Partially Bio-Based Benzoxazine Monomers Derived from Thymol: Photoluminescent Properties, Polymerization Characteristics, Hydrophobic Coating Investigations, and Anticorrosion Studies.

In this work, four thymol-based benzoxazines were synthesized using four primary amines with different chain lengths, namely methylamine, ethylamine, 1-propylamine, and 1-butylamine, which are then named T-m, T-e, T-p, and T-b, respectively. The optical properties of the synthesized thymol-based benzoxazines were examined via the photoluminescent study of their solutions in acetone. The results show that all the prepared benzoxazines emitted blue light with the maximum wavelengths from 425 to 450 nm when irradiated by the excitation wavelengths from 275 to 315 nm. The maximum excitation wavelengths are found to be 275 nm. The polymerization of the thymol-based benzoxazines is triggered by heat treatments with different conditions (160, 180, and 200 °C for 1 h). According to the FTIR results, the heat-curing process introduces a presence of the OH peak, of which intensity increases as the curing temperature increases. Thermal decompositions of thymol-based benzoxazines regarding TGA analyses reveal the enhancement of thermal stability of the benzoxazines with respect to the N-substituent chain length, as significantly observed the change in the first thermal decomposition at temperature ranged from 253 to 260 °C. Synthesized benzoxazine derivatives are further employed to coat the substrate, e.g., the glass slides. The investigation of the water contact angle shows that the coating of the benzoxazines onto the surface improves the hydrophobicity of the substrate, resulting in the enlargement of the contact angle from 25.5° to 93.3°. Moreover, the anticorrosion performance of the polybenzoxazine coatings is examined using potentiodynamic polarization techniques. The results illustrate the anticorrosion efficiency of the thymol-based polybenzoxazine up to 99.99%. Both hydrophobic and electrochemical studies suggest the feasibility for employing benzoxazines in anticorrosion coating applications.

Cs and Br tuning to achieve ultralow-hysteresis and high-performance indoor triple cation perovskite solar cell with low-cost carbon-based electrode.

With high efficacy for electron-photon conversion under low light, perovskite materials show great potential for indoor solar cell applications to power small electronics for internet of things (IoTs). To match the spectrum of an indoor LED light source, triple cation perovskite composition was varied to adjust band gap values via Cs and Br tuning. However, increased band gaps lead to morphology, phase instability, and defect issues. 10% Cs and 30% Br strike the right balance, leading to low-cost carbon-based devices with the highest power conversion efficiency (PCE) of 31.94% and good stability under low light cycles. With further improvement in device stack and size, functional solar cells with the ultralow hysteresis index (HI) of 0.1 and the highest PCE of 30.09% with an active area of 1 cm2 can be achieved. A module from connecting two such cells in series can simultaneously power humidity and temperature sensors under 1000 lux.

Metal-insulator transition effect on Graphene/VO[Formula: see text] heterostructure via temperature-dependent Raman spectroscopy and resistivity measurement.

High-quality VO[Formula: see text] films were fabricated on top of c-Al[Formula: see text]O[Formula: see text] substrates using Reactive Bias Target Ion Beam Deposition (RBTIBD) and the studies of graphene/VO[Formula: see text] heterostructure were conducted. Graphene layers were placed on top of [Formula: see text] 50 and [Formula: see text] 100 nm VO[Formula: see text]. The graphene layers were introduced using mechanical exfoliate and CVD graphene wet-transfer method to prevent the worsening crystallinity of VO[Formula: see text], to avoid the strain effect from lattice mismatch and to study how VO[Formula: see text] can affect the graphene layer. Slight increases in graphene/VO[Formula: see text] T[Formula: see text] compared to pure VO[Formula: see text] by [Formula: see text] 1.9 [Formula: see text]C and [Formula: see text] 3.8 [Formula: see text]C for CVD graphene on 100 and 50 nm VO[Formula: see text], respectively, were observed in temperature-dependent resistivity measurements. As the strain effect from lattice mismatch was minimized in our samples, the increase in T[Formula: see text] may originate from a large difference in the thermal conductivity between graphene and VO[Formula: see text]. Temperature-dependent Raman spectroscopy measurements were also performed on all samples, and the G-peak splitting into two peaks, G[Formula: see text] and G[Formula: see text], were observed on graphene/VO[Formula: see text] (100 nm) samples. The G-peak splitting is a reversible process and may originates from in-plane asymmetric tensile strain applied under the graphene layer due to the VO[Formula: see text] phase transition mechanism. The 2D-peak measurements also show large blue-shifts around 13 cm[Formula: see text] at room temperature and slightly red-shifts trend as temperature increases for 100 nm VO[Formula: see text] samples. Other electronic interactions between graphene and VO[Formula: see text] are expected as evidenced by 2D-peak characteristic observed in Raman measurements. These findings may provide a better understanding of graphene/VO[Formula: see text] and introduce some new applications that utilize the controllable structural properties of graphene via the VO[Formula: see text] phase transition.

