PbS Thin Films Research Articles

Cd2+doped PbS thin films for photovoltaic applications: Novel low-cost perspective

In the present study, we have investigated the effect of Cd2+ nominal content (xsolution = [Cd2+]/[Pb2+] = 0.5at%, 1at%, 1.5at% and 2at%) on PbS thin films grown on ordinary glass substrates using the chemical bath deposition (CBD) technique. The effect of Cd2+ content on structural, morphological, optical and electrical properties of PbS thin films was studied. X-ray diffraction (XRD) and scanning electron microscopy (SEM) showed that Cd2+ doped PbS thin films have good polycrystalline nature with cubic structure. It was found that the chemical bath deposition made (xsolution = 1at%) Cd2+ doped PbS has an excellent optical and electrical characteristics, which shows its applicability in p–n junction solar cells in combination with indium oxide (In2O3) thin films. Being illuminated under 100mW/cm2 sunlight, from the current–voltage characteristic of the FTO/In2O3(n)/Cd:PbS(p)/Al device the photovoltaic parameters were extracted: Open circuit voltage (Voc=635mV), short circuit current density (Jsc=12.36mA/cm2), fill factor (FF=0.32), and conversion efficiency (η=2.5%).

Influence of Li+ doping on the optical properties of PbS

We investigate the influence of Li+ in the optical properties of PbS thin films. PbS and PbS:Li doped films were prepared by chemical bath deposition. Optical studies using the first derivative absorption spectra reveals the multiple exciton generation process associated to the excitonic transitions. The refractive index (n), extinction coefficient (k), and dielectric parameters (ε1 and ε2) were obtained. The analysis of current-temperature measurement in the 12–320 K range shows that the activation energy exhibits lower values with increasing Li+ concentration. The mechanism of current conduction in the films is discussed.

Optical, electrical, and photovoltaic properties of PbS thin films by anionic and cationic dopants

Lead sulfide (PbS) thin films were deposited by CVD method to examine the effects of anionic and cationic dopants on optical and electrical properties for photovoltaic applications. XRD diffractograms verified the formation of cubic phase of multicrystalline PbS thin films. FESEM images showed surface morphologies in nano-dimensions (rods and flowers). UV–Vis–NIR spectrum revealed absorbance in the visible and NIR regions for all samples, in which dopants decreased the intensity of absorbance. Se as an anionic dopant for PbS thin films increased electrical resistance, acceptor concentrations, and crystallite defects, and decreased flat-band voltage and depletion width. Finally, photovoltaic measurements indicated that Zn-doped PbS thin film, as a photovoltaic cell, exhibited higher conversion efficiency and external quantum efficiency (EQE).

A Study on Fabrication and Structural Characterization of PbS Thin Films

PbS thin films are fabricated from 99.9% PbS powder on glass substrates using the vacuum evaporation method. Some of the samples are then treated in an advanced process called annealing. Samples are annealed in temperatures of 80, 100, 120 and 150°C for two h. Characterization using an X-Ray Diffractometer (XRD) resulted in values of lattice constant of the films ranging from (5.782±0,010) A to (5.919±0,006) A. These values are quite different from the standard, probably because the films are stressed and strained. The grains have sizes ranging from (266.440±0.001) A to (694.059±0.002) A, where the greatest grain size was found as deposited thin film because it was directly condensed from powder vapor during the deposition process and after they are annealed, the grain size becomes smaller. The average internal stress has values ranging from (0.36±0,006) × 109 N/m2 to (3.247±0.010) ×109 N/m2 and microstrain ranging from (2,864±0.006) × 10-3 to (25.94±0,01) ×10-3. It was found that the film which has the greatest stress and microstrain is the film with the annealing temperature of 150°C, showing that the annealing process exerts force on the film following the rising of temperature. Use of a Scanning Electron Microscope (SEM) shows the surface pictures of the deposited thin film and the film annealed at 120°C. Furthermore, the thickness of the samples is obtained by using the cross section of the films and showed that the thickness of the deposited thin film is between 0.63 and 1.30 microns and the thickness of the film annealed at 120°C is between 3.37 and 4.34 microns. The best quality thin film from this research is that annealed at 120°C, because it showed more peaks than the other samples. It can be concluded that the annealing process had effects on the structures, grain size, strain and stress of the crystals.

