PbS Thin Films Research Articles

PbS and InAs Quantum-Dot Thin Films for Short-Wave Infrared Detectors

PbS and InAs Quantum-Dot Thin Films for Short-Wave Infrared Detectors

Unusual Defect Chemistry of Thorium Doping of PbS.

The unusual defect chemistry of thorium doping in the PbS system was investigated computationally to answer several open questions arising from the experimental observations. These include finding Th in a +4 oxidation state in contrast to Pb, attracting more than two oxygen atoms on average per thorium and affecting the growth morphology of PbS and its electronic properties. We find Th to be energetically stable at the lead lattice position in PbS and to attract 2-3 oxygens, including in the adjacent interstitial position, which binds strongly to Th. This adjacent interstitial atom allows the +4 oxidation state of Th in PbS as observed experimentally. Furthermore, the bandgap of the ideal material increased due to Th incorporation, in agreement with experimental observations. Finally, we calculated the surface energies of the (100), (110), and (111) surfaces for the systems with and without thorium incorporation. Surfaces (100) and (110) were found to have negative surface energies; however, (111) surface energy was positive and, thus, preferred for the growth of Th-doped PbS thin films. These results correlate well with the experimentally observed surface topography change for PbS thin film growth from the (100) to the (111) surfaces with addition of Th.

Investigation of structural, morphological, optical and electronic properties of Cu-doped PbS thin films: a comparative experimental and theoretical study

Thin film technology has emerged as a cornerstone in optoelectronics, enabling the fabrication of compact, lightweight devices with enhanced performance and efficiency through precise control of the nanoscale thicknesses of functional materials. The current study explores the impact of copper (Cu) doping (3.125%, 6.25%, and 12.5%) on lead (Pb) sites in PbS to examine the structural, morphological, electronic, optical, and thermoelectric characteristics, employing both experimental and theoretical approaches. Polycrystalline thin films of PbS are deposited by spin coating technique on glass substrates. The XRD study discloses the cubic crystal structure of pristine and Cu-doped PbS with nominal variation in d-spacing. Surface morphological investigations reveal that Cu-doping transforms the coffee beans like grains to nanoplates that significantly affect the surface homogeneity and porosity. The tuning of band structure in the visible range, 1.64–2.21 eV is witnessed in the band structure analysis. Moreover, the experimental results are complemented by a theoretical study using WIEN2k software. Theoretical study exhibits the direct bandgap nature and with the incorporation of Cu, it increases from 0.89 to 2.11 eV. The density of states spectra for Cu-doped PbS exhibits strong hybridization between p-states of Pb and S, and d-states of Cu. Optical findings demonstrate significant variations in the absorption spectrum, which result in modifications in the optical energy band gap and peculiar optical parameters of doped samples. At room temperature, the increase in electrical conductivity (σ/τ) from 0.2 × 1020 (Ω.m.s)−1 for PbS to 0.3 × 1020, 3.1 × 1020 and 7.8 × 1020 (Ω.m.s)−1, thermal conductivity from 0.25 × 1014 W m.K.s−1 to 0.30 × 1014, 2.4 × 1014 and 5.2 × 1014 W m.K.s−1 and decrease in Seebeck coefficient from 72 to 35, 13 and 8 μV/K with the inclusion of Cu up to 3.125, 6.25 and 12.5% offer the potential for advancing thermoelectric technology. This could lead to improved efficiency and practical utilization in energy harvesting and waste heat recovery.

Facile synthesis and characterization of PbS thin films doped with various aluminum concentrations for photovoltaic applications

