CdS Layer Research Articles

Dual CdS Nanoparticle-Deposited Vertically Aligned Titanate Nanotube Heterostructure Photoanode

Dual CdS nanoparticles improve the photoelectrochemical (PEC) performance of vertically aligned titanate nanotubes (i.e. VA-TNTs). This is achieved by first depositing a CdS layer via an ion-exchan...

Hybrid chemical bath deposition-CdS/sputter-Zn(O,S) alternative buffer for Cu2ZnSn(S,Se)4 based solar cells

To replace the conventionally used CdS buffers in Cu2ZnSn(S,Se)4 (CZTSSe) based thin-film solar cells, sputtered Zn(O,S) buffer layers have been investigated. Zn(O,S) layers with three different [O]/([O] + [S]) ratios (0.4, 0.7, and 0.8)—and a combination of Zn(O,S) and CdS (“hybrid buffer layer”) were studied. In comparison to the CdS reference, the external quantum efficiency (EQE) of the Zn(O,S)-buffered devices increases in the short- and long-wavelength regions of the spectrum. However, the average EQE ranges below that of the CdS reference, and the devices show a low open-circuit voltage (VOC). By adding a very thin CdS layer (5 nm) between the absorber and the Zn(O,S) buffer, the VOC loss is completely avoided. Using thicker intermediate CdS layers result in a further device improvement, with VOC values above those of the CdS reference. X-ray photoelectron spectroscopy (XPS) measurements suggest that the thin CdS layer prevents damage to the absorber surface during the sputter deposition of the Zn(O,S) buffer. With the hybrid buffer configuration, a record VOC deficit, i.e., a minimum difference between bandgap energy Eg (divided by the elementary charge q) and VOC (Eg/q – VOC) of 519 mV could be obtained, i.e., the lowest value reported for kesterite solar cells to date. Thus, the hybrid buffer configuration is a promising approach to overcome one of the main bottlenecks of kesterite-based solar cells, while simultaneously also reducing the amount of cadmium needed in the device.

The role of CdS doping in improving SWIR photovoltaic and photoconductive responses in solution grown CdS/PbS heterojunctions

Low cost short wavelength infrared (SWIR) photovoltaic (PV) detectors and solar cells are of very great interest, yet the main production technology today is based on costly epitaxial growth of InGaAs layers. In this study, layers of p-type, quantum confined (QC) PbS nano-domains (NDs) structure that were engineered to absorb SWIR light at 1550 nm (Eg = 0.8 eV) were fabricated from solution using the chemical bath deposition (CBD) technique. The layers were grown on top of two different n-type CdS intermediate layers (Eg = 2.4 eV) using two different CBD protocols on fluoride tin oxide (FTO) substrates. Two types of CdS/PbS heterojunction were obtained to serve as SWIR PV detectors. The two resulting devices showed similar photoluminescence behavior, but a profoundly different electrical response to SWIR illumination. One type of CdS/PbS heterojunction exhibited a PV response to SWIR light, while the other demonstrated a photo-response to SWIR light only under an applied bias. To clarify this intriguing phenomenon, and since the only difference between the two heterojunctions could be the doping level of the CdS layer, we measured the doping level of this layer by means of the surface photo voltage (SPV). This yielded different polarizations for the two devices, indicating different doping levels of the CdS for the two different fabrication protocols, which was also confirmed by Hall Effect measurements. We performed current voltage measurements under super bandgap illumination, with respect to CdS, and got an electrical response indicating a barrier free for holes transfer from the CdS to the PbS. The results indicate that the different response does, indeed, originate from variations in the band structures at the interface of the CdS/PbS heterojunction due to the different doping levels of the CdS. We found that, unlike solar cells or visible light detectors having similar structure, in SWIR photodetectors, a type I heterojunction is formed having a barrier at the interface that limits the injection of the photo-exited electrons from the QC-PbS to the CdS side. Higher n-doped CdS generates a narrow depletion region on the CdS side, with a spike like barrier that is narrow enough to enable tunneling current, leading to a PV current. Our results show that an external quantum efficiency (EQE) of ∼2% and an internal quantum efficiency (IQE) of ∼20% can be obtained, at zero bias, for CBD grown SWIR sensitive CdS/PbS-NDs heterojunctions.

Efficiency Enhancement of Cu(In,Ga)(S,Se)2 Solar Cells by Indium-Doped CdS Buffer Layers.

