Effect Of Sulfurization Temperature Research Articles

Sulfurization temperature induced enhancement in thermoelectric properties of polycrystalline WS2 nanomaterials

We have presented an interesting study about the evolution of vibrational modes in WS2 nanostructures and their effect on material thermoelectric performance. High purity polycrystalline nanostructures of WS2 were prepared by sulfurizing the hydrothermally prepared WS2 powders at different temperatures. The effect of sulfurization temperature on the structure of WS2 nanomaterials was probed by XRD and Raman Spectroscopy. XRD data confirmed the crystal structure of WS2 along with the presence of WO3 based secondary phases. An experimental investigation of the phase changes with sulfurization temperature has been made by Raman scattering methods. Both in Plane (E12g) and out of plane (A1g) Raman modes exhibited red shift by 45 and 11 cm−1 respectively and variation in Raman peak intensity with sulfurization temperature was also observed. For all samples, the room temperature thermoelectric measurements reveal that an increase in sulfurization temperature from 300 to 823 k resulted in the enhancement of electrical conductivity and the Seebeck coefficient. The observed thermoelectric data was linked with the structural changes occurred during the increase of sulfurization temperature. Power factor of WS2 nanostructures increase up to 5.09x 10−3 Wm−1K−2 with increasing sulfurizing temperature.

Fabrication of SnS thin film by rapid thermal processing: effect of annealing temperature in sulfurization process

In this study, the effect of sulfurization temperature on properties of SnS thin films was investigated. The SnS thin films were fabricated by two-stage method includes deposition of SnS films by magnetron sputtering using a single SnS target, followed by annealing/sulfurization treatment in Rapid Thermal Processing (RTP) system at 225, 300 and 375 °C temperatures. Several characterization techniques such as XRD, Raman spectroscopy, EDX, optical transmission and Van der Pauw were used for analyses of the films. The EDX analyses showed that all the samples had almost stoichiometric (S/Sn~1) chemical composition. However, the amount of sulfur in the samples increased slightly as the sulfurization temperature increased. XRD pattern of the films exhibited constitution of orthorhombic SnS structure regardless of annealing temperature. The SnS2 secondary phase was observed in addition to orthorhombic SnS phase in the sample annealed at highest reaction temperature (375°C). Raman spectroscopy measurements of the films verified constitution of orthorhombic SnS structure. The band gap of the films exhibited distinction from 1.42 to 1.81 eV regarding to annealing temperature. The electrical characterization of the most promising SnS thin film sulfurized at 300°C had resistivity and charge carrier concentration values 1.07x104 Ω.cm and 1.70x1014 cm-3, respectively. Based on the all characterizations, it can be deduced that SnS thin film sulfurized at 300°C exhibited more outstanding structural and optical properties for potential solar cell applications.

Effect of sulfurization temperature on the efficiency of SnS solar cells fabricated by sulfurization of sputtered tin precursor layers using effusion cell evaporation

Earth-abundant tin monosulfide (SnS) thin films have attracted considerable interest for eco-friendly and low-cost thin film solar cells. However, less attention has been paid on the fabrication of SnS solar cell by the industrial processes. In view of that the current study aimed to fabricate the SnS solar cells via two-stage (sputtering + sulfurization) industrial process. For the preparation of SnS thin films, first tin metallic precursor layers were deposited by DC sputtering and then sulfurized using the rapid thermal effusion cell evaporation process. The effect of sulfurization temperature on the physical properties of SnS thin films and the efficiency of SnS solar cells was examined. Formation of the single phase SnS thin films was confirmed when the tin metallic precursor layers sulfurized in the range of 450–470 °C, whereas secondary phases of Sn, SnS2, and Sn2S3 were noticed at the sulfurization temperature lower than 450 °C and re-evaporation of deposited SnS thin films was observed at the sulfurization temperature higher than 470 °C. Solar cell fabricated with SnS absorber sulfurized at a temperature of 470 °C showed the conversion efficiency of ∼ 2.3%. The causes for lower efficiency of these solar cells were recombination in the SnS absorber and non-uniform compositional distribution of Cd, S and Sn as a function of depth in the CdS/SnS/Mo structure.

