[en] KZnF₃:Er³⁺,Yb³⁺ was prepared by hydrothermal synthesis. For all samples (ErYb0-ErYb4), Er³⁺ concentration was fixed at 0.5 mol.%. Yb³⁺ concentration was changed from 0 to 4 mol.%. We observed upconversion luminescence at 653 and 553 nm (525 nm) when the samples were excited by 980 nm light. All samples were annealed at 400 deg. C under vacuum of 10^-5 Torr for 1 h. The upconversion intensity that was measured in the same condition changed when the sample was annealed. The upconversion mechanism of annealed samples is a two-photon process

[en] In this paper, YLiF₄ codoped with Tm³⁺ and Yb³⁺ ions was synthesized by hydrothermal method. Yb³⁺ concentration is fixed at 1.5%, and Tm³⁺ concentration is changed from 0.1 to 0.4%. Intense upconversion luminescence is observed when the samples are excited by 980 nm. The dependence of upconversion luminescence on Tm³⁺ concentrations is presented. The results show that upconversion luminescence increases with the Tm⁺ concentration and gets its peak at 0.3 mol%. Under the excitation of 980 nm, the blue emission of 479 nm and the red emission of 647 nm are both duo to two photons process, and the UV emission of 361 nm is attributed to the three photons process. We also analyse the upconversion mechanism and process

[en] In bottom-gated organic field-effect transistors (OFETs) carrier transport and device performances show strong dependencies on the dielectric and surface properties of gate insulating materials. A single-layer gate dielectric cannot meet the requirements of large permittivity (k) and low surface polarity for fabricating low-operating-voltage, high-performance OFETs. Here, we have designed a bilayer gate dielectric consisting of a low-k cross-linked poly(4-vinylphenol) (CL-PVP) in contact with an active layer to provide a low polar surface and an underneath high-k polyvinyl alcohol (PVA) layer to ensure a high capacitance. The results show that the CL-PVP/PVA bilayer not only offers a smooth and uniform surface with low polarity and low surface energy as well as good solvent resistance for efficient carrier transport, but also possesses a relatively high capacitance and low leakage current for low threshold and operating voltages. We have utilized this bilayer dielectric to fabricate OFETs based on a conventional semiconducting polymer poly(3-hexylthiophene) (P3HT). High overall device performances have been achieved in the devices with a mobility of 0.1 cm² V⁻¹ s⁻¹. The maximum density of trap states at the interface between the P3HT film and the CL-PVP/PVA bilayer is estimated to be 7.10 × 10¹² cm⁻² eV⁻¹, further proving that this bilayer dielectric provides a high quality interface for P3HT. The CL-PVP/PVA bilayer is thus a promising candidate as a gate dielectric for fabricating high-performance organic or even organic-inorganic hybrid perovskite transistors by a solution processing technique.

[en] The two categories of organic photodetectors (OPDs) can be distinguished as the photodiode mode and the photoconductor mode. The role of the contact between the electrode and active layer in determining the specific type of photodetector is of utmost importance. In this study, the transition of working modes between the photodiode type and the photoconductor type in OPDs is demonstrated. Specifically, OPDs based on the indium tin oxide/Cs${}_2$CO${}_3$/P3HT: PC${}_{61}$BM/Al (or Au) structure are fabricated. In the corresponding characterization results, distinct working modes are showcased. For the device with the Au electrode, under reverse bias, the photo-generated charges can efficiently transport to their respective electrodes and subsequently be collected. This behavior aligns with the photodiode type. Conversely, in the device with the Al electrode, the photo-generated charges accumulate near the interface between the Cs${}_2$CO${}_3$ layer and the active layer. Subsequently, under reverse bias, tunneling charge injection occurs, resulting in the photoconductor type with an external quantum efficiency exceeding 100%. Both the photodiode and photoconductor devices exhibit a high signal-to-noise ratio ranging from 10${}^4$ to 10${}^5$ and fast response on the order of microseconds at -0.5 V. In these findings, the possibility of obtaining desirable working-mode OPDs by manipulating the electrode work function is suggested. (© 2023 Wiley‐VCH GmbH)

[en] In this study, electrically bistable devices were fabricated by incorporating cuprous sulfide (Cu₂S) nanospheres with mean size less than 10 nm into a poly(N-vinylcarbazole) (PVK) matrix. A remarkable electrical bistability was clearly observed in the current–voltage curves of the devices due to an electric-field-induced charge transfer between the dodecanethiol-capped Cu₂S nanospheres and PVK. The maximum ON/OFF current ratio reached up to value as large as 10⁴, which was dependent on the mass ratios of Cu₂S nanospheres to PVK, the amplitude of the scanning voltages, and the film thickness. The charge-transport mechanisms of the electrically bistable devices were described on the basis of the experimental results using different theoretical models of organic electronics.

