In this work two cytokines were used in combination with inactivated bacteria (bacterin) to test the bovine conjuctival immune response to the pathogen Moraxella bovis, the causative agent of ...Infectious bovine keratoconjunctivitis (IBK). Treatments using the bacterin vaccine combined with interleukin-2 and interferon-α as adjuvants (Group A), the bacterin vaccine only (Group B), and controls without treatment (Group C), were applied by ocular spraying to evaluate the local immune response in the corneal structure of cattle experimentally infected with M. bovis. Six weeks after infection, 14 out of a total of 34 animals presented different corneal lesions; 9 corresponding to the control group C, 4 to the group B and only one to the group A. According to the clinical manifestations, a numeric score was calculated. Control animals presented the highest score value (12 points), followed by group B (7.5 points) and group A (1 point). These results suggest that the addition of cytokines to M. bovis treatments can reduce not only eye injuries caused by IBK but also the number of diseased animals.
The power conversion efficiency (PCE) of NiO based perovskite solar cells has recently hit a record 22.1% with a hybrid organic-inorganic perovskite composition and a PCE above 15% in a fully ...inorganic configuration was achieved. Moreover, NiO processing is a mature technology, with different industrially attractive processes demonstrated in the last few years. These considerations, along with the excellent stabilities reported, clearly point towards NiO as the most efficient inorganic hole selective layer for lead halide perovskite photovoltaics, which is the topic of this review. NiO optoelectronics is discussed by analysing the different doping mechanisms, with a focus on the case of alkaline and transition metal cation dopants. Doping allows tuning the conductivity and the energy levels of NiO, improving the overall performance and adapting the material to a variety of perovskite compositions. Furthermore, we summarise the main investigations on the NiO/perovskite interface stability. In fact, the surface of NiO is commonly oxidised and reactive with perovskite, also under the effect of light, thermal and electrical stress. Interface engineering strategies should be considered aiming at long term stability and the highest efficiency. Finally, we present the main achievements in flexible, fully printed and lead-free perovskite photovoltaics which employ NiO as a layer and provide our perspective to accelerate the improvement of these technologies. Overall, we show that adequately doped and passivated NiO might be an ideal hole selective layer in every possible application of perovskite solar cells.
The power conversion efficiency of NiO based perovskite solar cells has recently hit a record 22.1%. Here, the main advances are reviewed and the role of NiO in the next breakthroughs is discussed.
The operation of halide perovskite optoelectronic devices, including solar cells and LEDs, is strongly influenced by the mobility of ions comprising the crystal structure. This peculiarity is ...particularly true when considering the long‐term stability of devices. A detailed understanding of the ion migration‐driven degradation pathways is critical to design effective stabilization strategies. Nonetheless, despite substantial research in this first decade of perovskite photovoltaics, the long‐term effects of ion migration remain elusive due to the complex chemistry of lead halide perovskites. By linking materials chemistry to device optoelectronics, this study highlights that electrical bias‐induced perovskite amorphization and phase segregation is a crucial degradation mechanism in planar mixed halide perovskite solar cells. Depending on the biasing potential and the injected charge, halide segregation occurs, forming crystalline iodide‐rich domains, which govern light emission and participate in light absorption and photocurrent generation. Additionally, the loss of crystallinity limits charge collection efficiency and eventually degrades the device performance.
A multi‐technique in situ structural and optoelectronic characterization on planar perovskite solar cells reveals perovskite amorphization and phase segregation as the crucial degradation mechanisms due to ion migration on a daily timescale. The degradation has a severe negative impact on the charge collection, which reduces the photocurrent and the power conversion efficiency. The mechanism is partially reversible after rest in the dark.