Robust perovskite formation via vacuum thermal annealing for indoor perovskite solar cells.

Perovskite materials are fascinating candidates for the next-generation solar devices. With long charge carrier lifetime, metal-halide perovskites are known to be good candidates for low-light harvesting. To match the irradiance spectra of indoor light, we configured a triple-cation perovskite material with appropriate content of bromide and chloride (FA0.45MA0.49Cs0.06Pb(I0.62Br0.32Cl0.06)3) to achieve an optimum band gap (Eg) of [Formula: see text]1.80 eV. With low photon flux at indoor condition, minimal recombination is highly desirable. To achieve such goal, we, for the first time, combined dual usage of antisolvent deposition and vacuum thermal annealing, namely VTA, to fabricate a high-quality perovskite film. VTA leads to compact, dense, and hard morphology while suppressing trap states at surfaces and grain boundaries, which are key culprits for exciton losses. With low-cost carbon electrode architecture, VTA devices exhibited average power conversion efficiency (PCE) of 27.7 ± 2.7% with peak PCE of 32.0% (Shockley-Queisser limit of 50-60%) and average open-circuit voltage (Voc) of 0.93 ± 0.02 V with peak Voc of 0.96 V, significantly more than those of control and the vacuum treatment prior to heat.

All green sulfolane-based solvent enhanced electrical conductivity and rigidity of perovskite crystalline layer.

Industrial commercialization of perovskite solar cells not only depends on sufficient device performance, but also requires complete elimination of hazardous solvents in the fabrication process to enable sustainable development of the technology. This work reports a new solvent system based on sulfolane, [Formula: see text]-butyrolactone (GBL), and acetic acid (AcOH) as a significantly greener alternative to common but more hazardous solvents. Interestingly, this solvent system not only resulted in densely-packed perovskite layer of bigger crystal size and better crystallinity, the grain boundaries were found to be more rigid and highly conductive to electrical current. The physical changes at the grain boundaries were due to the sulfolane-infused crystal interfaces, which were expected to facilitate better charge transfer and provide stronger barrier to moisture within the perovskite layer, yielding higher current density and longer performance of the device as a result. In fact, by using a mixed solvent system consisting of sulfolane, GBL, and AcOH in the volume ratio of 70.0:27.5:2.5, the device stability was better and the photovoltaic performance was statistically comparable with those prepared using DMSO-based solvent. Our report reflects unprecedented findings of enhanced electrical conductivity and rigidity of the perovskite layer simply by using an appropriate choice of the all-green solvent.

Photoexcitation of perovskite precursor solution to induce high-valent iodoplumbate species for wide bandgap perovskite solar cells with enhanced photocurrent.

Solution-processed organic-inorganic hybrid perovskite solar cells are among the candidates to replace the traditional silicon solar cells due to their excellent power conversion efficiency (PCE). Despite this considerable progress, understanding the properties of the perovskite precursor solution is critical for perovskite solar cells (PSCs) to achieve high performance and reproducibility. However, the exploration of perovskite precursor chemistry and its effects on photovoltaic performances has been limited thus far. Herein, we modified the equilibrium of chemical species inside the precursor solution using different photoenergy and heat pathways to identify the corresponding perovskite film formation. The illuminated perovskite precursors exhibited a higher density of high-valent iodoplumbate species, resulting in the fabricated perovskite films with reduced defect density and uniform distribution. Conclusively, the perovskite solar cells prepared by the photoaged precursor solution had not only improved PCE but also enhanced current density, confirmed by device performance, conductive atomic force microscopy (C-AFM), and external quantum efficiency (EQE). This innovative precursor photoexcitation is a simple and effective physical process for boosting perovskite morphology and current density.