Improving power conversion efficiency of photovoltaic devices has been widely investigated; however, most research studies mainly focus on the modification of the absorber layer. Here, we present an approach to enhance the efficiency of Cu(In,Ga)(S,Se)2 (CIGSSe) thin-film solar cells simply by tuning the CdS buffer layer. The CdS buffer layer was deposited by chemical bath deposition. Indium doping was done during the growth process by adding InCl3 into the growing aqueous solution. We show that the solar cell efficiency is increased by proper indium doping. Based on the characteristics of the single CdS (with or without In-doping) layer and of the CIGSSe/CdS interface, we conclude that the efficiency enhancement is attributed to the interface-defect passivation of heterojunction, which significantly improves both open circuit voltage and fill factor. The results were supported by SCAPS simulations, which suggest that our approach can also be applied to other buffer systems.

Hexagonal diameter in cadmium sulfide/anodic alumina nanoporous bi-layer membrane by a sol–gel spin coating and their sensing application

Cadmium sulfide/anodic alumina nanoporous bi-layer film was designed for the first time by two-step anodization followed by a sol–gel spin coating method. The chemical composition, morphological, electrical and structural properties of the AA and Cd/AA nanoporous membranes have been examined. The morphological investigation of AA layer demonstrates the development of an exceptionally ordered hexagonal exhibit of nanoporous anodic alumina of pore diameter ~ 55 nm and inter-pore distance ~ 125 nm. Though, CdS/AA demonstrated the deposition of nanoporous CdS layer from agglomerated CdS nanoparticles on the surface of the membrane of AA. The energy-dispersive X-ray spectrum of CdS/AA outlined signs of O, Al, Cd, and S, which shows its high purity. The X-ray diffraction affirmed the development of cubic-phase CdS in the favored (220) orientation with normal ~ 86.2 nm crystallite size. The present voltage and resistance–concentration attributes of the CdS/AA layer as a glucose biosensor are fitted well with second-order polynomial behavior (correlation coefficient = 0.981). The glucose concentration changed from 0 to 400 mg/dl. In light of the upsides of the fabrication approach, this new age of minimal effort biosensors can be utilized as a guarantee building block for nanophotonic and nanoelectronic gadgets.

Solution-Processed Anti Reflective Transparent Conducting Electrode for Cu(In,Ga)Se2 Thin Film Solar Cells

Silver nanowire (AgNW) networks have been adopted as a front electrode in Cu(In,Ga)Se2 (CIGS) thin film solar cells due to their low cost and compatibility with the solution process. When an AgNW network is applied to a CIGS thin film solar cell, reflection loss can increase because the CdS layer, with a relatively high refractive index (n ~ 2.5 at 550 nm), is exposed to air. To resolve the issue, we apply solution-processed ZnO nanorods to the AgNW network as an anti-reflective coating. To obtain high performance of the optical and electrical properties of the ZnO nanorod and AgNW network composite, we optimize the process parameters – the spin coating of AgNWs and the concentration of zinc nitrate and hexamethylene tetramine (HMT – to fabricate ZnO nanorods. We verify that 10 mM of zinc nitrate and HMT show the lowest reflectance and 10% cell efficiency increase when applied to CIGS thin film solar cells.

Three‐Dimensional GeSe Microstructured Air Brick Photocathode for Advanced Solar Water Splitting

Air brick‐structured GeSe is first synthesized by a rapid box thermal deposition method, and the GeSe thin film with such air brick novel structure demonstrates advanced photoelectrochemical (PEC) performance. It is found that the electrode position of a few CdS nanoparticles (NPs) on a GeSe microair brick (MAB) prior to the chemical bath deposition (CBD) of CdS buffer affects the coverage/passivation efficiency of CdS onto GeSe MAB. In this case, the electrodeposited CdS particles were likely to be the seed for CdS growth/adsorption of Cd2+ during the subsequent CBD process and also could serve as active sites between the adsorbed layer and buffer layer for collecting electrons and facilitating their transfer, ultimately reducing the recombination loss. The PEC performance, especially the current density, is obviously improved (8 mA cm−2 at 0 VRHE) compared with that of a device without CdS NPs (3.6 mA cm−2 at 0 VRHE). Moreover, surface modification with an 80 nm atomic layer deposition TiO2 protective layer not only slows the photocorrosion of the CdS layer to 5 h but also promotes the half‐cell solar‐to‐hydrogen efficiency to 1.47%. More than 180 μmol H2 and 90 μmol O2 are evolved during 3 h of sustained solar light illumination with the final Pt–TiO2/CdS/CdS‐NP/GeSe MAB device.

