A universal co-solvent dilution strategy enables facile and cost-effective fabrication of perovskite photovoltaics

Cost management and toxic waste generation are two key issues that must be addressed before the commercialization of perovskite optoelectronic devices. We report a groundbreaking strategy for eco-friendly and cost-effective fabrication of highly efficient perovskite solar cells. This strategy involves the usage of a high volatility co-solvent, which dilutes perovskite precursors to a lower concentration (<0.5 M) while retaining similar film quality and device performance as a high concentration (>1.4 M) solution. More than 70% of toxic waste and material cost can be reduced. Mechanistic insights reveal ultra-rapid evaporation of the co-solvent together with beneficial alteration of the precursor colloidal chemistry upon dilution with co-solvent, which in-situ studies and theoretical simulations confirm. The co-solvent tuned precursor colloidal properties also contribute to the enhancement of the stability of precursor solution, which extends its processing window thus minimizing the waste. This strategy is universally successful across different perovskite compositions, and scales from small devices to large-scale modules using industrial spin-coating, potentially easing the lab-to-fab translation of perovskite technologies.

Direct Z-scheme MgIn2S4/TiO2 heterojunction for enhanced photocathodic protection of metals under visible light

To improve the photocathodic protection performance of traditional TiO2 photoanodes for metals, constructing a Z-scheme heterojunction is one of the most promising and creative strategies. Herein, we fabricated a novel Z-scheme MgIn2S4 nanosheets/TiO2 nanotube nanocomposite through anodization and hydrothermal method. The optimized Z-scheme MgIn2S4/TiO2 nanocomposites exhibited stronger visible light absorption, higher separation efficiency of photoelectrons and photocathodic protection performances in comparison to pure TiO2. The theoretical analysis and experimental results show that the Z-scheme heterojunction and oxygen vacancies jointly improved the separation efficiency of photogenerated electron-hole pairs and visible light absorption capacity, thereby improving the photoelectric conversion performance of the MgIn2S4/TiO2 nanocomposites. Furthermore, the influence of the precursor solution concentration on the photocathodic protection performances of the composites was investigated. As a result, when the concentration of magnesium source in the precursor solution was 0.06 mmol, the prepared MgIn2S4/TiO2-0.06 displayed the best photocathodic protection performance. In addition, the hydroxyl radicals (•OH) generated in the electron spin resonance (ESR) experiment verified the Z-scheme heterojunction mechanism of the MgIn2S4/TiO2 composite, and also demonstrated the excellent redox performance of the composite. This work provides valuable reference for the construction of high-performance Z-scheme heterojunctions for photocathode protection of metals.

The Rational Control of Precursor Concentration in Perovskite Light-Emitting Diodes

Perovskite light-emitting diodes (PeLEDs) have attracted tremendous attention due to their ideal optoelectronic properties, such as high color purity, high fluorescence quantum yield, and tunable light color. The perovskite layer plays a decisive role in the performance of PeLEDs and the solvent engineering of the perovskite layer is the key technological breakthrough in preparing high quality films. In this study, we have proposed the strategy of adding different amounts of solvents to the perovskite precursor solution to optimize the morphology of perovskite films and device performance. As a result, with the decreasing concentration of perovskite precursor solution, the perovskite film morphology is smoother and more favorable for carrier injection and combing, which induces an enhanced external quantum efficiency. The maximum luminance of PeLEDs was increased from 1667 cd/m2 to 9857 cd/m2 and the maximum current efficiency was increased from 6.7 cd/A to 19 cd/A. This work provides a trend to achieve improved film morphology and device performance for perovskite optoelectronic devices.

Solvent and cosolute dependence of Mg surface enrichment in submicron aerosol particles

The formation of multicomponent aerosol particles from precursor solution droplets often involves segregation and surface enrichment of the different solutes, resulting in non-homogeneous particle structures and diverse morphologies. In particular,...

Effects of Preheating Treatments on the Performance of Perovskite Solar Cells

Perovskite solar cells (PSCs) have fascinated widespread focus for prominent perfomances recently. The processing parameters in spin-coating have great influence on the efficiency of PSCs. Herein, we have researched the influence of different preheating treatments on the perfomance of PSCs. The power conversion efficiency (PCE) has a significant enhancement to 15.89% through preheating the substrate together with precursor solution simultaneously. This work promotes the development of high performance PSCs and their industrialization.

