Properties Of CdSe Thin Films Research Articles

Tunability of the photoelectric properties of CdSe thin films through doping with manganese toward photovoltaic applications

Tandem solar cells have been demonstrated to surpass the Shockley-Queisser limit, promising the transition to third-generation solar cell technology. Tandem solar cells comprise thin film layers of various band gap semiconductors, and CdSe is a promising candidate for the top cell. In this study, we explore the properties of thermally evaporated CdSe thin films doped with 0 to 5 wt% Mn and report a significant five-fold increase in carrier concentration. Furthermore, our optoelectrical studies indicate a band gap energy of 1.681eV, experiencing up to a 28 meV shift with 5 wt% Mn doping and identifies 1 wt% as the optimal doping concentration, offering the best electrical properties and photo-response while maintaining a stable band gap.

Photodetector properties of CdSe thin films grown by close space sublimation method

Photodetector properties of CdSe thin films grown by close space sublimation method

Structural, optical, and gas sensing properties of CdSe thin films deposited by SILAR method

Structural, optical, and gas sensing properties of CdSe thin films deposited by SILAR method

Studies on modulated physical and photoelectrochemical properties of CdSe thin films by means of Indium doping

Studies on modulated physical and photoelectrochemical properties of CdSe thin films by means of Indium doping

Effect of oxygen on the properties of CdSe thin films prepared by RF-sputtering

CdSe has been widely used as an absorber for CdTe solar cells due to its ability to lower the optical band gap of CdTe, enhancing device performances. In this study, the effect of oxygen on the microstructural, morphology, composition and hoptoelectrical properties of CdSe films during sputtering and post chloride treatment has been investigated. CdSe:O film transfers to amorphous as oxygen content exceeds 3% in sputtering ambient according to XRD results. The band gap calculated from optical transmission spectra shows the oxygen content in sputtering ambient could tune the band gap of CdSe film from 1.52 eV to 1.97 eV.

Comprehensive investigation on influence of copper doping on physical properties of CdSe thin films for solar cell applications

Incorporation of foreign dopant in CdSe host lattice is fascinating approach to tune absorbance, grain-size, conductivity, morphology, topography and stoichiometric-compositions for absorber layer solar cell applications. Herein, thin films of CdSe:Cu alloys having 1%, 3% and 5% Cu contents are grown using thermal-evaporation technique and subsequently annealed at 350 °C. Structural exploration unveils phase-transformation from (103) orientation of hexagonal to (111) orientation of cubic CdSe at 3% and 5% Cu doping with appropriate substitution of Cd2+ by Cu2+ ions at 5% Cu doping. Different Cu concentrations considerably affect optical-response where higher Cu doping leads to augment in refractive-index and visible-light-absorption. PL spectra exhibit two peaks with stronger near-band-edge luminescence at ∼685 nm. Two-dimensional AFM micrographs show spherical-elliptical grains at lower Cu concentration whereas agglomerated-interlinked grains at higher concentration. FESEM micrographs display elongated-nanospherical grains having size in 45-60 nm range. Thus, present investigation offers comprehensive insights for tailoring properties of CdSe films with Cu dopant for solar cells.

Structure and Optical Properties of Cdse:Ga Thin Films Prepared by Thermal Evaporation Method