Characterization of CdS sputtering deposition on low temperature pulsed electron deposition Cu(In,Ga)Se2 solar cells

The present paper reports the investigation of sputtered CdS as a buffer layer in Cu(In,Ga)Se2 (CIGS) solar cells, for a dry-low temperature all in-line production technology method. The CdS film is deposited using radio-frequency magnetron sputtering in argon atmosphere. Compared to the well-known CdS grown by chemical bath deposition, the sputtering technology is feasible for the serial manufacturing process. The morphology and optical transmittance of CdS thin films are studied, as well as the CdS/CIGS interface and the solar cell characteristic. We observe that CdS layer deposited on glass is uniform and continuous with optical transmittance above 90% in the wavelengths range corresponding to the energy gap of the absorber. Current density-voltage (J-V) curve shows an overall efficiency of 6% affected by inhomogeneity at the CIGS/CdS interface. Sputtering deposition is not able to create a homogeneous layer on the absorber irregularities due its growth process. Moreover, Auger depth profile shows oxygen contamination at the interface, due to absorber surface oxidation. Within this work, the main crucial aspects of a new solar cell production technology, as well as related solutions, are reported.

Single-step growth of high quality CIGS/CdS heterojunctions using Pulsed Laser Deposition

This work reports on the utilization of pulsed laser deposition (PLD) for the preparation of CdS thin films and CdS/Cu(In,Ga)Se2 heterojunction structures on soda-lime glass (SLG) and Mo-coated SLG substrates, respectively, under various process conditions. Single phase, stoichiometric and high optical quality CdS films are obtained at a fluence of 1.1 J/cm2 and at deposition temperatures of 200–400 °C. The results of this investigation were used to grow CdS on Cu(In,Ga)Se2/Mo/SLG. Both Cu(In,Ga)Se2 and CdS layers have been deposited sequentially using PLD without interrupting the deposition process. The influence of CdS deposition temperature on the properties of CdS/Cu(In,Ga)Se2 heterojunction has been extensively studied and is reported herein for the first time. Low series and high shunt resistances are obtained for the samples where CdS was grown at 200 and 300 °C. The CdS/Cu(In,Ga)Se2 diode grown at CdS deposition temperature of 300 °C exhibits the lowest ideality factor and leakage current, indicating the better quality of the diode. The results of this work demonstrate that high-quality CdS/Cu(In,Ga)Se2 diodes are obtained using pulsed laser deposition in a single-step growth process, eliminating the need for selenization of Cu(In,Ga)Se2 and the use of other growth techniques such as chemical bath deposition for CdS.

Influence of III–V substrates on the texture, structural, and optical properties of CdS thin films deposited by chemical bath deposition

We have studied the influence of texture distribution and crystalline structure of the CdS thin films on their optical properties. CdS samples were grown by chemical epitaxy on III–V substrates. Ga-V materials (c-GaAs and h-GaN) were selected due to the newly renovated interest in CdS/III–V heterostructures and their importance in the development of current optical devices, such as light emitter diodes and solar cells. Texture analysis was realized in pole diagrams obtained in a High-Resolution X-ray diffractometer. Measurements were carried out at 2θ = 26.6° and 2θ = 43.9° because these 2θ angles correspond to diffraction signal for cubic and hexagonal CdS phases, respectively. Pole diagrams show fourfold symmetry in the CdS layers deposited on GaAs (100) substrates and sixfold symmetry in CdS layers deposited on GaN (0002) substrates, which indicates that epitaxial CdS films with both crystal structures is possible by a low-cost technique (Chemical Bath Deposition). The structural study was completed with a surface analysis of the CdS samples by atomic force microscopy; the images obtained showed a greater surface roughness in the CdS layers grown on GaN substrates, this result agrees with the texture distribution observed in pole diagrams. Optical properties of radiative and non-radiative recombination were studied by Raman and photoluminescence (PL) spectroscopies. According to PL results, cubic CdS films have better efficiency in the recombination of radiative bands. In addition, we determined that the CdS–A1LO phonon for the cubic monocrystalline phase is located at 302.35 cm−1, which is 0.84 cm−1 smaller than hexagonal structure.

