Interfacial Passivation of Perovskite Solar Cells by Reactive Ion Scavengers

Lead halide perovskites suffer from uncontrolled ion migration and the interactions at the external contacts play a fundamental role in the hysteretic response and performance degradation kinetics. In this work, we passivate the external interfaces by a reaction of migrating iodide ions with a silver buffer layer placed between Spiro-OMeTAD and Au layers. In the presence of an electrical field, iodine migration occurs and ions that are close to the perovskite/contact interface irreversibly form a layer of AgI. Overall, the interfacial reaction of iodide ions totally suppresses hysteresis and leads to more stable devices. A new sample preparation method unburies the reactive interface, which is then probed by X-ray photoelectron spectroscopy measurements. The kinetics of the layer formation are monitored by impedance spectroscopy highlighting that in the presence of an electrical field and light, the reaction occurs in the order of minutes. We further identify the resistive response of AgI in operating devices. The present work provides a new approach to passivate the external interfaces in lead halide perovskites.Funding for open access charge: CRUE-Universitat Jaume

Graphene quantum dots from chemistry to applications

Graphene quantum dots (GQDs) have been widely studied in recent years due to its unique structure-related properties, such as optical, electrical and optoelectrical properties. GQDs are considered new kind of quantum dots (QDs), as they are chemically and physically stable because of its intrinsic inert carbon property. Furthermore, GQDs are environmentally friendly due to its non-toxic and biologically inert properties, which have attracted worldwide interests from academic and industry. In this review, a number of GQDs preparation methods, such as hydrothermal method, microwave-assisted hydrothermal method, soft-template method, liquid exfoliation method, metal-catalyzed method and electron beam lithography method etc., are summarized. Their structural, morphological, chemical composition, optical, electrical and optoelectrical properties have been characterized and studied. A variety of elemental dopant, such as nitrogen, sulphur, chlorine, fluorine and potassium etc., have been doped into GQDs to diversify the functions of the material. The control of its size and shape has been realized by means of preparation parameters, such as synthesis temperature, growth time, source concentration and catalyst etc. As far as energy level engineering is concerned, the elemental doping has shown an introduction of energy level in GQDs which may tune the optical, electrical and optoelectrical properties of the GQDs. The applications of GQDs in biological imaging, optoelectrical detectors, solar cells, light emitting diodes, fluorescent agent, photocatalysis, and lithium ion battery are described. GQD composites, having optimized contents and properties, are also discussed to extend the applications of GQDs. Basic physical and chemical parameters of GQDs are summarized by tables in this review, which will provide readers useful information

Preparation of high-performance supercapacitor electrode with nanocomposite of CuO/NCNO flower-like

Abstract Due to the importance of energy storage systems based on supercapacitors, various studies have been conducted. In this research CuO, NCNO and the flower like CuO/NCNO have been studied as a novel materials in this field. The resulte showed that the synthesized CuO nanostructutes have flower like morphology which studied by FE-SEM analisis. Further, the XRD pattern confirmed the crystalline properties of the CuO/NCNO nanocomposite, and the Raman verified the functional groups and vibrations of the components of CuO/NCNO nanocomposite. In a two-electrode system at a current density of 4 A/g, the capacitance, power density, and energy density were 450 F/g, 3200 W/kg, and 98 Wh/kg, respectively. The charge transfer resistances of CuO and NCNO/CuO electrodes obtained 8 and 2 Ω respectively, which show that the conductivity and supercapacitive properties of nanocomposite are better than pure components. Also, the stability and low charge transfer resistance are other advantages obtained in a two-symmetrical electrode investigation. The stability investigation showed that after 3000 consecutive cycles, only 4% of the initial capacitance of the CuO/NCNO electrode decreased

Preparation of a Ni-Mo-P-PCTFE nanocomposite coating and evaluation of its nano-tribological, mechanical and electrochemical performance

WOS: 000382539300065In this study, the tribological, mechanical and electrochemical performances of electrodeposited nickel- molybdenum- phosphorus (Ni-Mo-P) coating containing polychlorotrifluoroethylene (PCTFE) nanoparticles were investigated. The nanocomposite coatings were deposited from potassium sodium tartrate containing electrolytes at four different concentrations of PCTFE (0, 4, 8 and 20 g L-1). The surface morphology, chemical and phase compositions of the Ni-Mo-P/PCTFE coatings were investigated using field-emission scanning electron microscopy (FE-SEM), Energy Dispersive X-ray Analysis (EDAX) and X-ray Diffractometry (XRD), respectively. Corrosion behaviour of the coatings was examined using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Atomic force microscopy (AFM) was used to investigate the tribological properties of the surfaces and in addition, their water-repellency was determined. The results show that there is a significant enhancement in corrosion resistance with the incorporation of PCTFE particles into the Ni-Mo-P matrix. It was also observed that the addition of PCTFE in the Ni-Mo-P alloy matrix has resulted in a smoother surface with a low friction coefficient and excellent water repellency.Office in Charge of Research of Iranian Nanotechnology Society; Office of Vice chancellor in charge of research of University of TabrizThe authors would like to acknowledge the financial support of the Office in Charge of Research of Iranian Nanotechnology Society and the financial support of the Office of Vice chancellor in charge of research of University of Tabriz

Electrochemical determination of imatinib mesylate using TbFeO3/g-C3N4 nanocomposite modified glassy carbon electrode

A new electrochemical sensor based on a glassy carbon electrode (GCE) modified by Tb (Terbium) FeO3/g-C3N4 (graphitic carbon nitride) nanocomposite has been developed. In order to characterize the nanocomposite produced, several techniques were employed, including X-ray diffraction (XRD), Fourier transform infrared, Field Emission Scanning Electron Microscope, Energy Dispersive X-ray Spectroscopy, Brunauer-Emmett-Teller, vibrating sample magnetometry, and Transmission Electron Microscopy (TEM). According to XRD data, the nanocomposite produced contained particles of about 36 ± 2 nm in size. TEM examination of the voltammetric response of the offered sensor (TbFeO3/g-C3N4 nanocomposite/glassy carbon electrode (GCE)) demonstrated a catalytic effect against imatinib. In optimized solution pH and scan rate conditions, this sensor demonstrated an excellent electrocatalytic response for detecting imatinib. Furthermore, the fabricated sensor demonstrated acceptable accuracy, reproducible behavior, and a high level of stability during all electrochemical tests. In addition, analytical parameters were determined and the results were compared with those from previous studies

New strategy to overcome the instability that could speed up the commercialization of perovskite solar cells

Current efficiency of perovskite solar cells has reached 23.7%, which is comparable with silicon solar cells. However commercial development is seriously hindered by the instability of the perovskite, especially under moisture conditions. Therefore it is crucial to gain clear understanding of the mechanism of degradation of organic-inorganic perovskite in order to achieve stable perovskite devices. In this paper, the formation and the degradation of perovskite film on different charge transport layers such as a compact TiO2 layer, compact ZnO layer, and ZnO foil, Si nanowires, and porous Si are studied. In addition, density functional theory studies are carried out to better understand the interaction between the perovskite film and substrates. Experimental and theoretical results are combined to draw more reliable conclusion regarding the degradation mechanism. Most notably, the investigations show that the interaction between the iodine (I) atom in the perovskite layer and substrate determine the stability of perovskite cells. As a result, Si has minimum interaction with I atoms and shows maximum stability, while perovskite film degrades on TiO2 film almost immediately