Effect of sulfurization temperature on optical and compositional properties of sputtered Zn(O, S) thin films

Zinc oxysulfide or Zn(O,S) is emerging as an alternate n-type buffer layer for kesterite, chalcogenides and CdTe based thin film solar cell due to it is being made from non-toxic elements and tunable bandgap, its suitable optical and electrical properties required for a buffer layer. Generally, buffer layers of these solar cells are deposited using chemical bath deposition (CBD) techniques, but these require breaking of vacuum and again inserting the sample in vacuum during solar cell fabrication, which is not economical and is cumbersome. Sputtering is considered to be industrial process and therefore, here we have deposited Zn(O,S) thin film by sputtering technique and effect of sulfurization temperature on bandgap and composition of Zn(O,S) films have been studied. The bandgap of deposited films changed from 3.36 eV to 3.15 eV by changing the sulfurization temperatures. By changing the sulfurization temperature, the composition of films also changed. Crystallite size (D) of Zn(O,S) films increased from 12.1 nm to 22.3 nm by varying the sulfur content for samples S1-S4, respectively. Optical, morphological, compositional and structural properties have been studied using UV-Vis-NIR spectroscopy, Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDS) and X-ray diffractometer (XRD), respectively.

Effect of sulfurization temperature on the phase purity of Cu2SnS3 thin films deposited via high vacuum sulfurization

In this study, the deposition of Cu2SnS3 (CTS) thin films was carried out at different sulfurization temperatures in the range of 350–550°C under high vacuum of 1 Pa using the sputtered Cu/Sn/Cu metal precursor layers in the sulfur vapor atmosphere. In order to reduce the Sn loss, a particular metal stack of Cu/Sn/Cu was used. Single phase monoclinic (M)-CTS thin film was obtained at 500 °C. The high intensity Raman modes at 292 cm−1 and 350 cm−1 further confirmed the formation of M-CTS. The M-CTS thin film sulfurized at 500 °C showed a composition of Cu/Sn = 1.89 and an optical band gap energy of 0.94 eV. Hall effect measurement of the film sulfurized at 500 °C with Cu/Sn ratio of 1.82 showed an electrical resistivity of 7.30 Ω-cm, carrier concentration of 6.29 × 1017 cm−3, and mobility of 1.36 cm2/Vs. Our results indicate that the copper-poor composition with a stacking order of Cu/Sn/Cu is favored in order to attain the single phase M-CTS.

Effect of sulfurization temperature on the properties of CuIn(S,Se)2 thin films fabricated from electrodeposited CuInSe2 precursors

This paper reports the analysis of S diffusion into electrodeposited CuInSe2 (CISe) precursors during post-sulfurization treatment at different sulfurization temperatures. The morphology, composition, structure and optical properties of CuIn(S,Se)2(CISSe) films were characterized by SEM, EDS, XRD, Raman scattering and UV-Vis-NIR spectrophotometer. It was found that high sulfurization temperatures can facilitate the incorporation of sulfur into the precursor film and improve the crystalline properties of the sulfurized films. The best sample is the one prepared by sulfurization at 500 °C.Itexhibitsrelatively homogeneous CuIn(SxSe1-x)2 phase structure. In addition, we observed a sulfur concentration difference between top part and bottom part of the sulfurized films. All these films exhibit high transmission and their optical band gapsincrease with the increase of annealing temperature.

Effect of sulfur annealing on the morphological, structural, optical and electrical properties of iron pyrite thin films formed from FeS2 nano-powder

Iron pyrite (FeS2) thin films were fabricated by spin coating the solution of FeS2 nanocrystals of ∼40 nm in size on glass substrates, followed by annealing in a sulfur environment at different temperatures. The effect of sulfurization temperature on the morphology, structural, optical and electrical properties was investigated. With increase of the sulfurization temperature, the grain size and crystallinity of the films was improved, although some cracks and voids were observed on the surface of thin films. The band gap of the FeS2 films was decreased at higher sulfurization temperature. The electrical properties were also changed, including the increasing in resistivity and the decrease in Hall mobility, with increase of sulfurization temperature. The change in the optical and electrical properties of the FeS2 thin films was explained based on the changes of phase, morphology, surface, and grain boundary property.