Efficient and Stable Carbon-Based Perovskite Solar Cells Enabled by Mixed CuPc:CuSCN Hole Transporting Layer for Indoor Applications.

Perovskite solar cells (PSCs) are an innovative technology with great potential to offer cost-effective and high-performance devices for converting light into electricity that can be used for both outdoor and indoor applications. In this study, a novel hole-transporting layer (HTL) was created by mixing copper phthalocyanine (CuPc) molecules into a copper(I) thiocyanate (CuSCN) film and was applied to carbon-based PSCs with cesium/formamidinium (Cs0.17FA0.83Pb(I0.83Br0.17)3) as a photoabsorber. At the optimum concentration, a high power conversion efficiency (PCE) of 15.01% was achieved under AM1.5G test conditions, and 32.1% PCE was acquired under low-light 1000 lux conditions. It was discovered that the mixed CuPc:CuSCN HTL helps reduce trap density and improve the perovskite/HTL interface as well as the HTL/carbon interface. Moreover, the PSCs based on the mixed CuPc:CuSCN HTL provided better stability over 1 year due to the hydrophobicity of CuPc material. In addition, thermal stability was tested at 85 °C and the devices achieved an average efficiency drop of approximately 50% of the initial PCE value after 1000 h. UV light stability was also examined, and the results revealed that the average efficiency drop of 40% of the initial value for 70 min of exposure was observed. The work presented here represents an important step toward the practical implementation of the PSC as it paves the way for the development of cost-effective, stable, yet high-performance PSCs for both outdoor and indoor applications.

Improving morphology and optoelectronic properties of ultra-wide bandgap perovskite via Cs tuning for clear solar cell and UV detection applications.

With growing population, vertical spaces from skyscrapers are vast. Semi-transparent solar cells enable an effective pathway for vertical energy harvesting. With composition tunability, perovskite materials can be designed with different transparencies and colors. In this work, an ultra-high bandgap layered triple cation perovskite system was developed for the first time to meet the demand of clear optoelectronic applications; low dimensional triple cation perovskite thin films were fabricated using perovskite with the formula (PEA)2(CsxMA0.61-xFA0.39)39(Pb)40(Cl0.88-0.32xBr0.12+0.32x)121, 0 ≤ x ≤ 0.02 with DMSO as the appropriate solvent. The absorption edge of the material is around 410-430 nm, achieving great transparency to visible light. The structural, optical, and photovoltaic performances of the clear perovskite materials are explored with the variation of Cs contents via CsBr. The relation between thickness, transparency, and optoelectronic properties of the clear perovskite materials along with other physical properties were investigated. The highest photovoltaic conversion efficiency (PCE) of clear perovskite solar cells with 1.5% Cs was achieved to be 0.69% under xenon lamp irradiation at 100 mW/cm2 (1.5 mW/cm2 of UVA within 100 mW/cm2) and 5.24% under 365 nm UV irradiation at 2.4 mW/cm2. Photoresponsivity, external quantum efficiency (EQE), and detectivity were also determined for photodetector applications.

Graded multilayer triple cation perovskites for high speed and detectivity self-powered photodetector via scalable spray coating process.

