Electrodeposition Of CdTe Films Research Articles

Photovoltaic applications of electrodeposited CdTe films: impact of deposition time

Photovoltaic applications of electrodeposited CdTe films: impact of deposition time

WITHDRAWN: Electrodeposition of CdTe from a reusable ionic liquid bath

Abstract Electrodeposition (ED) from ionic liquid (IL) medium is of much importance due to a variety of architectures can be synthesized by IL assisted growth. However, these liquids are relatively new for the fabrication of compounds and alloys with a great control over the stoichiometry and thickness. In this regard a well-defined route needs to be established for their wider acceptance as greener alternatives to deposit materials like CdTe, CdS, CdSe, etc. via ED. In this MethodsX article, we have discussed the prerequisites, tricks and methodology to develop stoichiometric CdTe thin films from IL medium with required thicknesses in a highly controlled way compared to conventional ED techniques. This method provides a greener alternative to aqueous electrolytes which are considered to be hazardous media for the ED of CdTe films. We have found that the required precursor ratio of Te:Cd can be lower down to 1:10 for [Bmim]Cl IL medium which is 1:1000 for the aqueous electrolytes. As-grown nanostructured CdTe films can be directly utilized for the devices like IR sensors, schottky rectifiers and solar cells without any post-annealing. Moreover, the aspect ratio of nanostructures can be tuned by changing the precursors’ ratio in IL bath. Nevertheless, IL can be reused multiple times to develop identical thin films which guarantee the low cost pathway. • Nanostructured CdTe thin films • Low cost • Reuse of ionic liquid

Electrodeposition of CdTe from BmimCl: Influence of substrate and electrolytic bath

Potentiostatic electrodeposition of Cadmium Telluride (CdTe) films from the alkaline ionic liquid (IL), butyl methyl imidazolium chloride (BmimCl) at 80 °C has been carried out at an applied potential of −1.45 V vs. platinum (Pt) wire. The influence of the substrate and electrolytic IL bath content on the morphology and composition of electrodeposited CdTe thin films has been presented. The sheet resistivity of the modified FTO substrate increases to ~17.7 Ω/sq. While treatment of the substrate prior deposition changes the individual CdTe morphology, the composition as well as the film compactness has been found to vary with the treatment of the IL based electrolytic bath. SEM micrograph shows inter-connected needle-like and herring bone morphology of electrodeposited CdTe along with agglomerated lumps of Te and flecks of Cd. Interdependency of surface morphology and elemental composition of electrodeposited CdTe films were observed by SEM & EDX analysis. It has been shown that hydroxylated FTO surface facilitates three dimensional (3D) nucleation and growth in the presence of O2 in the electrolytic bath. 3D nucleation and growth mechanism leads to Cd-rich CdTe films. Electrodeposition that does not proceed through 3D nucleation and growth shows only Te-rich layer. Also, the net charge transfer was found more in Cd-rich CdTe layers as compared with Te-rich CdTe deposits.

Effect of sodium chloride on the electrochemistry activity of electrodeposited CdTe films with various morphologies

In this paper, a cadmium telluride (CdTe) film is successfully synthesized on Ni foils via a simple electrochemical deposition method.

Electrical, photoelectrical, and photoelectrochemical properties of electrodeposited CdTe films subjected to high-energy irradiation

The general goal of this work is to study the structure and photoelectrical properties of the electrochemically deposited thin CdTe films. The conducted investigation has shown that (i) as-deposited films have the single-phase structure with a grain size of 1–10 μm and are of the n-type conductivity; (ii) photosensitivity abruptly decreases when the film thickness is over 10 μm; (iii) annealing at temperatures less than 500 °C improves the film quality with retention of the n-type conductivity; and (iv) photosensitivity of the films is not impaired under irradiation by 6 MeV electrons with a fluence of 5 × 10 14 cm − 2 .

