respectively. The investigations show that CuInSe 2 thin films grown above 423 K are single phase, having preferred orientation of grains along the (112) direction, and having near stoichiometric composition of elements. The surface morphology of CuInSe 2 films, deposited at different substrate temperatures, has been studied using the atomic force microscopy to estimate its surface roughness. An analysis of the transmission spectra of CuInSe 2 films, recorded in the wavelength range of 500–1500 nm, revealed that the optical absorption coefficient and the energy band gap for CuInSe 2 films, deposited at different substrate temperatures, are ∼10 4 cm −1 and 1.01–1.06 eV, respectively. The transmission spectrum was analyzed using iterative method to calculate the refractive index and the extinction coefficient of CuInSe 2 thin film deposited at 523 K. The Hall effect measurements and the temperature dependence of the electrical conductivity of CuInSe 2 thin films, deposited at different substrate temperatures, revealed that the films had electrical resistivity in the range of 0.15–20 ohm cm, and the activation energy 82–42 meV, both being influenced by the substrate temperature.

Growth and vacuum post-annealing effect on the properties of the new absorber CuSbS 2 thin films

Post-growth treatments in vacuum atmosphere were performed on CuSbS 2 films prepared by the single-source thermal evaporation method on glass substrates. The films were annealed in vacuum atmosphere for 2 h in temperature range 130–200 °C. The effect of this thermal treatment on the structural, optical and electrical properties of the films was studied. X-ray diffraction (XRD) patterns indicated that the films exhibited an amorphous structure for annealing temperature below 200 °C and a polycrystalline structure with CuSbS 2 principal phase. For the films annealed at temperatures below 200 °C one direct optical transition in range 1.8–2 eV was found. For the films annealed at 200 °C, two optical direct transitions emerged at 1.3 and 1.79 eV corresponding to the CuSbS 2 and Sb 2S 3 values respectively. The electrical measurements showed a conversion from low resistivities (3.10 − 2 –9.10 − 2 ) Ω cm for the samples annealed at temperatures below 200 °C to relatively high resistivities (2 Ω cm) for the samples annealed at 200 °C. In all cases the samples exhibited p-Ztype conductivity.

Structural, morphological and optical properties of thermal annealed TiO thin films

Structural, morphological and optical properties of TiO thin films grown by single source thermal evaporation method were studied. The films were annealed from 300 to 520 °C in air after evaporation. Qualitative film analysis was performed with X-ray diffraction, atomic force microscopy and optical transmittance and reflectance spectra. A correlation was established between the optical properties, surface roughness and growth morphology of the evaporated TiO thin films. The X-ray diffraction spectra indicated the presence of the TiO2 phase for the annealing temperature above 400 °C.

Role of oxygen in enhancing N-type conductivity of CuInS 2 thin films

Post-growth treatments in air atmosphere were performed on CuInS 2 films prepared by the single-source thermal evaporation method. Their effect on the structural, optical and electrical properties of the films was studied by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), optical reflection and transmission and resistance measurements. The films were annealed from 100 to 350 °C in air. The stability of the observed N-type conductivity after annealing depends strongly on the annealing temperature. Indeed it is shown that for annealing temperatures above 200 °C the N-type conductivity is stable. The resistance of the N-CuInS 2 thin films correlates well with the corresponding annealing temperature. The samples after annealing have direct bandgap energies of 1.45–1.50 eV.

Structural, electrical and optical properties of Bi‐doped CuInS 2 thin films grown by vacuum evaporation method

Structural, electrical and optical properties of Bi-doped CuInS2 thin films prepared by a single-source thermal evaporation method were investigated. The as-deposited films were annealed in the temperature range between 100 and 500 °C for 10 min in air. The film of chalcopyrite CuInS2 single phase was obtained by annealing at 200 °C successfully. It was found that Bi atoms enhanced the growth of CuInS2 single phase at lower temperature. Furthermore, the crystalline quality of doped films was higher compared with the non-doped ones. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Structural, electrical and optical properties of AgInS 2 thin films grown by thermal evaporation method

Structural electrical and optical properties of AgInS 2 (AIS) thin films grown by the single-source thermal evaporation method were studied. The X-ray diffraction spectra indicated that the AIS single phase was successful grown by annealing above 400 °C in air. The AIS grain sizes became large with increasing the annealing temperatures. All polycrystalline AIS thin films were sulfur-poor from the electron probe microanalysis and indicated n-type conduction by the Van der Pauw technique. It was deduced that the sulfur vacancies were dominant in the films and enhanced n-type conduction.

Optical constants of Na-doped CuInS2 thin films

Optical properties of sodium-doped CuInS2 thin films grown by the single-source thermal evaporation method have been studied. The optical constants of the deposited films were obtained from the analysis of the experimental recorded transmission and reflectance spectral data over the wavelength range 300–1800 nm. It is observed that there is decrease in optical band gap with increase in sodium concentration. It has been found that the refractive index and extinction coefficient are dependent on the sodium concentration. The complex dielectric constants of CuInS2:Na films have been calculated in the investigated wavelength range. It was found that the refractive index dispersion data obeyed the single oscillator of the Wemple–Di Domenico model, from which the dispersion parameters and the high-frequency dielectric constant were determined. The electric free carrier susceptibility and the carrier concentration on the effective mass ratio were estimated according to the model of Spitzer and Fan.

Structural and electrical characterization of AgInS2 thin films grown by single-source thermal evaporation method

Structural and electrical properties of AgInS2 (AIS) thin films grown by single-source thermal evaporation method were studied. The X-ray diffraction spectra indicated that the AIS single phase was successfully grown by annealing above 400∘C in air. The grain size of the AIS crystals was above 2.5 μm from the surface photograph. Furthermore, the AIS grain sizes became large with increasing the annealing temperatures. All the samples indicated n-type conduction by the Van der Pauw technique. The carrier concentrations and the resistivities of the AIS films at room temperature were in the range of 1019–1022 cm−3 and 10−1–10−3 Ωcm, respectively. Therefore the mobilities increased from 0.6 to 6.0 cm2/Vs with increasing the grain sizes.

Structural and optical characterization of Sb-doped CuInS 2 thin films grown by vacuum evaporation method

Structural, electrical and optical properties of Sb-doped CuInS 2 thin films grown by single source thermal evaporation method were studied. The films were annealed from 100 to 500 °C in air after the evaporation. The X-ray diffraction spectra indicated that polycrystalline CuInS 2 films were successfully obtained by annealing above 200 °C. This temperature was lower than that of non-doped CuInS 2 films. Furthermore, We found that the Sb-doped CuInS 2 thin films became close to stoichiometry in comparison with non-doped CuInS 2 thin films. The Sb-doped samples annealed above 200 °C has bandgap energy of 1.43–1.50 eV.

Structural and optical characterization of CuInS2 thin films grown by vacuum evaporation method

Structural and optical properties of CuInS2 thin films grown by the single-source thermal evaporation method have been studied. The films were annealed from 100 to 500 °C after an evaporation in air. The surface morphology was investigated by scanning electron microscopy. The maximum grain size of the samples after annealing at 400 °C was over 500 nm. The EPM analysis concluded that the polycrystalline CuInS2 thin films after annealing below 100 °C were Cu-rich, and those annealed above 200 °C were In-rich. The bandgap energy of the CuInS2 films after annealing above 300 °C was about 1.48 eV.