Rapid advancements in perovskite materials have led to potential applications in various optoelectronic devices, such as solar cells, light-emitting diodes, and photodetectors. Due to good photoelectric properties, perovskite enables low-cost and comparable performance in terms of responsivity, detectivity, and speed to those of the silicon counterpart. In this work, we utilized triple cation perovskite, well known for its high performance, stability, and wide absorption range, which is crucial for broadband photodetector applications. To achieve improved detectivity and faster response time, graded multilayer perovskite absorbers were our focus. Sequential spray deposition, which allows stacked perovskite architecture without disturbing lower perovskite layers, was used to generate single, double, and triple-layer perovskite photodetectors with proper energy band alignment. In this work, we achieved a record on self-powered perovskite photodetector fabricated from a scalable spray process in terms of EQE and responsivity of 65.30% and 0.30 A W-1. The multilayer devices showed faster response speed than those of single-layer perovskite photodetectors with the champion device reaching 70 µs and 88 µs for rising and falling times. The graded band structure and the internal electric field generated from perovskite heterojunction also increase specific detectivity about one magnitude higher in comparison to the single-layer with the champion device achieving 6.82 × 1012 cmHz1/2 W-1.

Rational La-doped hematite as an anode and hydrous cobalt phosphate as a battery-type electrode for a hybrid supercapacitor.

In recent years, modern appliances require high energy density with a burst power supply. Hybrid supercapacitors show high performance based on high energy density without compromising power density and stability over thousands of charge-discharge cycles. In this work, the optimized hybrid electrodes using lanthanum-doped hematite (lanthanum-doped iron oxide) noted as 7.5%La-HMT as a negative electrode and hydrous cobalt phosphate (CoPO) as a battery-type positive electrode have been successfully fabricated via a simple hydrothermal method and a facile co-precipitation method, respectively. The 7.5%La-HMT showed excellent electrochemical performance due to doping of rare-earth La3+ metal ions, resulting in improvised active sites and reduction in the equivalent resistance. The 7.5%La-HMT operated at a high potential window (0 to -1.2 V) with an ultra-high specific capacitance (Sp) of 1226.7 F g-1 at 1 A g-1 with capacitance retention of 89.3% over 1000 cycles. CoPO could be operated at a high working window (0 to 0.45 V) with a specific capacity of 121.7 mA h g-1 at a current density of 2 A g-1 with capacitance retention of 85.4% over 1000 cycles. The configured CoPO//KOH//10%La-HMT aqueous hybrid capacitor device (Aq-HSC) could be operated at a potential window of 1.6 V and delivered a maximum energy density (E.D) of 83.6 W h kg-1 at a power density (P.D) of 3.2 kW kg-1 with Sp of 235.0 F g-1 at 2 A g-1 and 89.0% Sp retention over 5000 cycles. The simplicity of the synthesis methods for CoPO and 7.5%La-HMT along with their superior super-capacitive properties make them suitable for advanced electrical devices and hybrid vehicles.

Crystallographic and Spectroscopic Investigations on Oxidative Coordination in the Heteroleptic Mononuclear Complex of Cerium and Benzoxazine Dimer.

Among lanthanide-based compounds, cerium compounds exhibit a significant role in a variety of research fields due to their distinct tetravalency, high economic feasibility, and high stability of Ce(IV) complexes. Herein, a systematic investigation of crystallographic information, chemical properties, and mechanistic formation of the novel Ce(IV) complex synthesized from cerium(III) nitrate hexahydrate and 2,2'-(methylazanediyl)bis(methylene)bis(4-methylphenol) (MMD) ligand has been explored. According to the analysis of the crystallographic information, the obtained complex crystal consists of the Ce(IV) center coordinated with two nitrate ligands and two bidentate coordinated (N-protonated and O,O-deprotonated) MMD ligands. The fingerprint plots and the Hirshfeld surface analyses suggest that the C-H⋯O and C-H⋯π interactions significantly contribute to the crystal packing. The C-H⋯O and C-H⋯π contacts link the molecules into infinite molecular chains propagating along the [100] and [010] directions. Synchrotron powder X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) techniques have been employed to gain an understanding of the oxidative complexation of Ce(IV)-MMD complex in detail. This finding would provide the possibility to systematically control the synthetic parameters and wisely design the precursor components in order to achieve the desired properties of novel materials for specific applications.

The implementation of graphene-based aerogel in the field of supercapacitor.

