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Structural, Morphological, Optical and Photoluminescence Properties of Hafnium Oxide Nanoparticles Synthesized by Sol-Gel Method
摘要： The novel HfO2 nanoparticles have been synthesized using sol-gel method. The samples were characterized by X-ray powder diffraction, scanning electron microscopy with elemental analysis, Fourier transform infrared spectrometer, UV-visible spectroscopy. The XRD patterns revealed the transition of cubic to monoclinic phase and calculated particle sizes are 34.92 and 35.66 nm in cubic phase and increase in molar concentration increased the size to 60.31 and 60.33 nm. The optical band gap energy decrease with increasing molar concentrations. We expect that this sol-gel method may be extended to the preparation of nanostructures of other kinds of metal oxides.
关键词： Sol-gel,Hafnium oxide,Nanoparticles,Photoluminescence
更新于2025-09-23 15:22:29
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[IEEE 2020 IEEE Latin America Electron Devices Conference (LAEDC) - San Jose, Costa Rica (2020.2.25-2020.2.28)] 2020 IEEE Latin America Electron Devices Conference (LAEDC) - Impact of the Hafnium Oxide as Hole Blocking Layer on the Performance of Organic Solar Cells
摘要： The effects of hafnium oxide (HfO2) as hole blocking layer (HBL) on the stability and degradation under air environment of inverted bulk heterojunction organic solar cells (iOSC), using as donor material thieno[3,4b]thiophene-alt-benzodithiophene (PTB7) and as acceptor material [6,6]-phenyl C71 butyric acid methyl ester (PC70BM) are presented. The ultrathin films of HfO2 layers 0.9 nm of thick were deposited by thermal evaporation. The highest power conversion efficiency obtained (PCE) was of 8.33%. The current density-voltage characteristic (J-V) was modeled through the ideal-diode equivalent circuit model. For comparison, cells with poly [(9,9-bis (30- (N,N-dimethylamino) propyl) -2,7-fluorene) -alt-2,7- (9,9-dioctylfluorene)] (PFN) and Zinc Oxide (ZnO) as hole blocking layer were fabricated. The three groups of cells were exposed to air for 1000 h. The electrical parameters extracted from the current density–voltage characteristic (J–V) were analyzed. The PCE for cells manufactured with HfO2 as HBL remains around 30% after 1000 h under air environment, showing less degradation than iOSCs with ZnO.
关键词： electron transport layer,HfO2,PFN,PTB7:PC70BM solar cells,hafnium oxide,organic solar cells,ZnO,Degradation,OSC stability
更新于2025-09-23 15:19:57
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Enhanced photocurrent in organic photodetectors by the tunneling effect of a hafnium oxide thin film as an electron blocking layer
摘要： To achieve high detectivity of organic photodetectors (OPDs), we investigated hafnium oxide (HfO2) as an electron blocking layer in an attempt to obtain a low leakage current and high photocurrent by the tunneling effect. The prepared devices consisted of indium tin oxide (ITO)/HfO2/(poly(3-hexylthiophene-2,5-diyl)[P3HT]:PC60BM)/Yb/Al. To explore the tunneling effect in a hafnium oxide thin film, we fabricated a thin film using successive ionic layer deposition. The results for hafnium oxide were compared with those for aluminum oxide and poly(3,4-ethylenedioxythiophene)poly(styrenesulfonate) (PEDOT:PSS). We found that hafnium oxide results in a low leakage current and high photocurrent owing to the tunneling effect in the OPDs. The resulting detectivity of 1.76 × 1012 Jones for a film thickness of 5.5 nm and bandwidth of ～100 kHz is suitable for commercialization.
关键词： detectivity,tunneling effect,organic photodetectors,hafnium oxide,electron blocking layer
更新于2025-09-16 10:30:52
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The peculiarities of structural and optical properties of HfO2-based films co-doped with silicon and erbium
摘要： The effect of deposition conditions and further annealing treatment on microstructure and optical properties of (Si,Er)-codoped HfO2 thin films is investigated. The films are grown on silicon substrates by RF magnetron co-sputtering of Si and erbium oxide pellets on a HfO2 target. As-deposited and annealed samples are examined by means of spectroscopic ellipsometry, Fourier transform infrared spectroscopy and photoluminescence method. It is demonstrated that the variation of RF power density allows monitoring the dopant content. An annealing of the samples at 800-1100°C for 10-60 min in nitrogen atmosphere results in the phase separation and the formation of HfO2, SiO2 and pure silicon phases. The films annealed at 900-950°C demonstrate the red luminescence that is ascribed to the carrier recombination in Si nanocrystals. Annealing at higher temperatures causes an enhancement of rare-earth luminescence under non-resonant excitation providing an additional argument toward the formation of silicon nanoclusters. The mechanism of the excitation of Er ions is found to be similar to that of Si-rich-SiO2 films doped with rare-earths. The Si nanocrystals are considered as the main sensitizer at visible excitation while the energy transfer from host defects dominates at ultraviolet-deep blue illumination.
关键词： erbium,hafnium oxide,silicon,nanocrystals,photoluminescence
更新于2025-09-09 09:28:46