In this study, aluminum doped lead sulfide (PbS:Al) thin films were deposited on soda lime glass substrates using chemical bath deposition (CBD) technique. The structural, morphological, optical and electrical properties of as-deposited PbS thin films were studied as a function of Al concentration (0, 2, 4, 6, 8 at. %). The deposited films can be analyzed using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), x-ray diffraction (XRD), UV-Vis-NIR spectroscopy and Hall measurement. From SEM, it was evident that the thickness of the films decreased from 750 nm (0 at. %) to 280 nm (8 at. %) with increased Al concentration. XRD analysis revealed that the prepared films exhibited face centered cubic structure without any other binary phases. The average crystallite size of the films decreased from 33.71 to 20.45 nm. The direct optical band gap values were increased from 0.90 to 1.29 eV. The optical parameters such as refractive index (n), extinction coefficient (k), real (ɛ 1) and imaginary (ɛ 2) parts of the dielectric constant were 1.51–2.04, 0.0035–0.0075, 2.50–6.20 and 0.005–0.16 respectively. The absorption coefficient (α) of all the deposited films was in the range of ≈105 cm−1. The electrical resistivity of the deposited films was found in the range of 102–103 Ω·cm. The overall analysis indicate that the deposited PbS:Al thin film shows promise as an absorbing layer for heterojunction solar cell devices.

Fabrication of pbs films for air mass filter of solar simulator

The production of solar panels is continuously increasing due to increasing demands at industrial and residential levels. This also leads to an increasing demand for solar simulator testing tools. A solar simulator is a tool to assess a solar panel's performance in lab and industry scales. One of the main components of the solar simulator is the Air Mass Filter (AMF). The primary function of AMF is to remove unwanted wave bands from the solar simulator light source (e.g., Xe arc lamp) so that the filtered spectrum is commensurate to that of solar irradiation. An AMF can be produced by fabricating a thin material layer on a transparent substrate like glass. The film would absorb certain wave bands in different ways. This paper reports the fabrication of the chalcogenide PbS thin films for applying AMF. The thermal evaporation technique is used for the film fabrication. PbS is known for its versatility for applications in different optical devices due to its tailorable optical properties. Different amounts (in grams) of PbS source powders are used to deposit the PbS thin films. The optical properties of the films are then examined using UV-Vis spectroscopy. The distributions of the transmittance intensity of the Xe-arc-lamp light with and without the use of the films as an optical filter are then examined using a solar simulator. From the experiments, the film deposited using a 0.012 g PbS powder source is regarded as the optimum one regarding the transmittance intensity distribution.

Influence of the DEA Concentration on Structural and Optical Properties of Nanodot PbS Thin Films Growth by Chemical Solution Deposition: Unveiling Dual Optical Absorption Edges

The present paper presents a straightforward method for producing thin film layers of sulfide quantum dots (PbS-QDs) on a glass substrate using chemical solution deposition (CSD) assisted by dipcoating technique. The deposited PbS-QDs films were subjected to a comprehensive analysis using atomic force microscopy (AFM), energy dispersive X-ray (EDX) scanning electron microscopy (SEM), X-ray diffraction (XRD), UV–vis–IR absorption, and photoluminescence spectroscopic (PL) techniques to investigate the effects of varying concentrations of diethanol amine (DEA) on their morphology, crystal structure, elemental composition, light absorption, and emission characteristics. The spherical shape of the PbS-QDs was confirmed by AFM and SEM images with average sizes around 100 and 50 nm, respectively. The energy dispersive X-ray (EDX) analysis provides evidence the existence of Pb and S elements within the PbS matrix. X-ray diffraction (XRD) results validate that the deposited films exhibit high crystallinity, with a preferential orientation along the (111) plane and a face-centered cubic lattice structure of PbS. The crystallite size of PbS is measured to be 46.6 nm. Based on the optical absorption measurements, we have determined the size range of PbS nanocrystals to be between 4.3 and 11.5 nm. The optical studies reveal the presence of two optical absorption edges within the visible and infrared spectrum, two direct band gap energy, two cut-off wavelengths, two confinement energy, two Urbach energy tail, and dual emission peaks of PbS-QDs at room temperature. The analysis reveals the presence of two distinct band gap energies, one in the visible range (1.3–2.28 eV) and the other in the infrared range (0.65–0.88 eV), which can be attributed to the formation of two distinct sizes of quantum dots situated in two different layers. The first layer, deposited directly on the glass substrate, comprises quantum dots with an average size of approximately 5.2 nm, while the second layer contains quantum dots with an average size of about 9.5 nm. This ability to tune the band gap of PbS in the visible range up to the IR band (0.65–2.28 eV) is a critical feature that holds the potential for the development of innovative optoelectronic devices.

