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PbS films grown on quartz substrates by the chemical bath deposition method were annealed in an O2 atmosphere to investigate the role of oxygen in the sensitization process at different annealing temperatures. The average grain size of the PbS films gradually increased as the annealing temperature increased from 400 °C to 700 °C. At an annealing temperature of 650 °C, the photoresponsivity and detectivity reached 1.67 A W−1 and 1.22 × 1010 cm Hz1/2 W−1, respectively. The role of oxides in the sensitization process was analyzed in combination with X-ray diffraction and scanning electron microscopy results, and a three-dimensional network model of the sensitization mechanism of PbS films was proposed. During the annealing process, O functioned as a p-type impurity, forming p+-type PbS layers with high hole concentrations on the surface and between the PbS grains. As annealing proceeds, the p+-type PbS layers at the grain boundaries interconnect to form a three-dimensional network structure of hole transport channels, while the unoxidized p-type PbS layers act as electron transport channels. Under bias, photogenerated electron–hole pairs were efficiently separated by the formed p+-p charge separation junction, thereby reducing electron–hole recombination and facilitating a higher infrared response. [ABSTRACT FROM AUTHOR]

The performance improvements of AlGaN‐based deep ultraviolet light‐emitting diodes (DUV‐LEDs) with multigradient electron blocking layer (EBL) and triangular last quantum barrier (LQB) are investigated. The results show that the maximum internal quantum efficiency (IQE) is improved by 44.9% and light output power (LOP) is improved by 58.1% at 200 A cm−2, exhibiting a tremendous improvement compared to the conventional structure. These improvements are mainly attributed to the fact that both multigradient EBL and triangular LQB can generate negative polarization charges in the graded composition layer, which leads to a significant increase in hole concentration compared to the conventional EBL and LQB structures. Meanwhile, the multigradient EBL can transform the conventional triangular barrier into an arc‐shaped barrier, increasing the electron potential barrier height and decreasing the hole potential barrier height. This unique design suppresses electron leakage and enhances hole injection, leading to a significant enhancement of the IQE and alleviation of the efficiency droop. [ABSTRACT FROM AUTHOR]

• 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]

Conventional PbSe infrared photodetectors typically demands a substantial external electric field, posing challenges in energy-constrained environments. Self-powered photodetectors present a promising avenue for addressing such electricity-related challenges. Nevertheless, the inherent limitations of symmetric Schottky contacts in metal-semiconductor-metal (MSM) photodetectors constrain their self-powered performance, resulting in opposing photocurrents. Constructing asymmetric MSM structures usually requires intricate design or sustained external fields. In this study, we propose a novel contact engineering strategy based on iodine doping to modulate surface work functions of PbSe film. Utilizing Cr electrodes, we achieve Ohmic contact on the iodine-doped top surface of PbSe film and Schottky contact on the as-grown bottom surface. This approach establishes a self-powered PbSe infrared photodetector with an asymmetric top-bottom MSM structure. We comprehensively investigate contact engineering by investigating surface chemical states, elemental variations, and surface work functions variation. Remarkably, the photodetector demonstrates an exceptional zero-bias detectivity of 1.13 × 109 Jones, with an extremely low dark current of 3.67 pA, high I light /I dark ratio exceeding 104, and extremely short response times of less than 1 ms, respectively. Our work introduces a new strategy for modifying the band structure, contributing to the fabrication of high-performance self-powered photodetectors. [Display omitted] • Iodine sensitisation is used to modulate the PbSe surface work function. • I light /I dark ratios are dramatically improved by device type conversion and response times are extremely short (<1 ms). • The device achieves a zero-bias detectivity of 1.13 × 109 Jones and has an ultra-low dark current of 3.67 pA. [ABSTRACT FROM AUTHOR]