Interface Formation between CdS and Alkali Postdeposition-Treated Cu(In,Ga)Se2 Thin-Film Solar Cell Absorbers-Key To Understanding the Efficiency Gain.

A combination of X-ray photoelectron/Auger electron spectroscopy and soft X-ray emission spectroscopy has been employed to investigate the impact of different alkali postdeposition treatments (PDTs) on the chemical structure of the (buried) CdS/Cu(In,Ga)Se2 heterojunction: the key interface in chalcopyrite-based thin-film solar cells. Chemical bath deposited (CBD) CdS layers of different thicknesses on NaF PDT (CIGSeNaF) and NaF + KF PDT (CIGSeNaF+KF) Cu(In,Ga)Se2 absorbers prepared at low temperature (to facilitate the use of flexible, e.g., polyimide, substrates) were studied. While we find the CdS/CIGSeNaF interface to be mainly free of significant chemical interaction, in the proximity of the CdS/CIGSeNaF+KF interface, an elemental redistribution involving Cd, In, K, S, and Se is revealed. For the early stages of the CBD-CdS process, our findings are in agreement with the conversion of the K-In-Se-type layer present on the CIGSeNaF+KF surface into a mixed Cd-In-(O,OH,S,Se)-type layer, probably having some Cd-In and (S,O)-Se composition gradients. For long CBD times-independent of employed PDT-we find the buffer material to be best described by a Cd(O,OH,S)-like species rather than by a pure CdS buffer. These findings shed light on the observed performance leap of corresponding CdS/CIGSeNaF+KF-based solar cells.

Impact of RbF-PDT on Cu(In,Ga)Se2 solar cells with CdS and Zn(O,S) buffer layers

Alkali-fluoride post-deposition treatments (PDTs) of Cu(In,Ga)Se2 (CIGS) absorbers have repeatedly resulted in device efficiency improvements, observed mainly due to an open-circuit voltage (Voc) enhancement. Replacement of the CdS buffer layer with a higher band gap alternative can increase the short-circuit current density (Jsc) and also eliminate the use of Cd. In many alternative-buffer attempts, however, the Jsc gain was accompanied by a Voc loss, resulting in some degree of performance loss. In order to better understand the impact of RbF-PDT, we analyze a combination of experimental devices produced in the same in-line CIGS run with and without RbF-PDT in combination with chemical-bath-deposited CdS and Zn(O,S) buffers. Low-temperature current–voltage curves indicate a difference in Rb impact on the CIGS/CdS and CIGS/Zn(O,S) p-n junctions. For example, the diode-current barrier which creates a rollover often observed in RbF-treated CIGS/CdS current–voltage curves is significantly reduced for the CIGS/Zn(O,S) junction. Although the RbF-PDT had a positive impact on both junction partner combinations, the CIGS/Zn(O,S) devices' Voc and fill factor (FF) benefited stronger from the RbF treatment. As a result, in our samples, the Jsc and FF gain balanced the Voc loss, thus reducing the efficiency difference between cells with CdS and Zn(O,S) buffers.

Revealing the relationship between photoelectrochemical performance and interface hole trapping in CuBi2O4 heterojunction photoelectrodes.

p-Type CuBi2O4 is considered a promising metal oxide semiconductor for large-scale, economic solar water splitting due to the optimal band structure and low-cost fabrication. The main challenge in utilizing CuBi2O4 as a photoelectrode for water splitting, is that it must be protected from photo-corrosion in aqueous solutions, an inherent problem for Cu-based metal oxide photoelectrodes. In this work, several buffer layers (CdS, BiVO4, and Ga2O3) were tested between CuBi2O4 and conformal TiO2 as the protection layer. RuOx was used as the co-catalyst for hydrogen evolution. Factors that limit the photoelectrochemical performance of the CuBi2O4/TiO2/RuOx, CuBi2O4/CdS/TiO2/RuOx, CuBi2O4/BiVO4/TiO2/RuOx and CuBi2O4/Ga2O3/TiO2/RuOx heterojunction photoelectrodes were revealed by comparing photocurrents, band offsets, and directed charge transfer measured by modulated surface photovoltage spectroscopy. For CuBi2O4/Ga2O3/TiO2/RuOx photoelectrodes, barriers for charge transfer strongly limited the performance. In CuBi2O4/CdS/TiO2/RuOx, the absence of hole traps resulted in a relatively high photocurrent density and faradaic efficiency for hydrogen evolution despite the presence of pronounced deep defect states at the CuBi2O4/CdS interface. Hole trapping limited the performance moderately in CuBi2O4/BiVO4/TiO2/RuOx and strongly in CuBi2O4/TiO2/RuOx photoelectrodes. For the first time, our results show that hole trapping is a key factor that must be addressed to optimize the performance of CuBi2O4-based heterojunction photoelectrodes.

