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Recent studies of lead halide perovskites demonstrate outstanding optoelectronic properties for thin-film semiconductor device application. Perovskite photovoltaic and light-emitting diodes are on the way to the mass production and spread in commercial semiconductor devices. The lab-to-fab transition of perovskite devices requires adaptation of perovskite deposition methods to industrial semiconductor fabrication standards. In this work, we demonstrated the formation of highly luminescence perovskite films by single-source chemical vapor deposition (ssCVD). Several stoichiometry compositions were prepared from inorganic precursors of CsBr and PbBr2 by dry mechanochemical synthesis with following evaporation. The combination of mechanochemical synthesis and ssCVD is an attractive approach due to the ability to scale up to industrial level and the precise control over the evaporation rate with a single source. Among all compositions CsBr:PbBr2, we show that CsPb2Br5 maintains phase composition and photoluminescent properties for powder and film. This work provides a comparative study of evaporated film properties (PL, XRD, TEM) and modeling calculations of interphase optical transitions.

Contribution of mobile ions to current transport in double cation FA1−xCsxPbI3 p–i–n solar cell structures with NiOx hole transport layers and electron transport layers (ETLs) formed by Phenyl-C61-butyric acid methyl ester (PCBM) or C60 was studied by means of our previously developed suite of techniques comprising admittance spectroscopy, Deep Levels Transient Spectroscopy with standard (DLTS) and reversed (RDLTS) sequence of biasing/pulsing, and Photoinduced Open-Circuit Voltage Voc Spectroscopy (PIVTS). These studies show that the amplitudes of mirror-like peaks in DLTS/RDLTS, the hallmark of mobile ions, strongly decrease when switching from PCBM to C60 and further decrease with the addition of Cl to the growth solution. A similar effect is observed in PIVTS spectra monitoring changes in long-time open circuit Voc relaxations with temperature. The activation energies of peaks in DLTS, PIVTS, and low-frequency admittance spectra are similar to each other. The results indicate that switching the ETL type from PCBM to C60 and adding Cl in the perovskite ink for improved crystallization result in alleviating adverse effects of mobile ions, which correlates with observed changes in solar cell performance and reliability. Possible reasons for the described phenomena will be discussed.

The structural and electronic properties of the methylammonium lead iodide (MAPbI3, MA ¼ CH3NH3) perovskite are investigated as a function of temperature by transport measurements, in situ x-ray diffraction, and optical emission. Lowering the temperature, a transition from the tetragonal to the orthorhombic phase takes place, around 160 K. Such structural transition, monitored by temperature-dependent in situ x-ray diffraction and optical emission, is followed by an inversion of the temperature dependence of the electrical resistivity from a semiconductor-like dependence to a metal-like one. The temperature for such semiconductor-metal transition, depending both on the applied electric field and on the optical excitation, is always below the phase transition temperature. The results demonstrate that perovskite materials display interesting scenarios in which lattice structural transitions combined with optical or electrical excitation strongly affect transport properties. The consequences of these characteristics are analyzed in fundamental and applied science perspectives.

Designing and implementing means of locally trapping magnetic beads and understanding the factors underlying the bead capture force are important steps toward advancing the capture-release process of magnetic particles for biological applications. In particular, capturing magnetically labeled cells using magnetic microstructures with perpendicular magnetic anisotropy (PMA) will enable an approach to cell manipulation for emerging lab-on-a-chip devices. Here, a Co (0.2 nm)/Ni (0.4 nm) multilayered structure was designed to exhibit strong PMA and large saturation magnetization (Ms). Finite element simulations were performed to assess the dependence of the capture force on the value of Ms. The simulated force profile indicated the largest force at the perimeter of the disks. Arrays of Co/Ni disk structures of (4–7) μm diameter were fabricated and tested in a microchannel with suspended fluorescent magnetic beads. The magnetic beads were captured and localized to the edge of the disks as predicted by the simulations. This approach has been demonstrated to enable uniform assembly of magnetic beads without external fields and may provide a pathway toward precise cell manipulation methods.

This work presents a study of trap levels in a mesoscopic multication lead halide perovskite solar cell structure. The investigation is performed by combining capacitance measurements, admittance measurements, Deep Level Transient Spectroscopy (DLTS), and Optical DLTS. We found a donor level with an energy of 0.2 eV below the conduction band of perovskite. The donor density reaches a concentration of 1018 cm−3 in the accumulation region present at the interface between the perovskite and transporting layers. Other two deep trap levels are found with energies of 0.57 eV and 0.74 eV. The first level is related to a hole trap while the second one to an electron trap.

The optical properties of polysubstituted α-conjugated quaterthiophene crystals display marked differences depending on substitution pattern and molecular conformation. The combination of optical spectroscopy and x-ray diffraction elucidates the correlation among molecular functionalization, crystalline structure, and electronic states. The data are quantitatively interpreted by a semiempirical technique that provides the excited state energies starting from the measured molecular geometry.

We present a theoretical and experimental study on the mid-infrared electroluminescence associated with transitions between electric-field-induced conduction states, forming the Wannier–Stark ladder, in strongly coupled GaAs/AlAs superlattices. The interwell and intrawell radiative transitions in the whole range of electric fields from the moderate localization to the resonance-induced delocalization regimes have been experimentally investigated. Monte Carlo simulations show a very good agreement between experimental and theoretical electroluminescence spectra. Results show that the application of an electric field in the range from 100 to 250 kV/cm shifts the emission peak, related with interwell diagonal transitions between Stark-localized ground states of two adjacent wells, up to the limit corresponding to the merging of this electroluminescence peak with the intersubband emission between excited and ground state of the same well. The theoretical investigation indicates that interwell scattering via LO phonons is responsible for the population of the excited state of the ladder.

