White-color organic light-emitting diodes (WOLEDs) have aroused wide interests for future lighting because of low energy consumption in principle, while still suffer from the degradation by Joule heating and polaron-induced quenching under high luminance caused by high current in practical. To obtain high current efficiency, which means high luminance at low current density, tandem WOLEDs with multiple electroluminescence (EL) units connected in series with charge generation layers (CGLs) have been developed. Here we report the improved hybrid tandem WOLED with two EL units, EL1 and EL2, where EL1 and EL2 generate fluorescent blue and phosphorescent yellow emissions from a metal-free material BCzVBi and a Ir-complex (fbi)₂Ir(acac), respectively, with CGL composed of a HATCN/NPB bilayer. The white-light emitting device shows the maximum current efficiency and power efficiency of 60.2 cd/A and 29.6 lm/W, respectively, without out-coupling structure. A low driving voltage of 6.5 V at 1,000 cd/m² is realized, which is an important value because such a luminance is required for actually employed lighting device. The blue emission appears from 5.4 V, and the light color changes from yellowish to bluish white during 5.4 V to 13.4 V, which could be explained by the energy level structures of the device and proved by the J-V characteristics. Additionally, this tandem WOLED also shows photovoltaic effect. This work provides a design of room light source whose color temperature could be tuned through applied voltage when needed, and a display system for low-current operated amorphous Si-TFT due to its high current efficiency.

Blue emitters are highly desired in organic light-emitting diodes (OLEDs), but their electroluminescence efficiencies and roll-offs are always less than satisfactory. In this work, a triazine-based deep-blue emitter (2PhCzTRZ-Cz) is designed and synthesized. It prefers high thermal stability with a decomposition temperature of up to 543 °C, and possesses strong deep-blue photoluminescence. The doped OLEDs using 2PhCzTRZ-Cz as an emitter attain deep-blue lights at 418-424 nm, with high maximum external quantum efficiencies (η_extS) of 4.46-5.68%, maximum luminances of 2,820-7,400 cd m^-2, CIE_y values < 0.1 and small efficiency roll-offs. In addition, multiple-resonance thermally activated delayed fluorescence OLED by using 2PhCzTRZ-Cz as host realizes a high maximum η_ext of 21.5%, significantly higher than those of the device based on traditional mCBP host (12.9%). These outstanding performances demonstrate the great potential of 2PhCzTRZ-Cz as an emitter and host for OLEDs.

Nitrogen/boron-based multi-resonance thermally activated delayed fluorescence (MR-TADF) materials offer advantages in terms of high photoluminescence quantum yield (PLQY) and narrowband emission, making them highly promising for display applications. Represented by ν-DABNA, diboron MR-TADF materials demonstrate the potential for high-efficiency narrowband emission. However, their large planar structures are susceptible to intermolecular interactions, thus increasing the complexity of device fabrication. In this research, our objective was to enhance the anti-aggregation capabilities of the diboron-based ν-DABNA by incorporating sterically hindered terphenyl groups. We synthesized two luminescent materials, DTPF-ν-DABNA and DTP-ν-DABNA, with intermolecular distances exceeding 4 Å in single-crystal stacking, significantly inhibiting intermolecular interactions. Both materials achieved an external quantum efficiency (EQE) exceeding 30% and full width at half maximum (FWHM) of no more than 22 nm, demonstrating characteristics of high-efficiency narrowband emission. Our research provides a straightforward and practical method to obtain MR-TADF materials with high device efficiency and low sensitivity to doping concentration.

Incorporation of two dimensional (2D) materials into a polymer matrix is an efficient way to prepare high performance coatings. Here we report the in-situ mechanical exfoliation of graphite in a mixture of hydroxyethylacrylate terminated polybutadiene urethane (HTPU) prepolymer and reactive diluent. The mixture containing exfoliated graphite nanoplatelets (GN) is directly used to prepare UV cured composite resins (G/HTPU) with various GN concentrations. Various techniques, such as scanning electron microscopy (SEM), Raman, atomic force microscopy (AFM), have been used to characterize the GN, confirming that few-layered GN are obtained after the in-situ mechanical exfoliation. The incorporation of GN exerts little effect on the curing of the coatings with a gelation around 95%, but greatly enhances the elastic modulus. Tafel polarization curves, electrochemical impedance spectroscopy (EIS) and salt-spray testing were conducted to comparatively evaluate the G/HTPU coatings with different GN loadings. The results indicate that the incorporation of GN greatly improves the corrosion resistance of the HTPU UV coatings. The self-corrosion current density (I _corr) and the charge transfer resistance (R _c) of G/HTPU-2 (0.2% GN loading) are greatly reduced to 1.03 × 10^-8 A·cm^-2 and increased by two magnitudes, respectively, compared to those of the parent HTPU coating. Additionally, the G/HTPU-2 coating with thickness of 100 μm can protect galvanized sheet against 0.5 mol/l sulfuric acid for at least 24 h. The practical application in protection of electronics was illustrated by coating the G/HTPU-2 on a standard printed circuit board (PCB, IPC-B-24A). No corrosion was observed after it was immersed in an artificial sweat solution even under open-circuit voltage of 12 V for 72 h and then 24 V for 48 h.

