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We demonstrate the effect of air exposure on optical and electrical properties of ZnMgO nanoparticles (NPs) typically exploited as an electron transport layer in Cd-based quantum-dot light-emitting diodes (QLEDs). We analyze the roles of air components in modifying the electrical properties of ZnMgO NPs, which reveals that H2O enables the reduction of hole leakage while O2 alters the character of charge transport due to its ability to trap electrons. As a result, the charge balance in the QDs layer is improved, which is confirmed by voltage-dependent measurements of photoluminescence quantum yield. The maximum external quantum efficiency is improved over 2-fold and reaches the value of 9.5% at a luminance of 104 cd/m2. In addition, we investigate the problem of electron leakage into the hole transport layer and show that trap-mediated electron transport in the ZnMgO layer caused by adsorbed O2 ensures a higher leakage threshold. This work also provides an insight into the possible disadvantages of device contact with air as well as problems and challenges that might occur during open-air fabrication of QLEDs.

In this study, the role of a zinc acetate precursor in improving the luminescence stability of purple-emitting CdS nanocrystals is investigated. The oleate-capped core of CdS nanocrystals exhibits intense photodarkening under prolonged UV excitation. From the results of photoluminescence experiments, we can observe that photobleaching is responsible for the degradation of temporal stability, i.e., decline in photoluminescence intensity. Herein, we demonstrate that by adding zinc acetate to the synthesis solution, one can enhance the photoluminescence stability by the complete suppression of the bleaching processes of nanocrystals. We can distinguish between the effects caused by zinc ions and those caused by acetate ligands. Acetate ligands improve the photoluminescence stability of the core of CdS nanocrystals. However, only when zinc acetate is used, the PL stability can be conserved at high excitation power. Simultaneously, we have studied the influence of zinc cations and acetate ligands on the kinetics of nanocrystal growth. The presented results underline the importance of short surface capping ligands and zinc cations in CdS nanocrystal synthesis. This study exhibits a new advantage of exploiting zinc acetate reagents in one-pot nanocrystal synthesis.

In this work modification of TiO2 thin films structure by doping with europium was described. Nanocrystalline films were prepared by high energy magnetron sputtering process. The influence of europium on the microstructure of TiO2 was determined based on the results of X-ray diffraction, transmission electron microscopy, Raman spectroscopy and photoluminescence measurements. It was found that undoped film had rutile structure directly after deposition (without additional annealing), while 0.2 at.% and 0.4 at.% of the dopant was sufficient to receive TiO2 films with anatase form. The type of structure was confirmed with the aid of Raman spectroscopy and by TEM observations. The amount of Eu-dopant had direct impact on PL intensity as well as presence of defect (voids) in the film.

Terbium-doped silicon-rich silicon oxide films were deposited and hydrogenated at elevated temperatures. The influence of hydrogenation on defects-mediated non-radiative recombination of excited Tb 3+ ions was investigated by means of photoluminescence and photoluminescence decay measurements. An increase in photoluminescence intensity and photoluminescence decay time was observed upon hydrogenation for the main 5 D 4 – 7 F 5 transition of Tb 3+ ions. This observation was ascribed to saturation of non-radiative recombination defect centers with hydrogen. It was found that the number of emitted photons increases upon passivation as a result of two effects: (1) a reduction of the non-radiative recombination rate, and (2) optical activation of new Tb 3+ emitters. Based on the obtained results and literature data, Forster energy-transfer was suggested as the interaction responsible for the non-radiative coupling between Tb 3+ ions and defects.

TiO2 and TiO2:Nd thin films were deposited using reactive magnetron sputtering process from mosaic Ti–Nd targets with various Nd concentration. The thin films were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM) and spectroscopic techniques. Photoluminescence (PL) in the near infrared obtained upon 514.5 nm excitation was also examined. The relationship between the Nd concentration, structural, optical and photoluminescence properties of prepared thin films was investigated and discussed. XRD and TEM measurements showed that an increase in the Nd concentration in the thin films hinders the crystal growth in the deposited coatings. Depending on the Nd amount in the thin films, TiO2 with the rutile, mixed rutile–amorphous or amorphous phase was obtained. Transmittance measurements revealed that addition of Nd dopant to titania matrix did not deteriorate optical transparency of the coatings, however it influenced on the position of the fundamental absorption edge and therefore on the width of optical band gap energy. All TiO2:Nd thin films exhibited PL emission that occurred at ca. 0.91, 1.09 and 1.38 μm. Finally, results obtained for deposited coatings showed that titania with the rutile structure and 1.0 at.% of Nd was the most efficient in VIS to NIR photon conversion.

