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The electron transport layer (ETL)‐free perovskite solar cells (PSCs) have gained significant interest by simplifying the manufacture process and reducing the time/energy required for the fabrication of ETLs. Unfortunately, the performance of these ETL‐free PSCs still lags behind those of the conventional counterparts due to the slow electron extraction and undesired interfacial charge recombination loss at the buried interface. In this work, a facile and multifunctional biocolina thin layer is incorporated on the bottom electrodes to regulate the interface energy level alignment by forming an interface dipole layer, resulting in a suppressed nonradiative recombination and an improved charge extraction. Furthermore, the biocolina thin layer possess the capability to passivate the surface defects within the perovskite films while simultaneously facilitate the formation of perovskite crystals. Consequently, a remarkable enhancement in photovoltaic performance is observed in the biocolina‐based ETL‐free PSCs with an increase from 15.96 % to an outstanding 20.01 %. Additionally, the biocolina extends the stability and relieves the hysteresis effect through the interface defect passivation and inhibition of interface charge accumulation. This research contributes to the development of cost‐effective, simplified designs for highly efficient ETL‐free PSCs by modifying the bottom electrodes. [ABSTRACT FROM AUTHOR]

Halide perovskite materials are considered a promising optical gain medium for stimulated emission and have aroused tremendous interest in the field of laser research. The development of low‐threshold optically pumped amplified spontaneous emission (ASE) is critical for the advancement of continuous wave (CW) and electrically pumped micro‐nano lasers. In this work, an efficient ZnS additive is incorporated into the FA0.85MA0.15PbI2.55Br0.45 perovskite films to diminish the ASE threshold and extend the photostability by the dual‐site synergistic passivation. The experimental measurements and first‐principles calculations based on the density functional theory (DFT) are employed to elucidate the doping mechanism. The designed ZnS‐based perovskite films yield a mitigated ASE threshold of 8.5 µJ cm−2 with an elevated optical gain coefficient of 109.06 cm−1, which outperform those of the control films (12.7 µJ cm−2 and 74.10 cm−1). The in‐depth experimental characterizations and theoretical calculations have corroborated that the improvement of ASE performance can be ascribed to the dual‐site synergistic passivation effects of Zn2+ and S2−, which reduces the surface defects of perovskite films, suppresses the nonradiative charge recombination and improves the optical stability. This work provides a resultful strategy to construct the solution‐processed perovskite lasers with low thresholds and superior stability. [ABSTRACT FROM AUTHOR]

Metal halide perovskites are considered as a prospective candidate as optical gain media for stimulated emission, and the advancement of amplified spontaneous emission (ASE) of perovskite materials is gradually becoming the key to realize the commercialization of perovskite lasers. Nonetheless, the ASE of solution‐processed polycrystalline perovskite films still experiences a high threshold and poor optical stability due to their high defect density and poor crystalline quality. In this scenario, a noticeably ameliorated ASE performance with decreased threshold and greater photo‐stability is demonstrated in solution‐processed (FAPbI3)0.85(MAPbBr3)0.15 polycrystalline perovskite films by introducing a neoteric 4′‐Aminoacetophenone hydrochloride (APCl) additive with cost‐effective fabrication. The ASE threshold of the APCl‐embedded perovskite films is prominently curtailed from 12.8 to 5.3 µJ cm−2, with an augmented optical gain, ASE output intensity, and optical durability. The ameliorated ASE performance can be credited to multifunctional effects of the APCl additive in the perovskite films, presenting a low defect density, an unambiguously elevated photoluminescence, a prolonged decay lifetime and thus enabling the easily achieved population inversion caused by the attenuated nonradiative carrier recombination in the optical gain media. These findings provide a significant foundation and pave the way for realizing the electrically excited lasing based on the perovskite materials. [ABSTRACT FROM AUTHOR]

The advancement of electron transport layer (ETL)‐free perovskite solar cells (PSCs) is crucial for the commercialization of PSCs. At present, the slow electron extraction and significant carrier recombination, related to the energy‐level alignment at the FTO/perovskite interface, restrict the performance of ETL‐free PSCs. The facile modification of bottom electrodes is pivotal for tackling these issues and stimulating the photovoltaic potential of perovskite. Herein, a cost‐competitive and neoteric 1‐hydroxyethyl‐3‐methylimidazolium chloride, [HOEtMIM]Cl, ionic liquid is employed to modify the surface of rigid and flexible electrodes, and thus enable an energetically well‐aligned interface with perovskite layer via the electric dipole effects. The resulting barrier‐free FTO/perovskite contact can tremendously ameliorate the electron extraction and collection, with mitigated nonradiative interfacial carrier recombination loss. Additionally, the lone pair on the nitrogen of the imidazole group passivates the surface defects of perovskite layers, and the chloride anion plays a role in the crystallinity improvement of perovskite. Leveraged by the [HOEtMIM]Cl modification, the resulting ETL‐free rigid and flexible devices deliver an outstanding power conversion efficiency of 19.60 % and 15.57 %, along with the ameliorated hysteresis and long‐term tenability. This finding highlights the drastic potential of the engineered [HOEtMIM]Cl in manufacturing stable and high‐performance ETL‐free PSCs for their scaled‐up production. [ABSTRACT FROM AUTHOR]