• A liquid sensitization of lead selenide thin films for mid-infrared detection. • Iodination of PbSe films in KI solution followed by high temperature sensitization. • The maximum detectivity of the sensitized films was 2.27 × 109 Jones. In pursuit of addressing the inherent challenges associated with gas partial pressure control and non-uniform diffusion of solid iodine encountered in conventional sensitization methods, this study delves into the impact of liquid sensitization on the structural and electrical properties of lead selenide (PbSe) films. The sensitization process entails iodination of PbSe films within varying concentrations of potassium iodide (KI) solutions, followed by high-temperature sensitization. The phase composition, surface morphologies, carrier concentration and mobility, and detectivity of the PbSe films after sensitization were investigated systematically. Our findings illuminate the transformative potential of liquid iodine sensitization in the modification of the crystal boundary barrier within PbSe films, thereby engendering substantial enhancements in both structural and electrical attributes. Iodine assumes a pivotal role in the orchestration of this boundary barrier modulation, which, in turn, has birthed an innovative methodology for crafting high-performance PbSe photodetectors. Remarkably, when films were sensitized with a KI concentration of 0.05 M, the maximum detectivity achieved reached an impressive 2.27 × 109 Jones. This study not only deepens our understanding of the underlying mechanisms responsible for the optoelectronic response of PbSe films but also underscores the immense potential of liquid iodine sensitization as a promising way for elevating their overall performance. [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]

In this work, TiAlN/NiCr composite coatings were prepared by reactive magnetron sputtering technique. Firstly, a single absorber layer was prepared, and at the substrate temperature of 300 °C, a "prismatic" structure is formed on the surface of the TiAlN film, which has good light absorption properties under these conditions. In order to further improve its absorption, the TiAlN/NiCr bilayer coating was designed, and the effects of etching in two different solutions and subsequent annealing treatments on the surface microstructure and reflectivity of the bilayer coating were investigated. These results show that TiAlN/NiCr bilayer coatings fabricated in various etching solutions can further improve light absorption performance, with the TiAlN/NiCr-CAN coating showing particularly good thermal stability and exhibiting further improvements in absorption performance after 500 °C/2 h of annealing. Low-temperature applications are the only ones for which the TiAlN/NiCr–HF coating is suitable, since it fails at the annealing condition of 300 °C/2 h. [Display omitted] • TiAlN/NiCr composite coatings prepared by reactive magnetron sputtering technique. • Investigation of effects of etching in two solutions. • Subsequent annealing treatments on surface microstructure and reflectivity of the bilayer coating. • The coating has high thermal stability and absorption performance even after 500 °C/2 h of annealing. [ABSTRACT FROM AUTHOR]

[Display omitted] • In 2 O 3 -loaded CeO 2 nanorods was applied to hydrogen sensor in the air for the first time. • In 2 O 3 -loaded CeO 2 nanorods exhibited enhanced hydrogen sensing performance. • Enhanced hydrogen sensing performance is due to n-n junction and the larger specific surface area. Hydrogen (H 2) detection sensors based on pure CeO 2 nanorods (NRs) and In 2 O 3 -loaded CeO 2 NRs with different In 2 O 3 contents (5 wt%, 10 wt%, and 15 wt%) were investigated. The crystal phase evolution, morphology features, and response characteristics of the In 2 O 3 -loaded CeO 2 NRs were analyzed in detail using characteristic techniques. Gas sensing results showed that the In 2 O 3 -loaded CeO 2 gas sensors exhibited superior H 2 sensing performances compared with pure CeO 2 NRs under low operating temperature (100 °C). Notably, the gas sensors based on the 10 wt% In 2 O 3 -loaded CeO 2 nanocomposite showed the most refined performance, with response values of 2.79 and 2.43 times higher than those of the pure CeO 2 NRs sensors for 1000 ppm and 4000 ppm H 2 , respectively. The response values exhibited a linear relationship with the detection concentration. Moreover, the In 2 O 3 -loaded CeO 2 gas sensor demonstrated enhanced H 2 selectivity, good recyclability, and long-term stability. Finally, the improved gas sensing mechanism of the In 2 O 3 -loaded CeO 2 gas sensor for H 2 was also proposed. [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]