Cadmium Selenide (CdSe and CdSe:Ga) alloy has been prepared successfully in an evacuated quartz tube at a pressure (10−2 Torr). The structure of the CdSe alloy (powder) was tested by X-ray diffraction (XRD) and found as a polycrystalline (hexagonal) structure. CdSe and CdSe: Thin films have been deposited with a thermal evaporation process on the glass and Si substrates. The aim of this kind of study was to determine the ultrastructural morphology and optical properties of pure CdSe and Ga doped films produced using a method of thermal evaporation. The effect of Gallium on the structural and optical properties of CdSe thin film were doped at 0, 1, 3 and 5%. For all Ga doping ratios, the structural features such as the size of the grain and the micro strain of the thin film have been clarified with XRD technique and XRD pattern. The chosen orientation (002) for all prepared film has been polycrystal structures (hexagonals). With an increase in Ga from 37,54 to 21,37 nm, the grain volume decreases. AFM and SEM were used to study the morphology and surface roughness of the CdSe pure and doping films. All films were homogeneous with a characteristic spherical grain size depending on Ga concentration. The roughness of the films increases with the increase of Ga dopant. UV-Visible spectra photometer is used to investigate the visible properties such as absorption, absorption coefficient and energy gaps in thin films. The absorption value subsequently increased with Al doping concentration of localized states in the band gap of the films increases with the increasing of Al dopant, where optical energy gap values decreased with increasing the proportion of the doping in the range between 1.74 and 1.62. The grain size for pure and Ga- doped CdSe of thin films were decreased with Ga ratios. The absorption coefficient determined depends on photon energy incident (hv), the energy gap of the semiconductor as well as the form of transitions. In conclusions, CdSe and CdSe:Ga were successfully prepared from pure elements Cd, Se and Ga. XRD patterns showed the CdSe and CdSe:Ga films are polycrystalline of hexagonal structure directions by Ga doping that orientated a peak became less intensity from undoped CdSe film. The XRD patterns and AFM measurements of Ga-doped and undoped CdSe thin films agree with each other of the grain size within nanocrystal range and decrease as Ga doping concentration increases. AFM images indicate that the increasing in Ga doping that showed smooth surface films compared to the CdSe films. The optical bands gaps of the films have a direct band transition and slightly decreased with the increasing Ga doping.

Fabrication of Nanostructured Cadmium Selenide Thin Films for Optoelectronics Applications.

There is lot of research work at enhancing the performance of energy conversion and energy storage devices such as solar cells, supercapacitors, and batteries. In this regard, the low bandgap and a high absorption coefficient of CdSe thin films in the visible region, as well as, the low electrical resistivity make them ideal for the next generation of chalcogenide-based photovoltaic and electrochemical energy storage devices. Here, we present the properties of CdSe thin films synthesized at temperatures (below 100°C using readily available precursors) that are reproducible, efficient and economical. The samples were characterized using XRD, FTIR, RBS, UV-vis spectroscopy. Annealed samples showed crystalline cubic structure along (111) preferential direction with the grain size of the nanostructures increasing from 2.23 to 4.13 nm with increasing annealing temperatures. The optical properties of the samples indicate a small shift in the bandgap energy, from 2.20 to 2.12 eV with a decreasing deposition temperature. The band gap is suitably located in the visible solar energy region, which make these CdSe thin films ideal for solar energy harvesting. It also has potential to be used in electrochemical energy storage applications.

Influence of Ni-Co dual doping on structural and optical properties of CdSe thin films prepared by chemical bath deposition method

Pure and Ni-Co dual doped CdSe thin films were deposited on glass substrate by chemical bath deposition (CBD) technique. The deposited thin films were annealed for 1 h at 500 °C. X-ray diffraction (XRD) and UV–vis Spectroscopy were used to study the structural and optical properties of the prepared thin films. XRD studies revealed the hexagonal phase for pure CdSe, CdSe: 0%Ni-8%Co, CdSe: 2%Ni-6%Co, CdSe: 6%Ni-2%Co and CdSe: 8%Ni-0%Co thin films, while CdSe: 4%Ni-4%Co produced the cubic phase. The XRD results revealed that the dual doping affected strongly the preferred orientation of the crystallites. The optical band gap energy, Urbach energy, Extinction coefficient, refractive index, real and imaginary dielectric constants and optical conductivity were calculated for all obtained thin films. The direct optical band gap energy of pure CdSe film was 1.43 eV and it decreased with Ni and Co dual doping. The lowest optical band gap energy was observed for CdSe: 4%Ni-4%Co. The dual doping with Ni and Co increased the efficiency of CdSe thin films to be used as solar cells.

Annealing temperature assisted microstructural and optoelectrical properties of CdSe thin film grown by RF magnetron sputtering