Poly (triaryl amine) (PTAA) is one of the promising hole transport materials (HTM) for perovskite solar cells. Highly efficient PTAA-devices have been demonstrated in both direct (n-i-p) and inverted ...(p-i-n) architectures. In the inverted structures, the device suffers from poor coverage of the perovskite film over the hydrophobic PTAA surface. To address this issue, we exploited an easy and efficient approach utilizing a short-time UV treatment of the PTAA layer prior to the perovskite deposition. The UV-treatment improved the optical properties of PTAA layers, which synergistically helps the light harvesting of the perovskite. Enhanced grain sizes, together with the decrease of recombination centers in the UV treated dopant-free PTAA, lead to efficient perovskite solar cell with PCE reaching 19.17% for 0.09 cm2 active area. Moreover, the device retains over 75% of its initial efficiency after 1400 h storage in ambient condition with average relative humidity (RH) of 50%. Additionally, the effect of UV light was studied on PTAA with different molecular weights. Non-destructive UV exposure more predominantly improved the efficiency of lower molecular weight PTAA-based device. A maximum PCE of 12.3% for 1 cm2-sized cells using 5 min-UV PTAA with low MW is achieved.
This investigation points to the main roles of the HTL quality for the development of high-efficiency photovoltaic solar cells and provides a fast, easy and cost-effective method toward upscaling.
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•A high quality perovskite film based on PTAA hole transport layer was fabricated.•Uniform hydrophilicity of PTAA was carried out by its UV treatment.•An improvement in performance and stability was observed by the UV treatment.•Effect of UV treatment on PTAA layers with different molecular weights was studied.
In perovskite solar cells (PSCs), the interfaces are a weak link with respect to degradation. Electrochemical reactivity of the perovskite's halides has been reported for both molecular and polymeric ...hole selective layers (HSLs), and here it is shown that also NiO brings about this decomposition mechanism. Employing NiO as an HSL in p–i–n PSCs with power conversion efficiency (PCE) of 16.8%, noncapacitive hysteresis is found in the dark, which is attributable to the bias‐induced degradation of perovskite/NiO interface. The possibility of electrochemically decoupling NiO from the perovskite via the introduction of a buffer layer is explored. Employing a hybrid magnesium‐organic interlayer, the noncapacitive hysteresis is entirely suppressed and the device's electrical stability is improved. At the same time, the PCE is improved up to 18% thanks to reduced interfacial charge recombination, which enables more efficient hole collection resulting in higher Voc and FF.
Hysteresis in the dark, attributable to bias induced degradation of the p‐type interface, is investigated and eliminated in NiO‐based inverted perovskite solar cells. Enhanced stability to forward bias is obtained with the introduction of a low‐temperature hybrid magnesium‐based interlayer.
Electrodeposition of NiOOH is an attracting route toward nanosized films of NiO, a p-type semiconductor used in many advanced applications. In this paper, the deposition mechanism is thoroughly ...investigated aiming at the clarification of the deposition dynamics and the chemical nature of the deposit. We focused on initial stages of the potentiostatic deposition on ITO, which yields a nanostructured film. In the potential range investigated the process is mass transport controlled and strongly overlaps with oxygen evolution reaction. The nucleation regime, which is finely tunable, correlates with the surface extension of the film. Supporting electrolytes are found to suppress the deposition, likely by modifying the nickel speciation in the aqueous electrolyte. Further, through XPS investigation we shed light on the mixed γ−β NiOOH nature of the deposited film and its electrochemistry. This work provides precious understanding for future exploitations of anodic electrodeposited NiO, especially in applications where a strict control on surface morphology and thickness at the nanoscale level is mandatory.
In this study, a Maxwell–Rayleigh-type model is investigated, describing a unidimensional lattice with a finite length, where the unit cell includes hosting and resonant masses mutually connected by ...elastic springs. The configuration selected is inspired by the specific engineering design to be discussed: however, the theoretical approach pursued is rather general and can be easily generalized to different scenarios. By the heuristic homogenization based on a Piola’s Ansatz, an equivalent continuum is specified: through a variational approach, resting on the minimization of the Hamilton’s action functional, a dispersion relation is deduced, revealing the existence of a band gap. Such a continuous interval of frequencies, inside which the propagation of waves is inhibited, can be tuned controlling the features of the original system. Thereafter, exploiting the same equations, the stationary elasto-dynamic response for a chain with a finite length is also deduced, corresponding to standing waves. On the basis of such results, the preliminary design of a linear chain with a finite number of cells is carried out. By the present strategy proper boundary conditions are deduced to be prescribed at the ends of the 1D lattice sample, and not over the unit cell (as it occurs in Bloch–Floquet approach with periodicity conditions). To realize the mutual elastic connections between unequal masses fitting the problem constraints, tensegrity prisms are selected, including compressed bars and tensioned cables, for which it is possible to govern the tangent axial stiffness through the cable pre-tensioning. We analyze the scenario in which the band gap coincides with the interval 1−10Hz, indicating an appropriate geometry and suitable engineering materials for the tensegrity elements.