Electrodeposition of cadmium telluride from electrolytes based on ethylene glycol

Electrochemical behavior of cadmium and tellurium ions in their joint reduction on a glassy carbon electrode in a nonaqueous electrolyte based on ethylene glycol was studied. An X-ray phase analysis and transmission electron microscopy were used to determine the phase composition and particle size of the electrodeposited CdTe films.

Anneal induced recrystallization of CdTe films electrodeposited on stainless steel foil: The effect of CdCl2

Electrodeposited CdTe films were treated with a saturated solution of CdCl2, and later annealed in air at various temperatures and time durations in order to investigate the influence of post deposition CdCl2 annealing treatments on the structure of the films. The XRD results showed that the CdCl2 treatment has a noticeable influence on the stress, grain growth and the re-crystallization of CdTe. The value of activation energy for 20% re-crystallization in CdTe was estimated as 1.17 ± 0.4 eV and 0.99 ± 0.1 eV respectively for untreated and CdCl2 treated CdTe films. In the early stages of annealing the re-crystallization is dominated by random orientation of the grains followed by a second phase in which once again the crystallites tend to orient in a particular direction. The Lattice constant (a) increases upon annealing and reaches a maximum and on further annealing for a long time it decreases and attains a value less than that of the powder sample.

Microstructural investigations on CdTe thin films electrodeposited using high current pulses

CdTe thin films were electrochemically deposited over FTO-coated glass substrates by singular unipolar current pulses of high magnitude. A wide range of periodic current pulse parameters was investigated in CdTe thin film deposition and the growth properties of the deposited film were determined as a function of variables viz. applied current density, average current and ON/OFF pulse duration and the conditions were optimized for stoichiometric CdTe film growth. A detailed investigation has been carried out to understand the effect of pulse parameters on CdTe growth phases and film microstructure. As evidenced by the diffraction patterns of pulse electrodeposited CdTe films mean current density of 0.36 mA/cm 2 represents an upper limit to form crystalline—CdTe film without secondary phases. Increase in pulse current show inclusion of secondary growth phases. A highly oriented cubic phase was obtained at low current pulse, due to low nucleation rate and surface diffusion of adions on the substrate to growth sites. The crystalline structure and morphology of films were analyzed using powder X-ray diffraction and scanning electron microscopy suggest that OFF time contributes more on the grain size, whereas ON time affects the rate of deposition and grain morphology.

Electrodeposition of CdTe Films from Ammonia-Chloride Buffer Electrolyte

Voltammetry was applied to a study of joint electroreduction of Cd(II) and Te(IV) on a glassy carbon electrode from an ammonia-chloride buffer electrolyte with pH 8.4. The optimal conditions of electrodeposition of CdTe films were determined and their structure was examined by means of X-ray phase analysis.

Growth of CdS and CdTe thin films for the fabrication of n-CdS/p-CdTe solar cell

Abstract Thin n-CdS and p-CdTe films were prepared by chemical spray pyrolysis and electrochemical deposition respectively. Excessive sulphur in the spray solution has promoted grain growth in CdS film. Microstructural features of CdS film with stoichiometric Cd:S concentration in the spray solution were more heterogeneous with grains, whereas film sprayed with excessive S show more uniformity, reduced grain boundary losses of current and improved shunt resistance through inhibition of leakage of current at narrow grain boundary or void site is expected and is indeed observed. Electrodeposition of CdTe films, beside the effect of the inherent process parameters, is also affected by crystalline and microstructural features of the underlying CdS. Nucleation of CdTe film is remarkably affected by CdS film spray deposited over glass substrate. Cell performance considerably depends upon the window layer CdS and the properties of sprayed CdS film depends considerably on the Cd:S ratio in the spray solution. A higher S content in the CdS film affects it optical transmission without changing the optical energy gap. This improves cell efficiency through reduction in CdS film resistivity. A typical increase in cell efficiency was found to increase from 8% to 10.5% using CdS film with Cd:S ratio as 1:1.1 and 1:1.3 respectively.