Narrow Band Gap Ternary Absorber Layer for Solar Cell for Small Business Enterprises in Equatorial Africa

According to recent studies, on the Daily nation newspaper, in Kenya of 6 th January 2017 featured the story, the number of people doing the same thing in surrounding villages was so high that many of them had to leave their phones behind at the charging centre (for up to three days) before returning to pick them. To fight darkness, up to 80 percent of Africans depend on personal generators, candles and kerosene (paraffin) lamps to provide basic lighting. Let’s not even talk about all the other things we desperately need electricity for – iron clothes, pump water, charge mobile phones etc. In this article, we shall focus on the types of solar cell materials that can be used to fabricate solar cell to be installed on roof tops to generate electricity used by individuals and households. Photovoltaic devices are used to convert solar radiation energy into electrical forms of energy for various uses. Current research is geared towards using thin films with wide band gaps to allow optimum penetration of radiation within the VIS - NIR region. Inorganic wide band gap, Cd x Zn 1- x S thin films and narrow band gap, PbS thin films were optimized through chemical solution technique in this study. Wide band gap thin films of Cd x Zn 1- x S were grown at about 82 0 C while those of narrow band gap thin films of PbS were grown at room temperature utilizing aqueous conditions. Their optical constants were investigated and found to be suitable for solar cells applications.

Optical and magnetic properties of PbS thin films doped with Fe2+ ions

PbS and Fe-doped PbS thin films were deposited on glass substrates by spray technique using perfume atomizer. Fe concentration is varied as 0, 1, 2, 3 and 4wt.% and the effect of Fe doping concentration on the structural, morphological, optical, photoluminescence and magnetic properties of the PbS thin films are studied and the results obtained are discussed in this paper. Structural studies show that all the films have face-centered cubic crystal structure with a strong (2 0 0) preferential orientation. Crystallite size estimated from the Scherrer formula decreased from 55.73nm to 31.97nm with Fe doping. Elemental analysis confirmed that the undoped and doped PbS thin films are deficient with sulfur and the presence of emission peak at 485nm in the photoluminescence spectra strongly supports this. Optical band gap is blue shifted with Fe doping. Improved magnetic properties were observed for the doped PbS thin films. The obtained results infer that Fe2+ ions strongly enhanced the optical and magnetic properties of pure PbS thin films.

Structural and Optical Properties of PbS Thin Films Deposited by Pulsed Laser Deposited (PLD) Technique at Different Annealing Temperature

Lead sulphide (PbS) thin films has attracted interest due to its potential applications in optoelectronics devices, gas sensors, solar cell technology and transparent conducting electrodes. Thin films were grown on glass substrates by pulsed laser deposition (PLD) technique at room temperature and different annealing temperatures (573, 673 and 773) K. The structural measurements for PbS thin film show face-centered-cubic structure. Atomic force microscopy (AFM) was used to examine PbS surface. The films exhibit more homogeneity. The root mean square(r.m.s), surface roughness and average grain size were increased After annealing. The optical properties of PbS thin films are studied as a function to wavelength in region (375 - 1100) nm. The optical transmittance of PbS thin films shown that the transparency decreases with increase of annealing temperature. The direct energy gap for PbS thin film was decreases with increasing of annealing temperature for all sample due to the growth of the crystallites. The optical constants such as refractive index, extinction coefficient and dielectric constant were also calculated.