Abstract Cadmium selenide (CdSe) thin films are widely used in electronic devices as well as a potential window material in solar cell applications. In this study, 100 nm CdSe thin films were grown on borosilicate glass substrates by using Radio Frequency (RF) magnetron sputtering technique at room temperature (25 °C). Deposited films were annealed in a vacuum furnace at 100 °C, 200 °C, 300 °C, 400 °C and 500 °C for 10 min, respectively. In-depth analysis of the microstructural and optoelectrical properties of annealed films were performed using X-ray diffraction (XRD), UV–Vis spectrometry and Hall Effect measurements. From XRD results, the films illustrated hexagonal structure with preferred orientation (002) at 2θ = 24.12°. UV–Vis study indicated that the transmission ranges were from 75% to over 85% for annealed samples and the calculated optical band gap was in the range 1.65 eV–1.73 eV. Optical properties demonstrated that CdSe had the potential to be incorporated as a window layer in solar cells. Meanwhile, the electrical measurements showed n-type conductivity with the carrier concentration of 1014 cm−3 for all the annealed films. The optimized results recommend sputtered CdSe thin films annealed at 400 °C as a possible window layer to the Cd-based solar cells.

Influence of post-deposition selenization and cadmium chloride assisted grain enhancement on electronic properties of cadmium selenide thin films

We report on the growth, grain enhancement, doping, and electron mobility of cadmium selenide (CdSe) thin films deposited using the thermal evaporation method. The optical measurement shows CdSe is a direct bandgap material with an optical bandgap (Egap) of 1.72 eV. CdSe thin films were deposited on fluorine doped tin oxide glass substrates with different thicknesses, and grain size and mobility were measured on the films. CdCl2 was deposited on the films, and the films were subjected to high temperature treatment for several hours. It was found that both grain sizes increased significantly after CdCl2 treatment. The mobility of electrons was measured using the space charge limited current technique, and it was found that the mobility increased significantly after CdCl2 treatment. It was discovered that postdeposition selenization further improved the electrical properties of CdSe thin films by increasing the electron mobility-lifetime product and the photo/dark conductivity ratio. CdSe films after postselenization also showed significantly lower values for midgap states and Urbach energies for valence band tail states.

Optical and surface properties of CdSe thin films prepared by sol-gel spin coating method

In this work, L-cysteine capped CdSe nanocrystals thin films were grown on glass substrate by using spin-coating method. The annealing temperature effect on structural, morphological, and optical properties of CdSe thin film is investigated by X-ray diffraction (XRD), Differential scanning calorimetry (DSC), Atomic force microscopy (AFM), UV–Vis and photoluminescence (PL) techniques. XRD analysis showed crystallization and phase transformation of CdSe thin films from cubic (Zinc Blende, β-CdSe) to hexagonal (Wurtzite, α-CdSe) structure are obtained after air-annealing at 250 °C during 30 min. DSC analysis showed the exothermic peak in the range of 170–225 °C, indicating the structural phase transformation of CdSe thin film. AFM analysis exhibited a change in the surface roughness of thin films and the shape of CdSe nanoparticles from hemispherical nanocrystals into microrods as a function of annealing temperature. The surface and volume energy loss (VELF and SELF) functions show different dependences on the incident photon energy for the CdSe films in the energy range 1.5–4 eV as a function of air-annealing temperature. The dispersive optical parameters such as refractive index (n), extinction coefficient (k), and the dielectric constants were found to vary with the annealing temperature. PL measurements showed that the increase in the annealing temperature up to 200 °C results an improvement in the crystalline quality of the CdSe thin film, a decrease in their optical band gap, and an enhancement in the PL peak intensity.

Annealing temperature dependence of properties of CdSe thin films by RF-sputtering

Cadmium Selenide (CdSe) is a II-VI group compound semiconducting material with a direct band gap about 1.74 eV, which is widely applied in thin film transistors, light emitting diodes and photoelectrochemical (PEC) cells. In recent years, the application of CdSe thin films to CdTe thin film solar cells has attracted the attention of people. CdSe thin films were synthesized using radio frequency magnetron sputtering method on Corning glass substrates at room temperature. The as-deposited films were annealed at various temperatures (200°C, 300°C, 400°C and 500°C) in N2 atmosphere for 1h and the effect of annealing temperature on structural, morphological, compositional, optical and electrical properties was studied. X-ray diffraction (XRD) indicates that the structure of CdSe thin films transforms from cubic to hexagonal structure when annealing temperature changes from room temperature to 500°C. Scanning electron microscope (SEM) images show that the crystallite size of CdSe thin films has no obvious increase with annealing temperature increasing from 200°C to 400°C, which is all about 33 nm. However, grains with size of 200 nm were precipitated on the surface of CdSe thin film annealed at 500°, and the Se content of CdSe thin film decreased. The band gaps of CdSe thin films were found to firstly decrease, and then gradually increase with the increase of annealing temperature. The minimal band gap of CdSe thin film is 1.63eV when annealed at 300°C. The conductivity of CdSe thin film annealed at 500° increased by two orders of magnitude compared with as-deposited CdSe thin film.

