Undoped CdS Research Articles

Regulating the Surface State of Carbon Dots as Ultrahigh-Capacity Adsorbents for Water Treatment.

Adsorption is one of the most widely researched and highly effective methods for mitigating the environmental threat posed by recalcitrant dyes in aqueous solutions. This paper presents a solvent-free synthesis method for the rapid and large-scale production of nitrogen (N) and phosphorus (P) co-doped carbon dots (N, P-CDs) which possess specific surface states and outstanding dye adsorption properties. Compared to the undoped CDs, the N, P-CDs not only exhibit a higher yield of solid-state luminescence but also endow them with the efficient adsorption and removal of Congo red (CR) from water. Due to the synergistic effects of π-π stacking, hydrogen bonding and electrostatic attraction, the N, P-CDs exhibit an ultra-high adsorption capacity (3118.87mgg-1) and a removal efficiency (97.4%, at 500mgL-1) for CR, and also display excellent selective adsorption in both single-dye and dual-dye systems. This method offers a rational strategy for synthesizing novel CDs-based adsorbents for CR, which provides a demonstration for future dye adsorption studies and practical wastewater treatment applications of CDs.

Influence of deposition temperature and fluorine doping on CdS properties: Exploring applications in CdTe solar cells

CdS and CdS:F thin films were synthesized at 75 °C and 90 °C by CBD with NH4F as the fluorine dopant. The structural, morphological, optical, and electrical properties were investigated with varying F wt.%. XRD analysis revealed a coexistence of cubic and hexagonal phases with small crystallite sizes. Raman spectroscopy exhibited characteristic peaks of 1LO and 2LO, corresponding to longitudinal optical phonons. Scanning electron microscopy (SEM) images displayed dense films with excellent substrate adhesion and crystalline morphology. Optical analyses unveiled noticeable alterations in optical transmittance due to F doping, with bandgap values ranging between 2.3 to 2.4 eV. Electrical resistivity, typically in the order of kΩcm, was influenced by incorporating F atoms within the CdS lattice. Notably, the fabrication of CdS/CdTe solar cells yielded efficiencies of 5.53 % for undoped CdS films and 7.47 % when utilizing films doped with 0.00455 wt% fluoride, highlighting the beneficial impact of F incorporation on solar cell performance.

Physical characterizations of Se-doped CdS nanostructures

The investigation thoroughly analyzes undoped and Se-doped CdS nanostructures using multiple techniques. Elemental composition analysis via EDS showed pure Cd and S in the undoped sample, while successful Se incorporation was confirmed in Se-doped samples. XRD revealed distinct CdS phases, with reduced intensity and broadening after Se-doping, indicating lower crystalline quality. The (111) peak shift confirmed Se substitution in the CdS lattice. Williamson-Hall and Monshi-Scherrer analyses demonstrated smaller crystallite sizes and increased lattice strain after Se-doping. FESEM displayed smaller grain sizes after Se-doping. PL analyses showed diminished crystalline quality and reduced intensity. UV–Vis indicated increased absorption and reduced transmission after Se-doping. Bandgap energy declined due to Se-doping and potential CdSe phase formation. Raman spectroscopy confirmed reduced crystalline quality. Se-doping enhances photon absorption, potentially improving optical properties for diverse applications. The study provides a detailed assessment of Se-doped CdS nanostructures, highlighting structural, optical, and morphological changes, valuable for various technological applications.

Improving photovoltaic characteristics of CdS-based hybrid solar cells through Mn incorporation

CdS thin films, both with and without Mn-doping, were grown via chemical bath deposition on indium tin oxide-coated glass substrates for application in hybrid solar cells. X-ray diffraction analysis revealed that Mn doping led to a deterioration in the crystal quality of CdS samples, evidenced by increased microstrain and dislocation density. Mn atoms were interstitially incorporated into the CdS structure, resulting in an expansion of the unit cell volume. Morphological analysis indicated a decrease in grain size from 390 nm to 140 nm for 0 % and 2 % Mn-doped CdS samples, respectively, while maintaining the spherical shape of the CdS thin films. Mn doping also increased the transmittance of CdS thin films, with the highest transparency of 95 % at 580 nm achieved for the 2 % Mn-doped CdS sample. In comparison to undoped CdS (2.38 eV), the band gap of CdS samples initially decreased to 1.84 eV for 1 % Mn doping but significantly increased to 3.03 eV for 2 % Mn-doped CdS. Photoluminescence (PL) data indicated that 2 % Mn-doped CdS thin films exhibited the lowest peak intensity, suggesting that a high concentration of Mn atoms caused non-radiative charge recombination. Additionally, efficient exciton dissociation was observed between CdS:Mn and P3HT:PCBM (poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM)) layers in the 2 % Mn-doped CdS-based device, as per the PL results. Photovoltaic measurements demonstrated that compared to undoped CdS, 2 % Mn doping increased the power conversion efficiency of the CdS-based device from 0.070 % to 0.202 %, indicating an almost threefold increase in hybrid solar cell efficiency. This improvement is likely attributed to the development of a better interface between the CdS:Mn and P3HT:PCBM layers.

