Femtosecond to nanosecond excited states dynamics of novel Corroles

We report a comprehensive photphysical investigation of some corrole molecules employing fs/nanosecond (ns) transient-absorption and time-resolved photoluminescence spectroscopy with support from the time-dependent density-functional theory calculations to understand their intramolecular charge transfer and polaron-absorption character

Influence of Charge Transport Layers on Open Circuit Voltage and Hysteresis in Perovskite Solar Cells

Perovskite materials have experienced an impressive improvement in photovoltaic performance due to their unique combination of optoelectronic properties. Their remarkable progression, facilitated by the use of different device architectures, compositional engineering, and processing methodologies, contrasts with the lack of understanding of the materials properties and interface phenomena. Here we directly target the interplay between the charge-transporting layers (CTLs) and open-circuit potential (VOC) in the operation mechanism of the state-of-the-art CH3NH3PbI3 solar cells. Our results suggest that the VOC is controlled by the splitting of quasi-Fermi levels and recombination inside the perovskite, rather than being governed by any internal electric field established by the difference in the CTL work functions. In addition, we provide novel insights into the hysteretic origin in perovskite solar cells, identifying the nature of the contacts as a critical factor in defining the charge accumulation at its interface, leading to either ionic, electronic, or mixed ionic-electronic accumulation

Three-Dimensional Self-Assembly of Networked Branched TiO2 Nanocrystal Scaffolds for Efficient Room-Temperature Processed Depleted Bulk Heterojunction Solar Cells

In this work, we report on 4% power conversion efficiency (PCE) depleted bulk heterojunction (DBH) solar cells based on a high-quality electrode with a three-dimensional nanoscale architecture purposely designed so as to maximize light absorption and charge collection. The newly conceived architecture comprises a mesoporous electron-collecting film made of networked anisotropic metal-oxide nanostructures, which accommodates visible-to-infrared light harvesting quantum dots within the recessed regions of its volume. The three-dimensional electrodes were self-assembled by spin-coating a solution of colloidal branched anatase TiO2 NCs (BNC), followed by photocatalytic removal of the native organic capping from their surface by a mild UV-light treatment and filling with small PbS NCs via infiltration. The PCE = 4% of our TiO2 BNC/PbS QD DBH solar cell features an enhancement of 84% over the performance obtained for a planar device fabricated under the same conditions. Overall, the DBH device fabrication procedure is entirely carried out under mild processing conditions at room temperature, thus holding promise for low-cost and large-scale manufacturing

Exploring characteristics associated with first benzodiazepine prescription in patients with affective disorders and related diagnoses

Objective In patients with affective disorders, benzodiazepines (BZDs) are frequently administered at the onset, sometimes inappropriately. We sought to identify clinical variables associated with first BZD prescription in a large sample of patients with affective disorders. Methods Four hundred sixty patients with mood or anxiety disorders attending different psychiatric services were assessed comparing those who received BZD as first treatment (BZD w/) and those who did not (BZD w/o). Results More than one third (35.7%) of the total sample had received BZDs as first prescription. In relation to mood disorders, BZD w/ subjects more frequently (a) had not a psychiatrist as first therapist, (b) had anxious symptoms at onset, (c) had adjustment disorder as first diagnosis, (d) were treated as outpatients. In relation to specific diagnoses, (a) personal decision of treatment for major depressive disorder, (b) outpatient status for bipolar disorder and (c) longer duration of untreated illness for adjustment disorder were more frequently associated with first BZD prescription. For anxiety disorders, the presence of stressful life events and the diagnoses of panic disorder or specific phobias were more frequently observed in BZD w/ patients. Conclusion Patients with affective disorders frequently received BZDs as first prescription with significant differences between and within mood and anxiety disorders

Turning molecular springs into nano-shock absorbers: the effect of macroscopic morphology and crystal size on the dynamic hysteresis of water intrusion-extrusion into-from hydrophobic nanopores

Controlling the pressure at which liquids intrude (wet) and extrude (dry) a nanopore is of paramount importance for a broad range of applications, such as energy conversion, catalysis, chromatography, separation, ionic channels, and many more. To tune these characteristics, one typically acts on the chemical nature of the system or pore size. In this work, we propose an alternative route for controlling both intrusion and extrusion pressures via proper arrangement of the grains of the nanoporous material. To prove the concept, dynamic intrusion-extrusion cycles for powdered and monolithic ZIF-8 metal-organic framework were conducted by means of water porosimetry and in operando neutron scattering. We report a drastic increase in intrusion-extrusion dynamic hysteresis when going from a fine powder to a dense monolith configuration, transforming an intermediate performance of the ZIF-8 + water system (poor molecular spring) into a desirable shock-absorber with more than 1 order of magnitude enhancement of dissipated energy per cycle. The obtained results are supported by MD simulations and pave the way for an alternative methodology of tuning intrusion-extrusion pressure using a macroscopic arrangement of nanoporous material

Tuning Halide Composition allows low dark current perovskite photodetectors with high specific detectivity

Tuning halide composition in perovskites is a powerful approach demonstrated to enhance the performance of perovskite photovoltaic devices where such compositional modifications drive improvements in open-circuit voltage (Voc) and a reduction in nonradiative voltage losses. Similarly, photodetectors (PDs) operate as light to current conversion devices hence it is relevant to investigate whether performance enhancements can be achieved by similar strategies. Herein, perovskite PDs are fabricated with an inverted photodiode configuration based on a MAPb(I1-xBrx)3 perovskite (MA = methylammonium) active layer over the x = 0–0.25 composition range. Interestingly, it has been found that increasing the Br content up to 0.15 (15%) leads to a significant reduction in dark current (Jd), with values as low as 1.3 × 10−9 A cm−2 being achieved alongside a specific detectivity of 8.7 × 1012 Jones. Significantly, it has been observed an exponential relationship between the Jd of devices and their Voc over the 0–15% Br range. The superior performances of the 15% Br-containing devices are attributed to the reduction of trap states, a better charge extraction of photogenerated carriers, and an improvement in photoactive layer morphology and crystallinity

Hyperbranched Quasi-1D TiO2 Nanostructure for Hybrid Organic-Inorganic Solar Cells

The performance of hybrid solar cells is strongly affected by the device morphology. In this work we demonstrate a Poly(3-hexylthiophene-2,5-diyl)/TiO2 hybrid solar cell where the TiO2 photoanode comprises an array of tree-like hyperbranched quasi-1D nanostructures self-assembled from the gas phase. This advanced architecture enables us to increase the power conversion efficiency to over 1%, doubling the efficiency with respect to state of the art devices employing standard mesoporous titania photoanodes. This improvement is attributed to several peculiar features of this array of nanostructures: high interfacial area; increased optical density thanks to the enhanced light scattering; and enhanced crystallization of Poly(3-hexylthiophene-2,5-diyl) inside the quasi-1D nanostructure