Properties Of CdS Thin Films Research Articles

Thermal evolution of physical properties of evaporated CdS thin films for perovskite solar cell applications

The thermal evolution to microstructural and optoelectrical properties of CdS thin films have been investigated in this short communication where the films were grown on glass and indium-doped tin oxide coated substrates using electron-beam evaporation. The pristine (as-deposited) films were annealed in air atmosphere within temperature range of 150–450 °C. The XRD patterns indicated that the formation of cubic phase with F4¯3m space group of deposited films along with (111) preferential orientation. The transmittance and direct optical energy band gap were observed to increase with annealing and the current-voltage characteristics showed ohmic behaviour while conductivity is decreased with annealing. The films are found to be homogenous, well covered and without any voids and cracks and the EDS analysis confirmed the deposition of CdS films. The experimental results warrant that the annealed films may be used in perovskite solar cells as electron transport layer.

Growth process and properties of CdS thin films prepared by chemical bath deposition at different pH values

CdS thin films were successfully fabricated on glass substrates in different pH solutions by chemical bath deposition (CBD). The influences of pH value on the thickness, growth process, structure as well as on the optical properties of CdS film were investigated. The as-deposited films exhibited pure cubic phase structure, indicating that the pH had no significant effect on the crystal structure of CdS film. The optical transmittance spectra demonstrated that the films deposited at 11.7 and 11.8 pH exhibited relatively high transmittance in the long wavelength. And the optical band gaps decreased from 2.42 to 2.31 eV with increasing pH values. Subsequently, the growth process of CdS films was studied by analyzing the morphologies and particles sizes at different growing stages of the deposition. It was found that the particle clusters produced by homogeneous reaction acted as nucleation sites during the deposition process, and CdS preferred to grow on their surface. As a result, the sizes of clusters expanded with deposition time until a continuous film was formed, and the duration to obtain a continuous film reduced with decreasing pH values. Hence, a growth mode of CdS film on the glass substrate was proposed, i.e. the film was formed by the connection of expanded particle clusters produced by homogeneous reaction.

Structural and Optical Properties of Cds Thin Films Prepared at Room Temperature by Chemical Bath Deposition Technique

Structural and Optical Properties of Cds Thin Films Prepared at Room Temperature by Chemical Bath Deposition Technique

Topological, Morphalogical, Structural and optical properties of CdS thin film with complex agents TEA /Ammonia mixer

Topological, Morphalogical, Structural and optical properties of CdS thin film with complex agents TEA /Ammonia mixer

Substrate temperature effects on structural and photoelectric properties of CdS thin films

Cadmium sulfide thin films were deposited on quartz substrates by magnetron sputtering method with varying substrate temperatures. X-ray diffraction patterns of prepared samples showed preferred orientation of (002) with pure hexagonal phase. Atomic force microscopy and scanning electron microscopy images exhibited a surface morphology with uniform and homogeneous grains. X-ray photoelectron spectroscopy (XPS) revealed peaks corresponding to cadmium, sulfur, carbon and oxygen atoms, and the high-resolution XPS surveys for cadmium 3d and sulfur 2p showed an obvious shift to lower binding energy as the substrate temperature raised. Meanwhile, the optical absorption coefficient gradually increased, and the transmittance was approximately 75%. The optical energy gap was as high as 2·40 eV at the substrate temperature of 200°C. Photoconductivity curves presented a rapid response, the lowest conductivity at steady state (only 1·6257 × 10−4 Ω−1 cm−1) and a high solar photoconductivity gain (G p = 296·36) at substrate temperatures of up to 200°C.

Optical and magnetic properties of Ba-doped CdS thin films

ABSTRACTSpray technique using perfume atomiser is used to deposit Ba-doped CdS (CdS:Ba) thin films on glass substrates. Barium concentration is varied as 0, 1, 2 and 3 wt-% and the effect of Ba doping level on some physical properties of the CdS films is reported in this paper. XRD studies confirm that the undoped and doped films exhibit hexagonal crystal structure with a strong (0 0 2) preferential orientation. Nanosized rod shaped grains are evinced for the heavily doped films. The mapping images confirm the distribution of the host ions Cd, S and the dopant ion Ba on the film surface. Increased transparency is observed for the doped films. Magnetic studies confirm that the doped films exhibit ferromagnetic behaviour. The obtained results confirm that barium, a cationic dopant ion enhances the optical and magnetic properties of CdS thin films to a large extent.