Synthesis and characterization of Ag-doped CdS quantum dots for enhanced photovoltaic performance of quantum dot sensitized solar cells

In this work, Ag-doped and undoped CdS quantum dots (QDs) were prepared via successive ionic layer adsorption and reaction (SILAR) technique, followed by their characterization. The synthesized QDs were employed in the devices based on iodide/triiodide (I−/I3−) and polysulfide (Sx2−/S2−) electrolytes, while carbon (C) and platinum (Pt) were used as counter electrodes (CEs). The structural properties of the synthesized QDs were examined using X-ray diffraction (XRD), while to analyze the elemental composition of the samples, energy-dispersive X-ray (EDX) spectroscopy technique was employed. To study absorption properties, UV–Visible spectroscopy was performed. The influence of Ag on passivation of defects in CdS QDs was investigated via photoluminescence spectroscopy. Photovoltaic performance and impedance spectroscopic measurements on the fabricated QDSSCs were made under an AM1.5G illumination and dark, respectively. The photovoltaic studies on the devices revealed an increase of efficiency by 131 %, 161 %, 151 %, and 93 % for Ag–CdS QDs/Iodolyte/Pt, Ag–CdS QDs/Polysulfide/Pt, Ag–CdS QDs/Iodolyte/C, Ag–CdS QDs/Polysulfide/C type devices, respectively. The doped device with a polysulfide electrolyte and C as counter electrode (CE) revealed superior performance, exhibiting an efficiency of 1.72 %, followed by the doped polysulfide-based device with Pt as CE, revealing 1.67 % efficiency. The stability test conducted on the fabricated devices demonstrated a long-term stability for the doped device containing polysulfide electrolyte and C as CE, retaining 80 % of its initial efficiency for 12 days, and then falling to 0 % in 22 days. Moreover, the impedance spectroscopic measurements revealed lowest series resistance (Rs) and Series Capacitance (Cs) for the superior performance device.

Transition Metal Ions Influence the Performance of Photodetector of Two-Dimensional CdS Nanoplatelets.

Transition metal-doped two-dimensional (2D) semiconductor nanoplatelets (NPLs) with atomically precise thickness have attracted much research interest due to their inherent photo-physical properties. In this work, we have synthesized 2D Cu-doped CdS NPLs, investigated the charge transfer dynamics using ultrafast transient absorption spectroscopy, and fabricated an efficient photodetector device. A large Stoke's shifted emission at ~685 nm with an average lifetime of about ~1.45 μs is observed in Cu-doped CdS NPLs. Slower bleach recovery kinetics leads to large charge carrier separation in Cu-doped NPLs which is beneficial for photodetector applications. Cu-doped NPLs-based photodetectors exhibit high photocurrent, fast response (~120 ms), ~600 times higher photoresponsivity, and ~300 times higher detectivity (~4.1×1013 Jones) than undoped CdS NPLs. These excellent properties of Cu-doped CdS NPLs make this material an efficient alternative for next-generation optoelectronic devices.

Hydrothermal Synthesis of Nitrogen and Phosphorus Codoped Carbon Dot Interfacial Modification Layer for Efficient Charge Transfer between ZnO Electron Transport Layer and PTB7:PC70BM Active Layer

