The technology of perovskite solar cells (PSC) is getting close to breaching the consumer market. Yet, one of the current challenges is to reduce the toxicity during their fabrication by reducing the use of the toxic solvents involved in the perovskite fabrication process. A good solubilization of lead halides used in hybrid perovskite preparation is required, and it is only possible with polar solvents. A mixture of dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) is the most popular solvent combination for a perovskite precursor solution. DMF is necessary to ensure a good dissolution of lead iodide, but it is also the most toxic solvent. In this paper, we study the replacement of the dimethylformamide with presumably less toxic alternatives, such as N-methyl-2-Pyrrolidone (NMP) and ethyl acetate (EA), for the preparation of the K_0.1FA_0.7MA_0.2PbI_2.8Cl_0.2 (KFAMA) hybrid perovskite. The perovskite thin films were investigated by various characterization techniques: X-ray diffraction, atomic force microscopy, scanning electron microscopy, and UV–vis spectroscopy, while the photovoltaic parameters were determined by measuring the IV curves of the corresponding solar cells. The present study shows that by keeping the same deposition parameters as when only DMF solvent is used, the partial solvent substitution with NMP and EA gives promising results for reducing the toxicity of the fabrication process of KFAMA-based PSCs. Thus, with no specific optimization of the deposition process, and for the maximum possible partial substitution of DMF with NMP and EA solvents, the loss in the power conversion efficiency (PCE) value is only 35% and 18%, respectively, associated with the more structural defects promoted by NMP and EA.

Structural and electrical properties of epitaxial Pb(Zr_0.2Ti_0.8)O₃ films grown by pulsed laser deposition from targets with different purities are investigated in this study. One target was produced in-house by using high purity precursor oxides (at least 99.99%), and the other target was a commercial product (99.9% purity). It was found that the out-of-plane lattice constant is about 0.15% larger and the a domains amount is lower for the film grown from the commercial target. The polarization value is slightly lower, the dielectric constant is larger, and the height of the potential barrier at the electrode interfaces is larger for the film deposited from the pure target. The differences are attributed to the accidental impurities, with a larger amount in the commercial target as revealed by composition analysis using inductive coupling plasma-mass spectrometry. The heterovalent impurities can act as donors or acceptors, modifying the electronic characteristics. Thus, mastering impurities is a prerequisite for obtaining reliable and reproducible properties and advancing towards all ferroelectric devices.

Composites of magnetite (Fe₃O₄) nanoparticles dispersed in a polydimethylsiloxane (PDMS) matrix were prepared by a molding process. Two types of samples were obtained by free polymerization with randomly dispersed particles and by polymerization in an applied magnetic field. The magnetite nanoparticles were obtained from magnetic micrograins of acicular goethite (α-FeOOH) and spherical hematite (α-Fe₂O₃), as demonstrated by XRD measurements. The evaluation of morphological and compositional properties of the PDMS:Fe₃O₄ composites, performed by SEM and EDX, showed that the magnetic particles were uniformly distributed in the polymer matrix. Addition of magnetic dispersions promotes an increase of thermal conductivity compared with pristine PDMS, while further orienting the powders in a magnetic field during the polymerization process induces a decrease of the thermal conductivity compared with the un-oriented samples. The shape of the magnetic dispersions is an important factor, acicular dispersions providing a higher value for thermal conductivity compared with classic commercial powders with almost spherical shapes.

Polarization switching in ferroelectric films is exploited in many applications, such as non-volatile memories and negative capacitance field affect transistors. This can be inhomogeneous or homogeneous, depending on if ferroelectric domains are forming or not during the switching process. The relation between the polarization switching, the structural quality of the films and the negative capacitance was not studied in depth. Here, Pb(Zr_0.2Ti_0.8)O₃ (PZT) layers were deposited by pulse laser deposition (PLD) and sol-gel (SG) on single crystal SrTiO₃ (STO) and Si substrates, respectively. The structural quality was analyzed by X-ray diffraction and transmission electron microscopy, while the electric properties were investigated by performing hysteresis, dynamic dielectric measurements, and piezo-electric force microscopy analysis. It was found that the PZT layers grown by PLD on SRO/STO substrates are epitaxial while the layers deposited by SG on Pt/Si are polycrystalline. The polarization value decreases as the structure changes from epitaxial to polycrystalline, as well as the magnitude of the leakage current and of the differential negative capacitance, while the switching changes from homogeneous to inhomogeneous. The results are explained by the compensation rate of the depolarization field during the switching process, which is much faster in epitaxial films than in polycrystalline ones.

This study presents a systematic approach to engineering the electron transport layer (ETL) in perovskite solar cells using a spray deposition technique to fabricate sequentially compact and mesoporous titanium dioxide (c-TiO₂, m-TiO₂) films. The spray coating method leads to the development of a distinct reticulated morphology characterized by well-defined wavy-like surface features and significantly increased roughness—at least twice that of spin-coated mesoporous films. The increased interfacial area between the mesoporous TiO₂ and the perovskite layer facilitates more efficient charge transfer, contributing to higher device performance. By optimizing the deposition parameters, particularly the number of spray cycles for the m-TiO₂ layer, we achieve a significant enhancement in device performance, with improvements in power conversion efficiency (PCE), reduced series resistance, and minimized hysteresis. Our results demonstrate that an optimal film thickness promotes better perovskite anchoring, while excessive deposition impedes light transmission and increases sheet resistance. These findings advance the practical fabrication of high-performance perovskite solar cells using simple solution-processing techniques and highlights the potential of scalable spray deposition methods for industrial-scale fabrication.

This chapter provides an overview of the versatile applications and properties of epitaxial ferroelectric materials obtained using the pulsed laser deposition technique. These materials can play a significant role in various electronic and sensing applications or energy harvesting. Materials that are ferroelectric and have a perovskite structure (ABO3 type) show spontaneous polarization that can be changed by an electric field, temperature, mechanical stress, or light. Here, we present results obtained on epitaxial ferroelectric thin films with different compositions, lead-based or lead-free, and the correlation with structural quality of the layers and with different electrostatic conditions induced either by the substrate or by the different dopants. Our studies revealed that the utilization of pulsed laser beam deposition technique is suitable for obtaining ultrathin films depositions with thicknesses measuring less than 5 nm. These results allowed us to reveal the impacts caused by polarization orientation on the band structure or the presence of self-doping phenomena. We also found that the conduction type can be modified by introducing 1% Fe and Nb on PbZrTiO₃ (PZT) epitaxial layers. In the last part of this chapter, we report on obtaining of a lead-free epitaxial thin film and its properties in the energy storage field.