[en] Herein, a single-layer light-emitting transistor with a good on/off ratio of more than 10${}^6$ is presented based on the iridium complex as a light-emitter layer. Comprehensive experiments and simulations demonstrate that the thickness of the emitting layer can significantly improve the majority carrier injection in the source electrode. The electrode work function determines the minority carrier injection in the drain electrode, which is crucial for the light emission of the transistor. Furthermore, the increased source injection allows for a higher channel current, thereby increasing drain injection. Most importantly, although the above methods can improve the device channel current and light-emitting brightness, the electroluminescence efficiency cannot be optimized since the increased minority carriers are much less than the increased majority carriers, resulting in most increased majority carriers cannot be contributed to the charge recombination. To achieve a higher efficient device, the channel current is supposed to be low when a conductive channel is well formed. This goal is achieved by using an ionic liquid gate to replace SiO${}_2$ gate for fabricating the light-emitting single-layer transistor. The efficiency is improved from ≈0.1 to 1.5 cd A${}^{-<!--\; ???\; -->1}$. This work provides a new strategy for constructing high-performance single-layer light-emitting transistors. (© 2023 Wiley‐VCH GmbH)

[en] Mild cognitive impairment (MCI) in Parkinson’s disease (PD) is related to the disrupted connectivity in networks involved in cognition, primarily in the default mode network (DMN). The DMN contains a midline core and two distinct subsystems (dorsal medial prefrontal cortex (DMPFC) and medial temporal lobe (MTL) subsystems). The strength of functional connectivity (FCS) in intra- and inter-subsystems of DMN and the regional FCS were compared between any two groups from 28 drug-naïve PD patients with MCI (PD-MCI), 19 drug-naïve PD patients with cognitive unimpaired (PD-CU), and 28 age- and sex-matched healthy controls (HCs) by using the nonparametric permutation method (10,000 permutations) with age, sex, and education as covariates and False Discovery Rate (FDR) correction. For intra-subsystems, the decreased FCS was only detected in the DMPFC subsystem of PD-MCI patients compared with HCs. For inter-subsystems, PD-MCI patients displayed decreased FCS between the posterior cingulate cortex (PCC) and DMPFC subsystem compared with HCs. Furthermore, the temporal parietal junction (TPJ) in the DMPFC subsystem showed decreased regional FCS in the PD-MCI subgroup relative to the HC group. No significant change of FCS was found between PD-MCI and PD-CU patients, and between PD-CU patients and HCs. The sum of FCS values within the DMPFC subsystem and FCS values between the PCC and DMPFC subsystem had a significant power to distinguish PD-MCI patients from PD-CU patients (area under curve (AUC) = 0.703). The DMPFC subsystem was predominantly disrupted in the PD-MCI subgroup and may have the potential to discriminate PD with MCI.

[en] The mutations of the glucocerebrosidase (GBA) gene are the greatest genetic risk factor for Parkinson's disease (PD). The mechanism underlying the association between GBA mutations and PD has not been fully elucidated. Using resting-state functional magnetic resonance imaging and graph theory analysis to investigate the disrupted topological organization in PD patients with GBA mutation (GBA-PD). Eleven GBA-PD patients, 11 noncarriers with PD, and 18 healthy controls (HCs) with a similar age and sex distribution were recruited. Individual whole-brain functional connectome was constructed, and the global and nodal topological disruptions were calculated among groups. Partial correlation analyses between the clinical features of patients with PD and topological alterations were performed. The GBA-PD group showed prominently decreased characteristic path length (L${}_p$) and increased global efficiency (E${}_g$) compared to HCs at the global level; a significantly increased nodal betweenness centrality in the medial prefrontal cortex (mPFC) and precuneus within the default mode network, and precentral gyrus within the sensorimotor network, while a significantly decreased betweenness centrality in nodes within the cingulo-opercular network compared to the noncarrier group at the regional level. The altered nodal betweenness centrality of mPFC was positively correlated with fatigue severity scale scores in all patients with PD. The preliminary pilot study found that GBA-PD patients had a higher functional integration at the global level. The nodal result of the mPFC is congruent with the potential fatigue pathology in PD and is suggestive of a profound effect of GBA mutations on the clinical fatigue in patients with PD.

[en] Graphical abstract: Within the 10 hybrids, M06 in the frame of DFT and TDDFT with a polarizable continuum model and a medium sized basis set emerges as the most effective strategy to investigate DCDPC. The figure displays absorption (red dash) and emission (green solid) spectra calculated in acetone for DCDPC using TD-M06 functional. Inserts are the structure of DCDPC. Research highlights: → Red emitter DCDPC is studied by density functional theory (DFT) and time dependent (TD)DFT. → The electronic and geometrical structures for the ground and first excited state are given. → The experimental absorption and fluorescence spectra are reproduced by calculations. → The performance of 10 exchange-correlation functionals is given. → M06 emerges as the most effective functionals. - Abstract: The ground and excited state properties of DCDPC, particularly designed as a red emitter for organic light emitting diodes applications have been studied by means of density functional theory (DFT) and time-dependent (TD)DFT. The electronic and geometrical structures of DCDPC in acetone, tetrahydrofuran and benzene solvents are reported for the first time. The experimental absorption and fluorescence spectra are reproduced by calculations. By comparison with experimental data, insight on the performance of 10 exchange correlation functionals is also given. M06 in the frame of DFT and TDDFT with a polarizable continuum model and a medium sized basis set emerges as the most effective strategy. Beside the good agreement between the calculational and experimental spectra proving the accuracy of the strategy, the calculations allow further insights into the electronic structure for the family of isophorone-based light emitting materials with D-π-A structure, especially the electronic and geometrical structures for the excited states.

[en] REBCO tapes, known as second generation (2G) high temperature superconducting (HTS) tapes, are promising for their application in high field magnets and high current cables. However, in practical applications 2G HTS tapes always need to be bent, which causes the degradation of critical current. Therefore, it is necessary to study the bending characteristics of 2G HTS tapes. Studies have been carried out regarding easy bending and hard bending characteristics, but there has been no research into the characteristics of out-of-plane bending with different bending angles. This paper theoretically analyzes the out-of-plane bending with different bending angle characteristics of 2G HTS tapes and deduces the strain formula of different bending modes. Experiments on the bending characteristics of 2G HTS tapes were performed in liquid nitrogen. The experiments verified the theoretical calculation, and the results have significance for the applications of 2G HTS tapes. (paper)