The interface between the active layer and the charge-transporting layer is critical for performance improvement in polymer solar cells (PSCs). The use of zinc oxide (ZnO) as an electron transport layer (ETL) in PSCs was limited due to inherent defects in the surface of ZnO prepared by the sol-gel method, mismatched energy bands with the photoactive layer, and incompatibility between the photoactive layer and ZnO ETL. In this study, nitrogen and phosphorus codoped carbon dots (N & P-CDs) were prepared from Ensete ventricosum (false banana) and used as an interfacial modification layer for ZnO ETL. The inverted devices with structures ITO/ZnO/N & P-CD/PTB7:PC70BM/Al were fabricated to investigate the charge transfer dynamic between the active layer and ETL interface modification with N & P-CDs. We have observed that the interfacial modification between the ZnO ETL and the active layer, using N & P-CDs, improves the charge transfer between ZnO ETL and PTB7:PC70BM active layer. The obtained result shows that the ETL/BHJ interface resistance of the devices with ZnO:undoped CDs, ZnO:N-CDs, ZnO:P-CDs, and ZnO:N & P-CD ETLs decreases dramatically from 103.4 to 84.04, 78.16, 37.88, and 28.9 Ω, respectively. This is due to the improvement of charge extraction efficiency by smoothing ZnO surface defects and minimizing the band mismatch between the active layer and ZnO using N & P-CDs. The results indicate that the water-soluble N & P-CDs developed in this study have the potential to be used for efficient free charge carrier extraction for PSCs.

Enhanced anodic electrochemiluminescence due to efficient exchange recombination and its sensing application

To obtain semiconductor nanocrystals (NCs) with strong anodic electrochemiluminescence (ECL) remains a challenge due to their insufficiency to resist following corrosion upon holes injection to the NCs. Herein, we report strong and stable anodic ECL generated from 0.8 at% Mn2+ doped CdS NC films on indium tin oxide (ITO) electrode in the presence of coreactant triethanolamine (TEOA) under potential scan to +1.5 V vs. saturated calomel electrode (SCE), which is much more negative than the valence band potential of host NCs. The Mn2+ doping leads to an 8-fold enhancement in anodic ECL intensity in comparison with undoped CdS NC films due to efficient Mn excitation via nonradiative recombination energy transfer, i.e., exchange recombination. The efficiency is dependent on Mn2+ doping amount as well as applied potential for holes injection with the maximum obtained when the charge transfer to Mn dopants is possible and the energy gap between conduction band and applied potential matches with Mn excitation. This anodic ECL was used to detect dopamine, a model analyte, showing a wide linear range from 5 nM to 1 μM with a detection limit of 1 nM at S/N=3. This work provides a new insight into ECL generation in doped semiconductor NCs. The Mn2+ doped CdS NCs passivated by carboxylic groups display great potential in future development of biosensors.

Studying the impact of Mg doping on the physical properties of CdS nanocrystals for the fabrication of hybrid solar cells–based organic P3HT : PCBM polymers and inorganic Mg‐doped CdS nanocrystals

Herein, the influence of Mg-doped CdS nanocrystals (NCs) on the performance of hybrid solar cells (HSCs) is investigated for the first time. Pristine and Mg-doped CdS NCs at different concentrations (0.25, 0.5, and 0.75 mol%) are synthesized using the heating up method. The effect of Mg on structural, compositional, morphological, optical, and electrical properties of CdS NCs is examined. The structural analysis showed a peak shift toward a higher wavelength, while lattice parameters a and c are decreased. As the Mg concentration increases, the shape and size of the CdS NCs are considerably changed, while the bandgap is tuned from 2.66 to 2.44 eV. Besides, the resistivity of CdS is significantly decreased while carrier concentration increases. Then, the device is fabricated with a configuration of FTO/TiO2/P3HT:PC61BM/MoO3/Ag, wherein the influence of different concentrations of undoped and Mg-doped CdS NCs on the performance of HSCs is explored. The Mg-doped CdS NCs exhibited a power conversion efficiency of 2.92%, 2.5 times higher than the polymer device. Thus, the results revealed that the Mg doping significantly improved the properties of CdS NCs and the performance of HSCs. Henceforth, this work would provide a new path to enhance the power conversion efficiency of the HSCs in a low-cost approach.

Boron and nitrogen co-doped carbon dots as a chemiluminescence probe for sensitive assay of rifampicin

In the present work, the outstanding behavior of boron and nitrogen co-doped carbon dots (B,N-CDs) in a chemiluminescence (CL) reaction was investigated and utilized for the assay of antibiotic drug, rifampicin. A strong amplifying effect was observed for B,N-CDs on the Ce(IV) – SO32- CL system with the enhancement factor reaching up to 800. This effect was compared to that of corresponding single atom-doped and undoped CDs, demonstrating the unique enhancing activity of B,N-CDs. According to the CL spectrum, the emitting species in this system was B,N-CD. Besides, it was found that even nanomolar quantities of rifampicin can remarkably reduce the CL intensity. The possible mechanism of this action was studied by UV–vis and fluorescence spectroscopy. These observations formed a basis for developing a chemosensor for assay of rifampicin in the range of 0.2 to 150 nM with a limit of detection of 0.05 nM. The assessment of selectivity and recoveries confirmed that the CL probe has suitable accuracy and precision for the analysis of biological samples.

