Tuning optical properties of CsPbBr3 by mixing Nd3+trivalent lanthanide halide cations for blue light emitting devices.

In recent years, significant progress has been made in the red and green perovskite quantum dots (PQDs) based light-emitting devices. However, a scarcity of blue-emitting devices that are extremely efficient precludes their research and development for optoelectronic applications. Taking advantage of tunable bandgaps of PQDs over the entire visible spectrum, herein we tune optical properties of CSPbBr3 by mixing Nd3+ trivalent lanthanide halide cations for blue light-emitting devices. The CsPbBr3 PQDs doped with Nd3+ trivalent lanthanide halide cations emitted strong photoemission from green into the blue region. By adjusting their doping concentration, a tunable wavelength from (515 nm) to (450 nm) was achieved with FWHM from (37.83 nm) to (16.6 nm). We simultaneously observed PL linewidth broadening thermal quenching of PL and the blue shift of the optical bandgap from temperature-dependent PL studies. The Nd3+ cations into CsPbBr3 PQDs more efficiently reduced non-radiative recombination. As a result of the efficient removal of defects from PQDs, the photoluminescence quantum yield (PLQY) has been significantly increased to 91% in the blue-emitting region. Significantly, Nd3+ PQDs exhibit excellent long-term stability against the external environment, including water, temperature, and ultraviolet light irradiation. Moreover, we successfully transformed Nd3+ doped PQDs into highly fluorescent nanocomposites. Incorporating these findings, we fabricate and test a stable blue light-emitting LED with EL emission at (462 nm), (475 nm), and successfully produce white light emission from Nd3+ doped nanocomposites with a CIE at (0.32, 0.34), respectively. The findings imply that low-cost Nd3+ doped perovskites may be attractive as light converters in LCDs with a broad color gamut.

Higher Light Extraction Efficiency in Organic Light-Emitting Devices by Employing 2D Periodic Corrugation

Photons trapped in the form of waveguide (WG) modes associated with the organic–organic interface and in the form of surface plasmon polariton (SPP) modes associated with the metallic electrode–organic interface result in a large energy loss in organic light-emitting devices (OLEDs). Introducing gratings onto the metallic electrode is especially crucial for recovering the power lost to the associated SPP modes. In our research, we demonstrate the efficient outcoupling of SPP modes in TE mode by two-dimensional (2D) grating, which cannot excited in one-dimensional (1D) grating OLED. This causes a 62.5% increase in efficiency from 2D grating OLED than 1D grating OLED. The efficient outcoupling of the WG and SPP modes is verified by the numerical simulation of both the emission spectra and the field distribution.

A systematic review on 1,8-naphthalimide derivatives as emissive materials in organic light-emitting diodes

Organic light-emitting devices (OLEDs) have garnered significant research attention owing to their immense application prospects in leading technologies for full-color flat panel displays and eco-friendly solid-state lighting. They demonstrate exceptional features such as mercury-free construction, wide viewing angle, superior color quality and captivating flexibility. The requirements of light-emitting organic materials pertaining to high stability, lifetime and luminescence quantum yield, combined with the fabrication of devices with high performance efficiency, are highly challenging. Rational molecular design of 1,8-naphthalimide (NI) derivatives can offer quite promising results in achieving standard-light-emitting materials with a wide range of colors for OLED applications. This review is mainly focused on the synthesis and usage of varyingly substituted NI frameworks as luminescent host, dopant, hole-blocking and electron-transporting materials for OLEDs that emit not only red, orange, green and blue colors, but also function as white emitters, which can really have an impact on reducing the energy consumption. The future prospects that could be explored to improve the research in the highly promising field of OLEDs are also discussed. Graphical abstract

Air-processed stable near-infrared Si-based perovskite light-emitting devices with efficiency exceeding 7.5%

Two composite layers are used to enhance the efficiency of Si-based near-infrared perovskite light-emitting devices, which are produced in ambient air, and the external quantum efficiency increased to 7.5%.

Dependence of InGaN Quantum Well Thickness on the Nature of Optical Transitions in LEDs

The design of the active region is one of the most crucial problems to address in light emitting devices (LEDs) based on III-nitride, due to the spatial separation of carriers by the built-in polarization. Here, we studied radiative transitions in InGaN-based LEDs with various quantum well (QW) thicknesses—2.6, 6.5, 7.8, 12, and 15 nm. In the case of the thinnest QW, we observed a typical effect of screening of the built-in field manifested with a blue shift of the electroluminescence spectrum at high current densities, whereas the LEDs with 6.5 and 7.8 nm QWs exhibited extremely high blue shift at low current densities accompanied by complex spectrum with multiple optical transitions. On the other hand, LEDs with the thickest QWs showed a stable, single-peak emission throughout the whole current density range. In order to obtain insight into the physical mechanisms behind this complex behavior, we performed self-consistent Schrodinger–Poisson simulations. We show that variation in the emission spectra between the samples is related to changes in the carrier density and differences in the magnitude of screening of the built-in field inside QWs. Moreover, we show that the excited states play a major role in carrier recombination for all QWs, apart from the thinnest one.

Realization of Efficient Phosphorescent Organic Light-Emitting Devices Using Exciplex-Type Co-Host

High-performance phosphorescent organic light-emitting devices with an exciplex-type co-host were fabricated. The co-host is constituted by 1,3,5-tris(N-phenylbenzimidazol-2-yl) benzene, and 4,4,4-tris (N-carbazolyl) triphenylamine, and has obvious virtues in constructing efficient devices because of the thermally activated delayed fluorescence (TADF) resulting from a reverse intersystem crossing (RISC) process. The highest external quantum efficiency and luminance are 14.60% and 100,900 cd/m2 for the optimal co-host device. For comparison, 9.22% and 25,450 cd/m2 are obtained for a device employing 4,4,4-tris (N-carbazolyl) triphenylamine as a single-host. Moreover, the efficiency roll-off is notably alleviated for the co-host device, indicated by much higher critical current density of 327.8 mA/cm2, compared to 120.8 mA/cm2 for the single-host device. The alleviation of excitons quenching resulting from the captured holes and electrons, together with highly sufficient energy transfer between the co-host and phosphorescent dopant account for the obvious boost in device performances.

Electrical and Optical Characteristics of SSI-LED Made from Capacitor Containing Tri-Layer WOx Embedded Zr-Doped HfOx Gate Dielectric

Solid-state incandescent light emitting devices made from MOS capacitors with the WOx embedded Zr-doped HfOx gate dielectric were characterized for electrical and optical characteristics. Devices made from capacitors containing Zr-doped HfOx and WOx, gate dielectrics were also fabricated for comparison. The device with the WOx embedded gate dielectric layer had electrical and light emitting characteristics between that with WOx gate dielectric layer and that with the Zr-doped HfOx but no WOx embedded gate dielectric layer. The difference can be explained by the nano-resistor formation process and the content of the high emissivity W in the nano-resistor. The device made from the WOx embedded Zr-doped HfOx gate dielectric MOS capacitor is applicable to areas where uniform emission of warm white light is required.