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• AlGaN-based DUV LEDs adopt the triangular island-shaped p-electrode structure. • The proposed structure has been proven to have more uniform optical emission distribution and current spreading. • After 500 h of aging, the optical power of the triangular island-shaped structure is still maintained at 97.6%. • The L70 predicted lifetime of the new structure is extended by 45% compared to the traditional structure. Current crowding and poor reliability due to uneven current distribution are significant challenges limiting the widespread application of AlGaN-based flip-chip deep-ultraviolet (DUV) LEDs. Herein, a novel triangular island-shaped chip structure designed to mitigate current crowding and enhance device reliability. Although this structure exhibits increased leakage current due to etching damage and the reduced effective light-emitting area compared to the interdigitated structure, it demonstrates lower operating voltage and higher wall-plug efficiency at high currents. Optical emission distribution tests confirm that the triangular island-shaped structure effectively reduces current crowding and achieves uniform light emission. After 500 h of aging, the optical power retention of the triangular island-shaped structure remains at 97.6%, and the L70 lifetime, as predicted by a lifetime model, is extended by 45% compared to the interdigitated structure. These findings highlight the critical role of mitigating current crowding in improving the reliability of AlGaN-based DUV LED chip structures. [ABSTRACT FROM AUTHOR]

276 nm AlGaN-based deep-ultraviolet light-emitting diodes (DUV-LEDs) with varying p-GaN thicknesses were investigated. The simulation results demonstrate that DUV-LEDs with an ultra-thin 4 nm p-GaN layer exhibit a 96.9% increase in full-angle total radiant intensity compared to those with a 350 nm p-GaN layer. Meanwhile, the total radiant intensity of the DUV-LEDs with 4 nm p-GaN were all elevated during the degree of polarization (DOP) transition from 1 to −1. The experimental results demonstrate that the maximum external quantum efficiency (EQE) and wall-plug efficiency (WPE) values of 5.3% and 4.0%, respectively, at 4 A/cm2 for the DUV-LEDs with a 4 nm p-GaN layer. These figures represent remarkable improvements of 60.6% and 42.8% when compared to DUV-LEDs featuring a 350 nm p-GaN layer. Nevertheless, it's worth noting that the adoption of an ultra-thin p-GaN ohmic contact layer introduced some surface irregularities, potentially affecting the ohmic contact of the p-type layer and resulting in a slight voltage increase, thus tempering the WPE improvement. The light extraction efficiency (LEE) values of 10.0%, 7.4%, 6.7% and 6.3% were extracted for the four samples after fitting the experimental EQE curves by the ABC model. [ABSTRACT FROM AUTHOR]

High-efficiency 278 nm AlGaN-based deep-ultraviolet light-emitting diodes (DUV-LEDs) adopting the bidirectional-staircase-barrier (BSB) structure have been investigated. The experimental results show that the maximum external quantum efficiency (EQE) and wall-plug efficiency (WPE) for the proposed BSB structure reach 8.47% and 7.01%, respectively. Furthermore, compared with the reference structure, showing a tremendous improvement of 32% and 31%, respectively. Numerical simulation results show that the BSB structure enhances the electron confinement of the quantum barriers (QBs) as well as improves the hole injection, resulting in a 170% increase in the hole concentration for the active region. Meanwhile, integrating a 2-nm-thick thin-strip-barrier on two QBs close to the p-side can modulate the energy band flatter, which facilitates hole migration and achieves a more uniform distribution of holes in the active region. The more uniform carrier distribution improves the radiative recombination rate of the BSB structure by 147% compared to the reference structure. Furthermore, the dramatic increase of the radiative recombination rate in the three quantum wells (QWs) close to the n-side proves that the BSB structure achieves more QWs to participate in effective radiative recombination, which significantly enhances the quantum efficiency of the DUV-LEDs. • AlGaN-based DUV-LEDs adopt the bidirectional-staircase-barrier structure. • The proposed structure enhances the electron confinement and the hole injection. • Integrating the thin-strip-barrier can modulate the energy band flatter. • The more uniform carrier distribution improves the radiative recombination rate. • The bidirectional-staircase-barrier structure can mitigate the efficiency droop. [ABSTRACT FROM AUTHOR]

Numerical simulation results reveal that introducing polarization-induced doping hole injection layer (HIL) in the DUV-LEDs results in a downward band-bending at the EBL/HIL interface, which causes more severe electron leakage. The effect of optimizing EBL thickness on the performance of DUV-LEDs was investigated to mitigate the side-effects due to the introduction of polarization-induced doping HIL. The experimental results show that as the EBL thickness increases, the external quantum efficiency (EQE) and wall-plug efficiency (WPE) of the DUV-LEDs increase and then decrease, while the efficiency droop in an opposite trend. The maximum EQE and WPE of 5.95% and 5.48%, respectively, were achieved when the EBL thickness was 20 nm. Meanwhile, increasing the EBL thickness can improve the DUV-LED reliability. However, an excessively thick EBL will deteriorate the reliability due to generating more Joule heat. Therefore, the reliability of DUV-LED was optimal when the EBL thickness was 25 nm. • Experimental studies were performed based on the polarization-induced doping hole injection layer structure. • Introducing polarization-induced doping hole injection layer causes severe electron leakage. • Increasing the thickness of the triangular hole potential barrier hinders hole injection. • DUV-LED reliability does not monotonically improve as EBL thickness increases. [ABSTRACT FROM AUTHOR]

