Annealing effects on physical properties of doped CdTe thin films for photovoltaic applications (original) (raw)
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Chemical deposition technique is used to produce good quality tin sulphide (SnS) thin films of 450 nm in thickness, from a chemical bath containing tin chloride (SnCl22H2O) and thioacetamide. The SnS thin films were annealed at 300, 350 and 400 C for 1 h in vacuum, nitrogen and argon atmospheres, resulting in the modification of their optical and electrical properties. The optical band gap showed a decrease from 1.2 to 1 eV whereas the electrical conductivity increased by more than two orders in the heat treated films at 400 C in comparison with those of pristine samples. The morphology analysis of the as prepared and heat treated SnS thin films was done using scanning electron microscopy; X-ray diffraction patterns showed orthorhombic SnS phase and the chemical states of the elements were confirmed by X-ray photoelectron spectroscopy. The heat treated SnS thin films (1.8 lm thickness) were incorporated to photovoltaic structures of the type: Glass/TCO/CdS/SnS/C/Ag, showing open circuit voltages (Voc) from 270 to 330 mV and a short circuit current density (Jsc) up to 6 mA/cm2.
Investigation of the Properties of Cadmium Sulphide Thin Films for Solar Cell Applications
The paper presents an investigation of the properties of Cadmium Sulphide (CdS) thin films and their suitability for use as solar cell material. Thin films of cadmium sulphide with thicknesses ranging from 0.8-3.26 µm were deposited on microscope glass slides using the chemical bath deposition method (CBD). The paper also presents some findings on how to optimize the chemical bath deposition technique to achieve improved quality of CdS thin films deposited on glass substrates. Some of the samples were annealed while others were left unannealed. All the samples were tested to investigate the physical, electrical and optical characteristics of the deposited thin films. The physical properties measured were the thickness and surface morphology of the samples. The electrical properties were the resistivity, conductivity type and charge carrier mobility while the optical property was the band gap energy. The resistivity of the samples was measured using the four point probe method while the band gap energy was measured using a UV/VIS spectrophotometer. The unannealed samples were found to have an average resistivity of 1.01217 ×10 3 Ωcm and average band gap energy of 2.493 eV. The average charge carrier mobility of the unannealed samples was 2209.4 cm 2 v-1 s-1 measured based on the Hall Effect principle. From the galvanometer deflection as measured against standard using the hot probe method was observed that CdS is an n-type semiconducting material. Comparing results obtained for both annealed and unannealed samples, it was observed that there is a decrease of 4.63% on resistivity and 0.72% on band gap energy of the annealed samples. The charge carrier mobility increased by 12.3% for the annealed samples as well. The quality of CdS thin film can be improved through annealing. This implies that the thin film developed in the current study could be used as a window layer for heterojunction solar cells of the types; Cadmium sulphide/ Cupper Indium Selenide (CdS/CuInSe 2) or Cadmium Sulphide/ Cadmium Telluride (CdS/CdTe).
New Investigations Applied on Cadmium Sulfide Thin Films for Photovoltaic Applications
In this paper we present some new investigations made on nanocrystalline cadmium sulfide thin films used as photoactive components in CdS/CdTe photovoltaic cells. The cadmium sulfide (CdS) thin films were deposited by method of thermal vacuum evaporation, from a single source, on ITO covered optical glass substrates of different thicknesses and electrical resistances. In order to improve the structural and chemical properties of the prepared films, post-deposition thermal treatments combined with chemical treatments based on CdCl 2 vapors were performed on all samples. The transmission as well as the absorption spectra were recorded using a UV-VIS double beam spectrophotometer. From the absorption spectra, the optical band-gaps of the films were calculated. The structural characterization of the cadmium sulfide thin films was made by GIXRD (Grazing Incidence X – Ray Diffraction) for samples of different thicknesses. The morphological investigations were carried out by cross section ...
Annealing studies and electrical properties of sns-based solar cells
Thin Solid Films, 2011
Thin films of SnS (tin sulphide) were thermally evaporated onto glass and CdS/ITO (cadmium sulphide/indium tin oxide) coated glass substrates and then annealed in vacuum with the aim of optimising them for use in photovoltaic solar cell device structures. The chemical and physical properties of the layers were determined using scanning electron microscopy, energy dispersive x-ray analysis, x-ray diffraction, and transmittance versus wavelength measurements. "Superstrate configuration" devices were also made using indium tin oxide as the transparent conductive oxide, thermally evaporated cadmium sulphide as the buffer layer and evaporated copper/indium as the back contact material. Capacitance-voltage data are given for the fabricated devices. Capacitancevoltage, spectral response and I-V data are given for the fabricated devices.