Research implementing different dopants (M = Al, Sn, and Eu) on the properties of Schottky diodes with structure TCO/CdS/C and TCO/CdS:M/C

A metal-semiconductor interface is an integral part of numerous electronic devices such as Schottky barrier diodes, photodetectors, photovoltaic detectors, photoelectric converters for UV radiation, among others. On the other hand, semiconductor thin films of cadmium sulfide have been applied to several electronic devices. This study presents the synthesis of semiconductor thin films of pure cadmium sulfide and those doped with Al, Sn, and Eu by a chemical bath deposition technique. XRD, SEM, EDS, XPS, UV-Vis spectroscopy, I-V, and photocurrent measurement analyzed these semiconductor thin films. Afterwards, the doped and undoped CdS thin films were applied to the manufacture of Schottky diodes. The doped CdS thin films reveals differences in the size of the crystallites, which decreased by 5.7%, 11.5%, and 60.1% after doping with aluminum, tin, and europium, respectively. The CdS thin films show morphological differences, decreasing grain size by 5.3% in the case of tin doping and increasing by 21.9% with aluminum and 32.6% after being doped with europium. Additionally, the energy bandgap of the doped CdS thin films show a blue shift, except when doped with Eu, which shows a red shift. This enables the design of window layers by choosing the suitable dopant of CdS. The effect of the CdS doping on the electrical photoresponse of the Schottky diodes was also analyzed. Due to the incorporation of dopants, the photoresponse of the aluminum-doped CdS Schottky diodes improved by 176% compared to its undoped counterpart and by up to 493% with other reports in the literature. The Schottky diodes manufactured in this work show variation in height of the potential barrier, increasing by 6% in the case of aluminum doping and decreasing by 5% and 25% after being doped with europium and tin respectively. These results demonstrated the beneficial impact of dopants on the characteristics of the CdS-based Schottky diodes and elaborated photodiodes, exhibiting an impressive enhancement in their photoresponse, in the potential barrier reached for photosensitivity and in the energy band gap value. Overall, our extensive study reveals that there is great potential in the design of affordable multifunctional optoelectronic devices.

Synthesis, structure, and optical properties of nanopowders CdS: xAl (x=0, 1, 5, 10, 15 and 20%) via the sol–gel technique

The nanocrystalline Al-doped CdS semiconductors were produced accurately by the sol-gel calcination process. The aluminum was added with different percent’s (0, 1, 5, 10, 15, and 20 wt%) to the synthesized CdS. Both FT-Raman analysis and UV–VIS-NIR absorption measurements were utilized to characterize the studied semiconductors' structural and optical characteristics. The detected X-ray diffraction (XRD) patterns of the prepared CdS present a polycrystalline structure, and Al-doping does not significantly impact this range. Optical bandgaps were determined for undoped and Al-doped CdS, showing a significant change with the percentage of Al-dopants. With increasing Al-doping up to (20 percent), the optical bandgap for CdS (2.38 eV) grows to reach (2.47 eV) and the allowed transitions were found to be direct for the investigated samples. The blue shift may be the reason for the optical bandgap variations. Scanning Electron Microscope (SEM) micrographs were performed to establish the Al-doped CdS nanostructure to identify the morphological characteristics.

Structural, Morphology and Optical properties of Ag-doped Nanostructured CdS thin films

Chemical Spray Pyrolysis (CSP) method is employed to deposit CdS and Silver (Ag)-doped CdS films. The effect of Ag doping at 1, and 3 wt-% levels is considered. The principal X-ray diffraction peak was along (020) plane. Maximum grain size was observed at the (CdS:3% Ag) films. The dislocation density parameter increased from 53.04 to 37.08, whereas the strain(%) parameter decreases from 25.23 to 21.10. Atomic force Microscope (AFM) images indicate a polycrystalline structure, and reveal that the undoped CdS and doped CdS:Ag films have discontinuous surfaces with spherically grains decreased from (58.05 to 45.77 nm) with the increase of doping from 0% to 3%. Root-mean square (Rrms) roughness of surface is about (9.81-5.42) nm. Also, there was a clear decrement in transmittance as Ag increment. The optical energy bandgap Eg has been decreased from 2.47 to 2.37 eV due to increase in Ag content. The absorption coefficients with photon energy increase with increasing concentration doping in Ag.