PbSe film used for infrared detection is generally subjected to sensitization at ≤723 K in air, oxygen, and/or iodine vapor for enhancing its optoelectronic performance. In this work, the PbSe film deposited by chemical bath deposition (CBD) method was firstly sensitized at high temperatures (773–848 K) in argon atmosphere. The phase composition, surface and cross-sectional morphologies, carrier concentration and mobility, and detectivity of the PbSe films before and after sensitization were investigated systematically. The optimal PbSe film sensitized at 823 K processes the average grain size of ∼520 nm, carrier concentration of 9.9 × 1016 cm−3, carrier mobility of 13.9 cm2/N·s, and detectivity of 2.31 × 109 Jones for 1550 nm laser radiation. In particular, the optimized PbSe film displays high reproducibility, fast response and excellent high frequency stability. A potential barrier model is proposed to explain the highest optoelectronic performance, where the evaporation of the Se at grain boundaries can generate n-type semiconductor area and the diffusion of oxygen into PbSe grain lattice contributes to inhibit the recombination of carriers. This work provides a new strategy for sensitization of lead chalcogenides thin films. [Display omitted] • The PbSe film was firstly sensitized at high temperature (over 773 K) in Ar. • High reproducibility, fast response and excellent high frequency stability. • The detectivity of 2.3 × 109 Jones is achieved. • A potential barrier model is proposed. [ABSTRACT FROM AUTHOR]

• For the first time, ultrafine CuNi@ZrO 2 /NC/RGO was successfully synthesized. • CuNi@ZrO 2 /NC/RGO exhibit impressive activities of ABH duo to strong EMSI. • ZrO 2 /NC/RGO can configure novel electronic distribution for high kinetics of ABH. The exploration of heterogeneous supported nanocatalysts with high performance as well as low cost is vital but still challenged for utilization of sustainable hydrogen fuel. In this work, bimetallic CuNi nanoparticles are immobilized on zirconia/nitrogen doped porous carbon/reduced graphene oxide (ZrO 2 /NC/RGO) derived from NH 2 -UiO-66/GO precursor. Thanks to the usage of ZrO 2 /NC/RGO, the well-dispersed CuNi NPs with the size of 2.5 nm were successfully obtained via a facile wet-chemical co-reduction method. By virtue of the synergistic effect induced by solid supports, the resulted Cu 0.8 Ni 0.2 @ZrO 2 /NC/RGO nanocatalysts display excellent activity of catalyzing ammonia borane hydrolysis, with an outstanding overall turnover frequency (TOF) value of as high as 40.9 mol H2 mol cat −1 min−1 at mild condition. Such an enhanced catalytic performance is attributed that zirconium oxide combined with N species could induce a strong synergistic effect to efficiently adjust the electronic distribution, optimize the d-band center as well as favor the Femi level of CuNi catalytic sites, resulting in an improving kinetics of ammonia borane hydrolysis (ABH). This work not only deeply explores the catalytic mechanism of ABH, but also provides a promising strategy for construction of heterogeneous nanocatalytic systems with high performance for industrial application. [ABSTRACT FROM AUTHOR]

A novel approach to sensitize PbSe films utilizing iodine after subjecting them to high-temperature heat treatment was investigated, resulting in a noteworthy enhancement in the optoelectronic performance of PbSe photodetectors. The role of iodine was analyzed from the morphological evolution, phase composition transformation and electrical properties change during the iodine sensitization process. The manipulation of the crystal boundary barrier is supposed to be the key role of iodine. First principles calculations explain the variation of the optical band gap from the energy band structure. In photodetection at room temperature, the maximum detectivity of the iodine sensitized films was 1.02 × 109 Jones at an iodine concentration of 1.36 × 10−5 mol/L. In addition, the high frequency switching behavior at 500 Hz showed excellent stability. The results indicate that the new method investigated can be applied to high-performance lead selenide photodetectors. [ABSTRACT FROM AUTHOR]

PbSe films can be widely applied in many fields involving industrial temperature measurement, military guidance, agriculture detection and celestial observation due to their high reliability and sensitivity. The porous PbSe film with a grain size of ∼0.5 μm was firstly transformed from flaky pastry-like plumbonacrite (Pb 10 O(OH) 6 (CO 3) 6) precursor film by ion exchange process, where the precursor film was prepared by a low-toxicity chemical bath deposition (CBD) process. The variations of phase composition, surface morphology, and binding state of main surface elements, as well as the optical properties of films with immersion time were mainly investigated. The experimental results show that the flaky pastry-like Pb 10 O(OH) 6 (CO 3) 6 film can be fully converted to cubic PbSe film as the immersion time is over 1.5 h, and the grain size of PbSe is further increased with the immersion time prolonging from 1.5 to 2.5 h. Moreover, the presence of a large number of pores in PbSe film can produce low reflectance, leading to the improvement of optical performance of PbSe film in the infrared wavelength range. The XPS, Raman and TEM analyses demonstrate the presence of trace impurities and lattice defects, which can be related to the oxidation, incomplete transformation and mutual extrusion between grains. The calculated bandgap is decreased from 2.68 eV for Pb 10 O(OH) 6 (CO 3) 6 film to 0.39 eV for PbSe film. [Display omitted] • Flaky pastry-like plumbonacrite film was firstly prepared by a green CBD process. • The plumbonacrite film was converted to cubic PbSe film by ion exchange process. • Reflectance of porous PbSe film is less than 22.5% in the range of 450–5000 nm. • The bandgap of optimal PbSe film was 0.39 eV. [ABSTRACT FROM AUTHOR]