2014
Tin Sulphide (SnS) thin films have been deposited on glass slides by thermal evaporation using SnS powder. The improvements in the structural and optical properties of SnS thin films on annealing at different temperatures (200°C, 300°C, 400°C, and 500°C) in vacuum for one hour are presented in this work. The thin films annealed at 500°C were decomposed, which limits the annealing temperature below than 500°C. X-ray diffraction characterization showed an intensive peak at 31.8° originating from (111) reflection. Ellipsometry measurements were done for optical studies and optical absorption coefficient for as-deposited films was 2.02 x10 4 increased to 4.90 x10 4 (cm)-1 for films annealed to 300°C for incident photon energies 1.55eV, and direct band gap of 1.90 eV was indicated.
Characterisation of Electrodeposited Cadmium sulphide Thin Films for Application in CdTe Solar Cells
2018
Cadmium sulphide thin films have been grown from acidic electrolyte prepared from analytical grade reagent using electroplating technique. The films were grown on glass/FTO substrate in an acidic medium of pH 2.50 and temperature of 85oC. The layers were intended for use as window layers in CdTe thin film solar cells. The structural study show that the films were crystalline with the preferred orientation along the (100)H phase of cadmium sulphide (CdS). The optical study shows that the bandgaps matched well with the bulk bandgap of CdS (2.42 eV) after the cadmium chloride (CdCl2) treatment. The films also show improved morphology after CdCl2 with increased roughness than in the case of the as-deposited films. Photoelectrochemical (PEC) cell study indicate that all the layers in both the as-deposited and after the CdCl2 were n-type in electrical conduction.
OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS
The hexagonal cadmium sulphide (CdS) thin films with strong (002) orientation is prepared by thermal evaporation technique. The effect of substrate temperature on the structural, morphological, compositional, optical and electrical properties of CdS thin films is investigated. X-ray diffraction and transmission electron microscopy analysis of the films suggests that films presented hexagonal structure and no secondary or mixed phases are found. Scanning electron microscopy images revealed that the grain size increases with Ts while energy dispersive x-ray analysis confirms homogeneity and stoichiometry of films. The analysis of transmission spectra showed that CdS films deposited at different Ts had transmission and energy band gap in the range of 60-90% and 2.32-2.40 eV respectively. Electrical characterization of films deposited at different Ts carried out using Hall effect measurements suggests that films have resistivity and mobility value in the range of 10 4 Ω cm and 2-40 cm 2 /Vs respectively influenced by substrate temperature.
Electrical Characterization of Chemically Grown CdS and CdTe Thin Films for Solar Cell Application
Asian Journal of Research and Reviews in Physics, 2022
Thin films of Cadmium Sulphide and Cadmium Telluride have gained a great deal of interest due to their potential applications in solar cells. Deposition of and thin films were performed on Soda Lime glass and FTO substrate at respectively using spray pyrolysis technique. The Hall Effect property was measured for the deposited and films. These results shows the resistivity and mobility of CdS films deposited at were and , respectively, The annealed thin film had a resistivity value of , while the annealed and etched thin film had a resistivity value of , The resultant films are observed to be good to make a solar cell with CdS as a window layer and CdTe as absorber layer.
Thin Solid Films, 2003
The investigation of electronic quality of chemical bath deposited cadmium sulphide (CdS) layers was the main objective of this work. For completeness, the CdS layers were characterised using X-ray diffraction, atomic force microscopy, optical absorption, photoelectrochemical cell, DC electrical conductivity measurements, current-voltage and capacitance-voltage measurements using GoldyCdS Schottky contacts. It has been found that the CdS layers grown are hexagonal with (002) preferential orientation. The n-type CdS materials show 1-2 mm clusters consisting of 0.3-0.4 mm size crystallites. The optical band gap is 2.42 eV, which shows a red-shift to 2.25 eV upon heat treatment. Gold Schottky contacts produce large Schottky barriers of 1.02 eV with ideality factors of 1.50, indicating excellent electronic qualities. Schottky-Mott plots indicate a moderate doping concentration of 1.2=10 cm , suitable for electronic device fabrication. However, the DC electrical conductivity measurements 17 y3 carried out at room temperature indicate a very low electrical conductivity in the range (4-11)=10 (V cm). This indicates y5 y1 a very low mobility value of (2-5)=10 cm V s , which are five orders of magnitude below that of single crystal CdS. y3 2 y1 y1 The way forward for further improvement of the electrical conductivity is discussed.
CdS thin film post-annealing and Te–S interdiffusion in a CdTe/CdS solar cell
Solar Energy
Small area CdTe/CdS solar cells were fabricated using chemical bath deposited CdS and CSS deposited CdTe thin films to investigate the interface properties related to the CdS processing. The effect of post deposition annealing of CdS on the junction properties and the possible interdiffusion at the interface is discussed. The hypothesis of hardening of CdS due to annealing against the diffusion of "S" and "Te" is discussed using the quantum efficiency data in the blue and red regions. Devices prepared using as-deposited CdS films exhibited evidences of higher "S" and "Te" diffusion compared to devices made using CdS films annealed in oxygen. The maximum efficiency of the devices used in this study was 9.8%.