Ammonia borane (AB) hydrolysis is a sustainable and efficient method for hydrogen energy conversion and transportation. Designing a non-precious AB hydrolysis catalyst with high catalytic activity is considered to be promising but challenging. Herein, highly dispersed Cu0.9Ni0.1 alloy nanoparticles (NPs) were successfully fabricated via a conventional wet-chemical co-reduction method on transition metal carbides (Ti3C2Tx), facilitating hydrogen evolution during AB hydrolysis. The optimized Cu0.9Ni0.1/Ti3C2Tx catalyst exhibits an impressive turnover frequency (TOF) of 2429 h−1 at 323 K for AB hydrolysis, with 100% hydrogen selectivity, outperforming those of most non-precious metal catalysts. This enhanced performance is attributed to the synergistic effect between Cu and Ni, as well as the strong electronic metal–support interaction between Ti3C2Tx and Cu0.9Ni0.1 NPs. This study provides a general and simple method for synthesizing highly efficient non-precious metal AB hydrolysis catalysts. [ABSTRACT FROM AUTHOR]

Relationship between the external quantum efficiency (EQE) curves and the dominant non-radiative recombination mechanisms of InGaN green LEDs grown on silicon substrates were investigated. Through the analysis of the ABC+ f (n) model, the significant drop in EQE at low current levels is due to an increasingly defect-related Shockley-Read-Hall (SRH) recombination. Under extremely low current densities, the defect traps can even become the dominant channel for the leakage current through the tunneling process, thereby reducing the efficiency of carrier injection into the active region. These observations were further supported by the carrier lifetime measurement. However, this fails to explain the droop in EQE at high current densities, especially when SRH recombination has been saturated. Our results show that carrier leakage has becomes dominant at high current density when Auger recombination has been less impossible. Reduced carrier leakage may lead to increased carrier injection efficiency, which in turn alleviates EQE droop. • Highly efficient 525 nm green InGaN/GaN MQWs LEDs grown on Si substrate. • SRH recombination dominants the non-radiative recombination mechanism at low current levels. • Carrier leakage dominants the non-radiative recombination mechanism at high current levels. • Reduced carrier leakage can lead to increased carrier injection efficiency, which in turn alleviates EQE droop. • Carrier leakage can be minimized through well-designed MQWs architecture. [ABSTRACT FROM AUTHOR]

[Display omitted] The development of heterogeneous supported nanocatalysts with a high kinetics combined with low cost is off importance but remains still challenged for hydrazine hydrate served as a promising hydrogen storage material. Herein, by virtue of surficial functional groups, ultrafine NiRh NPs were monodispersed on the two-dimensional V 2 C surface via a conventional wet chemical co-reduction. The optimized NiRh/V 2 C system demonstrates an excellent catalytic performance toward selectively catalyzing dehydrogenation of hydrazine hydrate, affording 100% H 2 selectivity with the turnover frequency (TOF) value of 987.5 h−1 at 323 K. Such an enhancement is mainly attributed to synergistic effect of nanosystem, which will optimize local surface energy and promote electron transfer in NiRh/V 2 C system, thereby improving the kinetic selectivity of catalytic hydrazine hydrate decomposition. This work has provided a facile strategy for developing nanocatalysts with high kinetics that could enable huge industrial applications in the future. [ABSTRACT FROM AUTHOR]

Hole transport in InGaN/GaN multiple quantum wells (MQWs) LEDs has been proposed to be insufficient due to relatively large effective mass and low mobility. Here, for the first time, we have direct observed hole overflow from MQWs and enter into InGaN/GaN superlattices (SLs) layer in V-pits-containing GaN-based green LEDs at room temperature. To suppress the hole leakage, an n-AlGaN hole blocking layer (HBL) is inserted between SLs layer and MQWs. The experimental show an interesting and baffling result is that the HBL-containing sample not only exhibits severe hole leakage in high current density range, but also has higher external quantum efficiency (EQE). Numerical simulation reveals that the HBL can change the transportation path of carriers, forcing more electrons injecting from c-plane into the MQWs instead of from V-pit sidewalls. This will increase the carrier concentration in the MQWs, and eventually lead to higher EQE. Meanwhile, less electrons transported through V-pit allowed more holes injecting into deeper layers via V-pit sidewalls, and electroluminescence emission from the SLs layer became stronger when HBL was inserted. • Direct observed hole overflow from MQWs in V-pits-containing green LEDs at room temperature. • Sample with n-AlGaN HBL shows higher EQE at high current density range, even though exhibiting severe hole leakage. • Hole leakage is mainly due to the V-pit-assisted direct hole injection into the deeper layer. • The HBL changes the carrier flow path, reducing nonradiative recombination near the sidewalls of V-pit. [ABSTRACT FROM AUTHOR]