Effect of oxide layer state on the photoelectric properties of thermally sensitized PbS thin films

Lead sulfide (PbS) thin films were initially deposited through chemical bath deposition, followed by sensitization in a pure oxygen atmosphere at 600 °C. To investigate the influence of varying oxide layer states on the photoelectric properties of thermally sensitized PbS thin films, the surface oxide layer of the sensitized films was selectively removed using KOH etching. As the etching duration increased, a gradual decrease in surface oxygen content was observed, accompanied by an initial increase and subsequent decrease in detectivity. Notably, the optimum detectivity value (6.92 × 109 cm Hz1/2 W−1) was achieved after 10 s of KOH etching. Our investigation was further supplemented with field emission scanning electron microscopy and X-ray diffraction analyses to gain insights into the impact of the oxide layer state on the photoelectric properties of PbS thin films. Our findings led to the proposal of a dual conduction mechanism for carrier transport within PbS film. In the case of as-grown PbS films, carrier transport primarily occurs via crystal boundary transition. However, after oxygen sensitization, the formation of an oxygen-rich carrier channel at the crystal boundary shifts carrier transport dominance towards crystal boundary transport. The combined influence of both transmission mechanisms serves as a primary driver for the observed changes in the photoelectric properties of PbS films.

Solvation Shifts the Band-Edge Position of Colloidal Quantum Dots by Nearly 1 eV.

The optoelectronic properties of colloidal quantum dots (cQDs) depend critically on the absolute energy of the conduction and valence band edges. It is well known these band-edge energies are sensitive to the ligands on the cQD surface, but it is much less clear how they depend on other experimental conditions, like solvation. Here, we experimentally determine the band-edge positions of thin films of PbS and ZnO cQDs via spectroelectrochemical measurements. To achieve this, we first carefully evaluate and optimize the electrochemical injection of electrons and holes into PbS cQDs. This results in electrochemically fully reversible electron injection with >8 electrons per PbS cQDs, allowing the quantitative determination of the conduction band energy for PbS cQDs with various diameters and surface compositions. Surprisingly, we find that the band-edge energies shift by nearly 1 eV in the presence of different solvents, a result that also holds true for ZnO cQDs. We argue that complexation and partial charge transfer between solvent and surface ions are responsible for this large effect of the solvent on the band-edge energy. The trend in the energy shift matches the results of density functional theory (DFT) calculations in explicit solvents and scales with the energy of complexation between surface cations and solvents. As a first approximation, the solvent Lewis basicity can be used as a good descriptor to predict the shift of the conduction and valence band edges of solvated cQDs.

Preparation and Study of Structural and Optical Properties of PbS:Cu Nanostructured Thin Films

Thin films of lead sulfide (PbS) and various Cu mixing ratios (30%, 50%, and 70%) are used in this work. were made using the (PLD) method on glass substrates at a wavelength of 1064 nm and 600 mj of laser energy. X-ray diffraction experiments were used to determine the structural measurements for pure PbS, and other mixes present thin films demonstrated a face-centered-cubic structure. and discovered that the average grain size was 17.74 nm; this grew to 20.54 nm after combining with 30% Cd, 20.54 nm after mixing with 50% Cd, and 23.15 nm after mixing with 70% Cd. The optical characteristics of PbS thin films measured between 300 and 1100 nm in wavelength. For PbS thin films, the optical transmittance and transparency decrease as the o mixing ratio increases.The absorption coefficient rises as the mixing ratio does. When the mixing ratio is increased, the band gap for pure PbS thin film is 2.43, rises to 3.03, and thereafter falls to 2.01 and 1.5.