Joint Electrodeposition of Tellurium(IV) and Cadmium(II) from Acid Solutions in the Presence of 2,2'-Dipyridyl

Cyclic voltammetry was applied to study the effect of addition of 2,2'-dipyridyl on joint electroreduction of Te(IV) and Cd(II) from sulfuric acid solutions on glassy carbon and titanium electrodes. The optimal potentials of electrodeposition of CdTe films were determined and the structure of these films was studied by means of X-ray phase analysis.

Heteroepitaxial growth of CdTe on a p-Si(111) substrate by pulsed-light-assisted electrodeposition

Highly oriented CdTe(111) films of high-crystalline quality were grown on a Si(111) substrate by pulsed-light-assisted electrodeposition at room temperature. Strong photoluminescence peaks due to the bound exciton recombination were observed for the electrodeposited CdTe films, confirming the high quality of the films prepared by the present method. Atomic-force microscopy measurements showed an atomically ordered arrangement and demonstrated the epitaxial growth of the CdTe films.

Influence of the deposition potential on the structure and composition of the CdTe films electrodeposited on stainless steel substrates

The dependence of the chemical composition and grain growth on the deposition potential of CdTe films on stainless steel substrates has been investigated. The preliminary analysis using XRD, EPMA and AUGER techniques show that the preferential orientation of the CdTe grains and the percentage composition of the film depend on the potential applied between the reference electrode and the stainless steel substrate. It is possible to control the composition of the electrodeposited CdTe films by properly adjusting the deposition potential. AUGER analysis revealed the presence of oxygen throughout the thickness of the film.

ChemInform Abstract: Electrodeposition of CdTe Films from Ammoniacal Alkaline Aqueous Solution at Low Cathodic Overpotentials.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Photo-Induced Current Transient Spectroscopy (PICTS) of Deep Levels in Electrodeposited CdTe Films

The PICTS technique in conjunction with a highly absorptive excitation wavelength is used to characterize and to distinguish the electron and hole traps in electrodeposited CdTe films. All the deep levels measured are within two deep (donor-type and acceptor-type) energy bands and are related to only native defects and their complexes with chlorine. Except chlorine, no other trace-impurity levels could be detected, implying the effectiveness of electropurification of the bath solution prior to deposition of CdTe. Some results related to the effect of different annealing processes on the spectrum of deep levels are also discussed.

Charge Transport Mechanisms in Au–CdTe Space-Charge-Limited Schottky Diodes

Space-charge-limited Schottky diodes are fabricated by evaporation of gold on electrodeposited CdTe films. The charge transport mechanisms, in both polarities, are studied. Thermionic emission and space-charge-limited conduction theories can adequately describe the transport properties. The latter mechanism is controlled by a donor-type deep level whose ionization energy varies with the applied voltage according to the Poole-Frenkel effect. Bardeen's model in which the Fermi level is pinned to the interface states, can explain the voltage dependence of the barrier height in these devices. Some of the important parameters of CdTe films are measured from the characteristics of these diodes.

A comparative study of CdTe films prepared by different techniques

Three different methods, viz. (1) vacuum co-evaporation, (2) RF sputtering and (3) electrodeposition, have been applied to deposit thin films of CdTe. The films are cubic 〈111〉 in nature. The grains are found to grow better on textured rather than smooth surfaces. RF sputtered films are stoichiometric, the other two contain excess Te. Annealing reduces the Te content. Substrates and pH of the solution play important roles in determining the stoichiometry of the electrodeposited CdTe films. The carrier concentration, mobility and resistivity of the films are in the range of 10 13–10 14 cm −3, 25–35 cm 2/V·s and 10 3–10 4 Ω cm, respectively.

Observation of electron traps in electrochemically deposited CdTe films

The I–V and C-V data of Schottky devices formed on electrodeposited n-CdTe films are interpreted to determine the principle trap energy and density. The observed trap is an electron trap located at 0.55 eV below the conduction band with a density of ∼7 × 10 15/cm 3. This correlates well with the values reported for CdTe prepared by different methods. Nickel is found to be an injecting contact to electrodeposited CdTe films. Au/ n-CdTe barrier height is determined to be 0.75–0.85 eV for Schottky devices.