The implementation of a wide range of high-efficiency solar cell concepts is based on nanostructures with configuration-tunable optoelectronic properties. On the other hand, effective nano-optical light-trapping concepts enable the use of ultra-thin absorber architectures. In both cases, the local density of electronic and optical states deviates strongly from that of a homogeneous bulk material. At the same time, nonlocal and coherent phenomena like tunneling or ballistic transport become increasingly relevant. As a consequence, the semiclassical, diffusive bulk picture may no longer be appropriate to describe the physics of such devices. In this review, we provide a quantum-kinetic perspective on photovoltaic device operation that reaches beyond the limits of the standard simulation models for bulk solar cells. Deviations from bulk physics are assessed in ultra-thin film and nanostructure-based solar cell architectures by comparing predictions of semiclassical models with those of a more fundamental description based on nonequilibrium quantum statistical mechanics.

Electronic structures of single crystal pentacene are of great interest for the elucidation of charge carrier transport in organic semiconductor materials. Experimental observation of valence band dispersion was recently achieved on single crystal samples of pentacene; however, its intrinsic properties are still unresolved because past experiments were performed on specimens with surface oxides formed by exposure to the ambient atmosphere. In this work, X-ray photoelectron spectroscopy (XPS) and angle-resolved ultraviolet photoelectron spectroscopy (ARUPS) were conducted on single-crystal pentacene samples prepared without ambient exposure. The XPS results confirmed the reduction of the abundance of oxide impurities on the present samples. The ARUPS measurements clearly resolved the valence band structures of the single-crystal pentacene in four symmetry directions of the surface Brillouin zone, indicating anisotropy of at least a factor of 2.4 for the intermolecular transfer integral and hole effective mass at the valence band maximum.

For one-dimensional nanomaterials, the performances are strongly related to the diameters, lengths, morphologies, and structures, implying that it is of great significance to understand the related growth mechanisms and thus to achieve the desired nanostructures. Thermal oxidation of copper has been widely used to fabricate CuO nanowires (NWs), whereas the growth mechanism still remains controversial in spite of the extensive investigations. Therefore, this review aims to offer a critical discussion about the growth mechanisms. First, the effects of different growth conditions on the growth of CuO NWs are introduced for basic understanding. Subsequently, the proposed mechanisms in different literature studies, i.e., the vapor–solid, self-catalyzed growth, stress-induced growth, stress grain boundary (GB) diffusion, and oxygen concentration gradient, are discussed and summarized. It seems that the combination of “stress GB diffusion” and “oxygen concentration gradient” mechanisms could be relevant for the growth of CuO NWs via thermal oxidation of copper.

The large strain extrusion-machining process has been used to refine the microstructure in a Titanium alloy (Ti–6Al–4V). The unconstrained cutting or machining of Ti–6Al–4V entails the formation of shear localized chips at nearly all cutting speeds, thereby hindering the use of extrusion-machining to produce fine-grained materials. The present effort attempts to suppress shear localization by the suitable modification of texture in Ti–6Al–4V through the cold-rolling process prior to extrusion-machining. Ti–6Al–4V plates were cold rolled to 30, 40, 45, and 47% thickness reductions. These textured plates were extrusion machined using a suitably designed fixture leading to fine-grained continuous foils with increased hardness. Microscopy has revealed that the suppression of shear localization in the foils produced from plates which are cold rolled to more than 40% of thickness reduction is triggered by texture formation. For thickness reductions slightly lower than 40% (e.g., 30%), suppression can be achieved only by a combination of texture and extrusion.

Solution-processed metal oxide electronics on flexible substrates can enable applications from military to health care. Due to limited thermal budgets and mismatched coefficients of thermal expansion between oxides and substrates, achieving good performance in solution-processed oxide films remains a challenge. Additionally, the use of traditional photolithographic processes is incompatible with low-cost, high-throughput roll-to-roll processing. Here, we demonstrate solution-deposited oxide thin film transistors (TFTs) on a shape memory polymer substrate, which offers unique control of final device shape and modulus. The key enabling step is the exposure of the precursor film to UV-ozone through a shadow mask to perform patterning and photochemical conversion simultaneously. These TFTs exhibit mobility up to 160 cm2/(V s), subthreshold swing as low as 110 mV/dec, and threshold voltage between −2 and 0 V, while maintaining compatibility with a flexible form factor at processing temperatures below 250 °C.