The influence of malonic acid on the structural, morphological and optical properties of CdSe thin films prepared by chemical bath deposition method

Cadmium Selenide thin films were deposited on glass substrates by chemical bath deposition technique. The films have been characterized by using X-ray diffraction (XRD), UV–Vis spectroscopy, scanning electron microscopy (SEM), photoluminescence spectroscopy. The XRD study showed that the obtained thin films were CdSe with cubic crystal structure. The average crystallite size of 4.13–5.14 nm was obtained with different concentration of malonic acid. The relative intensities of the prominent diffraction peaks decreased with increasing concentration of malonic acid. The SEM images confirmed that there were considerable changes in the morphology of CdSe nanoparticles with the molar concentrations of malonic acid. The optical band gaps of the nanoparticle were estimated from the UV–Vis spectroscopy measurement and obtained in the range of 2.03 eV to 1.74 eV. The photoluminescence spectra showed a well-defined peak at 543 nm and shoulders around 487 nm and 530 nm for all CdSe thin films.

Thickness dependent variation in structural, optical and electrical properties of CdSe thin films

Cadmium selenide (CdSe) thin films of various thicknesses are deposited on ITO glass substrates by electrodeposition technique using a bath containing cadmium sulfate (3CdSO4·8H2O) and selenium dioxide (SeO2) solution. The structural, optical and electrical characteristics of these thin films are analyzed by X-ray diffraction (XRD), UV–Vis spectrophotometer and four probes setup with current–voltage (I–V) source meter. The XRD study confirmed that the thin films possess polycrystalline nature with cubic structure. The decrease in full width at half maximum and increase in peaks intensity revealed that the crystalline properties of CdSe thin films were enhanced with film thickness. Optical analysis shown that the CdSe thin films possess direct band gap which decreases from 2.67 to 2.47 eV with the increase in thickness. Photoluminescence analysis further revealed an enhancement in optical quality of CdSe thin films with thickness. Electrical analysis (I–V characteristics) showed that the resistivity of CdSe thin film also decreased with increase in thickness. The decrease in the resistivity with increase in CdSe film thickness also accredited to the enhancement of crystallization in thin films.

Investigation the effect of annealing temperature on the optical properties of CdSe thin films

Introduction: CdSe is an important II–VI semiconducting material dueto its typical optical properties such as small direct band gap (1.7 eV) anda high refractive index and, thus, a major concern is focused on the investigation of optical properties of CdSe thin films which is important topromote the performances of the devices of solid -state such as SC (solar cells), thin film transistors, LED (light-emitting diodes), EBPL (electron–beam pumped lasers) and electroluminescent devices. In the presentwork, CdSe thin films were deposited by thermal evaporation method andthe results have been analysed and presented. Materials and Methods:CdSe thin films has been deposited on glass microscopic slides as substrates of (75×25×1 mm) under room temperature using PVD technique.CdSe blended powders gets evaporated and condensed on the substrate.The film thickness (t = 100 5 nm) which is measured using Michelsoninterferometry method. Transmission spectrum, from 200-1100 nm, arescanned using two beams UV–VIS Spectrophotometer (6850 UV/Vis.Spectrophotometer-JENWAY). The deposited films then were annealedat temperature range of (1500C to 3500C) under vacuum to have a stable phase of the material and prevent surface oxidization. Results andDiscussion: A transmittance spectrum of CdSe thin film is scanned overwavelength range 200 to 1100 nm using a (6850 UV/Vis. Spectrophotometer-JENWAY) at room temperature. The transmittance percentagebetween the as-deposited film and the annealed films change varies from(17.0%) to (47.0%). It is clearly seen that there is a shift toward higher energy (Blue Shift) in the transmittance spectrum. As annealing temperatureincreased the transmittance edge is shifted to the longer wavelength (i.e.,after annealing the CdSe films shows red shifts in their optical spectra).The band gap was found within the range 1.966-1.7536 eV for CdSe thinfilm. As annealing temperature increases, the Eg continuously decreases.Conclusions: CdSe thin films have been deposited using Physical VaporDeposition (PVD) Technique. It is found that the transmission for asdeposited films is (17%) and increases to (47%) as annealing temperature increases. Beside this the energy gap for as- deposited CdSe film is(1.966eV) and decreased from (1.909 eV) to (1.7536eV) as the annealingtemperature increases. There is a strong red shift in optical spectrum ofthe annealed CdSe films. There is a gradual shift of the annealed filmsthin film spectra as compared of bulk CdSe films