Effects of Biologically Synthesized Iron Oxide Nanoparticles on Rhizospheric Microorganisms Associated with Tomato (Solanum lycopersicum L.)

In this study, the effect of iron oxide nanoparticles on soil rhizospheric microbial communities of tomato was investigated. Iron oxide nanoparticles were biologically synthesized using plant extract from Azadirachta indica, and characterized using a UV-VIS spectrophotometer. Varying concentrations (25, 50, 75, or 100 %) of biosynthesized iron oxide nanoparticles or precursor solution was rhizoinjected into soils in which tomato plants were grown. Plate count method was used to analyse population size and community structure of test subjects. Quantitative analysis of the bacterial and fungal community was determined and diversity indicies were calculated. The results obtained from the analysis revealed that the addition of iron oxide nanoparticles to the soil changed bacterial and fungal community with respect to the control. Also, the bacterial and fungal abundance were changed. Some tolerant microorganisms such as Micrococcus, Stapylococcus, Aspergillus, Trichoderma and Penicillium could withstand high concentrations of iron oxide nanoparticles. Shannon diversity indices showed that there was difference in the diverisity of each concentration of iron oxide nanoparticles for both fungal and bacterial communties. The study's findings showed that high concentration of iron oxide nanoparticles in the soil had adverse effect on both the tomato and the microorganisms associated with the root of the tomato. Further study needs to be conducted to ascertain the magnitude of impact iron oxide nanoparticles will have on plants and rhizosphere microbiome.

Effect of Surfactant Type on Synthesis and Characteristics of Nanonickel Hydroxide

Nickel hydroxide has a vital role in various applications, especially as a support material for energy storage materials. Nickel hydroxide can be synthesized through the hydroxide precipitation method. However, the product formed by this method may be large or more than 100 nm because the agglomeration step can occur easily. This present work aims to study the effect of surfactant types in the synthesis and characterization of nickel hydroxide nanoparticle. Nickel sulfate (NiSO4) solution was used as a precursor solution, while 5M sodium hydroxide (NaOH) solution was used as a precipitation agent. The surfactants studied were alkyl benzene sulfonate (ABS), sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB), and polyvinylpyrrolidone (PVP). The nickel hydroxide synthesis process was carried out at 50 oC for 1 hour. The surfactant concentration used was at the critical micelle concentration (CMC), where the CMC for ABS, SDS, CTAB, and PVP were 0.01; 0.05; 3; and 0.5 %w/v, respectively. The synthesis of nickel hydroxide nanoparticle was carried out successfully precipitated almost 100% of Ni2+ ions. The product characterization that has been carried out shows that ABS surfactant produces the best nickel hydroxide nanoparticle product where the particle size is 3.12–4.47 nm.

Supercritical hydrothermal synthesis of silver nanoparticles, composites, and their characterizations

Silver nanoparticles (AgNPs) and silver nanoparticles doped activated carbon (AC-Ag) composite materials were synthesized by hydrothermal processes in supercritical water conditions (29 MPa and 400 °C) using batch reactor. We studied the influence of the precursor solution concentration, reaction temperature under the hydrothermal conditions, and synthesis time on the properties of synthesized materials. The properties of plain AgNPs and AC-Ag composite materials synthesized in supercritical water, including crystallinity, particle size, and molecular interactions between AC and Ag were investigated, comprehensively. Compared to the plain AgNPs, the activated carbon-supported Ag nanocomposite was synthesized faster due to the active functional groups of activated carbon. Furthermore, the FTIR results reveal that the silver nanoparticles are attached to the activated carbon surface in the presence of oxygen bonded carbonyl and carboxyl groups. The nano-sized metal silver particles were observed on the AC surface when analyzed by TEM and XRD. All results imply that the supercritical water condition allows the formation of silver particles less than 100 nm either in the form of plain particles or deposited on the activated carbon surface using the silver acetate precursor solution. This environmentally benign supercritical hydrothermal process can replace the conventional method and become a novel synthesis method for preparing various new materials.