Thermal sulfurization effect on sprayed CZTS thin filmsproperties and CZTS/CdS solar cells performances

Cu2ZnSnS4 (CZTS) thin films were successfully deposited by a simple and inexpensive technique such as ultrasonic spray pyrolysis. The effect of sulfurization temperature on CZTS films properties and on Mo/CZTS/CdS/ZnO/ZnO:Al solar cell performances were studied. The investigated sulfurization temperatures were ranged from 450 °C to 550 °C. X-ray-diffraction pattern and Raman scattering spectroscopy confirmed the formation of monophase kesterite CZTS, the best crystallinity was obtained in the sample sulfurized at 450 °C. Atomic forces microscopy images indicated that annealing temperature increase yields to rough films with large grain size. UV–visible optical transmittance spectroscopy reveals that films enjoy a strong absorption with an absorption coefficient as high as 104 cm−3. Whereas, the optical band gap energy was found to decrease with sulfurization temperature. Hall effect measurements confirm the films p-type conductivity; the carriers concentration varies between 1014 and 1016 cm−3 when the sulfurization temperature changes from 450 °C to 550 °C. The I–V characteristics of the realized Mo/CZTS/CdS/ZnO/ZnO:Al cells indicated that all the devices show a rectification behavior with an ideality factor ranged from 1.6 to 1.8. The current transport is dominated by the interfacial recombination process. The photovoltaic effect was observed, the best performance was achieved in the device prepared with CZTS sulfurized film at 450 °C, the recorded characteristics are: 0.43% efficiency, 9.8 mA cm−2 short circuit current, 161 mV open circuit voltage and 28% fill factor. A comparison between the reported results obtained by different techniques reveals the superiority of the cells prepared with CZTS deposited by physical deposition technique such as thermal evaporation or sputtering.

Epitaxial growth of ReS2(001) thin film via deposited-Re sulfurization

In this paper, we present the formation of large-size rhenium disulfide (ReS2) films via the sulfurization of Re films deposited on sapphire substrates. The effects of sulfurization temperature and pressure on the crystal quality were investigated. A [001]-oriented single crystal of ReS2 films with 6 × 10 mm2 area was realized. By sulfurizing Re films at 1100 °C, ReS2 films with well-defined sharp interfaces to c-plane sapphire substrates could be formed. Below and above the sulfurization temperature of 1100 °C, incomplete sulfurization and film degradation were observed. The twofold symmetry of the monocrystalline in-plane structure composed of Re–Re bonds along with Re–S bonds pointed to a distorted 1T structure, indicating that this structure is the most stable atomic arrangement for ReS2. For a S/Re compositional ratio equal to or slightly lower than 2.0, characteristic Raman vibrational modes with the narrowest line widths were observed. The typical absorption peak of ReS2 can be detected at 1.5 eV.

Preparation of CuSbS2 thin films by a facile and low-cost chemical solution method

In this paper, CuSbS2 thin films were prepared by a facile and environmental-friendly chemical solution method at low temperature. The effect of sulfurization temperature was studied. The properties of CuSbS2 thin films were investigated by X-ray diffraction, scanning electron microscopy, UV–Vis and photocurrent response measurement. The results indicated CuSbS2 thin films sulfurized at 350 °C showed better crystallinity and no impurity phase. The as-prepared CuSbS2 film had a band gap of 1.5 eV and an obvious photoconductivity.

Effect of sulfurization temperature on the property of Cu2ZnSnS4 thin film by eco-friendly nanoparticle ink method

Cu2ZnSnS4 (CZTS) thin films were fabricated by a low-cost nanoparticle ink method. The eco-friendly hydrophilic CZTS nanoparticles were mixed with low-cost n-propanol to form nanoparticle ink. To improve crystallinity and remove oxygen element, the CZTS thin films were sulfurized further. The effects of sulfurization temperature on the structure, morphologies, and photovoltaic performances of CZTS thin films were investigated. The results showed that the crystallinity of CZTS thin film was improved with increasing sulfurization temperature. The surface morphology studies demonstrated the formation of compact and homogenous CZTS thin film at a sulfurization temperature of 600 °C. By optimizing thickness of CZTS thin film, the CZTS thin-film solar cell with an optimal efficiency of 2.1% was obtained.