Indium doping on the structural, surface and optical properties of CdS thin films prepared by ultrasonic spray pyrolysis method

CdS nanostructures are important and useful materials for photovoltaic applications. In this paper, pure CdS and In doped CdS (CdS:In) thin films were fabricated on soda lime glass substrate using ultrasonic spray pyrolysis (USP) method, to investigate the effect In concentration on the structural behavior, surface and optical properties of the CdS thin films by X-ray diffraction (XRD), Atomic Force Microscopy (AFM) and Ultraviolet–visible (Uv-vis) spectrophotometry. X-ray diffraction patterns of the pure and In doped CdS films indicated that pure CdS film had a mixed of cubic and hexagonal structure with polycrystalline nature while In doped CdS had a hexagonal structure with polycrystalline nature. Increasing the In doping ratio improve the (002) preferential orientation. The optical properties of the In-doped CdS and pure CdS films showed that the energy band gap of the In-doped CdS is a slightly lower than the energy band gap of the pure CdS film. The surface properties of the films showed that all thin films are compact and uniform.

Cu doping concentration effect on the physical properties of CdS thin films obtained by the CBD technique

Cu(In, Ga)Se2 (CIGS) and Cu2ZnSnS4 (CZTS) semiconductors are direct band gap materials; when these types of material are used in solar cells, they provide efficiencies of 22.1% and 12.6%, respectively. Most traditional fabrication methods involve expensive vacuum processes including co-evaporation and sputtering techniques, where films and doping are conducted separately. On the other hand, the chemical bath deposition (CBD) technique allows an in situ process. Cu-doped CdS thin films working as a buffer layer on solar cells provide good performing devices and they may be deposited by low cost techniques such as chemical methods. In this work, Cu-doped CdS thin films were deposited using the CBD technique on SnO2:F (FTO) substrates. The elemental analysis and mapping reconstruction were conducted by EDXS. Morphological, optical and electrical properties were studied, and they revealed that Cu doping modified the CdS structure, band-gap value and the electrical properties. Cu-doped CdS films show high resistivity compared to the non-doped CdS. The appropriate parameters of Cu-doped CdS films were determined to obtain an adequate window or buffer layer on CIGS and CZTS photovoltaic solar cells.

Influence of Substrate Material on Structure Formation and Optical Properties of CdS Thin Films by Chemical Spray Pyrolysis

Influence of Substrate Material on Structure Formation and Optical Properties of CdS Thin Films by Chemical Spray Pyrolysis

Optoelectronic, magnetic and antifungal properties of CdS thin films co-doped with zinc and bromine

This paper reports the results obtained on the optical, electrical, magnetic and antifungal properties of CdS thin films co-doped with zinc and bromine. XRD studies reveal that all the films exhibit hexagonal crystal structure of pure CdS. The undoped, Zn-doped and (Zn, Br) co-doped CdS thin films have a strong (0 0 2) preferential growth. Nanosized grains are evinced from the SEM images of all the samples. Optical transparency of undoped CdS increases from 76 to 81% for the Zn-doped film and to 90% for the co-doped films. Decreased electrical resistivity is observed for the co-doped films. Room temperature ferromagnetic orderings in the form of S-shaped loops are observed for all the films. Antifungal activity was performed against A. niger fungus strain and from the zones of inhibition developed around the samples it was observed that the Zn-doped and (Zn, Br) co-doped CdS thin films exhibit better antifungal efficiency.

A study on the enhancement of opto-electronic properties of CdS thin films: seed-assisted fabrication

A novel method of fabricating chemical bath deposited CdS thin films (CBD-CdS) by using electrodeposited CdS (ED-CdS) as a seed layer is reported. The resulting thin, compact, uniform and adherent seed-assisted CdS films (ED/CBD-CdS) show enhanced effective surface area compared to both ED-CdS and CBD-CdS. The phase of these CdS films was determined to be hexagonal. The fabricated ED/CBD-CdS films show higher photoelectrochemical (PEC) cell efficiency than either ED-CdS and CBD-CdS thin films. Carrier concentration and flat band potential values for ED/CBD-CdS systems are also found to be superior compared to both ED-CdS and CBD-CdS systems.

Bromine doping effect on some properties of CdS films

The suitability of bromine as an anionic dopant influencing the properties of CdS thin films is discussed in this paper. The as-deposited films were characterised respectively by XRD, SEM, UV-vis-NIR spectrophotometer and two-point probe setup. All the films appear to be polycrystalline in nature exhibiting hexagonal crystal structure with a (002) preferential growth texture. The 2θ value of the (002) plane shifts towards lower Bragg angle with doping inferring an expansion in their lattice volumes. Increased transparency and blue shift in optical band gap value are observed for the doped films. Electrical resistivity decreased with increase in Br-doping concentration. Increased transparency, widened band gap and decreased electrical resistivity values achieved confirm that Br is a suitable anionic dopant that can strongly influence the physical properties of pure CdS towards future optoelectronic devices.