Comprehensive Analysis of CuIn<sub>1-x</sub>Ga<sub>x</sub>Se<sub>2</sub> Based Solar Cells with Zn<sub>1-y</sub>Mg<sub>y</sub>O Buffer Layer

The development of cadmium-free CIGS solar cells with high conversion efficiency is crucial due to the toxicity of cadmium. Zinc-based buffer layers seem to be the most promising. In this paper, a numerical analysis using SCAPS-1D software was used to explore the Zn(Mg,O) layer as an alternative to the toxic CdS layer. The effect of several properties such as thickness, doping, Mg concentration of the Zn(Mg,O) layer on the current-voltage parameters was explored and their optimal values were proposed. The simulation results reveal that the optimal value of the ZMO layer thickness is approximately 40 nm, the doping at 1017 cm-3 and an Mg composition between 0.15 and 0.2. In addition, the effect of Gallium (Ga) content in the absorber as well as the Zn(Mg,O)/CIGS interface properties on the solar cell’s performance was examined. The results show that contrary to the CdS buffer layer, the best electrical characteristics of the ZMO/CIGS heterojunction are obtained using a Ga-content equal to 0.4 and high interface defect density or unfavorable band alignment may be the causes of poor performances of Zn(Mg,O)/CIGS solar cells in the case of low and high Mg-contents.

The performance study of CdTe/CdS/SnO2 solar cell

In this research, efficiency of cadmium telluride cell has been studied by relationship between efficiency and different parameters such as thickness of different layers in CdTe cell, temperature and doping density of cell layers. The simulation result showed that with increase of thickness of absorbent layer CdTe cell efficiency increases very rapidly, until the thickness of 1.5 µm. By reducing the thickness of CdS (n type) efficiency increases. The simulation result also showed that efficiency does not depend on the front contact layer SnO2. The cell showed high stability with high temperature. The efficiency of cell decreases linearly with increase of temperature. The efficiency is also affected by doping concentration of absorbent layer (NA). Efficiency increases with NA from 1 × 1015 to 1 × 1016 cm−3 by keeping ND of CdS layer fixed at 10−18 cm−3. Similarly by keeping doping concentration of absorbent layer NA = 5 × 1016 cm−3 constant, if doping concentration of CdS layer increases from 1 × 1016 to 1 × 1018 cm−3 efficiency of cell increases. In this study SCAPS 1D simulation software was used to evaluate the performance of cadmium telluride cell.

Photoluminescence-Based Method for Imaging Buffer Layer Thickness in CIGS Solar Cells

Recent improvements in Cu(In,Ga)Se <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> (CIGS) solar cells have made use of thinner CdS layers. The homogeneity of this layer is critical to maintain a high-quality CdS/CIGS heterojunction. We present an imaging method based on photoluminescence (PL) intensity ratios using UV and red excitation. UV light is partially absorbed by the CdS, while it is transparent to red photons. Hence, inhomogeneity in the CdS layer thickness produces different UV excitation of the underneath CIGS layer, while the red excitation is uniform, leading to contrast in the PL image ratio. The method is highly sensitive to detect defects or pinholes in the CdS layer and can be used as a rapid method for CdS deposition quality control.