In this study, Au-based nanoglasses in the form of thin films deposited by magnetron sputtering are comparatively dealloyed. The films have either nanograined or nanocolumnar microstructure, depending on the working pressure of Ar in the sputtering chamber. Nanocolumnar thin films exhibit much higher dealloying rate reducing effectively the dealloying time with respect to nanograined and homogenous thin films. Electrocatalysis experiments indicate that the resulting nanoporous films are active for the methanol electrooxidation, with promising results in term of stability especially for the dealloyed nanocolumnar film.

Formamidinium–tin–strontium halides (CH(NH2)2Sn1−ySryX3 (FASnX3), X = I, Br and 0.0 ≤ y ≤ 0.1) were investigated. X-ray diffraction analysis revealed orthorhombic FASnI3 (space group Amm2) and SnI2 for X = I as well as cubic FASnBr3 (space group $Pm\bar{3}m$) and SnBr2 for X = Br, respectively. For X = I, the optical spectra displayed a decrease of the absorption edges with increasing Sr content (1055 nm, y = 0.0; 950–960 nm, y > 0.0) and a direct semiconducting behavior with narrow band energy gaps (1.31–1.34 eV). For X = Br, on increasing the absorption edges (492 nm, y = 0.0; 975 nm, y = 0.075), a direct semiconducting behavior with band energy gaps between 2.65 eV (y = 0.0) and 1.38 eV (y = 0.075) were observed and the emission photoluminescence (PL) spectra (excitation wavelength λexc = 380 nm) showed an increase of the luminescence response after the thermal treatment.

Nanoindentation has been used to measure the elastic modulus of 5 and 18 μm thick high-purity vapor deposited polycrystalline lithium films at 31 °C. Over indentation depths ranging from 150 to 1100 nm, the modulus is found to vary with film thickness from 9.8 GPa ± 11.9% to 8.2 GPa ± 14.5%. These results are well within the range of lithium's orientation dependent elastic modulus, which spans approximately 3.1 to 21.4 GPa. The measured values may also indicate (111) and (100) texture for the 5 and 18 μm thick films, respectively. The potential effects of pileup and surface contamination are found to be negligible if any at all. Small but discernible changes in damping capability near the free surface may provide insight into the subsurface defect structure and the potential for localized heating. Numerous experimental challenges are addressed and key metrics are used to validate the measured elastic modulus.

Composite hydrogels based on hydroxypropyl cellulose (HPC) and graphene oxide (GO) were developed and used for adsorption of phenol. The single network composite hydrogel (SNCH) was first prepared by crosslinking of HPC and GO by epichlorohydrin; then the SNCH was treated with polyethyleneimine solution, forming the double network composite hydrogel (DNCH). The DNCH exhibited better adsorption capacity than the SNCH due to larger surface area and more functional groups. The possible adsorption mechanism of the composite hydrogels toward phenol involved electrostatic, hydrogen bonding, and π–π interactions. Study on dynamic adsorption behavior of phenol by SNCH and DNCH indicated that the breakthrough time increased when the initial concentration and feed flow rate of phenol decreased. Furthermore, the breakthrough time of DNCH was longer than that of SNCH at all operating conditions due to the relatively higher adsorption capacity of DNCH. The SNCH and DNCH could be repeatedly used without significant loss in the initial binding affinity after six adsorption–desorption cycles, which indicated that the composite hydrogels were qualified for practical application.

The phase stability, equilibrium lattice parameters, mechanical properties, and chemical bonding of M2B and M2B0.75C0.25 (M = Fe, Cr, W, Mo, Mn) were studied using first-principles calculations within density functional theory. These compounds are thermodynamic stability structures, and the M2B0.75C0.25 stability is worse than that of M2B. The equilibrium lattice parameters are consistent with other available experimental and theoretical data. Stress–strain and Voigt–Reuss–Hill approximations were used to estimate the elastic constants (Cij) and moduli (B, G, E), respectively. The bulk modulus and the ductility increased by adding an appropriate amount of C to the M2B. The compound hardness was studied using a theoretical method based on the work of Tian. The chemical bonding of these compounds was estimated using the Mulliken population analysis and density of states, and the results indicate that the bonding behaviors of these compounds are combinations of metallic and covalent bonds.