Quantum dots (QDs) laser has become an important way to solve micro-application problems in many fields. However, single wavelength distributed Bragg reflector (DBR) has many limitations in practical applications, such as signal transmission. How to realize multiwavelength DBR lasing output simply is a challenge. To achieve a stable multi-wavelength quantum dots laser in the near-infrared region, the perovskite CsPbI3 QDs laser with DBR structure is developed in this paper. A tetragonal crystal structure with complete bonding information and no defect is explained by X-ray diffractions (XRD) and Raman spectrum. The cross-section morphology of the DBR laser and the surface morphology of QDs is measured by scanning electron microscope (SEM) and transmission electron microscope (TEM), respectively. An elliptical light propagation field and a double wavelength laser radiation are obtained from the finite-difference time-domain (FDTD) simulation. The output of the three wavelength lasers at 770 nm, 823 nm, and 873 nm is measured. The emission time of a DBR laser is about 2 h, and the average fluorescence quantum yield is 60%. The cavity length selection and energy level model are put in place to clearly see the working mechanism. All the results suggest that an effective and stable CsPbI3 quantum dots DBR laser is realized. [ABSTRACT FROM AUTHOR]

Radiative thermal management has attracted increasing attention for the advantages of energy saving and carbon emission reduction. Infrared radiation coatings are widely adopted to alleviate the low infrared emissivity of commonly used metal alloy electrothermal materials. However, traditional infrared radiation coatings are faced with the issues of the unsteady waveband emissivity, low interfacial adhesion to substrates, and poor long‐term thermal stability. Herein, a bush‐shaped vertical graphene (BVG) grown on nichrome (Ni–Cr) wire is demonstrated, relying on which BVG/Ni–Cr wire presents a high blackbody‐like emissivity of ≈0.96 across a wide wavelength range (2.5–18 µm). When used for radiative heating, BVG/Ni–Cr wire achieves a high thermal radiation efficiency with an order of magnitude improvement compared with bare Ni–Cr wire, as well as the superior deformation and thermal stabilities. These findings reveal the impressive potentials of BVG as an excellent infrared radiation material for the energy‐efficient radiative thermal management. [ABSTRACT FROM AUTHOR]

Aluminum nitride (AlN) films are prepared on Si (100) substrates by pulsed direct current magnetron sputtering. The effect of sputtering power on the crystal quality, residual stress, surface morphology, and optical properties of AlN films is comprehensively studied using X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), atomic force microscope, and ellipsometer. It is found that the AlN film quality is strongly impacted by the sputtering power. When the sputtering power increases to 3 kW, the full width at half maximum of the AlN (002) rocking curve decreases to 2.66°. And the film crystal quality does not change significantly when the sputtering power exceeds 3 kW. Fourier transform infrared spectrum analysis shows that with increasing sputtering power, the compressive stress of AlN films first increases and then decreases. The high sputtering power also results in smoother surface and better optical performance for the AlN films. This work can serve as an important reference for growing high‐quality AlN films on cost‐effective silicon (Si) substrates via sputtering, which can facilitate the development and commercialization of III‐nitride based photonics and electronics on AlN‐on‐Si substrates. [ABSTRACT FROM AUTHOR]

Photogating effect based on vertical structure of 2D materials allows for the realization of a highly sensitive photodetector. A highly sensitive and broad‐spectrum (365–965 nm) photodetector is reported based on the indium selenide (InSe)/rhenium disulfide (ReS2) vertical heterostructure, where the top layer InSe serves as the photogate to regulate the channel current, enabling a large photoconductive gain of 106. The detectivity of the photodetector can reach 6.51 × 1013 Jones, making this one of the highest values among reported transition metal dichalcogenide photodetectors. The photodetector represents a high responsivity of 1921 A W−1, an ultrahigh external quantum efficiency (EQE) of 6.53 × 105%, and a fast response time of 21.6 ms. The outstanding properties of the InSe/ReS2 heterojunction reveal the promising potential in high‐efficient, ultrasensitive, broadband photodetectors. [ABSTRACT FROM AUTHOR]