Fabrication of Cu2ZnSnS4 thin films by simple solution method using citric acid as complexing agent

Cu2ZnSnS4 (CZTS) films were prepared by sulfurizing Cu–Zn–Sn precursor deposited via a simple solution method using environment-friendly citric acid as complexing agent. A single Cu2ZnSnS4 thin film was obtained at 500 °C under a mixed N2 + H2S (5%) atmosphere. The effects of sulfurization temperature on structural, morphological and optical properties were studied. The results showed that the CZTS thin film annealed at 500 °C exhibited large agglomeration of grains, ideal band gap (E g = 1.49 eV) and high optical absorption coefficient (>104 cm−1). The resulted carrier concentration and mobility were about 3.652 × 1018 cm−3 and 26.32 cm2/Vs, respectively.

Effects of sulfurization temperature on the structural and optical properties of Cu2CdSnS4 thin films prepared by direct liquid method

Cu2CdSnS4 (CCTS) appears to be a promising absorber material for thin film solar cells and have been deposited on glass substrate by a direct liquid coating method. Effects of sulfurization temperature on the composition, morphology, structural and optical properties of CCTS have been investigated systematically. X-ray diffraction and Raman measurements reveal that the increase of temperature would lead to an improved crystallinity of CCTS and the secondary phase of Cu2S confirmed by Raman spectrum can be suppressed by increasing annealing temperature. The grain size of CCTS thin films is demonstrated to be improved as the annealing temperature increases with slight S-poor and Sn-poor condition. All the thin films have estimated band gap in the range of 1.31–1.14eV, which decreases almost linearly with the increasing temperature and can be well suited for use in photovoltaics and thermoelectricity.

Ultra-high sulfurization temperature drives the growth of oxide-derived Cu2ZnSnS4 thin film with very large grain

Small grain size is one of the main obstacles for preparing high efficiency Cu2ZnSnS4 (CZTS) photovoltaic devices. The high thermal energy (high annealing temperature) is used to facilitate the driving force of grain growth. In this paper, the CZTS thin films were synthesized by means of sulfurizing oxide-precursors at relatively high sulfurization temperatures (550–700 °C). The effect of sulfurization temperature on properties of CZTS thin films was investigated through XRD, Raman, SEM, and energy dispersive x-ray spectroscopy. Both the crystallinity of the CZTS films and the size of their grains were greatly enhanced, which is attributed to the acceleration of atomic inter-diffusion during the growing process of thin films under ultra-high temperature.

Preparation and Characterization of Cu2SnS3 Thin Films by Two Stage Process for Solar Cell Application

Cu2SnS3 (CTS) thin films have been grown by a two stage process using sulfurization of co-sputtered Cu-Sn metallic precursors. The effect of sulfurization temperature (TS), varied in the range 250 - 450°C, on the properties of CTS films is investigated. The physical characteristics of CTS films are analyzed by their structural, morphological, elemental composition and optical properties. All the as-grown films are polycrystalline in nature with (112) peak as the preferred orientation, which indicates the tetragonal structure. The evaluated crystallite size is varied in the range, 72 - 113 nm with the change of TS. The optical band gap of CTS thin films is calculated from absorbance data and the values are found to be varied in the range of 1.19 - 1.61 eV. These results are presented and discussed in detail.

Cu2ZnSnS4 solar cells prepared by sulfurization of sputtered ZnS/Sn/CuS precursors

Cu2ZnSnS4 (CZTS) thin films were grown on Mo-coated Soda-lime-glass (SLG) substrates by sulfurization of sputtered ZnS/Sn/CuS precursors at different temperatures i.e. 560°C, 580°C and 600°C. The effects of sulfurization temperature on the quality of CZTS thin films and solar cells were investigated. The crystal structure, surface morphology, chemical composition, phase purity and surface roughness of CZTS thin films fabricated at different sulfurization temperatures were characterized by X Ray Diffraction (XRD), scanning electron microscopy (SEM) equipped with an energy dispersive spectrometer (EDS), Raman spectroscopy and atomic force microscope (AFM), respectively. The results show that all CZTS thin films exhibit a polycrystalline kesterite structure and preferred (112) orientation. For the sulfurization temperature of 580°C, the obtained CZTS thin films are dense and flat with larger grain size. Meanwhile composition studying indicates that the fabricated CZTS with single phase is copper poor and zinc rich. Furthermore, the surface roughness of CZTS film is the lowest. Finally, the CZTS solar cells with the structure of SLG/Mo/CZTS/CdS/i-ZnO/ITO/Al were fabricated and demonstrated the best power conversion efficiency of 3.59% when used sulfurization temperature was 580°C.

