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Charge extraction via graded doping of hole transport layers gives highly luminescent and stable metal halide perovskite devices
摘要： One source of instability in perovskite solar cells (PSCs) is interfacial defects, particularly those that exist between the perovskite and the hole transport layer (HTL). We demonstrate that thermally evaporated dopant-free tetracene (120 nm) on top of the perovskite layer, capped with a lithium-doped Spiro-OMeTAD layer (200 nm) and top gold electrode, offers an excellent hole-extracting stack with minimal interfacial defect levels. For a perovskite layer interfaced between these graded HTLs and a mesoporous TiO2 electron-extracting layer, its photoluminescence yield reaches 15% compared to 5% for the perovskite layer interfaced between TiO2 and Spiro-OMeTAD alone. For PSCs with graded HTL structure, we demonstrate efficiency of up to 21.6% and an extended power output of over 550 hours of continuous illumination at AM1.5G, retaining more than 90% of the initial performance and thus validating our approach. Our findings represent a breakthrough in the construction of stable PSCs with minimized nonradiative losses.
关键词： perovskite solar cells,stability,charge extraction,photoluminescence,hole transport layers,graded doping
更新于2025-11-14 15:25:21
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Acid-treated Fe-doped TiO2 as a high performance photocatalyst used for degradation of phenol under visible light irradiation
摘要： The photocatalytic activity of Fe-doped TiO2 nanoparticles is significantly increased by an acid-treatment process. The photocatalyst nanoparticles were prepared using sol–gel method with 0.5 mol% ratio of Fe:Ti in acidic pH of 3. The nanoparticles were structurally characterized by means of X-ray diffraction (XRD), high-resolution transmission electron microscope (HRTEM), energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS) and diffuse reflectance spectroscopy (DRS). It was observed that the photocatalytic activity suffered from an iron oxide contaminating layer deposited on the surface of the nanoparticles. This contamination layer was removed using an HCl acid-treatment process. The photocatalytic activity using 500 mg/L of Fe0.5-TiO2 in a 10 mg/L of phenol solution increased significantly from 33% to 57% (about 73% increase in the performance), within 90 min of reaction time under visible light irradiation. This significant improvement was achieved by removing the iron oxide contamination layer from the surface of the nanoparticles and adjusting pH to mild acidic and basic pHs.
关键词： Kinetics,Iron doping,Phenol degradation,Visible light,Photocatalyst
更新于2025-11-14 15:25:21
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Impact of doped metals on urea-derived g-C3N4 for photocatalytic degradation of antibiotics: Structure, photoactivity and degradation mechanisms
摘要： Metal doping is an appealing modification strategy of graphitic carbon nitride (g-C3N4) to improve its photocatalytic activity. The interactions of g-C3N4 precursors with metals, however, has often been underappreciated, which can induce great impacts on g-C3N4 formation and properties. Herein, the impacts of metals (Na, K, Ca, Mg) on the morphology, structure, and photoactivity of urea-derived g-C3N4 were investigated. Our TEM and XPS results confirmed that the interactions of doped metals with urea precursors lead to the incorporation of O atoms from urea molecules into the framework of g-C3N4. Due to the synergistic effects of the metals and structural O atoms, doped g-C3N4 performed an elevated photodegradation of antibiotics under the visible light irradiation, which was attributed to the enhanced light-harvesting and reduced charge recombination. In addition, the doped metals presented uneven regulation on the band structures and morphology of g-C3N4. As a result, both superoxide and hydroxyl radicals were generated by g-CN-Na and g-CN-K, whereas, only superoxide radicals were involved in g-CN, g-CN-Ca and g-CN-Mg. Consequently, diversified photodegradation mechanisms for enrofloxacin (ENR) were observed that the g-CN, g-CN-Ca and g-CN-Mg reaction systems mainly attacked the piperazine moiety of ENR while g-CN-Na and g-CN-K provided additional photodegradation pathway by attacking quinolone core of ENR. The present work could provide new insights into further understanding of doping chemistry with g-C3N4.
关键词： Metal doping,Photocatalytic degradation of antibiotics,g-C3N4,Visible light photocatalysis
更新于2025-11-14 15:24:45
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Efficient removal of cationic dyes from water by a combined adsorption-photocatalysis process using platinum-doped titanate nanomaterials
摘要： In this study, two types of titanate nanomaterials (TNMs) including titanate nanosheets (TNS) and titanate nanotubes (TNT) were hydrothermally prepared by controlling reaction times, and then the platinum (Pt)-doped TNMs were fabricated. The photocatalytic performance of as-prepared materials was compared with that of the commercially available TiO2 P25. It was revealed that changing the morphology of TiO2 particles could enhance their adsorption ability and photocatalytic activity for the removal of cationic dyes from water. In particular, all prepared materials displayed greater removal of methylene blue than of P25 through the synergy of adsorption and photocatalysis; however, such an effect was not so pronounced for anionic dyes. For cationic dyes (methylene blue and rhodamine B) and anionic dyes (methyl orange and naphthol blue–black), TNT presented higher photocatalytic activity than TNS. The TNMs, after Pt doping, significantly enhanced photocatalytic activity compared to the pristine ones. Remarkably, 0.5% by weight Pt-doped TNS achieved 100% removal of methylene blue and rhodamine B after 120 min and 140 min of UV irradiation, respectively, outperforming P25, although Pt-doped TNMs showed lower photocatalytic performance than P25 for anionic dyes.
