Improved Performance of Air-Processed Perovskite Solar Cells via the Combination of Chlorine Precursors and Potassium Thiocyanate.

Due to their low cost and high efficiency, hybrid perovskite solar cells (PSCs) have shown the most outstanding competitiveness among third-generation photovoltaic (PV) devices. However, several challenges remain unresolved, among which the limited stability is arguably the main. Chlorine (Cl) has been widely employed to yield PV performances, but the Cl-doping mechanism and its role in mixed-halide PSCs are not entirely understood.

High performance BiFeO ferroelectric nanostructured photocathodes.

Ferroelectric materials may be used as effective photoelectrocatalysts for water splitting due to enhanced charge carrier separation driven by their spontaneous polarization induced internal electric field. Compared to other ferroelectric materials, BiFeO exhibits a high catalytic efficiency due to its comparatively smaller bandgap, which enables light absorption from a large part of the solar spectrum and its higher bulk ferroelectric polarization. Here, we compare the photoelectrochemical properties of three different BiFeO morphologies, namely, nanofibers, nanowebs, and thin films synthesized via electrospinning, directly on fluorine-doped tin oxide (FTO) coated glass substrates.

Epitaxial patterned BiFeCrO nanoisland arrays with room temperature multiferroic properties.

Epitaxial multiferroic BiFeCrO nanoisland arrays with a lateral size of ∼100 nm have been successfully fabricated by patterned SiO template-assisted pulsed laser deposition. The as-grown island structure exhibits promising multiferroic properties ( ferroelectric and magnetic) even at nanometer dimensions at room temperature. This work demonstrates an effective strategy to fabricate high-density nonvolatile ferroelectric/multiferroic memory devices.

Halide Perovskite Nanocrystals for Next-Generation Optoelectronics.

Colloidal perovskite nanocrystals (PNCs) combine the outstanding optoelectronic properties of bulk perovskites with strong quantum confinement effects at the nanoscale. Their facile and low-cost synthesis, together with superior photoluminescence quantum yields and exceptional optical versatility, make PNCs promising candidates for next-generation optoelectronics. However, this field is still in its early infancy and not yet ready for commercialization due to several open challenges to be addressed, such as toxicity and stability.

Epitaxial BiFeCrO Multiferroic Thin-Film Photoanodes with Ultrathin p-Type NiO Layers for Improved Solar Water Oxidation.

The photoelectric properties of multiferroic double-perovskite BiFeCrO (BFCO), such as above-band gap photovoltages, switchable photocurrents, and bulk photovoltaic effects, have recently been explored for potential applications in solar technology. Here, we report the fabrication of photoelectrodes based on n-type ferroelectric (FE) semiconductor BFCO heterojunctions coated with p-type transparent conducting oxides (TCOs) by pulsed laser deposition and their application for photoelectrochemical (PEC) water oxidation. The photocatalytic properties of the bare BFCO photoanodes can be improved by controlling the FE polarization state.

Highly Efficient and Ultrasensitive Large-Area Flexible Photodetector Based on Perovskite Nanowires.

Hybrid organic-inorganic perovskites have shown exceptional semiconducting properties and microstructural versatility for inexpensive, solution-processable photovoltaic and optoelectronic devices. In this work, an all-solution-based technique in ambient environment for highly sensitive and high-speed flexible photodetectors using high crystal quality perovskite nanowires grown on Kapton substrate is presented. At 10 V, the optimized photodetector exhibits a responsivity as high as 0.

Solvent-Antisolvent Ambient Processed Large Grain Size Perovskite Thin Films for High-Performance Solar Cells.

In recent years, hybrid organic-inorganic halide perovskites have been widely studied for the low-cost fabrication of a wide range of optoelectronic devices, including impressive perovskite-based solar cells. Amongst the key factors influencing the performance of these devices, recent efforts have focused on tailoring the granularity and microstructure of the perovskite films. Albeit, a cost-effective technique allowing to carefully control their microstructure in ambient environmental conditions has not been realized.

