Electroplating of semiconductor Materials for Applications in Large Area Electronics: A Review

The attributes of electroplating as a low-cost, simple, scalable, and manufacturable semiconductor deposition technique for the fabrication of large-area and nanotechnology-based device applications are discussed. These strengths of electrodeposition are buttressed experimentally using techniques such as X-ray diffraction, ultraviolet-visible spectroscopy, scanning electron microscopy, atomic force microscopy, energy-dispersive X-ray spectroscopy, and photoelectrochemical cell studies. Based on the results of structural, morphological, compositional, optical, and electronic properties evaluated, it is evident that electroplating possesses the capabilities of producing high-quality semiconductors usable for producing excellent devices. In this paper we will describe the progress of electroplating techniques mainly for the deposition of semiconductor thin film materials and their treatment processes, and fabrication of solar cells

Benchmark performance of low-cost Sb2Se3 photocathodes for unassisted solar overall water splitting

Determining cost-effective semiconductors exhibiting desirable properties for commercial photoelectrochemical water splitting remains a challenge. Herein, we report a Sb2Se3 semiconductor that satisfies most requirements for an ideal high-performance photoelectrode, including a small band gap and favourable cost, optoelectronic properties, processability, and photocorrosion stability. Strong anisotropy, a major issue for Sb2Se3, is resolved by suppressing growth kinetics via close space sublimation to obtain high-quality compact thin films with favourable crystallographic orientation. The Sb2Se3 photocathode exhibits a high photocurrent density of almost 30mAcm(-2) at 0V against the reversible hydrogen electrode, the highest value so far. We demonstrate unassisted solar overall water splitting by combining the optimised Sb2Se3 photocathode with a BiVO4 photoanode, achieving a solar-to-hydrogen efficiency of 1.5% with stability over 10h under simulated 1 sun conditions employing a broad range of solar fluxes. Low-cost Sb2Se3 can thus be an attractive breakthrough material for commercial solar fuel production. While photoelectrochemical water splitting offers an integrated means to convert sunlight to a renewable fuel, cost-effective light-absorbers are rare. Here, authors report Sb2Se3 photocathodes for high-performance photoelectrochemical water splitting devices

Investigations of surface morphology and chemical composition of Ag/ZnS/glassceramic thin-film structure

The surface morphology and chemical composition of Ag/ZnS/glassceramic thin-film system obtained by close-spaced vacuum sublimation technique under different grow conditions were investigated. Examination of surface profile and morphology was performed by scanning electron and optical microscopy. Chemical composition was studied by Rutherford back scattering method. Results of morphology studies enabled to determine dependence of the growth mechanism, roughness Ra, grain size D of ZnS layers on the growth conditions. The researches of chemical composition allowed to determine the concentration of compound elements and impurities, deviation from stoichiometry and thickness distribution of chemical elements. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3013

Characteristics of nanocrystallite-CdS produced by low-cost electrochemical technique for thin film photovoltaic application: The influence of deposition voltage

Electrochemical deposition and characterization of nanocrystallite-CdS thin films for thin film solar cell application are reported. The two-electrode system used provides a relatively simple and cost-effective approach for large-scale deposition of semiconductors for solar cell and other optoelectronic devices application. Five CdS thin films were deposited for 45 minute each at different cathodic deposition voltages in order to study their properties. X-ray diffraction study reveals that the as-deposited films contain mixed phases of hexagonal and cubic CdS crystallites with large amounts of internal strain and dislocation density. Post-deposition annealing results in phase transformation which leaves the films with only the hexagonal crystal phase and reduced strain and dislocation density while increasing the crystallite sizes from (21.0 – 42.0) nm to (31.2 – 63.0) nm. Photoelectrochemical cell study shows that all the CdS films have n-type electrical conductivity. Optical characterization reveals that all samples show similar transmittance and absorbance response with the transmittance slightly increasing towards higher growth voltages. All the annealed films show energy bandgap of 2.42 eV. Scanning electron microscopy and energy dispersive x-ray analyses show that grains on the surface of the films tend to get cemented together after annealing following CdCl2 treatment while all the films are S-rich

