Imidazoanthraquinone Derivative as a Surface Passivator for Enhanced and Stable Perovskite Solar Cells.

Hybrid organic-inorganic perovskites have been investigated for their potential to serve in next-generation perovskite solar cells (PSCs). While PSC technology is approaching commercialization, thermal and moisture stabilities remain a concern. Here, we describe the assembly of PSCs using an imidazoanthraquinone derivative (AQ) as a small organic additive to enhance the device performance and stability. Unlike polymer additives, AQ is easy to synthesize and is more economical. AQ was synthesized because it has both carbonyl and imidazole functional groups. The presence of C=O and N-H groups results in coordination interaction with Pb2+ and I- of the perovskite. Addition of the AQ molecule to methylammonium lead iodide leads to the formation of a superior crystalline perovskite film with fewer defects and enhanced stability under humid conditions. The use of optimized perovskite films enhanced device power conversion efficiency (PCE = 17.21%) compared to pristine perovskite (PCE = 13.88%). Unencapsulated optimized devices retained 90% of the initial power conversion efficiency for 30 days at a relative humidity of nearly 35%. The optimized films also exhibited superior thermal stability to that of pristine perovskite films.

Linear-Shaped Low-Bandgap Asymmetric Conjugated Donor Molecule for Fabrication of Bulk Heterojunction Small-Molecule Organic Solar Cells.

A linear-shaped small organic molecule (E)-4-(5-(3,5-dimethoxy-styryl)thiophen-2-yl)-7-(5″-hexyl-[2,2':5',2″-terthiophen]-5-yl)benzo[c][1,2,5]thiadiazole (MBTR) comprising a benzothiadiazole (BTD) acceptor linked with the terminal donors bithiophene and dimethoxy vinylbenzene through a π-bridge thiophene was synthesized and analyzed. The MBTR efficiently tuned the thermal, absorption, and emission characteristics to enhance the molecular packing and aggregation behaviors in the solid state. The obtained optical bandgap of 1.86 eV and low-lying highest occupied molecular orbital (HOMO) level of -5.42 eV efficiently lowered the energy losses in the fabricated devices, thereby achieving enhanced photovoltaic performances. The optimized MBTR:PC71BM (1:2.5 w/w%) fullerene-based devices showed a maximum power conversion efficiency (PCE) of 7.05%, with an open-circuit voltage (VOC) of 0.943 V, short-circuit current density (JSC) of 12.63 mA/cm2, and fill factor (FF) of 59.2%. With the addition of 3% 1,8-diiodooctane (DIO), the PCE improved to 8.76% with a high VOC of 1.02 V, JSC of 13.78 mA/cm2, and FF of 62.3%, which are associated with improved charge transport at the donor/acceptor interfaces owing to the fibrous active layer morphology and favorable phase separation. These results demonstrate that the introduction of suitable donor/acceptor groups in molecular design and device engineering is an effective approach to enhancing the photovoltaic performances of organic solar cells.

Label-Free Myoglobin Biosensor Based on Pure and Copper-Doped Titanium Dioxide Nanomaterials.

In this study, using pure and copper-doped titanium dioxide (Cu-TiO2) nanostructures as the base matrix, enzyme-less label free myoglobin detection to identify acute myocardial infarction was performed and presented. The Cu-TiO2 nanomaterials were prepared using facile sol-gel method. In order to comprehend the morphologies, compositions, structural, optical, and electrochemical characteristics, the pure and Cu-TiO2 nanomaterials were investigated by several techniques which clearly revealed good crystallinity and high purity. To fabricate the enzyme-less label free biosensor, thick films of synthesized nanomaterials were applied to the surface of a pre-fabricated gold screen-printed electrode (Au-SPE), which serves as a working electrode to construct the myoglobin (Mb) biosensors. The interference study of the fabricated biosensor was also carried out with human serum albumin (HSA) and cytochrome c (cyt-c). Interestingly, the Cu-doped TiO2 nanomaterial-based Mb biosensor displayed a higher sensitivity of 61.51 µAcm-2/nM and a lower detection limit of 14 pM with a response time of less than 10 ms.

Photo-Charging of Li(Ni0.65Co0.15Mn0.20)O2 Lithium-Ion Battery Using Silicon Solar Cells.