Graphene and graphene-based hybrid materials have emerged as an outstanding supercapacitor electrode material primarily because of their excellent surface area, high electrical conductivity, and improved thermal, mechanical, electrochemical cycling stabilities. Graphene alone exhibits electric double layer capacitance (EDLC) with low energy density and high power density. The use of aerogels in a supercapacitor is a pragmatic approach due to its extraordinary properties like ultra-lightweight, high porosity and specific surface area. The aerogels encompass a high volume of pores which leads to easy soak by the electrolyte and fast charge-discharge process. Graphene aerogels assembled into three-dimensional (3D) architecture prevent there stacking of graphene sheets and maintain the high surface area and hence excellent cycling stability and rate capacitance. However, the energy density of graphene aerogels is limited due to EDLC type of charge storage mechanism. Consequently, 3D graphene aerogel coupled with pseudocapacitive materials such as transition metal oxides, metal hydroxides, conducting polymers, nitrides, chalcogenides show an efficient energy density and power density performance due to the presence of both types of charge storage mechanisms. This laconic review focuses on the design and development of graphene-based aerogel in the field of the supercapacitor. This review is an erudite article about methods, technology and electrochemical properties of graphene aerogel.

Quantum Dot Based Solar Cells: Role of Nanoarchitectures, Perovskite Quantum Dots, and Charge-Transporting Layers.

Quantum dot solar cells (QDSCs) are attractive technology for commercialization, owing to various advantages, such as cost effectiveness, and require relatively simple device fabrication processes. The properties of semiconductor quantum dots (QDs), such as band gap energy, optical absorption, and carrier transport, can be effectively tuned by modulating their size and shape. Two types of architectures of QDSCs have been developed: 1) photoelectric cells (PECs) fabricated from QDs sensitized on nanostructured TiO2 , and 2) photovoltaic cells fabricated from a Schottky junction and heterojunction. Different types of semiconductor QDs, such as a secondary, ternary, quaternary, and perovskite semiconductors, are used for the advancement of QDSCs. The major challenge in QDSCs is the presence of defects in QDs, which lead to recombination reactions and thereby limit the overall performance of the device. To tackle this problem, several strategies, such as the implementation of a passivation layer over the QD layer and the preparation of core-shell structures, have been developed. This review covers aspects of QDSCs that are essential to understand for further improvement in this field and their commercialization.

Modifying morphology and defects of low-dimensional, semi-transparent perovskite thin films via solvent type.

(PEA)2(MA) n-1Pb n I n+1Br2n perovskites are semi-transparent, color-tunable thin films with broader band gaps. They have the potential for semi-transparent solar cell and smart window applications. Solvent engineering significantly alters the morphology, absorbance, crystallinity, charge separation, and defects, thereby influencing the optoelectronic properties. Herein, we investigated the effect of the solvent type on the low dimensional, mixed halide perovskite thin films (n = 1, 3, and 5) and identified DMF : DMSO = 8 : 2 as the most suitable solvent. The mixed solvent regulated the growth rate of perovskites, which led to the smooth morphology and larger crystallite size. Through surface photovoltage spectroscopy and time resolved photoluminescence, good charge separation and low defects were linked to DD82 usage.

Symmetric supercapacitor: Sulphurized graphene and ionic liquid.

Symmetric supercapacitor is advanced over simple supercapacitor device due to their stability over a large potential window and high energy density. Graphene is a desired candidate for supercapacitor application since it has a high surface area, good electronic conductivity and high electro chemical stability. There is a pragmatic use of ionic liquid electrolyte for supercapacitor due to its stability over a large potential window, good ionic conductivity and eco-friendly nature. For high performance supercapacitor, the interaction between ionic liquid electrolyte and graphene are crucial for better charge transportation. In respect of this, a three-dimensional (3D) nanoporous honeycomb shaped sulfur embedded graphene (S-graphene) has been synthesized by simple chemical method. Here, the fabrication of high performance symmetric supercapacitor is done by using S-graphene as an electrode and [BMIM-PF6] as an electrolyte. The particular architecture of S-graphene benefited to reduce the ion diffusion resistance, providing the large surface area for charge transportation and efficient charge storage. The S-graphene and ionic liquid-based symmetric supercapacitor device showed the large potential window of 3.2 V with high energy density 124 Wh kg-1 at 0.2 A g-1 constant applied current density. Furthermore, this device shows good cycling performance (stability) with a capacitive retention of 95% over 20,000 cycles at a higher current density of 2 A g-1.