Titanium dioxide thin films, each doped with the same amount of neodymium (1 at.%) were deposited by Low Pressure Hot Target Reactive Sputtering and High Energy Reactive Magnetron Sputtering processes in order to obtain anatase and rutile thin film structures respectively. The microstructure and phase composition were analyzed using the transmission electron microscopy method including high resolution electron microscopy imaging. The measurements of the optical properties showed, that both prepared thin films were transparent in the visible light range and had a low extinction coefficient of ca. 3 ⋅ 10−3. The thin film with the anatase structure had a lower cut-off wavelength and refractive index and a higher value of optical energy band gap as-compared to the TiO2:Nd coating with the rutile structure. Simultaneously, more efficient photoluminescence emission was observed for the rutile thin films.

Silicon-rich silicon oxide films, with various Si concentrations, were deposited by plasma enhanced chemical vapor deposition and annealed at 1100 °C in order to form silicon nanocrystals. For these films, it has been found that the absorption edge shifts as a function of the nanocrystal size due to the quantum confinement of exciton. This result showed that the size-related effects are present in the investigated films. Next, we examined the influence of the nanocrystal size on the vibrational modes. In this case, the Raman line related to silicon nanocrystals significantly down-shifts as a function of the nanocrystal size, which is against the predictions of the phonon confinement model. It has been shown that this effect is due to stress exerted on the nanocrystals. It has been also found that this stress changes from compressive to tensile, and the stress character depends on the film stoichiometry.

Terbium doped silicon oxynitride host matrix is suitable for various applications such as light emitters compatible with CMOS technology or frequency converter systems for photovoltaic cells. In this study, amorphous Tb

In this work, silicon-rich silicon oxide films containing terbium were prepared by means of plasma enhanced chemical vapor deposition. The influence of hydrogen passivation on defects-mediated non-radiative recombination of excited Tb3+ions was investigated by photoluminescence,photoluminescence excitation, and photoluminescence decay measurements. Passivation was found to have no effect on shape and spectral position of the excitation spectra. In contrast, a gradual increase in photoluminescence intensity and photoluminescence decay time was observed upon passivation for the main 5D4-7F5 transition of Tb3+ions. This observation was attributed to passivation of non-radiative recombination defects centers with hydrogen. It was found that the number of emitted photons increases upon passivation as a result of two effects: (1) longer Tb3+ lifetime in the 5D4excited state and (2) optical activation of new Tb3+ emitters. The obtained results were discussed and compared with other experimental reports.

In this work, we will discuss the excitation and emission properties of Tb ions in a Silicon Rich Silicon Oxide (SRSO) matrix obtained at different technological conditions. By means of electron cyclotron resonance plasma-enhanced chemical vapour deposition, undoped and doped SRSO films have been obtained with different Si content (33, 35, 39, 50 at. %) and were annealed at different temperatures (600, 900, 1100 °C). The samples were characterized optically and structurally using photoluminescence (PL), PL excitation, time resolved PL, absorption, cathodoluminescence, temperature dependent PL, Rutherford backscattering spectrometry, Fourier transform infrared spectroscopy and positron annihilation lifetime spectroscopy. Based on the obtained results, we discuss how the matrix modifications influence excitation and emission properties of Tb ions.

Silicon nanocrystals embedded in a silicon-rich silicon-oxide matrix have been fabricated at different silicon contents (38%, 40%, and 49%) using plasma-enhanced chemical vapor deposition and annealing at different temperatures in the range from 900 °C to 1100 °C. Their optical properties have been investigated by photoluminescence and transmittance measurements. Strong, room-temperature emission bands at ∼1.6 eV have been observed for all samples, with intensities dependent on the annealing temperature and Si content of the samples. From transmittance measurements, a redshift of the absorption edge has been detected when increasing the annealing temperature or Si content.