关键词： Photocatalysis,Cationic dyes,Titanate nanomaterials,Adsorption,Platinum doping
更新于2025-11-14 15:13:28
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Gold doping induced strong enhancement of carbon quantum dots fluorescence and oxygen evolution reaction catalytic activity of amorphous cobalt hydroxide
摘要： Gold doping induced strong enhancement of carbon quantum dots fluorescence and oxygen evolution reaction catalytic activity of amorphous cobalt hydroxide. Water splitting using electrocatalysts is expected to provide an alternative green energy source to meet increasing energy demands as well as addressing environmental concerns related to fossil fuels. Herein, we report one-step synthesis of sulfur, nitrogen and Au-doped carbon quantum dots (Au-SCQDs) and strong enhancement of fluorescence intensity and oxygen evolution reaction (OER) catalytic activity of amorphous Co(OH)2 nanoparticles compared to pure Co(OH)2 as well as commercial RuO2 and Pt/C catalysts. Au doping into sulfur and nitrogen co-doped CQDs showed over seventy times enhanced fluorescence. OER studies of amorphous-Co(OH)2 incorporated Au-SCQDs produced current density of 178 mA cm?2 at the applied potential of 2.07 V whereas un-doped Co(OH)2 showed current density of 59 mA cm?2. To produce geometric current density of 10 mA cm?2, amorphous Co(OH)2-Au-SCQDs (CSA) required 388–456 mV overpotential depending on the Au ion concentration used for preparing the Au-SCQDs, which is equal to or lower than overpotential required by commercial electrocatalysts. The strongly enhanced OER activity of Co(OH)2-Au-SCQDs (CSA) was attributed to the presence of electronegative metallic conducting Au atoms along with the high catalytic surface area of amorphous Co(OH)2. The present studies demonstrate a new method of exploiting amorphous Co(OH)2NPs electrocatalysts that could provide more catalytically active sites by integrating an electronegative conducting Au atom doped SCQDs matrix.
关键词： amorphous cobalt hydroxide,fluorescence,water splitting,Gold doping,carbon quantum dots,oxygen evolution reaction,electrocatalysts
更新于2025-10-22 19:40:53
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Threshold Voltage Control in Organic Field-Effect Transistors by Surface Doping with a Fluorinated Alkylsilane
摘要： Doping is a powerful tool to control the majority charge carrier density in organic field-effect transistors and the threshold voltage of these devices. Here, a surface doping approach is shown, where the dopant is deposited on the prefabricated polycrystalline semiconducting layer. In this study, (tridecafluoro-1,1,2,2-tetrahydrooctyl)-trichlorosilane (FTCS), a fluorinated alkylsilane is used as a dopant, which is solution processable and much cheaper than conventional p-type dopants, such as 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ). In this work, the depositions from the gas phase and from solution are compared. Both deposition approaches led to an increased conductivity and to a shift in the threshold voltage to more positive values, both of which indicate a p-type doping effect. The magnitude of the threshold voltage shift could be controlled by the FTCS deposition time (from vapor) or FTCS concentration (from solution); for short deposition times and low concentrations, the off current stayed constant and the mobility decreased only slightly. In the low doping concentration regime, both approaches resulted in similar transistor characteristics, i.e., similar values of shift in the threshold and turn-on voltage as well as mobility, ION/IOFF ratio and amount of introduced free charge carriers. In comparison with vapor deposition, the solution-based approach can be conducted with less material and in a shorter time, which is critical for industrial applications.
关键词： self-assembled monolayers,fluorinated alkylsilanes,organic field-effect transistors,surface doping,p-type doping
更新于2025-09-23 15:23:52
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Surface doping of ZnO nanowires with Bi: Density-functional supercell calculations of defect energetics
摘要： Defect calculations using the density and hybrid functionals in combination with the supercell approach are employed to characterize the electrical properties of a number of ZnO nanowires of various thicknesses doped with Bi atoms occupying surface sites. The variation of the differences between the total energies of charged and neutral supercells with the supercell size is studied, which led the authors to devise an extrapolation procedure to obtain reliable defect energetics in the dilute defect limit. The calculated defect formation energies indicate that although the substitution of Bi into Zn or O sites can take place spontaneously under suitable thermodynamic conditions, the substitution into Zn sites is generally more likely. The defect (charge-state) transition energies are computed and parameterized as a function of the nanowire thickness. It is revealed that the substitution of Bi into O (Zn) sites on the surface of ZnO nanowires yields deep acceptor (shallow donor) levels (except for extremely thin nanowires). It is therefore concluded that the incorporation of Bi into the surface of ZnO nanowires results in n-type doping.