The effect of the sulfur concentration on the phase transformation from the mixed CuO-Bi2O3 system to Cu3BiS3 during the sulfurization process

The ternary semiconductor Cu3BiS3, as a promising light-absorber material for thin film solar cells, was creatively synthesized by sulfurizing the mixed metal oxides precursor film deposited by spin-coating chemical solution method. Two kinds of sulfurization techniques were introduced to study the effect of the sulfur concentration on the phase formation for the pure Cu3BiS3. It was found that Cu-poor S-rich phases such as Cu3Bi3S7 and Cu4Bi4S9 were easily generated at high S concentration and then can transform to Cu3BiS3 phase by a simple desulphurization process, which means the sulfur concentration had a significant influence on the formation of Cu3BiS3 during the sulfurization process. The probable transformation mechanism from the mixed metal oxides to the pure Cu3BiS3 phase during the sulfurization process was studied in detail through the XRD analysis and thermodynamic calculation. In addition, the electrical properties were characterized by Hall measurement and the effects of sulfurization temperature on the phase transformation, morphology and optical band gap of the absorber layer were also studied in detail.

SnS thin films grown by sulfurization of evaporated Sn layers: Effect of sulfurization temperature and pressure

SnS thin films were grown by sulfurization of Sn layers evaporated by electron beam. The effect of sulfurization parameters, such as temperature and pressure, on the properties of tin sulfide layers has been investigated. Ar pressure used during the sulfurization has a strong impact on the development of a proper SnS/Mo back interface. However, the sulfurization temperature is the parameter that regulates the formation of an orthorhombic single phase SnS thin film with the optimum properties to be used as absorber for solar cell devices. Sulfurization temperature of 220°C for 240min led to the formation of single phase tin sulfide layers. Direct band gap energy about 1.2eV has been determined.

Effects of Sulfurization Temperature on Cu(In, Ga)S2 Thin Film Solar Cell Performance by Rapid Thermal Process.

Cu(In, Ga)S2 (CIGS) absorbers were prepared using two-step process. Cu-In-Ga precursors were deposited by sputtering method and then were sulfurized by rapid thermal process based on H2S gas. Sulfurization temperature was changed from 470 degrees C to 510 degrees C. As the processing temperature increased, larger grains and denser absorbers were observed. The polycrystalline chalcopyrite structure of CuInGaS2 was shown in all samples, and their XRD peak was dominantly observed at (112) direction. CIGS thin film solar cells were fabricated with wide-bandgap absorbers obtained by varying sulfurization temperature. The best efficiency was shown with the processing temperature of 490 degrees C and 8.93% with 1.507 eV of wide optical bandgap.

Fabrication and characterization of Cu2ZnSnS4 thin films for photovoltaic application by low-cost single target sputtering process

Highly crystallized single-phase Cu2ZnSnS4 thin films were fabricated using a simple single-target sputtering technique followed by low-cost sulfurization treatment with sulfur powder. The effects of sulfurization temperature (ranging from 400 to 550 °C) on the structure, morphology, composition, optical and electrical properties of the synthesized CZTS thin film were investigated systematically. The increased sulfurization temperature was found to affect the elemental composition slightly but significantly improve crystallinity, carrier mobility and optical band gap of CZTS films. In particular, the CZTS film sulfurized at 500 °C had excellent optical and electrical properties (an optical band gap of 1.53 eV, a hole concentration of 3.2 × 1015 cm−3, and a carrier mobility of 57.6 cm2(V.s)−1). Furthermore, CZTS-based solar cells were successfully fabricated. Current-voltage (J-V) characteristics indicated that the current density had a tendency of increase with the increase of sulfurization temperature, which was attributed to the relatively large grains and high mobility achieved at a high sulfurization temperature. Importantly, the solar cell based on the CZTS thin film sulfurized at 500 °C had the best performance with a photovoltaic conversion efficiency of 4.4%, open-circuit voltage of 650 mV, short-circuit current density of 19.2 mA/cm2, and fill factor of 37%.