This study reports an integrated device in which a lithium-ion battery (LIB) and Si solar cells are interconnected. The LIB is fabricated using the Li(Ni0.65Co0.15Mn0.20)O2 (NCM622) cathode and the Li4Ti5O12 (LTO) anode. The surface and shape morphologies of the NCM and LTO powders were investigated by field emission scanning electron microscopy (FE-SEM). In addition, the structural properties were thoroughly examined by X-ray diffraction (XRD). Further, their electrochemical characterization was carried out on a potentiostat. The specific discharge capacity of the NCM cathode (half-cell) was 188.09 mAh/g at 0.1 C current density. In further experiments, the NCM-LTO full-cell has also shown an excellent specific capacity of 160 mAh/g at a high current density of 1 C. Additionally, the capacity retention was outstanding, with 99.63% at 1 C after 50 cycles. Moreover, to meet the charging voltage requirements of the NCM-LTO full-cell, six Si solar cells were connected in series. The open-circuit voltage (VOC) and the short-circuit photocurrent density (JSC) for the Si solar cells were 3.37 V and 5.42 mA/cm2. The calculated fill factor (FF) and efficiency for the Si solar cells were 0.796 and 14.54%, respectively. Lastly, the integrated device has delivered a very high-power conversion-storage efficiency of 7.95%.

Synthesis of Superionic Conductive Li1+x+yAlxSiyTi2-xP3-yO12 Solid Electrolytes.

Commercial lithium-ion batteries using liquid electrolytes are still a safety hazard due to their poor chemical stability and other severe problems, such as electrolyte leakage and low thermal stability. To mitigate these critical issues, solid electrolytes are introduced. However, solid electrolytes have low ionic conductivity and inferior power density. This study reports the optimization of the synthesis of sodium superionic conductor-type Li1.5Al0.3Si0.2Ti1.7P2.8O12 (LASTP) solid electrolyte. The as-prepared powder was calcined at 650 °C, 700 °C, 750 °C, and 800 °C to optimize the synthesis conditions and yield high-quality LASTP powders. Later, LASTP was sintered at 950 °C, 1000 °C, 1050 °C, and 1100 °C to study the dependence of the relative density and ionic conductivity on the sintering temperature. Morphological changes were analyzed using field-emission scanning electron microscopy (FE-SEM), and structural changes were characterized using X-ray diffraction (XRD). Further, the ionic conductivity was measured using electrochemical impedance spectroscopy (EIS). Sintering at 1050 °C resulted in a high relative density and the highest ionic conductivity (9.455 × 10-4 S cm-1). These findings corroborate with the activation energies that are calculated using the Arrhenius plot. Therefore, the as-synthesized superionic LASTP solid electrolytes can be used to design high-performance and safe all-solid-state batteries.

Efficient and additive-free synthesis of morphology variant iron oxyhydroxide nanostructures for phosphate adsorption application.

Iron oxyhydroxide (FeOOH) nanostructures of different shapes were successfully synthesized on flexible textile cloth of polyester using a novel and simple technique based on hydrolysis method. The technique used herein is newly designed specifically to improve the efficiency in terms of energy, simplicity and cost involved in large scale synthesis of nanostructured thin films. Additionally, the morphology of nano-sized iron oxyhydroxide could be tuned into different shapes through variation in the type of precursors used for synthesis. The uniformity and adhesion of the depositions were also found to be excellent as examined by qualitative techniques. The as-deposited samples exhibited monoclinic and orthorhombic structures of FeOOH. A significant variation in the shape of as-deposited FeOOH nanostructures with change in precursor was observed through morphological studies, which displayed lance-shaped, rounded clusters and rod-like growth features in different cases. The nanocrystalline FeOOH can be directly applied to attract and trap phosphate from water reservoirs, thus contributing to environmental solutions. The proposed technique can also be utilized to deposit larger areas, which could be suitable for practical applications.

Highly Sensitive Formaldehyde Detection Using Well-Aligned Zinc Oxide Nanosheets Synthesized by Chemical Bath Deposition Technique.

