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PubMed2026

Enhanced Performance in All-Inorganic AgBiS2 Photodetectors via Oxygen-Inhibited Spray Pyrolysis Deposition.

AgBiS2 has emerged as a promising optoelectronic material due to its broad spectral response and strong light absorption. However, the current use of high-boiling solvents and organic buffers restricts fundamental studies and further performance optimization of AgBiS2's intrinsic properties. In this study, we develop an organic buffer-free AgBiS2 photodetector prepared using a low-temperature ultrasonic spray pyrolysis technique. Our theoretical analysis revealed that oxygen doping alters the optoelectronic characteristics by enhancing the density of states near the Fermi level, leading to consequent severe nonradiative charge carrier recombination. By incorporating excess thiourea while maintaining optimal substrate temperature for enhanced crystallinity, we successfully suppress oxygen defects and consequently improve photodetection performance. The optimized device exhibits a high responsivity of 0.046 A W-1 at 1050 nm, a low noise level (<8.5 × 10-19 A2 Hz-1), and a fast response time (0.07 μs rise, 0.60 μs decay). Benefiting from the rapid response, the photodetector delivers high-resolution imaging with sharp edge definition. This work eliminates the interference of organic buffer layers to directly reveal how oxygen defect modulation affects the intrinsic optoelectronic properties of AgBiS2, offering a scalable pathway for high-performance, solution-processed photodetectors.

near-infrared detector↗

PubMed2005

Visible light-induced water oxidation on mesoscopic alpha-Fe2O3 films made by ultrasonic spray pyrolysis.

Alpha-Fe(2)O(3) films having a mesoscopic leaflet type structure were produced for the first time by ultrasonic spray pyrolysis (USP) to explore their potential as oxygen-evolving photoanodes. The target of these studies is to use translucent hematite films deposited on conducting fluorine doped tin oxide (FTO) glass as top electrodes in a tandem cell that accomplishes the cleavage of water into hydrogen and oxygen by sunlight. The properties of layers made by USP were compared to those deposited by conventional spray pyrolysis (SP). Although both types of films show similar XRD and UV-visible and Raman spectra, they differ greatly in their morphology. The mesoscopic alpha-Fe(2)O(3) layers produced by USP consist mainly of 100 nm-sized platelets with a thickness of 5-10 nm. These nanosheets are oriented mainly perpendicularly to the FTO support, their flat surface exposing (001) facets. The mesoscopic leaflet structure has the advantage that it allows for efficient harvesting of visible light, while offering at the same time the very short distance required for the photogenerated holes to reach the electrolyte interface before recombining with conduction band electrons. This allows for water oxidation by the valence band holes even though their diffusion length is only a few nanometers. Distances are longer in the particles produced by SP favoring recombination of photoinduced charge carriers. Open-circuit photovoltage measurements indicate a lower surface state density for the nanoplatelets as compared to the round particles. These factors explain the much higher photoactivity of the USP compared to the SP deposited alpha-Fe(2)O(3) layers. Addition of hydrogen peroxide to the alkaline electrolyte further improves the photocurrent-voltage characteristics of films generated by USP indicating the hole transfer from the valence band of the semiconductor oxide to the adsorbed water to be the rate-limiting kinetic step in the oxygen generation reaction.

Journal Article↗

PubMed2006

Translucent thin film Fe2O3 photoanodes for efficient water splitting by sunlight: nanostructure-directing effect of Si-doping.

Thin, silicon-doped nanocrystalline alpha-Fe2O3 films have been deposited on F-doped SnO2 substrates by ultrasonic spray pyrolysis and chemical vapor deposition at atmospheric pressure. The photocatalytic activity of these films with regard to photoelectrochemical water oxidation was measured at pH 13.6 under simulated AM 1.5 global sunlight. The photoanodes prepared by USP and APCVD gave 1.17 and 1.45 mA/cm2, respectively, at 1.23 V vs RHE. The morphology of the alpha-Fe2O3 was strongly influenced by the silicon doping, decreasing the feature size of the mesoscopic film. The silicon-doped alpha-Fe2O3 nano-leaflets show a preferred orientation with the (001) basal plane normal to the substrate. The best performing photoanode would yield a solar-to-chemical conversion efficiency of 2.1% in a tandem device using two dye-sensitized solar cells in series.

Journal Article↗

PubMed2005

Growth of well-aligned carbon nanotube structures in successive layers.

Layered structures of well-aligned carbon nanotubes were grown using three variations of vapor-phase chemical vapor deposition growth processes. The reactants (typically ferrocene and benzene) were introduced either directly to a heated furnace or carried into the furnace by evaporation or spray pyrolysis in an argon flow. Thick mats of densely packed, well-aligned nanotubes were produced when the reactants were continuously introduced to the reaction; however, when the reactant flow was interrupted, the pauses allowed growth to stop and then restart as a new layer. These pauses were achieved by either completely stopping the reactant flow for a given time or by modifying the dispensing system to introduce the reactants in discrete drops. Time intervals between drops were varied between 20 s and 120 s, with distinct layers observed for pauses of 30 s or greater. The best results were achieved when drops of a catalyst-rich solution were alternated with drops of pure benzene. Layers were grown with thicknesses ranging from several microns to several hundred microns, and structures were grown with well over 100 layers.

Journal Article↗

PubMedDate not supplied

The influence of the ethanol-water molar ratio in the precursor solution on morphology and photocatalytic activity of pyrolytic ZnO films.

Zinc oxide films were fabricated by a homemade spray pyrolysis system equipped with an optical setup ensuring the in situ control of the film growth. Zinc acetate (0.1 M) diluted in a mixture of ethanol and water was used as the precursor solution. The ethanol-water molar ratio, gamma, in the precursor solution was varied from 0 to 0.92. The deposition temperature and the pH of the precursor solution were kept at 350 degrees C and 4.5, respectively. X-ray diffraction patterns revealed that films were zincitelike with a grain size depending on the ethanol-water molar ratio in the precursor solution. The interference pattern obtained during film deposition was used to monitor the film roughness; it was found that this is related with those results of surfaces and optical analysis obtained by scanning electron microscopy and spectrophotometric measurements, respectively. The morphology of the ZnO films obtained from gamma equal to either 0 or 0.92 are dense with agglomerates uniformly distributed, whereas the films obtained from gamma equal to either 0.03 or 0.06 are very rough with irregular agglomerates. The films obtained from gamma equal to 0.12, 0.18 and 0.31 are rough. Photoelectrocatalytic results indicated that there is a correlation of the partial molar volume of ethanol with respect to water in the spraying solution, with the photocatalytic efficiency of the ZnO films. We found that the maximum photodegradation of methyl orange in the solution occurs using ZnO films obtained with gamma = 0.12.

Journal Article↗