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Photovoltaic devices are expected to display peak performance if fabricated with perfect single crystals. Since surfaces break the periodicity of a single crystal, there are regions of defects, which give rise to states inside the forbidden energy gap. In polycrystalline thin films, the main structural defect is the grain boundary. The presence of grain boundaries affects the optical absorption, carrier mobility and lifetime of the semiconductor. This review focuses on grain boundary passivation in thin film photovoltaic devices based on copper chalcogenides. Achieving enhanced performance in copper chalcogenide thin film Photovoltaic devices requires effective grain boundary passivation. This approach aims to mitigate the adverse effects of grain boundaries on the optoelectronic properties of the material, leading to improved efficiency and stability in Photovoltaic devices. The abstract discusses recent developments, methodologies and outcomes related to grain boundary passivation strategies, shedding light on their significance in advancing the performance of copper chalcogenide thin film Photovoltaic devices. The exploration of grain boundary passivation in this context contributes valuable insights to the ongoing efforts in optimizing the performance of thin film Photovoltaic technologies.

Using the successive ionic layer adsorption and reaction (SILAR) method, we successfully deposited thin films (TFs) of both pure cadmium oxide (CdO) and strontium (Sr) CdO onto glass slides. Analysis of the films’ structure and morphology, conducted via field emission scanning electron microscopy and X-ray diffraction, revealed a polycrystalline cubic structure with porous nanoflake agglomerates. Further characterization involved ultraviolet–visible spectroscopy and photoluminescence spectrum measurements to explore the optical attributes of the CdO films. Notably, we observed significant impacts of Sr doping on both optical transmittance and photoluminescence emission intensity in the CdO nanostructures. Electrical measurements, carried out using four-probe Iviumstat analysis, demonstrated variations in resistivity with different levels of Sr doping. These findings highlight the potential for controlling specific physical features of CdO through Sr doping, making it a promising candidate for various device applications.

Fe₂O₃ thin films were deposited on alumina substrates by using the physical vapor deposition technique “RF magnetron sputtering”. The impact of the thermal treatment on the structural, optical and morphological properties was systematically investigated. The results of the structural characterizations reveal that the elaborated thin films present a main peak whichcorresponds to the crystalline plane (104) of the hematite ($\alpha$-Fe₂O₃). Furthermore, the Raman spectra confirm the existence of the hematite phase of the iron oxide. UV-Visible spectrophotometer analysis of Fe₂O₃ thin films before and after annealing shows that the transmittance increases with heat treatment. Moreover, the heat treatment at 500^∘C significantly improves the absorption coefficient $\alpha$, extinction coefficient k, refractive index n, and the band gap of Fe₂O₃ thin films. Furthermore, a spinel polarization change was found to be responsible for the ferrobehavior of Fe₂O₃ thanks to the lattice crystallinity enhancement. The density functional theory calculations demonstrate that the magnetic properties are very sensible to any induced strain in the Fe₂O₃ lattices.

In this study, we synthesized Co₃O₄ thin films using a sol–gel spin coating method and investigated the effect of heat treatment on their carbon dioxide (CO₂) gas sensing properties. To optimize their crystallinity and enhance their CO₂ sensitivity, the thin films were annealed at temperatures ranging from 400^∘C to 550^∘C. We characterized the morphological, structural, electrical, and optical properties of the Co₃O₄ thin films to gain insights into their behavior in the low operating temperature range (OTR). Our X-ray diffraction (XRD) analysis revealed that all the thin films exhibited a cubic structure, with improved crystallinity observed at higher annealing temperatures. We observed a decrease in band edges in the optical transmittance spectra of the thin films as the annealing temperature increased, indicating a redshift in the absorption edge. Notably, the highest electrical conductivity was observed for the sample annealed at 550^∘C, suggesting enhanced crystallinity and improved CO₂ gas sensitivity. These findings provide valuable insights into the optimization of Co₃O₄ thin films for CO₂ gas sensing applications.