•Heuristic homogenization of a Maxwell–Rayleigh finite length lattice.•Boundary conditions through Hamilton’s action minimization.•A frequency band gap tunable by the unit cell parameters.•Design of a linear chain with a finite number of masses and tensegrity prisms.•Selection of suitable materials for band gap in the frequency range 1–10 Hz.
The mammalian brain stores and distinguishes among episodic memories, i.e. memories formed during the personal experience, through a mechanism of pattern separation computed in the hippocampal ...dentate gyrus. Decision-making for food-related behaviors, such as the choice and intake of food, might be affected in obese subjects by alterations in the retrieval of episodic memories. Adult neurogenesis in the dentate gyrus regulates the pattern separation. Several molecular factors affect adult neurogenesis and exert a critical role in the development and plasticity of newborn neurons. Orexin-A/hypocretin-1 and downstream endocannabinoid 2-arachidonoylglycerol signaling are altered in obese mice. Here, we show that excessive orexin-A/2-arachidonoylglycerol/cannabinoid receptor type-1 signaling leads to the dysfunction of adult hippocampal neurogenesis and the subsequent inhibition of plasticity and impairment of pattern separation. By inhibiting orexin-A action at orexin-1 receptors we rescued both plasticity and pattern separation impairment in obese mice, thus providing a molecular and functional mechanism to explain alterations in episodic memory in obesity.
The crystallization behavior of propene–ethylene (iPPC2), propene–butene (iPPC4), propene–pentene (iPPC5), and propene–hexene (iPPC6) isotactic copolymers, prepared with single center metallocene ...catalysis, is described. Thanks to the perfectly random distribution of comonomers along the macromolecules, these copolymers can be considered as model for the crystallization behavior of isotactic polypropylene (iPP) that is mainly defined by the average length of the regular propene sequences. A model of the crystallization behavior of iPP is described based on the definition of a double effect of defects (stereodefects and comonomers), the interruption effect of defects excluded from the crystals that shortens the length of the crystallizable propene sequences inducing crystallization of the γ form, and the effect of inclusion of defects in the crystals of α form, γ form or δ form that induces the crystallization of the form whose lattice is less disturbed by the defect.
The crystallization behavior of isotactic polypropylene is defined by a double role of defects, the interruption effect of defects excluded from the crystals that shortens the length of regular propene sequences and induces crystallization of γ form, and the effect of inclusion of defects into crystals driven by density increase that induces crystallization of α or δ forms.
Nanostructured NiO as hole selective contact for perovskite solar cells is deposited on ITO from the potentiostatic anodic electrodeposition of NiOOH. Along with the large surface extension due to ...the honeycomb-like morphology, the electrodeposition route imparts different electrochemical features in respect to the classic sol-gel derived NiO, which are two interesting features for optoelectronic applications. CH3NH3PbI3 is deposited in ambient atmosphere on the NiO substrates to fabricate p-i-n perovskite solar cells, with PCBM and solution processed BCP as electron selective contact and silver as counter electrode. We found that the performances are strongly dependent on the deposition potential, with the PCE increasing when going from 1.00 V to 1.10 V vs Ag/AgCl. The best efficiency obtained is 16.1%, thanks to a fill-factor of 78%. Notably, the electrodeposited layer outperformed the sol-gel spin-coated one, proving the effectiveness of electrosynthesis to achieve competitive selective contacts for perovskite photovoltaics.
•Anodic electrodeposition of NiO leads to nanosized and nanostructured thin film.•Perovskite solar cells are fabricated depositing CH3NH3PbI3 in air.•The nanoflakes morphology of NiO enlarges the area of contact between the hole selective contact and the perovskite layer.•Efficiency above 16% and FF of 78% are obtained when depositing the NiO HSL at the higher potential.
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