Black phosphorus (BP) thin film has highlighted its potential in the photoelectric detection field due to its wide-spectrum and high-absorption capacity. However, the fabrication of controllable and highly quality BP film in large dimensions remains a huge challenge. Herein, we creatively fabricated a centimeter-size highly crystalline BP thin film on the bare silicon substrate using a space-confined chemical vapor transport technique, and we in situ constructed a self-driven BP-based metal–semiconductor–metal photodetector. The as-constructed photodetector achieves a high responsivity of up to 500 mA/W, an external quantum efficiency of 42.1%, a maximum specific detectivity of 3.82 × 1010 cm Hz1/2 W−1, and a small noise-equivalent-power of 3.97 × 10−15 W Hz−1/2 under zero bias voltage at 1550 nm illumination. This work provides a strategy to effectively prepare BP thin film for in situ manufacturing self-driven photodetector, which marks a significant step forward in the integration of BP into the industrial settings. [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]

Phosphorene nanoribbons (PNRs) combine the flexibility of one-dimensional (1D) nanomaterials with the large specific surface area and the edge and electron confinement effects of two-dimensional (2D) nanomaterials. In spite of the substantial advances in bulk black phosphorus (BP) manufacturing, achieving PNRs without degradation is still a big challenge. In this work, we present a strategy for the space-confined chemical vapor transport synthesis of quasi-one-dimensional surface-passivated monocrystalline PNRs on a silicon substrate. The growth mechanism of the PNRs is proposed by combining experimental results and DFT calculations, indicating that the P4 molecules can break, restructure, and epitaxially nucleate on the surface of the Au3SnP7 catalyst, and finally prefer to grow along the zigzag (ZZ) direction to form PNRs. The low gas flow rate and an appropriate phosphorus molecule concentration allow the growth of PNRs with structural integrity, which can be regulated by the amount of red phosphorus and the confined space. [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]

Perovskite quantum dots (QDs) have garnered significant interest for their superior optical properties. Despite their attractive photovoltaic properties and chemical processing ability, the high defects density within QDs can result in the annihilation of luminescence. In this study, cesium trifluoroacetic acid (CsTFA) was used as the cesium source, replacing conventional cesium carbonate (Cs 2 CO 3) and introducing TFA ligands to improve the luminescence quality of QDs. As well as doping with Zn2+ to enhance both the stability and luminescence quality of the quantum dot solution. The doped QDs exhibit the highest photoluminescence (PL) intensity, which is further enhanced by the perovskite QDs with TFA as a ligand. Furthermore, the PL spectra of CsPbBr 3 and TFA-CsPbBr 3 : Zn (10 %) QDs with the temperature changes have also been analyzed. The result reveals the relationship between excitons and phonons. Based on the result, Zn2+ doped and TFA ligand induced perovskite QDs have the potential to serve as an optimal material. • Cesium trifluoroacetic acid as a cesium source to enhance the luminescence quality of perovskite quantum dots. • The doped QDs show the highest photoluminescence intensity, further enhanced by TFA as a ligand. • PL spectra of QDs with temperature changes, revealing the relationship between excitons and phonons. • The results suggest that Zn2+ doped and TFA ligand-induced perovskite QDs could be an optimal material. [ABSTRACT FROM AUTHOR]

Lead sulfide (PbS) thin films were initially deposited through chemical bath deposition, followed by sensitization in a pure oxygen atmosphere at 600 °C. To investigate the influence of varying oxide layer states on the photoelectric properties of thermally sensitized PbS thin films, the surface oxide layer of the sensitized films was selectively removed using KOH etching. As the etching duration increased, a gradual decrease in surface oxygen content was observed, accompanied by an initial increase and subsequent decrease in detectivity. Notably, the optimum detectivity value (6.92 × 109 cm Hz1/2 W−1) was achieved after 10 s of KOH etching. Our investigation was further supplemented with field emission scanning electron microscopy and X-ray diffraction analyses to gain insights into the impact of the oxide layer state on the photoelectric properties of PbS thin films. Our findings led to the proposal of a dual conduction mechanism for carrier transport within PbS film. In the case of as-grown PbS films, carrier transport primarily occurs via crystal boundary transition. However, after oxygen sensitization, the formation of an oxygen-rich carrier channel at the crystal boundary shifts carrier transport dominance towards crystal boundary transport. The combined influence of both transmission mechanisms serves as a primary driver for the observed changes in the photoelectric properties of PbS films. • Lead sulfide thin films were sensitized in a pure oxygen atmosphere at 600 °C. • A dual conduction mechanism for carrier transport within the films, with as-grown films crystal boundary transition. • Oxygen-rich channel shifts carrier transport dominance towards crystal boundary transport for photoelectric properties. [ABSTRACT FROM AUTHOR]