Modelling of high-efficiency substrate CIGS solar cells with ultra-thin absorber layer

Solar cells based on Cu(In,Ga)Se2 (CIGS) are very promising thin-film solar cells due to their high absorption coefficient and appropriate optical band gap. In this work, a model of substrate thin-film solar cell of structure ZnO:Al/CdS/CIGS/Mo/glass has been established to estimate the cell parameter of ultra-thin absorber layer. The quantitative assessment of the optical losses due to reflection at interfaces and absorption in window layer (ZnO:Al) and buffer layer (CdS) as well as the recombination losses at front and rear surface of CIGS layer has been studied. The optical losses are carried out based on the optical constants of the used materials, and the recombination losses are carried out in terms of the parameters of the absorber layer. The effect of antireflection coating and reflectivity from metal electrode on the short-circuit current density and hence on the cell efficiency has been studied. It has been shown that the optical losses can prevent 30% of the incident photons from reaching the absorber layer at 150 nm thickness for each of the ZnO:Al and CdS layers. The antireflection coating of 100 nm thickness is capable of increasing JSC by 8%. High efficiency of 19.56% has been obtained at 1 µm thickness of CIGS layer under certain parameters of the used materials, and this efficiency can reach 20.22% at 100% reflectivity from the back contact.

Energy level alignment and nanoscale investigation of a-TiO2/Cu-Zn-Sn-S interface for alternative electron transport layer in earth abundant Cu-Zn-Sn-S solar cells

Efficiency of earth abundant and pure sulfide kesterite Cu-Zn-Sn-S (CZTS) solar cell has been stagnant around 9.4% for years, while its counterpart Cu-In-Ga-Se (CIGS) reports an efficiency of more than 22%. Low open circuit voltage (VOC) is the major challenging factor for low efficiency due to severe nonradiative interface recombinations. The existence of higher defect states at the conventional CZTS-CdS interface due to undesirable energy level alignment and lattice misfit promotes trap-assisted recombinations and results in low VOC. In this work, amorphous TiO2 (Eg=3.8eV) is proposed as a promising substitute to the conventional and low bandgap CdS (Eg=2.4eV) layer. The surface and interface of the CZTS-TiO2 layer were investigated using X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). The result reveals favorable “spike”-like conformations at the CZTS-TiO2 interface with a conduction band offset value of 0.17 eV. The nanoscale probing of the interface by Kelvin probe force microscopy across CZTS-TiO2 layers shows a higher potential barrier for interface recombination at CZTS-TiO2 in contrast to the conventional CZTS-CdS interface. Finally, the fast decay response and lower persistent photoconductivity of photogenerated carriers for CZTS-TiO2 heterojunction based photodetectors further validate our results. The energy level alignment and nanoscale interface studies signify TiO2 as a promising alternate buffer layer for earth abundant CZTS solar cells.

Influence of Ga and Ag on the KF Treatment Chemistry for CIGS Solar Cells

The KF postdeposition treatment (KF-PDT) is compared on Cu(In,Ga)Se2 (CIGS) and CuInSe2 (CIS), as well as Ag alloyed CIGS and CIS (ACIGS and ACIS), with the focus on surface chemistry and resulting device performance. Ga does not affect the surface K content; however, X-ray photoelectron spectroscopy shows a preferential reaction of F with Ga, in which CIGS+KF forms GaF3 and CIS+KF forms InF3. KF-treated devices have lower Cu and Ag concentration on the surface, but Cu is reduced more strongly than Ag. Films with Ga show a greater Cu and Ag reduction on the surface than CIS or ACIS. The KF-PDT improves CIS and CIGS device performance and allows for both CIS and CIGS to tolerate reduced CdS thicknesses. In ACIS and ACIGS, device performance decreases with KF, and the open-circuit voltage and fill factor loss is reduced with thinner CdS layers.

Annealing and surface treatment effect on the optical and electrical properties of n-type CdS binary compound semiconductors

The preparation of CdS thin films were actualised with electrodeposition technique using cathodic voltage of 1200 milli – Volts (mV). The optical and electrical properties of three different classes of CdS semiconductors namely as – deposited CdS layers (AD-CdS), CdS layers heat-treated in air without any chemical treatment (HT-CdS) and CdS layers treated with CdCl2 and annealed in air (CC-CdS) have been investigated in this work. Results from optical analysis showed that AD-CdS layers have the least absorption edge and highest energy bandgap. Annealing the CdS thin films without and with CdCl2 treatment brings the energy bandgap to same value of ~2.42 eV. The main distinction between the HT- and CC-CdS layers is that the absorption edge of CC-CdS films is sharper than the HT-CdS. Results from electrical analysis revealed that the magnitude of photo-electro-chemical (PEC) cell signals which give a clue about the doping concentration of the semiconductor material is greater in CC-CdS layers than in AD- and HT-CdS layers.Keywords: AD-CdS, HT-CdS, CC-CdS, Energy Bandgap, Absorption Edge, PEC Cell Signal.