Improved efficiency of microcrystalline silicon thin film solar cells with wide band-gap CdS buffer layer

In this paper, we have reported a new structure based upon an optical simulation of maximum light trapping and management in microcrystalline silicon thin film solar cells by using multi texture schemes and introducing an n-type cadmium sulphide (CdS) buffer layer with the goal of extreme light coupling and absorption in silicon absorber layer. Photon absorption was improved by optimising the front and back texturing of transparent conductive oxide (TCO) layers and variation in buffer layer thickness. We have demonstrated that light trapping can be improved with proposed geometry of 1μm thick crystalline silicon absorber layer below a thin layer of wide band gap material. We have improved the short circuit current densities by 1.35mA/cm2 resulting in a total short circuit current of 25 mA/cm2 and conversion efficiency of 9% with the addition of CdS buffer layer and multi textures, under global AM1.5 conditions. In this study, we have used 2 Dimensional Full Vectorial Finite Element (2DFVFEM) to design and optimize the proposed light propagation in solar cell structure configuration. Our simulation results show that interface morphology of CdS layer thickness and textures with different aspect and ratios have the most prominent influence on solar cell performance in terms of both short circuit current and quantum efficiency

One-sided rectifying p-n junction diodes fabricated from n-CdS and p-ZnTe:Te semiconductors

The fabrication of a one-sided p-n hetero-junction (HJ) diodes have been successfully carried out using both p-type ZnTe and n-CdS semiconductors. Chemical bath deposition (CBD) and electrodeposition (ED) techniques have been used in the deposition of n-CdS and p-ZnTe layers respectively. Before the fabrication of the one-sided p-nHJ diodes, the electrical properties of glass/ FTO/p-ZnTe/Al and glass/FTO/n-CdS/Au rectifying structures were separately studied using capacitance-voltage (C-V ) technique so as to determine the doping density of each of the thin films. The results from C-V analyses showed that p-ZnTe is moderately doped with an acceptor density of 3.55×1015 cm3 while n-CdS is heavily doped with a donor density of 9.00×1019 cm3. The heavy doping of n-CdS and moderate doping of p-ZnTe will make the interface between n-CdS and p-ZnTe thin films a one-sided n+p diode. Therefore, to fabricate the CdS/ZnTe hetero-structure, it was ensured that approximately same thickness of CdS and ZnTe thin films being used in the initial experiment to study the electrical properties of glass/FTO/n-CdS/Au and glass/FTO/p-ZnTe/Al were also used in the development of the one-sided n+p junction diodes to obtain more accurate results. The electronic properties of the device structure were studied using both current-voltage (IV ) and C-V measurement techniques. The I-V results show that the one-sided n+pHJ diodes possess good rectifying quality with a series resistance (Rs) of35 and rectification factors exceeding 102.7 under dark condition. The results of theC-Vanalyses showed that the acceptor density of the onesided n+pHJ diode is of the order of 1015 cm3 while the donor density is of the order of 1018 cm3. The results obtained from this analysis still showed the moderate doping of p-ZnTe and the degenerate nature of n-CdS