A systematic investigation on structural and optical properties of sol–gel spin coating fabricated CdS nanocrystalline thin films: effect of Ni doping

In the present work, we have successfully fabricated undoped and Ni-doped nanocrystalline CdS thin film on an ultrasonically cleaned glass substrate employing the sol–gel spin coating technique. The structural and spectroscopic properties of the films were investigated using XRD spectra, UV–Vis spectroscopy and photoluminescence spectra, respectively. The X-ray diffraction spectra revealed the polycrystalline nature of films with cubic structure and (111) as preferred orientation. The average crystallite size evaluated by the Debye–Scherrer formula lying in the range of 6–12 nm for the deposited films. According to UV–VIS Spectroscopy, the average transmittance of films in the visible region varies between 70–90%. The optical band gap of CdS thin film was evaluated from absorption spectra. The bandgap of the deposited films is in the range of 2.48–2.70 eV which is higher than that of bulk CdS (2.42 eV). This verifies the blue shifting in band edge of CdS nanocrystalline thin films due to the quantum confinement effect. Photoluminescence spectra of the thin film showed that the fundamental band edge emission peak centred at 485 nm also called blue band emission. It is observed that the low temperature resistivity of the films was in the range of 107–103 Ω cm and also found to decrease with increasing Ni concentration, as a result from dc two probe measurements.

Effects of Heteroatom Doping of Carbon Dots from Sugar on Optical Properties, Phenolic Content, Antioxidant Activity, Photostability, and Cytotoxicity

AbstractCarbon dots (CDs) are fascinating nanomaterials with technologically relevant properties; however, the effects of heteroatom doping on several properties of CDs have not been studied. In this work, a facile method for the synthesis and heteroatom doping of carbon dots from table sugar was developed using nitric acid, phosphoric acid, and sulfuric acid as simultaneous catalysts and dopants. The optical properties, phenolic content, antioxidant activity, photostability, and cytotoxicity of the CDs were measured and compared. L‐ascorbic acid, a well‐known antioxidant, and avobenzone and oxybenzone, common UV absorbers in sunscreens, were used for comparison. Interestingly, heteroatom doping has adverse effects on several properties of the CDs as the undoped CDs yielded the highest UV‐vis absorption, phenolic content, antioxidant activity, photostability, and biocompatibility. Only fluorescence quantum yields were improved by heteroatom doping. These findings will be crucial for choosing precursors for the synthesis of CDs because heteroatoms inherently present in precursors can have negative effects on the properties of the resulting CDs.

Nitrogen-doped carbon dots aid in the separation of ssDNA molecules of different length by capillary transient isotachophoresis (ctITP) with laser-induced fluorescence (LIF) detection

This study demonstrates a novel application of nitrogen-doped carbon dots (NCDs) to enable the separation of different lengths of single-stranded DNA (ssDNA) by eletrokinetic means. Carbon dots have recently found widespread application in the fields of sensing, diagnostics, and healthcare due to their biocompatibility and low toxicity. In light of growing interest in the use of ssDNA aptamers over antibodies in the fields of biosensor development and drug delivery, it is important to establish a simple and effective method for aptamer separation. In this study, we employed NCDs as buffer additives in a capillary electrophoresis (CE)-based method, giving rise to the separation of FAM-labeled ssDNA samples ranging from 32 to 100 bases in length, with resolutions ranging from 1.30 – 1.77. In particular, we adopted a capillary transient isotachophoresis (ctITP) system with laser-induced fluorescence (LIF) detection, with both the separation and sample buffers modified by the addition of 30 μg/mL NCDs. These nanomaterials were prepared by a simple hydrothermal method from a mixture of citric acid and ethylenediamine. The NCDs themselves are highly fluorescent and photostable. As components in the background electrolyte, they did not interfere with the fluorescence emission of the FAM-labeled DNA samples. Under the conditions employed, no separation could be achieved in the absence of the NCDs nor with undoped CDs. The results show that NCDs function as buffer additives capable of enhancing electrokinetic-based separations of ssDNA, and hence, provide a new application for these carbon nanomaterials.