Influence of substrate heating on structural, optical and electrical properties of CdS thin film deposited from precursor solutions

In this work CdS thin films were deposited from precursor solution at various substrate temperatures for the application in solar cell photovoltaics. Cadmium acetate ((CH3COO)2Cd.2H2O), thiourea (CH4N2S) and methanol (CH3OH) were used for the very simple and efficient deposition process. The structural characteristics of the deposited CdS thin films were studied by using X-ray diffractrometry, atomic force microscopy and EDAX. The results confirm a primitive type hexagonal structure of the deposited films with an increase in crystallinity as the substrate temperature increases. The optical characteristics (transmittance and band gap) were analyzed using UV–Vis spectrophotometer in the range of 300–900 nm. Transmittance and band gap increases with the increase in substrate temperature. Hall Effect analysis has been done to investigate electrical characteristics (carrier concentration, mobility and conductivity). Results show that substrate temperature has a significant role on structural, optical and electrical characteristics of the deposited CdS thin films which can alter the performance of solar cells.

Enhancement in the optical and electrical properties of CdS thin films through Ga and K co-doping

In the presented work, Ga-doped CdS and (Ga-K)-co-doped CdS thin films are grown on glass substrates at a temperature of 400°C through spray pyrolysis. Influence of K-doping on structural, morphological, optical and electrical characteristics of CdS:Ga thin films are examined. K level is changed from 1at% to 5at% for CdS:Ga samples just as Ga concentration is fixed 2at% for all CdS thin films. It is observed from the X-ray diffraction data that all the samples exhibit hexagonal structure and an increase level of K in Ga-doped CdS samples causes a degradation in the crystal quality. Energy-dispersive X-ray spectroscopy measurements illustrate that the best stoichiometric film is acquired when K content is 2at% in Ga-doped CdS films. Optical transmission curves demonstrate that CdS:Ga thin films exhibit the best optical transparency in the visible range for 4at%K content compared to other specimens. A widening in the optical bandgap is unveiled after K-dopings. It is obtained that maximum band gap value is found as 2.45eV for 3at%, 4at% and 5at%. K -dopings while Ga-doped CdS thin films display the band gap value of 2.43eV. From photoluminescence measurements, the most intensified peak is observed in the deep level emission after incorporation of the 4at%K atoms. As for electrical characterization results, the resistivity reduces and the carrier density improves with the increase of K concentration from 1at% to 4at%. Based on all the data, it can be deduced that 4at%K-doped CdS:Ga thin films show the best optical and electrical behavior, which can be utilized for solar cell devices.

Structural, morphological, optical and electrical properties of spray deposited ternary CdAgS thin films towards optoelectronic applications

The effect of Ag doping on some physical properties of CdS thin films prepared by spray technique using perfume atomiser on glass substrates is reported in this paper. The doped films exhibit polycrystalline nature with hexagonal crystal structure similar to that of the undoped film. A (0 0 2) preferential orientation is observed for all the films. The presence of nanoneedles is evinced for the doped films from the SEM images. All the films have high transparency of nearly 80% in the visible region. The optical band gaps of the doped films exhibit a red shift from 2.44 to 2.23 eV which was attributed to Moss–Burstein (MB) effect. All the films have resistivity in the order of 10−2 Ω-cm, and with Ag doping it is found to decrease. The obtained results infer that the CdAgS thin films are well suited for optoelectronic applications.

Influence of (Zn + F) double doping on the structural, morphological, photoluminescence, optoelectrical properties and antibacterial activity of CdS thin films

The effects of (Zn + F) double doping on the structural, morphological, optical and electrical properties of CdS thin films is reported in this paper. Polycrystalline nature is observed for all the films. Zn-doped and (Zn + F) doubly doped CdS films exhibit a strong (0 0 2) preferential orientation similar to that of the undoped film. The (0 0 2) plane of the Zn-doped and (Zn + F) doubly doped films shift towards higher Bragg angles favoring a contraction in their lattice parameter values. Increased transparency and blue shift in optical band gap is observed for the doubly doped films. The electrical resistivity values of the undoped, Zn-doped, (Zn + F) doubly doped CdS thin films are found to be in the order of 10−1 Ω-cm. From the obtained results it is found that the physical properties of Zn-doped CdS films got enhanced when co-doped with fluorine, and the (Zn + F) doubly doped CdS thin films seem to be a potential candidate for future optoelectronic device applications. Antibacterial activity of the as deposited films were carried against E. coli gram negative bacteria and from the zone of inhibition it is confirmed that the (Zn + F) doubly doped CdS thin films can be used as a good antimicrobial agent against pathogenic microorganisms.