Silver Dopant-Induced Effect on Structural and Optoelectronic Properties of CdSe Thin Films

Thin films of CdSe and silver (Ag)-doped CdSe have been prepared on glass substrates by thermal evaporation in argon gas atmosphere. X-ray diffraction pattern indicates the presence of hexagonal structure with preferred orientation along (100) plane. Elemental composition of the thin films has been analyzed using energy dispersive X-ray analysis. Scanning electron microscopy has been used to investigate the morphology of the thin films. Transmission electron microscope reveals spherical nature of nanoparticles. A decrease in the band gap due to the formation of band tails in the band gap with increase in Ag doping in CdSe lattice has been observed. Photoluminescence spectra indicate redshift in band edge emission peak with increase in Ag doping in CdSe. Electrical conductivity measurements are also studied, and two types of conduction mechanisms taking part in the transport phenomena are observed. Hall measurements indicate n-type behavior of undoped and Ag-doped CdSe thin films.

Incorporation of tin in nanocrystalline CdSe thin films: a detailed study of optoelectronic and microstructural properties

Tin-doped nanocrystalline CdSe thin films were deposited onto glass substrate by simple chemical bath deposition technique. The films obtained were uniform and had good adherence to the substrate. The influence of Sn (0–5%) doping on the optical, photoluminescence, electrical, morphological, compositional and structural properties of the films was investigated. The optical absorption studies revealed that the optical band gap of the films varied from 2.62 eV for nano CdSe to 2.50 eV for 5% Sn:CdSe. These films are appropriate for application in different optoelectronics devices due to band gap tunability property. To analyze photoluminescence properties, the films were excited by UV (235 nm) and almost green spectrum was emitted by the films. It is observed that the low temperature resistivity of the thin films was in the range 107–104 Ω cm and also found to decrease with Sn concentration, as resulted from the dc two probe measurements. Activation energy was also calculated. Noticeable changes were observed in the optical and electrical properties of CdSe thin films due to the presence of Sn dopant. Surface morphology study using TEM/SEM showed almost uniform distribution of spherical grains. The elemental composition study using energy dispersive spectroscopy (EDAX) confirms the existence of the desired elements. X-ray diffraction pattern indicated that the formed structure is cubic with most prominent peak at (111). Some important structural parameters such as lattice constant, crystallite size, strain, dislocation density and number of crystallites per unit area were calculated and presented.

The Effect of Ag Doping on the Structural, Optical and Electrical Properties of CdSe Thin Films

The Effect of Ag Doping on the Structural, Optical and Electrical Properties of CdSe Thin Films

Nitrogen ion implantation effects on the structural, optical and electrical properties of CdSe thin film

In the present study, thin films of cadmium selenide (CdSe) are deposited on ITO substrate by electrodeposition method using aqueous solution of 3CdSO4·8H2O and SeO2. These films are implanted with 40 keV N+ ions with different fluencies i.e. 1 × 1015, 5 × 1015, 1 × 1016 and 5 × 1016 ions/cm2 using a beam current of 0.9 µA. The structural, morphological, optical and electrical properties of pristine and nitrogen ion-implanted CdSe thin films are analyzed using XRD, SEM, AFM, UV-PL Spectrophotometer and I–V four probes setup. XRD analysis revealed the effects of nitrogen ions on the structural parameters such as grain size, FWHM, micro strain and dislocation density etc. Crystallanity of the material increased with increase in implantation dose. SEM and AFM analysis show decrease in the surface roughness with implantation. From the optical studies, band gap value decreased from 2.50 to 2.29 eV with increase in N+ implantation doses. Noticeable changes in the electrical properties are also reported. The effect of N+ ion implantation on the properties of CdSe thin films are discussed on the basis of lattice disorder.