关键词： ZnO nanowires,defect energetics,n-type doping,bismuth doping,supercell calculations,density functional theory
更新于2025-09-23 15:23:52
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A high-performance photoelectrochemical water oxidation system with phosphorus doping g-C3N4 and simultaneous metal phosphide cocatalyst formation via a gas treatment
摘要： Graphitic carbon nitride (g-C3N4) has been widely explored as photocatalyst for water splitting. The anodic water oxidation reaction (WOR) remains the major obstacle for such process, with particular issues on low surface area of g-C3N4, poor light absorption as well as low charge transfer efficiency. In this work, such longtime concerned issues have been partially addressed with band gap and surface engineering of nanostructured graphitic C3N4. Specifically, surface area and charge transfer efficiency are significantly enhanced via architecturing g-C3N4 on nanorod TiO2 to avoid the aggregation of layered g-C3N4. Moreover, a simple phosphide gas treatment of TiO2/g-C3N4 configuration not only narrows the band gap of g-C3N4 by 0.57 eV into visible range, but also in-situ generates a metal phosphide (M=Fe, Cu) water oxidation cocatalyst. This TiO2/g-C3N4/FeP configuration significantly improves charge separation and transfer capability. As a result, our photoelectrochemical system yields outstanding visible light (> 420 nm) photocurrent: ca. 0.3 mA·cm-2 at 1.23 V and 1.1 mA·cm-2 at 2.0 V vs RHE, the highest using g-C3N4 as photoanode. We expect that our TiO2/g-C3N4/FeP configuration generating via simple phosphide gas treatment will bring in new insight for robust g-C3N4 for water oxidation.
关键词： doping,photoelectrochemical,cocatalyst,g-C3N4,high performance
更新于2025-09-23 15:23:52
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Tuning Ferroelectric, Dielectric, and Magnetic Properties of BiFeO <sub/>3</sub> Ceramics by Ca and Pb Co-Doping
摘要： Effects of Ca/Pb co-doping on structure, ferroelectric, dielectric, and magnetic properties of BiFeO3 ceramics are investigated. A structure transition from a rhombohedral phase (space group R3c) to a cubic phase (space group Pm3m) with the increment of Ca/Pb concentration is revealed by X-ray diffraction and Raman spectra. In order to compensate the valence change caused by Ca2+ dopant, Pb ions present tetravalent state under the existence of Ca ions. The room-temperature ferroelectric behavior depends upon Ca/Pb co-doping and the structural transition in BiFeO3 ceramics. Meanwhile, the variation of the dielectric loss tangent in the frequency range of 102–107 Hz and the leakage current at room temperature illustrate that Ca/Pb co-doping increases resistivity and reduces leakage current. Compared with that of Sr/Pb co-doping, the co-doping of Ca/Pb has improved the leakage current by two orders of magnitude, besides further increasing the ferroelectric polarization and dielectric properties under the same co-doping concentration. In addition, enhanced ferromagnetism is observed with the increase of Ca/Pb content, which can be attributed to the effective suppression of spiral cycloidal spin structure and spin canting resulting from the structural transition.
关键词： BiFeO3,ferroelectricity,co-doping,dielectricity,ceramics,magnetism
更新于2025-09-23 15:23:52
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The influence of nitrogen doping on the electronic structure of the valence and conduction band in TiO <sub/>2</sub>
摘要： X-ray emission spectroscopy (XES) and X-ray absorption spectroscopy (XAS) provide a unique opportunity to probe both the highest occupied and the lowest unoccupied states in matter with bulk sensitivity. In this work, a combination of valence-to-core XES and pre-edge XAS techniques are used to determine changes induced in the electronic structure of titanium dioxide doped with nitrogen atoms. Based on the experimental data it is shown that N-doping leads to incorporation of the p-states on the occupied electronic site. For the conduction band, a decrease in population of the lowest unoccupied d-localized orbitals with respect to the d-delocalized orbitals is observed. As confirmed by theoretical calculations, the N p-states in TiO2 structure are characterized by higher binding energy than the O p-states which gives a smaller value of the band-gap energy for the doped material.
关键词： TiO2 doping,X-ray absorption spectroscopy,electronic structure analysis,X-ray emission spectroscopy
更新于2025-09-23 15:23:52