In order to increase the light extraction efficiency (LEE) of AlGaN deep ultraviolet light-emitting diodes (DUV LEDs), this study employed a sapphire substrate with a microlens array. Light extraction efficiency is increased by increasing transverse electric (TE) polarized light output by the use of a microlens array (MLA) created by inductively coupled plasma (ICP) etching. The construction of 2D colloidal crystals of 400 nm polystyrene (PS) particles on sapphire substrates was made possible via air-liquid interfacial colloidal assembly. The diameter, height, and spacing size of the MLA hemispheres were tailored using two separate dry colloidal etching processes. The peak EQE of DUV-LEDs with microlens arrays at depths of 205 nm and 176 nm increased by 6.6% and 7%, respectively, in comparison to DUV-LEDs without microlens arrays. The integrated microlens arrays with changing refractive index at the LED-air interface widen the light escape cone angle, enabling more light to escape the LED and reducing the amount of light trapped or absorbed within the structure. The finite difference Time domain (FDTD) modeling software was also used to simulate the microlens array light output structures. A microlens array with 400 nm spacing and 200 nm hemisphere height had the highest light extraction efficiency, which was in agreement with our experimental findings. • Improved AlGaN DUV LED light extraction efficiency by using a sapphire substrate with a microlens array. • The microlens array increases transverse electric polarized light output, increasing efficiency. • A 400 nm array with 200 nm hemisphere height with high light extraction efficiency. [ABSTRACT FROM AUTHOR]

• The PbSe films were effectively sensitized using a two-step sensitization technique. • The detectivity of 2.25 × 109 Jones is achieved. • A potential carrier transport structure is proposed. An effective two-step sensitization technique was implemented in PbSe thin films, leading to a remarkable improvement in the optoelectronic performance of PbSe photodetectors. The phase composition, surface and cross-sectional morphology, temperature-dependent carrier concentration and mobility as well as the detectability of PbSe films after sensitization were systematically investigated using characteristic techniques. The optimal PbSe film oxygen sensitized at 450 °C exhibited a room-temperature photodetection with a carrier concentration of 5.31 × 1016 cm−3, carrier mobility of 16.52 cm2/V−1s−1, and detectivity of 2.25 × 109 Jones. High-temperature argon heat treatment and oxygen sensitization of PbSe films are expected to suppress recombination losses and significantly improve the optoelectronic properties of sensitized PbSe films due to enhanced carrier separation and transport. The enhanced photoresponse mechanism of the PbSe films through two-step sensitization method was also discussed. These results suggest that the proposed method can be applied to high-performance lead selenide photodetectors. [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]

[Display omitted] • MoO 3 /NiO was applied to hydrogen sensor in the air for the first time. • MoO 3 /NiO exhibited enhanced hydrogen sensing performance. • Enhanced hydrogen sensing performance is mainly due to p-n junction. In this work, pure MoO 3 and MoO 3 /NiO nanolamellas are fabricated and their hydrogen sensing properties are investigated for the first time. Various characterization methods are applied to investigate the structural and morphological properties of bare MoO 3 and MoO 3 /NiO nanolamellas. The gas sensing measurement demonstrated that MoO 3 /NiO-5MN exhibited the best hydrogen sensing capability and selectivity to hydrogen. The response of MoO 3 /NiO-5MN was 3.23 toward 1000 ppm hydrogen, which was nearly 1.85 times higher than that of bare MoO 3 at room temperature. The enhanced gas sensing performance of MoO 3 /NiO is mainly due to the p-n heterojunction. [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]