Detection of formaldehyde is very important in terms of life protection, as it can cause serious injury to eyes, skin, mouth and gastrointestinal function if indirectly inhaled. Researchers are therefore putting effort into developing novel and sensitive devices. In this work, we have fabricated an electro-chemical sensor in the form of a field effect transistor (FET) to detect formaldehyde over a wide range (10 nM to 1 mM). For this, ZnO nanosheets (NS) were first synthesized by hydrothermal method with in-situ deposition on cleaned SiO2/Si (100) substrate. The synthesized materials were characterized for morphology and purity and surface area (31.718 m²/g). The developed device was tested for formaldehyde detection at room temperature that resulted in a linear (96%) and reproducible response with concentration, sensitivity value of 0.27 mA/M/cm² with an error of ±2% and limit of detection (LOD) as 210 nM.

Perovskite Solar Cells: Influence of Hole Transporting Materials on Power Conversion Efficiency.

The recent advances in perovskite solar cells (PSCs) created a tsunami effect in the photovoltaic community. PSCs are newfangled high-performance photovoltaic devices with low cost that are solution processable for large-scale energy production. The power conversion efficiency (PCE) of such devices experienced an unprecedented increase from 3.8 % to a certified value exceeding 20 %, demonstrating exceptional properties of perovskites as solar cell materials. A key advancement in perovskite solar cells, compared with dye-sensitized solar cells, occurred with the replacement of liquid electrolytes with solid-state hole-transporting materials (HTMs) such as 2,2',7,7'-tetrakis-(N,N-di-4-methoxyphenylamino)-9,9'-spirobifluorene (Spiro-OMeTAD), which contributed to enhanced PCE values and improved the cell stability. Following improvements in the perovskite crystallinity to produce a smooth, uniform morphology, the selective and efficient extraction of positive and negative charges in the device dictated the PCE of PSCs. In this Review, we focus mainly on the HTMs responsible for hole transport and extraction in PSCs, which is one of the essential components for efficient devices. Here, we describe the current state-of-the-art in molecular engineering of hole-transporting materials that are used in PSCs and highlight the requisites for market-viability of this technology. Finally, we include an outlook on molecular engineering of new functional HTMs for high efficiency PSCs.

High sensitivity Schottky junction diode based on monolithically grown aligned polypyrrole nanofibers: Broad range detection of m-dihydroxybenzene.

Aligned p-type polypyrrole (PPy) nanofibers (NFs) thin film was grown on n-type silicon (100) substrate by an electrochemical technique to fabricate Schottky junction diode for the efficient detection of m-dihydroxybenzene chemical. The highly dense and well aligned PPy NFs with the average diameter (∼150-200 nm) were grown on n-type Si substrate. The formation of aligned PPy NFs was confirmed by elucidating the structural, compositional and the optical properties. The electrochemical behavior of the fabricated Pt/p-aligned PPy NFs/n-silicon Schottky junction diode was evaluated by cyclovoltametry (CV) and current (I)-voltage (V) measurements with the variation of m-dihydroxybenzene concentration in the phosphate buffer solution (PBS). The fabricated Pt/p-aligned PPy NFs/n-silicon Schottky junction diode exhibited the rectifying behavior of I-V curve with the addition of m-dihydroxybenzene chemical, while a weak rectifying I-V behavior was observed without m-dihydroxybenzene chemical. This non-linear I-V behavior suggested the formation of Schottky barrier at the interface of Pt layer and p-aligned PPy NFs/n-silicon thin film layer. By analyzing the I-V characteristics, the fabricated Pt/p-aligned PPy NFs/n-silicon Schottky junction diode displayed reasonably high sensitivity ∼23.67 µAmM(-1)cm(-2), good detection limit of ∼1.51 mM with correlation coefficient (R) of ∼0.9966 and short response time (10 s).

Effective D-A-D type chromophore of fumaronitrile-core and terminal alkylated bithiophene for solution-processed small molecule organic solar cells.