Narrow Band Gap Ternary Absorber Layer for Solar Cell for Small Business Enterprises in Equatorial Africa

According to recent studies, on the Daily nation newspaper, in Kenya of 6th January 2017 featured the story, the number of people doing the same thing in surrounding villages was so high that many of them had to leave their phones behind at the charging centre (for up to three days) before returning to pick them. To fight darkness, up to 80 percent of Africans depend on personal generators, candles and kerosene (paraffin) lamps to provide basic lighting. Let’s not even talk about all the other things we desperately need electricity for – iron clothes, pump water, charge mobile phones etc. In this article, we shall focus on the types of solar cell materials that can be used to fabricate solar cell to be installed on roof tops to generate electricity used by individuals and households. Photovoltaic devices are used to convert solar radiation energy into electrical forms of energy for various uses. Current research is geared towards using thin films with wide band gaps to allow optimum penetration of radiation within the VIS - NIR region. Inorganic wide band gap, CdxZn1-xS thin films and narrow band gap, PbS thin films were optimized through chemical solution technique in this study. Wide band gap thin films of CdxZn1-xS were grown at about 82°C while those of narrow band gap thin films of PbS were grown at room temperature utilizing aqueous conditions. Their optical constants were investigated and found to be suitable for solar cells applications.

Remarkable change of structural, optical, photoluminescence and electrical properties of chemically prepared nanocrystalline films of PbS with concentration of triethanolamine (TEA)

Although triethanolamine (TEA) is widely used as complexing agent in the preparation of nanocrystalline PbS thin film by chemical bath deposition method, not enough studies have been reported on how its concentration affects various properties of the films. In the present work, we studied the effect of concentration of TEA on structural, morphological, optical, photoluminescence and electrical conduction properties of the films. We observed that with the increase of molar concentration of TEA—the crystallinity deteriorates with reduced crystallite size and increased strain and dislocation density; the densities of the films have been reduced; the films become non stoichiometric; optically these become more transparent but less reflecting showing prominent blue shift in the optical band gap which increased with the concentration of TEA; the width of the localized states in the band gap has been increased. The refractive index and extinction coefficient of the films are observed to be wavelength dispersive. The refractive index decreases with the increase of TEA complexation. In the NIR region, the extinction coefficient also decreases as concentration of TEA increases. The real and imaginary parts of dielectric constant replicates the refractive index and extinction coefficient curves respectively against wavelength. The PL spectra reveal conduction band to valence band transition with reduced intensity at higher molarity of TEA. The current–voltage measurement shows that the conductivity decreases considerably with the increase of TEA concentration. Our measurement estimated the crystallite size in the range of 29–37.49 nm, strain ~10−3, dislocation density ~1011 cm−2, band gap 0.8–1.55 eV, bandtail width 0.27–0.57 eV, the refractive index 2.3–5.8 and conductivity 0.0011–0.20 (Ωcm)−1.

Photoelectrochemical performance of surfactant (polyvinyl alcohol) assisted PbS thin films grown by chemical route

Polyvinyl alcohol is used as a surfactant in the chemical bath deposition of PbS thin films, which causes compact, pinhole free and uniform PbS thin films. Influence of deposition time on the structural, optical, morphological, compositional, electro-chemical and photo-electrochemical (PEC) properties of the PbS thin films are studied. The charge transfer resistance is analysed using electrochemical impedance spectroscopy. The best PEC device fabricated using optimized deposition time (3 h) showed short circuit current density (Jsc) of 1.68 mA. After annealing the optimised P63 sample at 75 °C for 1.5 h the composition changed from Pb rich to near stoichiometric. For typical PA sample Jsc improves to 2.13 mA and photo conversion efficiency advances from 0.045 to 0.072%.

Synthesis and Characterization of Chemically Deposited Nanocrystalline PbS Thin Film

Synthesis and Characterization of Chemically Deposited Nanocrystalline PbS Thin Film

Optical and structural properties of PbSIn3 + nanocrystals grown by chemical bath

Herein, the growth of PbS doped systematically with solutions containing In3+ ions by using chemical bath as a green approach is reported, with the aim of studying the effects of such In3+-doping on the morphological, structural and some optical properties of the PbS thin films obtained. The morphological changes of the films were followed by Atomic Force Microscopy and Scanning Electron Microscopy. X-ray diffraction studies showed growth in all films of the zinc blende phase. The grain size was found to be ~32nm and ~24–14nm for the undoped and doped samples, respectively. The absorbance results in doped films showed excitonic peaks at ~1.6eV, ~1.8eV, ~2.2eV, owing to higher energy transitions from 1Dh→1De, 2Sh→2Sh and 2Ph→2Pe, states, respectively. By optical absorption, a shift for the band gap energy was observed from ~1.45eV to ~2.18–2.3eV range for the undoped and doped films, respectively. Gibbs energy calculation for the In3+ doping PbS process was also examined.