A distinctive method is used to achieve transverse-mode control by building and integrating a tunable liquid crystal (LC) mode filter on top of traditional vertical-cavity surface-emitting lasers (VCSELs). An LC cell is fabricated by injecting a type of nematic LC material (E7) in an annular groove patterned by SiO2. By electrically tuning the refractive index of the LC, a spatially dependent reflectivity profile can be achieved and optimized, which directly influences the threshold modal gain of each transverse mode provided by oxide-confined VCSELs. The flexible and accurate control performance of the LC mode filter structure have been demonstrated by the simulation results and our analysis. This design is a completely novel method to realize VCSELs with an accurate and real-time controllable transverse-mode, and it will probably play a significant role in the future. [ABSTRACT FROM AUTHOR]

The lateral wet-etching kinetics of an Al0.8Ga0.2As sacrificial layer, a typical configuration for optoelectronic devices, has been investigated in detail. Expanding the one-dimensional Si and AlAs oxidation modes to the Al0.8Ga0.2As sacrificial layer etching process, compact analytical formulas were obtained for the time evolution of the etch front and for the etch rate. Through both experiment and theoretical calculations, the lateral etching process parameters, A, B, and B/A, have been obtained for the different temperatures and etchant volume ratios. The etch rate is found to remain almost constant for a large range of etch length. However, when the etch temperature increases, a rapid increase in this rate is predicted. Activation energies for the process parameters, EA∼0.1 eV and EB∼0.5 eV, have also been obtained for the etchant volume ratio of 3:1 and the sacrificial layer thickness is 800 nm. [ABSTRACT FROM AUTHOR]

The lateral wet-etching kinetics of a [Al.sub.0.8][Ga.sub.0.2]As sacrificial layer is investigated. The etch rate is independent of the etch length but is affected by the temperature and hence they are very important for achieving a good control of the AlGaAs sacrificial layer etching process for microstructures in integrated optoelectronic devices.

Vertically oriented graphene (VG), owing to its sharp edges, non-stacking morphology, and high surface-to-volume ratio structure, is promising as a consummate material for the application of photoelectric detection. However, owing to high defect and fast photocarrier recombination, VG-absorption-based detectors inherently suffer from poor responsivity, severely limiting their viability for light detection. Herein, we report a high-performance photodetector based on a VG/indium tin oxide (ITO) composite structure, where the VG layer serves as the light absorption layer while ITO works as the carrier conduction channel, thus achieving the broadband and high response nature of a photodetector. Under the illumination of infrared light, photoinduced carriers generated in VG could transfer to the floating ITO layer, which makes them separate and diffuse to electrodes quickly, finally realizing large photocurrent detectivity. This kind of composite structure photodetector possesses a room temperature photoresponsivity as high as ~0.7 A/W at a wavelength of 980 nm, and it still maintains an acceptable performance at temperatures as low as 87 K. In addition, a response time of 5.8 s is observed, ~10 s faster than VG photodetectors. Owing to the unique three-dimensional morphology structure of the as-prepared VG, the photoresponsivity of the VG/ITO composite photodetector also presented selectivity of incidence angles. These findings demonstrate that our novel composite structure VG device is attractive and promising in highly sensitive, fast, and broadband photodetection technology. [ABSTRACT FROM AUTHOR]

p-GaAs/n-GaN heterojunction was fabricated by wafer bonding. Its current-voltage characteristic was systematically investigated at room temperature and at a variety of low temperature. The curves of different temperatures in the logarithmic scales indicate space-charge-limited currents (SCLCs) in the high voltage region (>0.4 V). SCLC current-transport mechanism was confirmed by fitting data. Single-charge injection and the amorphous layer at the bonding interface are presumably the reasons to cause SCLCs. [ABSTRACT FROM AUTHOR]

The use of two-dimensional materials and van der Waals heterostructures holds great potential for improving the performance of memristors Here, we present SnS 2 /MoTe 2 heterostructure synaptic transistors. Benefiting from the ultra-low dark current of the heterojunction, the power consumption of the synapse is only 19 p J per switching under 0.1 V bias, comparable to that of biological synapses. The synaptic device based on the SnS 2 /MoTe 2 demonstrates various synaptic functionalities, including short-term plasticity, long-term plasticity, and paired-pulse facilitation. In particular, the synaptic weight of the excitatory postsynaptic current can reach 109.8%. In addition, the controllability of the long-term potentiation and long-term depression are discussed. The dynamic range ( G max / G min ) and the symmetricity values of the synaptic devices are approximately 16.22 and 6.37, and the non-linearity is 1.79. Our study provides the possibility for the application of 2D material synaptic devices in the field of low-power information storage., (© 2024 IOP Publishing Ltd.)