The electrochemical technique has been used to prepare aluminum-doped zinc oxide (AZO) films on FTO substrates using zinc nitrate and aluminum chloride precursor solution at 70 °C. The crystal structure, surface morphology, optical and electrical features of AZO films were examined at different potential voltages from −1.7 to −2.3 V in the initial solution. Structural studies of the deposited films were carried out through X-ray diffraction; the AZO films exhibited a polycrystalline nature with hexagonal structure, and crystals preferentially grew along the (002) orientation. The morphology of the deposited films was characterized by scanning electron microscopy (SEM), and the images showed that the spherical- and nanorod-shaped particles are uniformly distributed on the entire AZO film surface. The average size is found to be in the range of 45–70 nm by SEM and 28–32 nm by using the Scherrer’s rule. The EDS spectrum confirmed the chemical composition of Zn, O, Al, Sn, and F elements over the film surface. The optical properties were studied using a UV-visible spectrophotometer, and the deposited film showed the highest optical transmittance of ∼80% in the visible range for −1.7 V. The calculated energy gap of the AZO films decreases from 3.09 to 2.97 eV with increasing potential voltages. AZO thin films have been studied using photoluminescence to identify the film’s optical quality with respect to the wavelength range. The electrical properties were studied by the room temperature Hall effect system, and the observed low resistivity (ρ) is 1.58 × 10−2 (Ω cm) for the film deposited using a −2.1 V potential voltage.

For instrumented spherical indentation, the presence of equibiaxial residual stress in a material will lead the indentation load–depth curve to shift upward or downward. The load differences between the stressed and stress-free curves were used to estimate the equibiaxial residual stress. Using dimensional analysis and finite element simulations, the equibiaxial residual stress was related to the elastic–plastic parameters and the relative load difference at a fixed normalized indentation depth (h/R = 0.1). Based on these expressions, and together with the method for determining elastic–plastic parameters established in our previous work, an integrated method was proposed to estimate the equibiaxial residual stress and elastic–plastic parameters of metals simultaneously via instrumented spherical indentation. This method avoids preknowledge of the yield strength and measuring the contact area. Applications were illustrated on Al 2024, Al 7075, and Ti Grade 5 with introduced stresses. By comparing the results determined by this integrated method with the reference values, the maximum relative error is generally within ±10% for the yield strength, within ±15% for the elastic modulus, and within ±20% for the equibiaxial residual stress.

Orbital-free density functional theory (OFDFT) is both grounded in quantum physics and suitable for direct simulation of thousands of atoms. This article describes the application of OFDFT for materials research over roughly the past two decades, highlighting computational studies that would have been impractical (or impossible) to perform with other techniques. In particular, we review the growing body of simulations of solids and liquids that have been conducted with planewave-pseudopotential (or related) techniques. We also provide an updated account of the fundamentals of OFDFT, emphasizing aspects—such as nonlocal density functionals for computing the kinetic energy of noninteracting electrons—that enabled much of the application work. The article concludes with a discussion of the OFDFT frontier, which contains brief descriptions of other topics at the forefront of OFDFT research.

Organic–inorganic halide perovskite solar cells (OIHPSCs) offer a fantastic opportunity to harness solar energy in a low cost and efficient way. This ambition for commercialization has been greatly encouraged by the surge in device performance from 3.8% in 2009 to the state-of-the-art 22.7%. For high device performance, tailoring the interfacial properties is demonstrated essentially important. Being in a molecular scale, the self-assembly monolayers (SAMs) are proved a facile but effective tool for interface modification. And lots of studies have demonstrated that SAMs have a variety of positive effects for perovskite solar cells, including mediating the morphology, improving energy level alignment, passivating trap states, etc. In this mini review, we give an insightful summary on the recent application of SAMs in OIHPSCs, analyze the mechanisms to improve device performance, and provide guidance to SAM-boosted perovskite solar cells for high performance and practical application. Finally, a landscape is depicted for future application of SAMs in perovskite solar cells.

One of the key aims of the OSCAR project (Optical Sensors based on CARbon-materials)—in the framework of the REXUS/BEXUS program—was to explore the use of organic-based solar cells for (aero)space applications through the in-flight investigation of devices’ performance during a stratospheric balloon flight. Next to the in-flight experiments, complementary lab stability assessment tests were performed. In this contribution, both the in-flight and lab experimental methodology and the corresponding technical aspects will be discussed in detail. Furthermore, attention will be paid to the issues of packaging and radiation. The importance of the OSCAR-balloon experiment is not only that it has demonstrated for the first time the use of organic-based solar cells in (aero)space conditions but also that it can be considered as the pioneering start of specific stability assessment methodologies for organic-based solar cells for (aero)space applications.