The chemical bath deposition method (CBD) was used to create thin films of calcium zirconate on a glass substrate. After that, the samples were annealed for an hour at three different temperatures: $100^{\circ }$C, $200^{\circ }$C, and $300^{\circ }$C. The structural parameters of the samples like lattice strain, dislocation density and crystallite size were calculated from XRD analysis. The lattice strain was found to be very low. The crystallite size confirms the nano-size of the synthesized sample. From UV analysis, the optical energy direct bandgap was calculated in the range of 3.98–4.16eV. A higher annealing temperature of $300^{\circ }$C causes the thin film’s bandgap to diminish, confirming the calcium zirconate thin film’s broad bandgap characteristics. From SEM analysis, morphology, and adhesive nature was analyzed, and from AFM analysis, the grain size of the sample was found to be in 300nm.

First principles investigation of PbTiO₃ in bulk and layer phases has been performed using full potential-linear augmented plane wave method (FP-LAPW) implemented in WIEN2K code, based on the density functional theory (DFT) within the generalized gradient approximation (GGA) to explore the structural, electronic, thermoelectric and optical properties of PbTiO₃. Total energy calculations, optimized structure, band structure, density-of-states (DoS), optical, and thermoelectric properties are computed and analyzed. The change in structural and electronic phases are observed. The optical properties of the compound can be studied by evaluating from the optical spectra and the changes in the properties such as complex dielectric function, absorption, energy loss function, refractive index and refractivity are studied. The thermoelectric properties are analyzed from Seebeck coefficient, power factor and thermoelectric figure of merit. The superior phase of PbTiO₃ is analyzed from the observation of all the above-mentioned properties for optoelectronic applications.

The polymorphism and isomorphism of Ge(OH)₂Pc and Si(OH)₂Pc (Pc: phthalocyanine ligand) are reported as well as those of the polymeric molecules of (GeOPc)_n and (SiOPc)_n. The polymeric Pcs were produced through dehydration polymerization by heating the respective monomer of Ge(OH)₂Pc or Si(OH)₂Pc. We also report the thin film structures of these phthalocyanine derivatives and discuss the similarities and differences in the structures formed by vacuum deposition, in relation to the coordinating metal species.

The synthesis of three novel porphyrins (that are models for mesoporphyrin) requires the synthesis of eight new pyrroles, one new alkyl-3-oxohexanoate and two new dipyrromethanes. The new porphyrin free bases have hydrophobic substitution patterns different from that in mesoporphyrin. We are seeking amphilic porphyrins that will form Langmuir–Blodgett (LB) multilayers without recourse to either long-chain alkyl substituents or fatty acid additives. In this way the influence of the conjugated tetrapyrrole unit on the properties of the multilayer films can be maximized. We report multilayer deposition for porphyrins having the following substituents: CH₃, C₂H₅, n-C₃H₇, (CH₂)₂COOMe; no additives such as stearic acid, cadmium stearate or mesitylene are required, Y-type deposition being exhibited by the simply substituted pure methyl esters. The variations in proton NMR chemical shift with concentration are reported and the action spectrum of an LB film of a porphyrinato-Zn(II) complex is described. Our observations and conclusions are in sharp (and optimistic) contrast with those of H. Chou et al. (J. Phys. Chem. 98, 383 (1994)), who found that in the absence of steric constraints from bulky aliphatic chains the Langmuir films are so rigid that either no multilayers or multilayers of poor quality are given. We obtain good-quality multilayers (60 layers) for porphyrins bearing eight small substituents.

Polyaniline (PA) and aniline black (AB) were prepared in powder form by the chemical method of oxidative polymerization, from which free-standing thin films were obtained by solvent evaporation using N-methyl pyrrolidinone (NMP). The thin films contained 2, 4, 6 or 8 wt% AB. Electrical measurements showed that the samples containing 4% AB exhibited the highest photoconductivity of the four concentrations. Thus there appears to be a critical ratio of PA to AB for maximum photoconductivity. Annealing up to 570 K has little effect on the conductivity. Upon adding a small quantity of copper phthalocyanine (CuPc) to the PA + AB, the electrical conductivity increased considerably and the optical absorption was extended from the UV to the near IR. The electrical conductivity mechanism is a consequence of a redox process, since AB is the oxidized state of PA and, upon illumination, there is an exchange of charge carriers. The extension of the range of optical absorption upon addition of CuPc is interpreted to suggest that CuPc photosensitizes the material and enhances the carrier transport process in the redox couple. The activation energy from the temperature-dependent conductivity and the band gap from the electrolyte electroreflectance method were determined. The activation energy for 0.4% CuPc is lowest (0.52 eV) and the corresponding band gap is determined to be 3.0 eV. This organic compound could be a good candidate for inexpensive, reliable and efficient solar energy-converting devices.