Thermal crosstalk and current crowding effects are pressing issues that significantly impact the beam quality and efficiency of vertical-cavity surface-emitting laser (VCSEL) arrays. In this paper, by taking advantage of the excellent current transmission characteristics of graphene, what we believe to be a novel VCSEL array based on graphene electrode is designed to realize vertical current injections. The series resistance and self-heating of arrays are reduced by controlling the transport direction of the current, effectively suppressing the thermal crosstalk effect. Furthermore, high array beam quality is obtained by optimizing the current density distribution in active regions. Ultimately, the high-power quasi-single mode emission of VCSEL arrays is achieved by introducing graphene electrodes (Gr-VCSEL array) designs. Compared to traditional VCSEL arrays, the 10 × 10 Gr-VCSEL array demonstrates a 41% reduction in series resistance, a side mode suppression ratio of 32 dB, and a divergence angle around 12 °. This structure simultaneously achieves quasi-single mode emission and effectively suppresses the thermal crosstalk effect, providing a new method for the development of high-beam quality VCSEL arrays.

Existing photonic couplers are limited by either large footprint or long interaction length. Here a highly efficient and ultracompact three-port trench-based coupler (TBC) is proposed on an InP platform in terms of the frustrated total internal reflection principle. A single slash-shaped narrow trench located at the "T" intersection of two InP/InGaAsP multiquantum well ridge waveguides forms the coupler. The finite-difference time-domain numerical method is utilized to optimize the parameterization of the couplers, such as splitting ratios and efficiency versus trench widths, lengths, locations, and angles. A single-mode 2 µm wide ridge waveguide coupler having a high aspect ratio trench filled with A l 2 O 3 was fabricated and characterized at 1.55 µm wavelength. The "trench-first" fabrication process is optimized to reduce its inherent insertion loss (IL), showing the IL within a range of 0.3-0.5 dB. The devices can outperform the state-of-the-art trench couplers by ≥∼24 times the figure of merit. These TBCs are thus promising candidates for applications in the next generation of photonic integrated circuits.

The prosperous development of stretchable electronics poses a great demand on stretchable conductive materials that could maintain their electrical conductivity under tensile strain. Previously reported strategies to obtain stretchable conductors usually involve complex structure-fabricating processes or utilization of high-cost nanomaterials. It remains a great challenge to produce stretchable and conductive materials via a scalable and cost-effective process. Herein, a large-scalable pyrolysis strategy is developed for the fabrication of intrinsically stretchable and conductive textile in utilizing low-cost and mass-produced weft-knitted textiles as raw materials. Due to the intrinsic stretchability of the weft-knitted structure and the excellent mechanical and electrical properties of the as-obtained carbonized fibers, the obtained flexible and durable textile could sustain tensile strains up to 125% while keeping a stable electrical conductivity (as shown by a Modal-based textile), thus ensuring its applications in elastic electronics. For demonstration purposes, stretchable supercapacitors and wearable thermal-therapy devices that showed stable performance with the loading of tensile strains have been fabricated. Considering the simplicity and large scalability of the process, the low-cost and mass production of the raw materials, and the superior performances of the as-obtained elastic and conductive textile, this strategy would contribute to the development and industrial production of wearable electronics.

Optical switches are key components in data links for optical communication networks requiring low crosstalk and insertion loss, high switching speed, and power efficiency. A multimode-interference (MMI)-coupler-based switch with multiple inputs and outputs serving as a switching unit is desired toward forming a large-scale switch matrix. Here we demonstrate a compact 3×3 MMI coupler electro-optic switch based on the carrier injection effect on InGaAsP/InP substrates. This switch device is 2780 μm long by 18 μm wide. The switching states can be controlled by two index-modulation regions through applied bias voltages. Our simulation results show that the device exhibits low crosstalk of <-22  dB, high extinction ratio of ≳23  dB, low electrical switching energy of ∼2.0  pJ/bit, maximum operational frequency of ∼1.0  GHz, and optical bandwidth of ∼20  nm in the C band. We experimentally validated one of the switching states on a fabricated device with maximum current injections of ∼25  mA under combined bias voltages of ∼2.5 and ∼3.0  V. Such monolithic integration schemes make them an ideal candidate for future on-chip photonic integrated circuits.