Synthesis and characterization of Mo-doped PbS thin films for enhancing the photocatalytic hydrogen production

Photocatalytic hydrogen production has gained considerable attention as a sustainable method for renewable energy production. Lead sulfide (PbS) compound has significant reserves and a suitable bandgap for the production of hydrogen gas via the water photo-splitting process. However, the charge recombination effect of the charge carriers severely limits their potential use in solar water splitting. Herein, the photoelectrodes of PbS were fabricated through the chemical bath deposition method and then doped with different Mo concentrations to optimize the hydrogen photo-production activity. Both structural and performance characterizations of the photoelectrodes have been carried out using various characterization techniques. The photoelectrochemical (PEC) performance of molybdenum (Mo)-doped PbS photoelectrodes exhibits a significant increase in the photocurrent density with the optimum photocurrent density of 1.2 mA/cm2 obtained at 0.8 % Mo doping atomic ratio which was twelve times higher than that of a pure PbS photoelectrode. The doping of Mo induces the electron-hole separation yield which results in improved electron transport characteristics. The Mo doping was as act as a donor site that increased the PbS film conductivity. The newly optimized Mo–PbS was used as a promising photoelectrode supported on commercial glass using the optimum Mo-doped PbS photoelectrode, the photoelectrochemical (PEC) hydrogen production rate was reached 122 μmol/h cm2 during the solar water splitting process and the conversion efficiency of the incident photon-to-current (IPCE) value was 7.0 % at 390 nm monochromatic exposure. Moreover, the stability of the optimum electrode was evaluated as a function of the number of runs and exposure time in addition to the electrochemical impedance study.

Nanostructured p-PbS/p-CuO sulfide/oxide bilayer heterojunction as a promising photoelectrode for hydrogen gas generation

Abstract Recently, the photoelectrochemical (PEC) water-splitting reaction for hydrogen (H2) production has been a competitive research route to realize clean and sustainable electric power. In this work, copper oxide (CuO) and PbS thin films were fabricated on commercial glass, respectively, using the techniques of successive ionic-layer adsorption and reaction and chemical bath deposition. These nanostructured thin films served successfully as photoelectrodes for the photogeneration of H2. In addition, a p-PbS/p-CuO bilayer system was also fabricated, and a remarkable boost in PEC efficiency was observed compared to pure CuO and PbS thin films. Optical examinations showed excellent absorbance properties of the p-PbS/p-CuO bilayer in the visible range, with a bandgap of ∼1.28 eV. X-ray diffraction analysis indicated a monoclinic CuO/cubic PbS crystalline structure with a particle size of ∼18 nm. The photocurrent density (J ph) values were obtained using a three-electrode electrochemical cell in 0.3 M Na2S2O3 electrolyte. The p-PbS/p-CuO photoelectrode demonstrated a J ph value of −0.390 mA cm−2, which is significantly higher than the values of −0.120 and −0.008 mA cm−2 for the pure PbS and CuO photoelectrodes, respectively. This improvement is attributed to the p-PbS/p-CuO oxide/sulfide bilayer heterojunction, which improved the visible light absorption and reduced the electron–hole (e–h) recombination. The effects of pH value, temperature light intensity, and wavelength were all additionally studied. Remarkably, the photoelectrodes were stable under a pH of ∼7, which makes them promising for H2 production using normal drinking/seawater. These findings confirm the ability of the prepared photoelectrodes to facilitate water splitting and H2 generation under various environmental, chemical, and illumination conditions.

Optical and photoconductivity properties of Mn doped nanocrystalline PbS thin films deposited by chemical bath deposition method

Mn doped nanocrystalline PbS thin films were deposited onto glass substrates by chemical bath deposition (CBD) method. All the deposited thin films were found to be crystalline having cubic phase structure. The optical properties of the Mn doped nanocrystalline PbS thin films have been studied. They have high absorbance in the UV-visible region. The linear nature of (αhν)2 vs (hν) plots of PbS thin films confirmed that the transition is direct and the optical band gap energy of PbS films is found to increase from 1.90 eV to 2.28 eV with decreasing crystallite size from 21 nm to 11 nm and the optical band gap values are higher than the bulk value (0.40 eV). The optical band gap of Mn doped PbS films are found to increase with increase in dopant concentrations. The Photoconductive rise time and decay time determined from the prepared films are found to decrease with increase in doping concentrations.