Soluble metal-free and Cu-, Ni- and Co-substituted 3,4-tetrapyridinoporphyrazines (Tpps)5–8 have been synthesized. Poly(methyl methacrylate) (PMMA) spin coated and Langmuir–Blodgett (LB) films containing these compounds have been prepared. Third-harmonic generation (THG) was used to measure the third-order-non-linear optical susceptibility of both types of films at 1.064 μm. For the spin-coated samples a strong enhancement of the THG response was found on increasing the Tpp concentration of the chlorobenzene solution used to prepare the samples. The enhancement was associated with the formation of molecular aggregates in the solution which were ‘frozen’ into the films. In order to facilitate comparison, the final Tpp concentration in the PMMA films was kept approximately constant in all cases. Metal incorporation (particularly Co) in the macrocycle strongly enhances the THG susceptibility of the films prepared using concentrated solutions, whereas the effect is efficiently inhibited in those obtained from less concentrated solutions. We conclude that the enhancement in the THG response occurs via the influence of the metal on the Tpp aggregation process in the solution. For the LB films the THG results are more comparable with those of the spin-coated samples prepared using low-concentration solutions. This indicates that dimers, previously identified in the LB films, and possibly other small-size oligomers are formed in the low-concentration Tpp solutions. On the other hand, larger aggregates should be formed in the spin-coated samples prepared from high-concentration solutions.

Transparent sols of crystalline gadolinium doped zirconia particles with the general formula Zr_{1 - x}Gd_xO_{2 - x/2} (where x = 0–0.20), were prepared by a hydrothermal sol-gel method using cheap inorganic precursors. The composition, structure, crystallite size and lattice parameters of the crystalline dried sol particles and heated powders were studied. Thin films were deposited on quartz substrates using a simple dipping process and the structure, composition and crystallite size found to be identical to the powders with respect to the variation in temperature. Spectral transmittance studies showed that the films were transparent in the region between 400 and 1100 nm. The refractive index increased with the increase in annealing temperature, varying between 1.56 and 1.74. Optical band gap calculations gave band of 5.52 to 5.55 eV. Refractive indices and optical band gaps were compared with those of films containing other lanthanide dopants previously reported in the literature.

We present calculations of the electronic and magnetic structure of thin films of Ni, using the recursion technique based on the tight-binding linearized muffin-tin orbitals basis. We find that the surface layers of free standing Ni thin films do carry enhanced magnetic moment.

Cadmium sulfide (CdS) thin films (d=0.15–1.15 μm) were deposited onto glass substrates by the quasi-closed volume technique under vacuum. The investigations shown that the films are polycrystalline and have a hexagonal structure. It was experimentally established that the films with stable structure can be obtained if they are submitted to a heat treatment, consisting of several succesive heating/cooling cycles within a given temperature range (ΔT=300–600 K), the temperature dependence of the electrical conductivity becomes reversible. For heat-treated samples, the values of thermal activation energy calculated from the temperature dependence of the electrical conductivity, ranged between 2.30–2.45 eV. The spectral dependences of the transmission and absorption coefficients were studied in the range 500–1400 nm. The influence of heat treatment on the shape of the absorption spectra and dispersion index of refraction is studied for samples with different thickness. Optical energy gap, calculated from the absorption spectra was in the range 2.30–2.5 eV.

The theory of Green's functions (GF) for thin films was formulated, where site indices were different also along the direction of broken symmetry. This approach results in the layer dependence of correlation functions in films, which did not appear in the previous investigations of thin films. The magnetizations of three layer thin ferromagnetic (FM) and four layer thin ferroelectric (FE) films were investigated using the GFs found in this way. It was shown that the transition temperature varies from layer to layer, which is the obvious consequence of the generalization of the formalism of the GF calculation for films.

In our studies we observed a self-doping effect in Bi 2212 epitaxial thin films, totally covered by a protective golden layer, after the irradiation of these films with heavy ions. The irradiation with heavy ions was made in order to create columnar defects in the samples. We studied Bi 2212 thin films having various oxygen contents before irradiation and we observed for all of them an increase of the oxygen content in the films due to this self-doping effect caused by irradiation.