Control of morphology and optical properties of PbS nanostructured thin films by deposition parameters: study of mechanism

ABSTRACTPbS thin films were grown on glass substrates by chemical bath deposition (CBD) using lead nitrate, thiourea and sodium hydroxide in aqueous solutions at three different temperatures (22, 36 and 50 °C). The microstructure and morphology evolution of the films were investigated using X-ray diffraction, scanning electron microscopy and atomic force microscopy. Optical properties were studied using UV–Vis–IR spectroscopy. The results indicate that temperature plays an important role in controlling the morphology and optical properties of nanostructured PbS thin films through changing deposition mechanism. The active deposition mechanism changed from cluster to ion-by-ion mechanism with an increase in deposition temperature from 22 to 50 °C, and consequently, film properties such as morphology, optical absorption and preferred orientation changed completely.

Fabrication and characterization of Sr-doped PbS thin films grown by CBD

In this work, undoped and Strontium-doped lead sulfide (PbS) thin films were deposited on glass substrates by chemical bath deposition (CBD) technique. The effect of Sr doping concentration on the structural, morphological and optical properties of the PbS thin films was studied. Changing in crystallite size, microstrain, dislocation density and band gap energy values of the PbS thin films as a function of Sr concentration were investigated by scanning electron microscopy (SEM), X-Ray diffraction (XRD) and UV–visible spectroscopy measurements. Energy dispersive X-Ray analysis (EDS) results indicated that nanostructured PbS films is doped with Sr without causing much lattice strain. According to XRD experiments crystallite size of the films is decreasing from 17.90 to 9.14nm with increasing Sr-doping. UV–visible analysis showed that the band gap value of PbS thin films increased from 1.73ev to 2.19eV by changing Sr doping concentration from 0% to 5%.

Growth and characterization of nanocrystalline PbS:Li thin films

The structural, electrical and opto-electronic properties of PbS thin films doped with Li+ ion were investigated. The crystallite size showed a strong dependence on Li doping, the crystal size changed from 36 nm to 12 nm due to Li incorporation in PbS. Optical band gap showed a shift in the range ∼1.5–2.3 eV with Li incorporation. Urbach tailing in the band gap was observed and the Urbach energy has a dependence on the amount of incorporated Li. SEM images showed a notable change in grain size with Li doping, however the morphology changes from large grains to agglomerations of smaller grains when doped with Li. The electric conductivity of the films showed a dependence on Li doping, reached a maximum value and later decreased for higher Li containing films. The doped samples showed better photosensitivity.

RETRACTED: Morphological, structural, optical and electrical properties of PbS nanocrystals doped with Fe2+ grown by chemical bath

Abstract Doping of PbS nanocrystals with Fe 2+ ions leads to changes in properties that make them useful in technology of thin films devices. In this paper we present the growth of PbS doped systematically with the solution containing the Fe 2+ ions (V [Fe2+] ) using the green chemical bath approach, with the goal of studying the effects of such Fe 2+ -doping on the morphological, structural, electrical and some optical properties of the PbS thin films obtained. The morphological changes of the films were followed by Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). X-ray diffraction showed growth of all films in the zinc blende phase. The grain size was found to be ∼29 and ∼21–17 nm, for the undoped and doped sample, respectively. The absorbance showed in doped films a weak shoulder located at ∼625 nm (1.98 eV), and this exciton peak was attributed to a 1 S e → 1 S h transition. A shift for the band gap energy was observed by optical absorption from ∼1.56 eV for the undoped sample to ∼2.20–2.25 eV range for the doped films. The resistivity increased from ∼26.13–295.7 (Ω cm), and with respect to the electrical conductivity, mobility decreased from ∼8.8 × 10 −4 –2.1 × 10 −7 (Ω cm) −1 , ∼720.1–2.1 cm 2 V −1 s −1 and carrier from ∼1.9 × 10 15 –4.2 × 10 12 cm −3 , while increasing V [Fe2+] .