A new and novel organic π-conjugated chromophore (named as RCNR) based on fumaronitrile-core acceptor and terminal alkylated bithiophene was designed, synthesized and utilized as an electron-donor material for the solution-processed fabrication of bulk-heterojunction (BHJ) small molecule organic solar cells (SMOSCs). The synthesized organic chromophore exhibited a broad absorption peak near green region and strong emission peak due to the presence of strong electron-withdrawing nature of two nitrile (-CN) groups of fumaronitrile acceptor. The highest occupied molecular orbital (HOMO) energy level of -5.82 eV and the lowest unoccupied molecular orbital (LUMO) energy level of -3.54 eV were estimated for RCNR due to the strong electron-accepting tendency of -CN groups. The fabricated SMOSC devices with RCNR:PC60BM (1:3, w/w) active layer exhibited the reasonable power conversion efficiency (PCE) of ~2.69% with high short-circuit current density (JSC) of ~9.68 mA/cm(2) and open circuit voltage (VOC) of ~0.79 V.

Exclusion of metal oxide by an RF sputtered Ti layer in flexible perovskite solar cells: energetic interface between a Ti layer and an organic charge transporting layer.

In this work, the effects of a titanium (Ti) layer on the charge transport and recombination rates of flexible perovskite solar cells were studied. Ti as an efficient barrier layer was deposited directly on PET-ITO flexible substrates through RF magnetic sputtering using a Ti-source and a pressure of ∼5 mTorr. A Ti coated PET-ITO was used for the fabrication of a flexible perovskite solar cell without using any metal oxide layer. The fabricated flexible perovskite solar cell was composed of a PET-ITO/Ti/perovskite (CH3NH3PbI3)/organic hole transport layer of 2,2',7,7'-tetrakis [N,N'-di-p-methoxyphenylamine]-9,9'-spirobifluorene (spiro-OMeTAD)-Li-TFSI/Ag. A high conversion efficiency of ∼8.39% along with a high short circuit current (JSC) of ∼15.24 mA cm(-2), an open circuit voltage (VOC) of ∼0.830 V and a high fill factor (FF) of ∼0.66 was accomplished by the fabricated flexible perovskite solar cell under a light illumination of ∼100 mW cm(-2) (1.5 AM). Intensity-modulated photocurrent (IMPS)/photovoltage spectroscopy (IMVS) studies demonstrated that the fabricated flexible perovskite solar cell considerably reduced the recombination rate.

Photocurrent induced by conducting channels of hole transporting layer to adjacent photoactive perovskite sensitized TiO2 thin film: solar cell paradigm.

A high performance perovskite solar cell was fabricated using the distinguished morphology of polyaniline nanoparticles (PANI-NPs) as an efficient hole transporting layer (HTL) with methylammonium lead iodide perovskite (CH3NH3PbI3) as sensitizer. PANI-NPs were simply synthesized by the oxidative chemical polymerization of aniline monomer at 0-5 °C. A reasonable solar-to-electricity conversion efficiency of ∼6.29% with a high short circuit current (JSC) of ∼17.97 mA/cm(2) and open circuit voltage (VOC) of ∼0.877 V were accomplished by Ag/PANI-NPs/CH3NH3PbI3/mp-anatase-TiO2/bl-TiO2/FTO perovskite solar cell. The transient photocurrent and photovoltage studies revealed that the fabricated solar cell showed better charge transport time, diffusion coefficient, diffusion length, and charge collection efficiency. Herein, the use of PANI-NPs as the HTL improved the charge carrier generation and the charge collection efficiency of the fabricated solar cell.

Structural, morphological and sensing properties of layered polyaniline nanosheets towards hazardous phenol chemical.

Reliable sensing properties towards hazardous phenol chemical were detected by the novel working electrode of layered polyaniline (PANI) nanosheets. The layered PANI nanosheets were synthesized by the chemical polymerization of aniline monomer in the presence of hydrochloric acid and ammonium persulphate at 5 °C. The morphological, structural, optical, electrical and electrochemical properties of layered PANI nanosheets were extensively studied. The electrochemical behavior of layered PANI nanosheets based electrode was demonstrated by the electrochemical impedance spectroscopy (EIS) and cyclovoltametry (CV) measurements. The layered PANI nanosheets electrode showed reasonably good electrocatalytic activity towards the detection of phenol chemical, which resulted from the high redox current and low RCT. The current-voltage (I-V) characteristics were used to elucidate the sensing parameters of the fabricated phenol chemical sensor with layered PANI nanosheets electrode. The fabricated phenol chemical sensor with layered PANI nanosheets electrode significantly attained the high sensitivity of ~1485.3 µA mM(-1)cm(-2) and the detection limit of ~4.43 µM with correlation coefficient (R) of ~0.9981 and short response time (10 s).

