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There is a growing interest in understanding how size‐dependent quantum confinement affects the photoluminescence efficiency, excited‐state dynamics, energy‐transfer and thermalization phenomena in nanophosphors. For lanthanide (Ln3+)‐doped nanocrystals, despite the localized 4f states, confinement effects are induced mostly via electron–phonon interactions. In particular, the anomalous thermalization reported so far for a handful of Ln3+‐doped nanocrystals has been rationalized by the absence of low‐frequency phonon modes. This nanoconfinement may further impact on the Ln3+ luminescence dynamics, such as phonon‐assisted energy transfer or upconversion processes. Here, intriguing and unprecedented anomalous thermalization in Gd2O3:Eu3+ and Gd2O3:Yb3+,Er3+ nanotubes, exhibiting up to one order of magnitude larger than previously reported for similar materials, is reported. This anomalous thermalization induces unexpected energy transfer from Eu3+ C2 to S6 crystallographic sites, at 11 K, and 2H11/2 → 4I15/2 Er3+ upconversion emission; it is interpreted on the basis of the discretization of the phonon density of states, easily tuned by varying the annealing temperature (923–1123 K) in the synthesis procedure, and/or the Ln3+ concentration (0.16–6.60%).

Blue organic light-emitting diodes require high triplet interlayer materials, which induce large energetic barriers at the interfaces resulting in high device voltages and reduced efficiencies. Here, we alleviate this issue by designing a low triplet energy hole transporting interlayer with high mobility, combined with an interface exciplex that confines excitons at the emissive layer/electron transporting material interface. As a result, blue thermally activated delay fluorescent organic light-emitting diodes with a below-bandgap turn-on voltage of 2.5 V and an external quantum efficiency (EQE) of 41.2% were successfully fabricated. These devices also showed suppressed efficiency roll-off maintaining an EQE of 34.8% at 1000 cd m−2. Our approach paves the way for further progress through exploring alternative device engineering approaches instead of only focusing on the demanding synthesis of organic compounds with complex structures.

By combining experimental and theoretical approaches, the electronic structure, molecular orientation, charge transfer dynamics and solar cell performance in donor/acceptor copolymer poly[2,7-(9,9-bis(2-ethylhexyl)-dibenzosilole)-alt-4,7-bis(thiophen-2-yl)benzo-2,1,3-thiadiazole] (PSiF-DBT) films and blended with 6,6.-phenyl-C 61-butyric acid methyl ester (PSiF-DBT:PCBM) were investigated. Good agreement between experimental and theoretical PSiF-DBT UV-Vis absorption spectrum is observed and the main molecular orbitals contributing to the spectrum were determined using DFT single point calculations. Non-coplanar configuration was determined by geometric optimization calculation in isolated PSiF-DBT pentamer and corroborated by angular variation of the sulphur 1s near-edge X-ray absorption fine structure (NEXAFS) spectra. Edge-on and plane-on molecular orientations were obtained for thiophene and benzothiadiazole units, respectively. A power conversion efficiency up to 1.58%, open circuit voltage of 0.51 V, short circuit current of 8.71 mA/cm2 and a fill factor of 35% was obtained using blended PSiF-DBT:PCBM as active layer in a bulk heterojunction solar cell. Ultrafast electron dynamics in the low-femtosecond regime was evaluated by resonant Auger spectroscopy using the core-hole clock methodology around sulphur 1s absorption edge. Electron delocalization times for PSiF-DBT and PSiF-DBT:PCBM polymeric films were derived for selected excitation energies corresponding to the main transitions in the sulphur 1s NEXAFS spectra. The mixture of PSiF-DBT with PCBM improves the charge transfer process involving the π* molecular orbital of the thiophene units.

Cubic Gd2O3:Eu3+ (0.30, 1.01, 2.78, and 4.60 mol %) nanorods with an average diameter of ca. 14 nm were synthesized at ambient pressure and mild temperature (70 °C), using a simple and cost-effective wet-chemical route. The emission-decay curves of the 5D1 and 5D0 levels, hereafter referred to as 5D1(C2) and 5D0(C2), were investigated. Although the decay time of the 5D0 level of the Eu3+ ions residing in the C2 site of cubic Gd2O3:Eu3+ nanostructures were previously reported, little is known about the rise time component in the 5D0 emission-decay curve and the energy-transfer pathways responsible for it. The 5D0(C2) rise time and the 5D1(C2) decay time exhibit similar and strong dependence on the Eu3+ concentration and temperature. The 5D1(C2) decay time matches well the rise time extracted from the rising component of the 5D0(C2) emission-decay curve. The decay time of the 5D0(C2) level (ranging from 1.4 to 2.1 ms, depending on the filing factor of the nanorods) is longer than that of the bulk counterpart mainly due to the reduction in the size of the nanorods, which introduces an effective-refractive index smaller than the refractive index of Gd2O3.

A molecular cross-linking approach of the perovskite grains combined with amine-based surface passivation leads to hysteresis-free perovskite transistors.

Polyfluorene based conjugated polyelectrolyte/silica nanocomposites are fabricated using sol‐gel processing. Ionic termination groups on the conjugated polyelectrolyte lateral chains are shown to control the interaction at the inorganic‐organic interface, leading to macroscale homogeneity and nanophase separation in a single material. The extent of nanophase separation is determined by the nature of the ionic groups, which may provide a means of controlling donor‐acceptor distances in hybrid systems.

RESUMOTomando como referência a evolução e as características do sistema brasileiro de educação superior discute-se neste artigo os fundamentos de uma efetiva reforma da educação superior. Procura-se mostrar que a adequação desse sistema para o enfrentamento dos desafios da sociedade do conhecimento, em um país como o Brasil, deve necessariamente resolver três questões: a modernização do sistema, o efetivo aprimoramento da qualidade da educação brasileira em todos os níveis, graus e modalidades e a democratização do ensino promovendo a inclusão social. Palavras-chave: Educação superior brasileira. R e f o r m a u n i v e r s i t á r i a . This paper aims to present the essential basis for an effective higher education reform. The strategies chosen by the authors to develop and to construct their proposals are based on studies of evolution and special features of the Brazilian Higher Education System. By analyzing this special and highly complex system the authors could conclude that in order to fit the challenges which emerge from the knowledge society the higher education system reform