Nanoarchitectures in dye-sensitized solar cells: metal oxides, oxide perovskites and carbon-based materials.

Dye-sensitized solar cells (DSSCs) have aroused great interest and been regarded as a potential renewable energy resource among the third-generation solar cell technologies to fulfill the 21st century global energy demand. DSSCs have notable advantages such as low cost, easy fabrication process and being eco-friendly in nature. The progress of DSSCs over the last 20 years has been nearly constant due to some limitations, like poor long-term stability, narrow absorption spectrum, charge carrier transportation and collection losses and poor charge transfer mechanism for regeneration of dye molecules. The main challenge for the scientific community is to improve the performance of DSSCs by using different approaches, like finding new electrode materials with suitable nanoarchitectures, dyes in composition with promising semiconductors and metal quantum dot fluorescent dyes, and cost-effective hole transporting materials (HTMs). This review focuses on DSSC photo-physics, which includes charge separation, effective transportation, collection and recombination processes. Different nanostructured materials, including metal oxides, oxide perovskites and carbon-based composites, have been studied for photoanodes, and counter electrodes, which are crucial to achieve DSSC devices with higher efficiency and better stability.

The role of ligands in the mechanical properties of Langmuir nanoparticle films.

Langmuir monolayers of ligand-capped inorganic nanoparticles exhibit rich morphologies under lateral compression such as wrinkling, folding, and multilayer nucleation. We demonstrate that the ligands play a crucial role in the mechanical properties of nanoparticle films by probing the morphology and anisotropic stress response during lateral compression of films with systematically varied ligand concentrations. Increasing the ligand concentration of the films past a threshold value inhibits monolayer wrinkling and folding in favor of multilayer formation, and sharply reduces the compressive and shear moduli. We attribute these drastic mechanical effects to modifications to the ligand interactions between adjacent particles as well as to two-dimensional crystalline structure changes occurring on the scale of tens of particles, as determined by transmission electron microscopy.

Perovskite energy funnels for efficient light-emitting diodes.

Organometal halide perovskites exhibit large bulk crystal domain sizes, rare traps, excellent mobilities and carriers that are free at room temperature-properties that support their excellent performance in charge-separating devices. In devices that rely on the forward injection of electrons and holes, such as light-emitting diodes (LEDs), excellent mobilities contribute to the efficient capture of non-equilibrium charge carriers by rare non-radiative centres. Moreover, the lack of bound excitons weakens the competition of desired radiative (over undesired non-radiative) recombination. Here we report a perovskite mixed material comprising a series of differently quantum-size-tuned grains that funnels photoexcitations to the lowest-bandgap light-emitter in the mixture. The materials function as charge carrier concentrators, ensuring that radiative recombination successfully outcompetes trapping and hence non-radiative recombination. We use the new material to build devices that exhibit an external quantum efficiency (EQE) of 8.8% and a radiance of 80 W sr-1 m-2. These represent the brightest and most efficient solution-processed near-infrared LEDs to date.

The In-Gap Electronic State Spectrum of Methylammonium Lead Iodide Single-Crystal Perovskites.

The density of trap states within the bandgap of methylammonium lead iodide single crystals is investigated. Defect states close to both the conduction and valence bands are probed. Additionally, a comprehensive electronic characterization of crystals is carried out, including measurements of the electron and hole mobility, and the energy landscape (band diagram) at the surface.

Crosslinked Remote-Doped Hole-Extracting Contacts Enhance Stability under Accelerated Lifetime Testing in Perovskite Solar Cells.

A crosslinked hole-extracting electrical contact is reported, which simultaneously improves the stability and lowers the hysteresis of perovskite solar cells. Polymerizable monomers and crosslinking processes are developed to obviate in situ degradation of the under lying perovskite. The crosslinked material is band-aligned with perovskite. The required free carrier density is induced by a high-work-function metal oxide layer atop the device, following a remote-doping strategy.