Enhanced photocatalytic properties of nanoclustered P-doped TiO2 films deposited by advanced atmospheric plasma jet.

A facile preparation of P-doped TiO2 nanoclusters onto fluorine-doped tin oxide (FTO) glass by an advanced atmospheric plasma jet (AAP jet) is reported here. Titanium tetrachloride (TiCl4) and phosphorus trichloride (PCl3) were used as precursors. Radio frequencies were used to generate plasma at fix powder with Argon as carrier gas. Films were deposited at 500 degrees C for 10 minutes. For comparison, as-prepared, annealed and deposited at 500 degrees C samples were studied for chemical/physical properties by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Optical properties were studied by using UV-Vis spectroscopy which indicated a reduction in optical band with P-doping. The rhodamine B (Rh-B) degradation by P-doped TiO2 deposited at 500 degrees C showed enhanced degradation efficiency than that of annealed TiO2. The suggested deposition method appears to be suitable for the synthesis of photocatalyst with proper control over dopants.

Fast one-step method to synthesize TiO2 nanoparticle clusters for dye sensitized solar cells.

We have successfully designed a rapid method for producing dye sensitized solar cells (DSSC) using TiO2 films prepared by a modified dielectric barrier discharge jet (m-DBD jet) method which uses a DBD jet with elevated substrate temperatures from room temperature (RT) to 500 degrees C for approximately 10 min. This facile process has several advantages over other methods such as (1) eliminating additional coating and annealing steps, (2) creating films with high speed electron mobility via hierarchical pore clusters, and (3) allowing controlled TiO2 bandgap by N doping using atmospheric nitrogen instead of supplying N2 gas. Depending on reaction conditions, the resulting nanostructured materials have various sizes and shapes, with those deposited at the highest substrate temperatures displaying hierarchical walnut-shaped morphology as revealed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). A possible growth mechanism of TiO2 nanoparticle clusters (TNC) is presented and discussed. Finally, this m-DBD jet method produces TNC films that exhibit approximately 4 times higher photo-conversion efficiency than the nanoparticle films by the unmodified DBD jet method.

Urea sensing characteristics of titanate nanotubes deposited by electrophoretic deposition method.

Urea sensing properties of titanate nanotubes (TNT) are presented here. TNT films were deposited by electrophoretic deposition (EPD) method on aluminum substrate. Prior to EPD, commercial nanoparticles of TiO2 were hydrothermally treated at 70 degrees C for 48 h after sonicating the solution for 8 h. Hydrothermal method resulted in the conversion of particles to tubular structure following the established method. Urease was covalently attached with TNT (by soaking in urease solution for 3 h). In general, conductivity of film increases after urease immobilization. The urease immobilized films were characterized for urea sensing in the concentration range of 1 mM to 500 mM. Three different sensitivity regions are observed viz. (i) lower concentrations (below 10 mM); (ii) linear region up to 100 mM and a (iii) saturation region above 100 mM. Sensors are extremely sensitive in region (i). From the elemental analyses of the films after urease immobilization, urease was found attached with TiO2, as evident by N 1s peak in the photoelectron spectra. Cyclic voltammetric studies indicated surface-confined redox couple is responsible for sensing behavior. A possible sensing mechanism is presented and discussed.

Mesoporous TiO2 films fabricated using atmospheric pressure dielectric barrier discharge jet.

TiO2 nanoparticles were synthesized by a facile method of dielectric barrier discharge jet (DBD jet) for the dye-sensitized solar cell (DSSC) and other potential applications. DBD jet is utilized as a method for deposition of TiO2 nanoparticles with a 9 µm/min growth rate which is more than ×25 faster than reported previously. Their performance was compared with cells fabricated using commercial TiO2 nanoparticles (P25). The crystallinity and chemical bonding states of samples were characterized by XRD and XPS. Photoanodes fabricated by the DBD jet method resulted in approximately 50% higher photoconversion efficiency than ones prepared from P25 nanoparticles.