Effect of substrate and Zn doping on the structural, optical and electrical properties of CdS thin films prepared by CBD method

CdS is an important and useful material for photovoltaic applications. In this paper, pure CdS and Zn-doped CdS (CdS:Zn) thin film were fabricated on glass and ITO substrate using chemical bath deposition (CBD) method, to systematically investigate the effect of substrate and Zn concentration on the crystallization behavior, and optical and electrical properties of the CdS thin films by X-ray diffraction, atomic force microscope, X-ray photoelectron spectroscopic, Raman scattering, UV–vis spectrophotometer, and transportation measurement system. The results indicated that no matter what substrate was used, whether glass or ITO substrate, the crystal structure of CdS thin film is always hexagonal phase with (002) as the preferential orientation. And CdS thin film deposited on ITO substrate have a good crystallinity and its morphology is very compact and uniformity. For doping thin films, the results revealed that Zn element has been successfully doped into the lattice of CdS thin film and the position of (002) diffraction peak shifted monotonically from 26.6° to 26.97° with the increase of Zn concentration. Finally, optical and electrical properties were discussed. The optical band gap for the CdS:Zn thin films is bigger than that of the pure CdS thin film, and suitable Zn doping can improve the electrical conductivity of thin film. Our results indicate the CdS:Zn thin films fabricated via CBD method may be more suitable for the application in optoelectronic devices, such as the window layer for cadmium telluride and copper zinc tin sulfide solar cell.

Effect of Cu incorporation on the physical properties of CdS thin films deposited by using the thermal evaporation technique

CdS thin films with different Cu concentrations were grown on glass substrates at room temperature by using the resistive thermal evaporation technique. The effect of Cu doping on the structural, optical and vibrational properties of CdS thin films was investigated. The structural, optical and vibrational analysis was completed using an X-ray diffractrometer and a Raman and a UV-VIS-NIR spectrophotometer. X-ray diffraction data revealed that incorporation of Cu ions improved the crystalline structure but did not change the cubic phase of the CdS thin film with a preferential orientation along the (111) direction. Various optical parameters, like the refractive index, extinction co-efficient, absorption co-efficient, urbach tail energy Ee and optical band gap, were determined by using transmission data at different copper concentrations. The Raman peaks appearing at 299 cm−1 and 592 cm−1 for CdS were attributed to the 1LO and 2LO phonons of cubic CdS, and a shift towards low wavenumber region was observed with increasing Cu concentration.

The influence of DMSO on the formation and photoelectrochemical properties of CdS thin films by electrodeposition method

The homodispersed CdS nanoparticles were prepared on Sn-doped indium oxide substrates (ITO) to form smooth and uniform CdS thin films by electrodeposition method from a dimethyl sulfoxide (DMSO) solution containing cadmium chloride and sulfur. The structure and morphologies of samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. The results indicate that DMSO played an important role in formation of CdS nanofilms by affecting the nucleation and growth of the CdS nanoparticles. So, a DMSO-assisted growth process was proposed as a plausible mechanism for the formation of smooth and uniform CdS nanofilms. According to the photoelectrochemical test, the CdS thin film prepared in 30 % DMSO + 70 % H2O system exhibited maximum photocurrent and open circuit potentials. This is because the deposited CdS nanoparticles had better dispersity on ITO, which facilitated the propagation and kinetic separation of photogenerated charges.

Growth mechanisms and their effects on the opto-electrical properties of CdS thin films prepared by chemical bath deposition

Chemically deposited CdS exhibits high sensitivity in the opto-electrical performance to the growth mechanisms. Hence it is of a great interest to study the effects of growth mechanisms on the opto-electrical performance in such films. Studies were carried out by the means of spectroscopic ellipsometry, and coupled with structural, optical, and electrical characterization. A range of bath temperatures (55°C–95 °C) were used as the means to alter the growth mechanisms. Ion-by-ion process dominated deposition at lower bath temperatures throughout the length of the deposition. This mechanism produced films composed of single phase cubic crystals with corresponding opto-electrical properties inherent to such structures. Complex formations at higher bath temperatures supplement the sole ion-by-ion mechanisms with the cluster-by-cluster mechanism. This results in a mixed cubic/hexagonal structure, and deviation from stoichiometry. As a result, carrier concentrations and mobility increased nearly eight and four fold respectively. Resistivity decreased more than four times from 33.2 to 7.5Ωcm. A noticeable decrease of, ~0.2 was observed in the refractive index and an increase of ~0.07eV in the band gap is also reported. Nuclear magnetic resonance analysis confirms deviation from stoichiometry in the cluster-by-cluster mechanisms, resulting in interstitially trapped Cd+2 and S−2 ions. The trapped ions act as donors in the film enhancing its electrical performance.