Photocatalytic Activity of Heavy Metal Doped CdS Nanoparticles Synthesized by Using Ocimum sanctum Leaf Extract

Green chemical approaches for the production of nanomaterials are currently attracted to research and industry development to minimize the use of hazardous chemicals and reduce industrial pollution. A green reagent Ocimum sanctum leaf extract was used to synthesize doped and undoped CdS nanoparticles in this work. The as-synthesized nanoparticles were characterized by using different characterization techniques such as UV-Vis spectroscopy, XRD, and TEM. The effect of doping on physicochemical properties was analyzed. Photocatalytic properties of these nanoparticles were investigated by sunlight-based photodegradation studies of methylene blue dye. The doping of these green synthesized CdS nanoparticles with heavy metals has improved photocatalytic efficiency over a given time.

Role of Cu dilute on microstructures, optical, photoluminescence, magnetic and electrical properties of CdS film

Thin films of CdS1-xCux (with 0 ≤ x ≤ 0.10) were deposited using electron beam evaporation. Using XRD, EDX, SEM and UV–Vis–NIR spectroscopy, the impact of [Cu]/[S] on the film properties was examined. The influences of various concentrations of Cu are also elucidated on the optical parameters of the films. The XRD analysis shows that the thin films of CdS1-xCux have been improved and have hexagonal polycrystalline structure with the increase of Cu doping ratio. Additionally, the crystallite size is reduced while the micro-strain ε increases with enhancement of the incorporation of Cu in CdS lattice. The envelope method was used to extract the optical parameters of the undoped and Cu-doped CdS films. With the increase of Cu concentration, the energy optical bandgap decreased, and the variation values of band gap could play an important role in solar cell applications. Another optical parameters such as, dissipation factor and real/imaginary dielectric constant parts were evaluated and demonstrated a strong Cu doping dependence. The shift observed in the photoluminescence spectra emission band confirmed Cu's substitution to CdS lattice. The measurements of magnetization using vibrating sample magnetometer illustrated a hysteresis loop in Cu-doped CdS films, and confirmed the room temperature ferromagnetism. Finally, the Hall effect results show that the pure CdS film corresponds to an n-type semiconductor with a resistivity of 8.11 × 10-2 Ω cm and a carrier concentration of 29.6 × 1019 cm-3, and the CdS:Cu film is a p-type semiconductor and the resistivity is reduced from 6.8 × 10-2 to 3.7 × 10-2 Ωcm, and the carrier concentration is reduced from 26.4 × 1019 to 4.1 × 1019 cm-3, which has potential application prospects in solar cells.

Role of Cobalt Doping in CdS Quantum Dots for Potential Application in Thin Film Optoelectronic Devices

Colloidal quantum dots (QDs) are promising materials for optoelectronic devices. In this paper, monodispersed and environment stable cobalt (Co)-doped CdS QDs have been synthesized and characterized for potential application in thin film optoelectronic devices. The Rietveld refinement profiles of X-ray diffraction data reveal that both undoped and Co-doped CdS QDs exhibit a zinc blende structure without any impurity phase. X-ray photoemission spectroscopy has been used for electronic structure and valence state analysis. The detailed information about the doping, coordination number, and local geometry has been studied with XANES and EXAFS measurements. Analysis of Raman spectra reveals that the intensity of longitudinal optical (LO) modes varies considerably due to short-range structural disorder. Absorption spectra also show the creation of a new doping band (DB) near the NIR region in Co-doped CdS QDs which is not observed for doping of many other transition metals. The width of this DB increases with an increase in the doping concentration, and enhancement of photoconductivity of the thin film heterojunction of the samples has been obtained. Evolution of the new DB and enhancement of the photocurrent upon Co doping make the prepared quantum dots very promising materials to exploit for fabricating UV–vis/NIR thin film optoelectronic devices.

CdS/CdSe HETEROSTRUCTURES GROWN BY CHEMICAL TECHNIQUES ON FLEXIBLE PET/ITO SUBSTRATES

Undoped and Mn-doped CdS films, CdSe films and CdS:Mn/CdSe heterostructures were deposited by chemical techniques. Undoped and Mn-doped CdS films were grown onto flexible PET/ITO substrates by chemical bath deposition at different temperatures. CdSe thin films were synthesized following a two stages process. In the first stage, CdO2 precursor films, were synthesized by chemical bath deposition at different deposition time. In the second stage, the CdO2 precursor films were transformed into CdSe films by immersion in a Se ionic solution. CdS, CdS:Mn, CdSe and CdS/CdSe samples were characterized by high-resolution transmission electron microscopy, UV-vis, Raman and room temperature photoluminescence spectroscopies. The structural characterization indicates that CdS and CdSe films with hexagonal phase were obtained. CdSe films showed the LO Raman mode with three order phonon replicas, an indication of the excellent crystalline quality of the samples.