We have investigated the electrical properties of organic thin-film transistors by way of two-dimensional drift-diffusion simulations. The dependence of the electrical characteristics on the mobility model and on the Schottky barrier height of the contacts is analyzed. We found that both the field dependence of the carrier mobility and the barrier height of the contacts are responsible for the nonlinearity of the output characteristics in the low bias region. We have then extracted the mobility from the simulated characteristics using standard metal–oxide–semiconductor analytic relations and compared to the mobility used in the simulation. The discrepancy found between the two mobilities is mainly induced by the presence of the contact barrier.

The critical temperature for Bose condensation of exciton polaritons in an AlGaN microcavity containing 9 GaN quantum wells is calculated to be T5460 K. We have modeled the kinetics of polaritons in such a microcavity device using the two-dimensional Boltzmann equation. Room-temperature lasing is found with a threshold as small as 100 mW. The kinetic blocking of polariton relaxation that prevents formation of the Bose-condensed phase of polaritons at low temperatures disappears at high temperatures, especially in n-doped samples. Thus, GaN microcavities are excellent candidates for realization of room-temperature polariton lasers.

A theoretical investigation of electron dynamics in superlattice InGaAs/AlInAs quantum cascade lasers(QCLs) is presented, based on a Monte Carlo simulation that includes both electron–electron and electron–phonon scattering. Nonequilibrium phonons and phonon quantization effects have been explicitly considered. Calculated luminescence and gain spectra are presented. Our analysis provides a clear physical insight into the QCL operational mode.

The many-body effects on excitons properties in GaN/AlGaN quantum wells are theoretically investigated by using a Green’s function model and the electron and hole wave functions calculated either in the envelope function approximation or in the frame of a self-consistent tight-binding model. We show that the built-in field induced by the piezoelectric and spontaneous polarization charge causes a reduction of the exciton binding energy and of the absorption coefficient well below the values expected for the quantum well with flat band. At high carrier concentrations, the many-body screening prevails over the screening of the built-in electric field, causing complete exciton bleaching at typical densities of the order of 1012 cm−2.

In polymer solar cells based on the blend of regioregular poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester, the hole collecting layer has to be endowed with its ionization potential close to or greater than that of P3HT (∼5 eV). Conductive polymer blends such as poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and metal oxides such as vanadium pentoxide (V2O5) and molybdenum trioxide (MoO3) satisfy this requirement and have been the most common materials used so far in bulk heterojunction structures. We report here cobalt sulfide (CoS) to be a promising hole collecting material deposited by convenient and room temperature electrodeposition. By simply tuning the CoS electrodeposition parameters, power conversion efficiencies similar (within 15%) to a reference structure with PEDOT:PSS were obtained.

We have investigated the focusing and dynamics of non-spherical polymeric particles in microfluidic flows at finite Reynolds number. The rotational diameter, Dmax, of a particle, regardless of its cross-sectional shape, was found to determine the final focused position, except for the case of asymmetric disks. Additionally, elongated particles with larger Dmax exhibited longer residence times in a horizontal orientation than those with smaller Dmax. These findings inform approaches to hydrodynamically control shaped and barcoded particles for multiplexed biochemical assays.

By identifying the right combination of laser parameters, in particular the integrated laser fluence Φ, we fabricated dye solar cells (DSCs) with UV laser-sintered TiO2 films exhibiting a power conversion efficiency η=5.2%, the highest reported for laser-sintered devices. η is dramatically affected by Φ and a clear trend is reported. Significantly, DSCs fabricated by raster scanning the laser beam to sinter the TiO2 films are made as efficient as those with oven-sintered ones. These results, confirmed on three batches of cells, demonstrate the remarkable potential (noncontact, local, low cost, rapid, selective, and scalable) of scanning laser processing applied to DSC technology.

We present the first simulation of an electrically injected polariton laser device based on Bose–Einstein condensation of exciton polaritons in a bulk GaN microcavity. Our simulator self-consistently describes carrier flow, exciton formation and dissociation, and relaxation of exciton polaritons toward the ground state. We find a density-current threshold of about 50 A/cm2 at room temperature, which could be further improved by using polariton lasers based on quantum wells.

We report unique electronic and transport properties of contacts between a molybdenum sulfide nanowire and a gold electrode. The pointlike contacts exhibit a remarkable transparency for the charge carrier injection, which is the consequence of the “task division” between sulfur and molybdenum atoms at the interface with the gold electrode, where sulfur binds the nanowire to the electrode, and the current flows unperturbed through the direct Au–Mo channels. The unique properties of the analyzed contacts solve some major drawbacks in the molecular electronics devices, such as the difficulties for the current injection from the electrodes into conjugated carbon-based molecules.

In this work, we discuss the influence of the large mobility difference between electrons and holes on the electrical injection properties of GaN based vertical cavity surface emitting lasers. This mobility unbalance is mainly responsible for the unfocusing of the electron and hole radiative recombination in the central region of the device where the electromagnetic field is confined.