Magnetorheological fluid (MRF) has broad application prospects in the field of engineering vibration damping due to its magnet-sensitive characteristics. However, owing to its dependence on external electric or magnetic fields, devices based on MRF can’t work once the power is turned off. Here we developed a magnetorheological shear thickening fluid (MRSTF) with both the magnet-sensitive and rate-sensitive characteristics. The shear thickening effect of MRSTF was examined, revealing that the critical shear rate ${\dot{\gamma }}_c$ of the suspension gradually decreases from 79.4 s^-1 to 30.2 s^-1 and the shear thickening power β of the suspension gradually decreases from 0.27 to 0.19 as the carbonyl iron powder (CIP) content increases from 0 to 30 vol.% when the mass fraction of SiO₂ is 54 wt.%. Besides, the MRSTF-based dampers were tested under different frequencies and amplitudes. The results show that the MRSTF-based dampers still exhibit the energy dissipation characteristics in the absence of magnetic field because of the rate-sensitive property of MRSTF. Under the condition of an applied magnetic field, the dampers exhibit stronger energy dissipation characteristics due to the magnetic-sensitive characteristics of MRSTF. Concurrently, the dissipation capacity of the dampers increases with the increase of frequency and amplitude. This work provides an approach to enhance the mechanical properties of dampers and widen the application field.

White-color organic light-emitting diodes (WOLEDs) have aroused wide interests for future lighting because of low energy consumption in principle, while still suffer from the degradation by Joule heating and polaron-induced quenching under high luminance caused by high current in practical. To obtain high current efficiency, which means high luminance at low current density, tandem WOLEDs with multiple electroluminescence (EL) units connected in series with charge generation layers (CGLs) have been developed. Here we report the improved hybrid tandem WOLED with two EL units, EL1 and EL2, where EL1 and EL2 generate fluorescent blue and phosphorescent yellow emissions from a metal-free material BCzVBi and a Ir-complex (fbi)₂Ir(acac), respectively, with CGL composed of a HATCN/NPB bilayer. The white-light emitting device shows the maximum current efficiency and power efficiency of 60.2 cd/A and 29.6 lm/W, respectively, without out-coupling structure. A low driving voltage of 6.5 V at 1,000 cd/m² is realized, which is an important value because such a luminance is required for actually employed lighting device. The blue emission appears from 5.4 V, and the light color changes from yellowish to bluish white during 5.4 V to 13.4 V, which could be explained by the energy level structures of the device and proved by the J-V characteristics. Additionally, this tandem WOLED also shows photovoltaic effect. This work provides a design of room light source whose color temperature could be tuned through applied voltage when needed, and a display system for low-current operated amorphous Si-TFT due to its high current efficiency.

High-performance and long-lifetime blue organic light-emitting diodes (OLEDs) are crucial for meeting the demands of advanced display and lighting technologies. Despite high device efficiency has been achieved in blue OLEDs, development of high-performance and long-lifetime blue OLEDs still lag far behind their red/green counterparts due to the presence of long-lived high-energy triplet excitons and polarons. Given the critical role of charge and exciton management in both the emission and degradation processes of OLEDs, this review systematically summarizes strategies for suppressing charge leakage and exciton quenching, as well as for enhancing exciton utilization in blue fluorescent, phosphorescent, and thermally activated delayed fluorescent (TADF) OLEDs. In this context, we further discuss the roles of conventional fluorescent hosts, triplet-triplet annihilation/hot exciton hosts, TADF assistant hosts, phosphorescent assistant hosts, and exciplex/electroplex hosts in regulating charge and exciton dynamics in blue OLEDs. Additionally, the modification of emitting layer materials is highlighted as a key strategy for managing charge and exciton processes in efficient and stable solution-processed blue OLEDs. Based on current insights into the efficiency and operational stability of blue OLEDs, this review proposes feasible charge and exciton management strategies to address the current challenges.

Blue emitters are highly desired in organic light-emitting diodes (OLEDs), but their electroluminescence efficiencies and roll-offs are always less than satisfactory. In this work, a triazine-based deep-blue emitter (2PhCzTRZ-Cz) is designed and synthesized. It prefers high thermal stability with a decomposition temperature of up to 543 °C, and possesses strong deep-blue photoluminescence. The doped OLEDs using 2PhCzTRZ-Cz as an emitter attain deep-blue lights at 418-424 nm, with high maximum external quantum efficiencies (η_extS) of 4.46-5.68%, maximum luminances of 2,820-7,400 cd m^-2, CIE_y values < 0.1 and small efficiency roll-offs. In addition, multiple-resonance thermally activated delayed fluorescence OLED by using 2PhCzTRZ-Cz as host realizes a high maximum η_ext of 21.5%, significantly higher than those of the device based on traditional mCBP host (12.9%). These outstanding performances demonstrate the great potential of 2PhCzTRZ-Cz as an emitter and host for OLEDs.