Studies on Lead Sulphide (PbS) Thin Film Prepared by Chemical Bath Deposition Method

Lead Sulphide, PbS thin films deposited on glass substrates by a chemical bath deposition method, which is a simple and easily controlled technique. The reactive substances used to obtain the PbS layers were (Pb(NO3)2), NaOH, Sc(NH2)2 and H2O for different dipping concentrations of lead nitrate, dipping times and temperatures. The films were structurally characterized by X-ray diffraction studies. The films are very adherent to the substrate and well crystallized according to the face centered cubic structure with the preferred orientation (1 1 1). The films were optically characterized by the transmission and reflectance spectrum, examined by a UV – VIS Spectrophotometer. In the infrared range, low transmittance and reflectance are detected (between 10% and 30%), while there is no transmittance or reflectance in the UV and visible regions. It can be seen from absorption spectra that absorption is stronger in the UV and UV-VIS region and gradually diminishes. Maximum absorption is observed in the visible and ultraviolet range, which indicates that the film prepared is of nanocrystalline. The band gap of PbS can be varied in the range of 0.41 to 2.71 eV, which is a significant material feature and opens the door to a new class of applications. The calculated band gap was determined to be between 1.88eV and 2.1eV.

Carbon Nanodots as Complexing Agent in the Formation of Lead(II) Sulfide Thin Films via Direct Deposition of Lead(II) Sulfide Powder

This study reveals for the first time the formation of lead(II) sulfide (PbS) thin films via direct deposition of PbS powder using carbon nanodots (Cdots) as a complexing agent. The chemical bath deposition (CBD) technique was utilized and the Cdots’ mass was varied, i.e., (in g) 3, 5, 7, and 9. The Cdots were prepared from the waste of a rice noodle production home industry via the low-temperature carbonization method. The Cdots were characterized using UV-Vis spectrophotometry, showing absorption peaks at 275 nm and 325 nm; PL, showing an emission peak at 500 nm with cyan luminescence; XRD, showing several peaks, indicating an incomplete carbonization process; FTIR, indicating the existence of C=C, C-H, C-O, and O-H functional groups; HRTEM, revealing the sizes of the Cdots in the range of 2 nm to 6 nm; and SEM, showing a smooth morphology of the Cdots’ surface. The thin films obtained were smooth with higher XRD peaks and better material distribution compared to pure PbS thin film. The band gap measurement indicated that the increase of the PbS band gap was caused by the increase of the Cdots’ mass. Hence, the thin films’ band gap may be tuned using the Cdots’ mass.

Fabrication of crack-free PbS thin films by Jet nebulizer spray pyrolysis technique for enhancing optoelectronic applications: An effect of Ce3+ doping concentrations

The current study describes the fabrication of 0, 1, 3, and 5% Ce- doped PbS thin films by Jet nebulizer spray pyrolysis technique (JNSP) for photo-sensing application. XRD spectra revealed the cubic structure of Ce-doped PbS thin films. The crystallite size of PbS decreased with increasing the Ce doping concentration, suggesting the inclusion of the Ce atom into the PbS crystal lattice. FESEM results revealed that the samples had triangle-shaped nanostructured PbS thin films and that Ce doping could change the morphology into an aggregated pattern. The XPS spectra confirmed the presence of Pb, S, and Ce. The optical absorbance of PbS thin films significantly improved with Ce doping. The red shift in the absorption spectrum indicated a decrement in the bandgap value of PbS after adding Ce. Finally, the photo-sensing experiments show that 5% Ce-doped PbS thin films had the highest Ps (2895.21%), R (208.33 mA/W), and D*(3.379 × 1010 Jones) than all other fabricated devices, suggesting that the Ce-doped PbS thin films may be promising photodiode for commercial optoelectronic devices application.

Improved optoelectronic, electrochemical and nonlinear optical properties of PbS thin films doped with Sr2+ ions

Strontium (Sr) doped lead sulfide (PbS) thin films have been deposited via spray pyrolysis for use in electrochemical and nonlinear optical applications. All films show the PbS fcc lattice. EDS spectra confirmed Sr in doped films. Doping PbS with Sr increases transparency and lowers the band gap from 1.99 to 1.87 eV. Lead sulfide heteropolar diatomic molecules produce FTIR peaks at 1446, 1384, and 993 cm−1. Adding Sr to PbS increased its nonlinear refractive index. The enhanced nonlinear absorption ability with Sr doping was corroborated by their wider valley range. Thin films of PbS:Sr exhibit reverse saturable absorption (RSA). Electrochemical impedance spectroscopy (EIS) studies indicated that PbS's charge transfer resistance (Rct) increased with Sr doping. The higher specific capacitance and lower Rct values realized for the 4 wt% Sr-doped sample confirmed its suitability for supercapacitor applications.