Hysteresis-Free 1D Network Mixed Halide-Perovskite Semitransparent Solar Cells.

The morphology of hybrid organic-inorganic perovskite films is known to strongly affect the performance of perovskite-based solar cells. CH NH PbI Cl (MAPbI Cl ) films have been previously fabricated with 100% surface coverage in glove boxes. In ambient air, fabrication generally relies on solvent engineering to obtain compact films.

An ultra-broadband perovskite-PbS quantum dot sensitized carbon nanotube photodetector.

Organic-inorganic perovskites have been hailed as promising candidates for optoelectronic and photovoltaic devices, but their operation remains limited to the visible spectrum. Here, we combine single-wall carbon nanotubes, PbS quantum dots and a perovskite to synthesize hybrid devices suitable for operation in both the visible and near-infrared. The photodetectors thus fabricated show responsivities as high as 0.

Highly Sensitive Switchable Heterojunction Photodiode Based on Epitaxial BiFeCrO Multiferroic Thin Films.

Perovskite multiferroic oxides are promising materials for the realization of sensitive and switchable photodiodes because of their favorable band gap (<3.0 eV), high absorption coefficient, and tunable internal ferroelectric (FE) polarization. A high-speed switchable photodiode based on multiferroic BiFeCrO (BFCO)/SrRuO (SRO)-layered heterojunction was fabricated by pulsed laser deposition.

Highly Efficient Thermoelectric Microgenerators Using Nearly Room Temperature Pulsed Laser Deposition.

Thermoelectric BiTe and SbTe thin films with high power factor were successfully obtained by pulsed laser deposition (PLD). Here, we demonstrate a well-controlled deposition of BiTe/SbTe structures on glass substrates, through a shadow mask with micrometer-scale features. We establish an optimal growth temperature of 45 °C to attain compounds with suitable stoichiometric composition, as well as structural and electrical properties, to achieve high thermoelectric power factor.

Combined magnetron sputtering and pulsed laser deposition of TiO and BFCO thin films.

We report the successful demonstration of a hybrid system that combines pulsed laser deposition (PLD) and magnetron sputtering (MS) to deposit high quality thin films. The PLD and MS simultaneously use the same target, leading to an enhanced deposition rate. The performance of this technique is demonstrated through the deposition of titanium dioxide and bismuth-based perovskite oxide BiFeCrO (BFCO) thin films on Si(100) and LaAlO (LAO) (100).

Epitaxial magnetite nanorods with enhanced room temperature magnetic anisotropy.

Nanostructured magnetic materials with well-defined magnetic anisotropy are very promising as building blocks in spintronic devices that operate at room temperature. Here we demonstrate the epitaxial growth of highly oriented FeO nanorods on a SrTiO substrate by hydrothermal synthesis without the use of a seed layer. The epitaxial nanorods showed biaxial magnetic anisotropy with an order of magnitude difference between the anisotropy field values of the easy and hard axes.

High-performance nanotube-enhanced perovskite photodetectors.

Organic-inorganic perovskites have already shown a tremendous potential for low-cost light-harvesting devices. Yet, the relatively low carrier mobilities in bulk perovskites still prevent large-area devices with performances competing with state-of-the-art technologies. Here, we tackle this fundamental challenge by incorporating single-wall carbon nanotubes within a perovskite matrix by means of a simple two-step method in ambient air.

Enhanced photovoltaic properties in bilayer BiFeO3/Bi-Mn-O thin films.

We report an external solar power conversion efficiency of ∼1.43% in BiFeO3(BFO)/BiMnO3(BMO) bilayer thin films. Both films are epitaxially grown on (111) oriented niobium doped SrTiO3 (NSTO) single crystal substrates by pulsed laser deposition.

Photovoltaic properties of Bi2FeCrO6 films epitaxially grown on (100)-oriented silicon substrates.