Effect of Reaction Time and Temperature on Chemical, Structural, Optical, and Photoelectrical Properties of PbS Thin Films Chemically Deposited from the Pb(OAc)2–NaOH–TU–TEA Aqueous System

Lead sulfide (PbS) thin films have been deposited on float glass substrates by the chemical bath deposition technique using a Pb(CH3COO)2–NaOH–(NH2)2CS–N(CH2CH2OH)3 definite aqueous system. The chemical and structural characteristics, as well as the variation of the optical and photoelectrical properties, were studied as functions of reaction time and temperature. For this purpose, the following characterization techniques were employed: x-ray diffraction analysis, x-ray photoelectron spectroscopy, ultraviolet–visible–near infrared spectrophotometry, and dark and light current measurements. Based on the results, it was observed that increase in the reaction temperature increased the deposition rate of the PbS thin film (associated with the cubic crystalline structure); increase of this parameter from 40°C to 70°C (with reaction time of 60 min) led to an increase of the thickness from ∼129 nm to ∼459 nm and the crystallite size (D) from 15.3 nm to 20.2 nm; on the other hand, increase in temperature decreased the energy bandgap (Eg) from 1.66 eV to 0.51 eV and the relative photosensitivity factor (Sph) from 0.468 to 0.032. A similar effect was obtained with increase of the reaction time for given temperature.

The deposition of PbS and PbSe thin films from lead dichalcogenoimidophosphinates by AACVD

Lead sulfide and lead selenide thin films have been deposited from dichalcogenoimidophosphinate lead(II) complexes by AACVD. The synthesis of the precursors, [Pb((S)PPh2)2N)2] and [Pb((Se)PPh2)2N)2], is reported and the single crystal X-ray crystal structure of [Pb((S)PPh2)2N)2] determined. The films were characterised by p-XRD and SEM.

AFM investigation and optical band gap study of chemically deposited PbS thin films

The interest into deposition of nanocrystalline PbS thin films, the potential of designing and tailoring both the topographical features and the band gap energy (Eg) by controlling growth parameters, has significant technological importance. Nanocrystalline thin films of lead sulfide were grown onto glass substrates by chemical bath deposition (CBD) method. The experiments were carried out by varying deposition temperature. We report on the modification of structural and optical properties as a function of deposition temperature. The morphological changes of the films were analyzed by using SEM and AFM. AFM was also used to calculate average roughness of the films. XRD spectra indicated preferred growth of cubic phase of PbS films in (200) direction with increasing deposition time. Optical properties have been studied by UV-Spectrophotometer. From the diffused reflectance spectra we have calculated the optical Eg shift from 0.649-0.636 eV with increasing deposition time.

Engineering of electronic and optical properties of PbS thin films via Cu doping

Copper-doped PbS polycrystalline thin films were deposited by chemical bath deposition by adding small amount of Cu (ysolution = [Cu2+]/[Pb2+]) between 0.5 and 2 at%. The composition, structure, morphology, optical and electrical properties of the films were investigated by means of X-ray diffraction (XRD), Rutherford backscattering spectrometry (RBS), atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray photoemission spectroscopy (XPS), UV–visible–near infrared (UV–Vis–NIR) spectrophotometry and Hall effect measurements. The XRD studies showed that the undoped films have PbS face centered cubic structure with (111) preferential orientation, while preferential orientation changes to (200) plane with increasing Cu doping concentration. The AFM and SEM measurements indicated that the film surfaces consisted of nanosized grains with pyramidal shape. Optical band gap was blue shifted from 0.72 eV to 1.69 eV with the increase in Cu doping concentration. The film obtained with the [Cu2+]/[Pb2+] ratio equal to 1.5 at% Cu showed the minimum resistivity of 0.16 Ω cm at room temperature and optimum value of optical band gap close to 1.5 eV. 1.5 at% Cu-doped PbS thin films exhibit the best optical and electrical properties, suitable for solar cells applications.