Improved Haacke's quality factor, third order nonlinear susceptibility and specific capacitance realized for PbS thin films through La3+ doping

The present study examines the third order NLO and electrochemical properties of spray deposited lanthanum doped PbS (PbS:La) thin films. FCC crystallization was confirmed by XRD patterns along the plane (2 0 0). PbS crystallites vary in size between 27 and 36 nm with La doping concentration. Surface morphology improved with La doping. La doping increases the band gap from 1.97 to 2.18 eV. Near band edge (NBE) emissions in PL spectra originates from electron-hole recombination. A low resistivity of 0.23 x10−3 Ω-m was realized for PbS film doped with 4 wt% La concentration. Figure of merit of pure PbS improves from 1.32 x 10−3 Ω−1 to 1.607 x 10−2 Ω−1 with La doping. La doping modifies the energy states and band gap of PbS favouring strong nonlinear optical absorption. PbS:La thin films demonstrate self-defocusing due to temperature effects caused by absorption of single photons or free carriers. As a result of the low cationic field strength and high polarizability of La3+ ions, PbS exhibits a higher nonlinear refractive index. The nonlinear susceptibility and refractive index were found to be in the range 3.23–5.33 x 10−6 esu and 2.74 to 3.64 x 10−9 cm2/W, respectively. From the electrochemical studies, increased specific capacitance (256.46 F/g) and decreased charge transfer resistance (12 x 103 Ω) was observed for the 4 wt% La doped film.

Nanocrystalline PbS thin film produced by alkaline chemical bath deposition: effect of inhibitor levels and temperature on the physicochemical properties

Abstract In this study, nanocrystalline PbS film coating on a glass slide was done using the chemical bath deposition method. PbS film was deposited in an alkaline solution using Pb(NO3)2, CS(NH2)2, and the inhibitor (Na2S2O3) for 30–120 min at room temperature (25 °C) and 40 °C, and inhibitor levels were investigated in the range of 3.2 mM–12.7 mM. The physicochemical properties of the obtained thin films were investigated by scanning electron microscopy, MAPPING, atomic force microscopy, fourier-transform infrared spectroscopy, water contact angle and X-ray diffraction analyses. The relationship between nanocrystallite size, distribution, pin-hole development, and synthesis conditions were examined using image processing and surface response methodology. The band gap of the produced PbS thin film was calculated using FT-IR analysis results (0.41 eV).

A Combinatorial Approach for the Solution Deposition of Thin Films

Optimization of thin film deposition is often the limiting step in the discovery of new materials and device development. Over the years, high-throughput combinatorial methods were developed for the deposition of thin films from the gas phase. However, very few reports focused on combinatorial thin film deposition from solution. Here, we introduce a combinatorial approach for the deposition of thin films from solution. The flow deposition setup allows for simultaneously studying the effect of two critical parameters, deposition time and deposition temperature, on a single sample. As a proof of concept, we demonstrate the solution deposition of PbS thin films, which resulted in a library of 25 deposition condition combinations on a single GaAs (100) substrate. X-ray diffraction and scanning electron microscopy combined with focused ion beam cross-sectional sample preparation confirmed the formation of high-quality PbS films and showed the morphology evolution as a function of these two deposition parameters. This method can be easily adapted for cost-effective and rapid combinatorial studies of a large variety of solution-deposited thin film materials.

Enhancement of optoelectronic properties of PbS thin films grown by Jet nebulizer spray pyrolysis technique for photodetector applications: an impact of substrate temperature

Enhancement of optoelectronic properties of PbS thin films grown by Jet nebulizer spray pyrolysis technique for photodetector applications: an impact of substrate temperature