We demonstrate the promising potential of using perovskite Bi2FeCrO6 (BFCO) for niche applications in photovoltaics (PV) (e.g. self-powered sensors that simultaneously exploit PV conversion and multiferroic properties) or as a complement to mature PV technologies like silicon.

Epitaxial Bi2 FeCrO6 Multiferroic Thin Film as a New Visible Light Absorbing Photocathode Material.

Ferroelectric materials have been studied increasingly for solar energy conversion technologies due to the efficient charge separation driven by the polarization induced internal electric field. However, their insufficient conversion efficiency is still a major challenge. Here, a photocathode material of epitaxial double perovskite Bi(2) FeCrO(6) multiferroic thin film is reported with a suitable conduction band position and small bandgap (1.

Photovoltaic effect in multiphase Bi-Mn-O thin films.

We report an external solar power conversion efficiency of ~0.1% in Bi-Mn-O thin films grown onto (111) oriented Niobium doped SrTiO3 (STO) single crystal substrate by pulse laser deposition (PLD). The films contain BiMnO3 (BMO) and Mn3O4 (MO) phases, which both grow epitaxially.

Remarkably enhanced photocatalytic activity of laser ablated Au nanoparticle decorated BiFeO3 nanowires under visible-light.

Hybrid photocatalysts consisting of single crystalline BiFeO3 nanowires and laser ablated Au nanoparticles were synthesized by a functionalization-step-free solution process. The 1.0 wt% Au nanoparticle decorated BiFeO3 nanowires exhibit ~30 times higher photocatalytic activity for water oxidation than that exhibited by the parent wires during the first 4 h.

Mechanical and electrical properties of epitaxial Si nanowires grown by pulsed laser deposition.

We report on the elastic and piezoresistive properties of individual epitaxial Si-NWs grown on n-doped Si(111) by pulsed laser deposition. Using scanning probe microscopy, we obtained a Young's modulus between 82 and 900 GPa for the nanowires, unaffected by the nanowire shape. A relative resistivity change is observed in the prestrained (curved) Si-NWs, which we attribute to a large piezoresistance coefficient in the NW along its axis.

Multiferroic nanoscale Bi2FeCrO6 material for spintronic-related applications.

We report the control of the growth mode of Bi(2)FeCrO(6) thin and ultrathin films by either tuning the pulsed laser deposition parameters or by using a buffer layer. The films are epitaxial and the heterostructures exhibit very smooth interfaces, thus eliminating the main obstacle in the realization of tunnel junctions. By characterizing the functional properties of thin films we find that Bi(2)FeCrO(6) retains its room temperature multiferroic character even at the nanoscale.

Coexistence of antiferromagnetic and ferromagnetic orders at remanent state in epitaxial multiferroic Bi2FeCrO6 nanostructures.

We report the local electronic and magnetic properties of Bi(2)FeCrO(6) nanostructures by element-specific polarized x-ray techniques. Sizable magnetic ordering in the remanent state is observed at room temperature for both Fe and Cr ions. The Bi(2)FeCrO(6) system offers an example of d(5)-d(3) magnetic superexchange interaction with a magnetic order for both Fe and Cr, which are both formally in the  + 3 valence state.

Multiferroic properties-structure relationships in epitaxial Bi(2)FeCrO(6) thin films: recent developments.

We report recent developments in the growth and characterization of epitaxial Bi(2)FeCrO(6) (BFCO) thin films. The body of experimental data stemming mostly from our investigations, and also considering the few available reports from other groups, allows us to explain the origin(s) of the thickness dependence of the multiferroic properties observed. A drastic reduction of the films' magnetization is observed for film thicknesses larger than 80 nm.

Bifunctional catalytic/magnetic Ni@Ru core-shell nanoparticles.

Core-shell structured Ni@Ru bimetallic nanoparticles are demonstrated as a bifunctional nanoplatform system for the hydrolysis reaction of ammonia-borane and also for magnetic separation.