Thin Films of Tin Sulphide for Application in Photovoltaic Solar Cells

Tin sulphide (SnS) is a promising new material for use in photovoltaic solar cells. With a direct energy band gap of about 1.3 eV, and a high optical absorption coefficient, only a few microns of SnS are needed to absorb most of the incident light. Not only is SnS made of abundant, environmentally acceptable elements, it is also amphoteric giving flexibility to device design. Structures that can be envisioned include p-type SnS (absorber layer) / n-type (window layer) heterojunction devices, buried p-n junction devices made using SnS and p-i-n structure devices where the i-layer is SnS. It is most likely that the grain boundaries in SnS can be passivated either by counter-doping the grain boundaries, or by oxidizing the grain boundaries to form wide energy bandgap n-type SnO2 within p-type SnS, as dopants or oxygen will diffuse preferentially down the grain boundaries and react first at the grain boundary surfaces. Thin film solar cell devices based on the use of SnS have now been produced with efficiencies > 2 %; these and other promising results indicate that it is most likely that devices with efficiencies > 10% will be produced in the near future. Given that tin layers are routinely coated in industry over large area substrates and that industrial sulphidization processes are also well established, the industrialization of this technology should be more straightforward than that encountered with the already commercialised cadmium telluride and copper indium gallium diselenide thin film technologies. This review discusses the chemical and physical properties of SnS, the methods of producing both bulk crystals and thin films of SnS, the literature available on studies of SnS2 based photovoltaic solar cell devices, and progress made so far in developing this exciting new material

Electrodeposition of CdTe thin films using nitrate precursor for applications in solar cells

Cadmium telluride (CdTe) thin films have been electrodeposited (ED) on glass/fluorine-doped tin oxide (FTO) substrates using simplified two-electrode system in acidic and aqueous solution containing Cd(NO3)2 4H2O and TeO2. The X-ray diffraction (XRD), optical absorption, photoelectrochemical (PEC) cell measurements, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) have been carried out to study the structural, optical, electrical and morphological properties of the CdTe layers. The XRD study shows that the ED-CdTe layers are polycrystalline with cubic crystal structure. Results obtained from optical absorption reveal that the bandgaps of the as-deposited and the CdCl2 treated CdTe layers are in the ranges ~1.50 to ~1.54 eV and ~1.46 to ~1.51 eV, respectively. Observation from PEC measurements indicates a p-, i- and n-type electrical conductivity for as-deposited CdTe layers grown in the cathodic voltage range (1,247–1,258) mV. The SEM images indicate noticeable change in CdTe grain size from ~85 to ~430 nm after CdCl2 treatment with uniform surface coverage of the glass/FTO substrate. The TEM images show the columnar growth structure for as-deposited and CdCl2 treated CdTe layers. The TEM images also indicate an increase in grain’s diameter from ~50 to ~200 nm after CdCl2 treatment

Hole Transport and Recombination in All-Solid Sb2S3-Sensitized TiO2 Solar Cells Using CuSCN As Hole Transporter

All-solid semiconductor-sensitized solar cells lack models allowing their characterization in terms of the fundamental processes of charge transport and recombination. Nanostructured TiO 2/Sb 2S 3/CuSCN solar cells were characterized by impedance spectroscopy, and a model was proposed for this type of cells. One important feature resulting from this analysis was the hole transport diffusion, which could be assimilated to a series resistance affecting the cell fill factor. The other important feature was the recombination rate, which could be described in a similar manner as other cells using nanostructured TiO 2 electrodes and which had an important impact on the open circuit. A simulation of the current-voltage curves using such model allowed us to get an approximate quantification of the losses caused by each process and to evaluate the possible improvements on the performance of this kind of cell

Unravelling complex nature of CdS/CdTe based thin film solar cells

Thin film solar cells based on CdS/CdTe hetero- structure has shown a drastic improvement changing from 16.5 to 22.1% efficiency during a short period of time from ~2013 to ~2016. This has happened in the industrial environment and the open research in this field has stagnated over a period of two decades prior to ~2013. Most of the issues of this hetero-structure were not clear to the photovoltaic (PV) community and research efforts should be directed to unravel its complex nature. Issues related to materials, post-growth treatment, chemical etching prior to metallisation and associated device physics are the main areas needing deeper understanding in order to further develop this device. After a comprehensive research programme in both academia and in industry on these materials, surfaces and interfaces and fully fabricated devices over a period of over three decades by the main author, the current knowledge as understood today, on all above mentioned complex issues are presented in this paper. Full understanding of this structure will enable PV developers to further improve the conversion efficiency beyond 22.1% for CdS/CdTe based solar cells