The epitaxial, single phase (100) Ba_0.5Sr_0.5TiO₃ (BST) films with thin interfacial layer of BST (x=0.4) were deposited on LAO (100) substrates using Pulse Laser Deposition (PLD). These films were characterized in terms of their phase formation and structural growth characteristics using X-ray diffraction and Atomic Force Microscopy respectively. The dielectric properties are strongly affected by the substrate type, post deposition annealing time, and temperature. In order to verify all these properties, thin interfacial-buffer layers of BST (10, 20, 50 nm) were introduced to relieve the stress induced between the film and the substrate. The variations of dielectric constant and ferroelectric properties of as deposited films are discussed in detail. The high tunability, low dielectric loss and low leakage current of these films make them attractive candidates for fabricating tunable dielectric devices. The observed dielectric properties of the BST-films are attributed to homo-epitaxial interfacial layer, which is responsible for the increase in the dielectric constant and tunability.

In this study, we have investigated the structural, interfacial and ferroelectric properties of Sr_1-xCa_xBi₂Ta₂O₉ thin films grown on Pt/TiO₂/SiO₂/Si substrates using pulsed-laser-deposition technique. The decrease in lattice parameters with increasing Ca content was attributed to the smaller ionic radius of Ca. Atomic force microscopy shows that the average grain size and surface roughness of the films increases with the incorporation of Ca. Films with x=0.2 exhibited a maximum remanent polarization of ~23.8 μC/cm² with a coercive field of 175 kV/cm. The higher remanent polarization was attributed to the increased grain size and to the increase in the lattice mismatch between TaO₂ and SrO planes. The presence of metallic bismuth at the interface of the film and the substrates was confirmed using XPS depth profile analysis. The current transport property of the thin film capacitors suggests a bulk-limited dc-current conduction mechanism.

Magnetotransport data on MgB₂ thin films, fabricated on Al₂O₃ substrates using electron–bean deposition and Mg diffusion method are reported for applied magnetic fields up to 9 T. The upper critical field anisotropy, lower critical field and irreversibility field versus temperature are determined. The Hall coefficient is slightly temperature-dependent and positive in the normal state. Using the extracted data, the electronic mean free path, coherence length ξ₀, anisotropic coefficient γ and penetration depth λ are calculated.

The thermo-gravimetric analysis (TGA) and differential thermal analysis (DTA) of the as-deposited and electrochemically oxidized Hg₁Ba₂Ca₁Cu₂O_6+δ(Hg-1212) samples were carried out in air, flowing oxygen and nitrogen environment in order to estimate the thermal decomposition temperature and hence to maintain the annealing temperature and atmosphere. After annealing, electrochemically synthesized films showed an increase in T_c from 104.7 K to 119 K and J_c values from 1.43×10³ to 4.3×10³A/cm². Electrochemically oxidized Hg-1212 films in under-, optimally- and over-doped states were irradiated with a Red He–Ne laser (2mW) and the T_c was found to increase from 104.7 K to 106 K and J_c from 1.43×10³ to 1.89×10³A/cm². The effects of annealing and photo-irradiation on structural, microstructural and superconducting properties of electrochemically synthesized Hg-1212 films were investigated and discussed in detail in this paper.

The optical properties of metal-free phtalocyanine (H₂Pc) in thin film form is investigated. X-ray diffractograms of the (H₂Pc) powder show that it has a α-polycrystalline form with a monoclinic structure. The thermal evaporation of (H₂Pc) powder leads to α-polycrystalline films, oriented preferentially to the (001) plane. After annealing at 623 K for two hours, a mixture of α- and β-phases is formed on an amorphous background. The optical properties of (H₂Pc) thin films have been studied using spectrophotometeric measurements of transmittance and reflectance in the range 200–2200 nm for a different film thickness. The refractive index and the absorption index show independence on the film thickness. The refractive index shows anomalous dispersion in the region of the fundamental absorption edge. The absorption measurements show the characteristic splitting of the Q-band and ΔQ is obtained as 0.22 eV. The absorption coefficient in the absorption region reveals indirect transitions. The fundamental and the onset energy gap are determined as 2.74 eV and 1.55 eV, respectively.