Two-dimensional silicon nanomaterials for optoelectronics

Silicon nanomaterials have been of immense interest in the last few decades due to their remarkable optoelectronic responses,elemental abundance,and higher biocompatibility.Two-dimensional silicon is one of the new allotropes of silicon and has many compelling properties such as quantum-confined photoluminescence,high charge carrier mobilities,anisotropic electronic and magnetic response,and non-linear optical properties.This review summarizes the recent advances in the synthesis of two-dimensional silicon nanomaterials with a range of structures(silicene,silicane,and multilayered silicon),surface ligand engineering,and corresponding optoelectronic applications.

Recent Advances in Strain-Induced Piezoelectric and Piezoresistive Effect-Engineered 2D Semiconductors for Adaptive Electronics and Optoelectronics

The development of two-dimensional(2D)semiconductors has attracted widespread attentions in the scientific community and industry due to their ultra-thin thickness,unique structure,excellent optoelectronic properties and novel physics.The excellent flexibility and outstanding mechanical strength of 2D semiconductors provide opportunities for fabricated strain-sensitive devices and utilized strain tuning their electronic and optic–electric performance.The strain-engineered one-dimensional materials have been well investigated,while there is a long way to go for 2D semiconductors.In this review,starting with the fundamental theories of piezoelectric and piezoresistive effect resulted by strain,following we reviewed the recent simulation works of strain engineering in novel 2D semiconductors,such as Janus 2D and 2D-Xene structures.Moreover,recent advances in experimental observation of strain tuning PL spectra and transport behavior of 2D semiconductors are summarized.Furthermore,the applications of strain-engineered 2D semiconductors in sensors,photodetectors and nanogenerators are also highlighted.At last,we in-depth discussed future research directions of strain-engineered 2D semiconductor and related electronics and optoelectronics device applications.

Two-Dimensional Metal-Halide Perovskite-based Optoelectronics: Synthesis, Structure, Properties and Applications

In the past decade, metal-halide perovskites have attracted increasing attention in optoelectronics, due to their superior optoelectronic properties.However, inherent instabilities of conventional three-dimensional(3D)perovskites over moisture, heat, and light remain a severe challenge before the realization of commercial application of metal-halide perovskites.Interestingly, when the dimensions of metal-halide perovskites are reduced to two dimensions(2D), many of the novel properties will arise, such as enlarged bandgap, high photoluminescence quantum yield, and large exciton binding energy. As a result, 2D metal-halide perovskite-based optoelectronic devices display excellent performance, particularly as ambient stable solar cells with excellent power conversion efficiency(PCE), high-performance light-emitting diodes(LEDs) with sharp emission peak, and high-sensitive photodetectors. In this review, we first introduce the synthesis, structure,and physical properties of 2D perovskites. Then, the 2D perovskite-based solar cells, LEDs, and photodetectors are discussed. Finally, a brief overview of the opportunities and challenges for 2D perovskite optoelectronics is presented.

Flexible electronics and optoelectronics of 2D van der Waals materials

Flexible electronics and optoelectronics exhibit inevitable trends in next-generation intelligent industries,including healthcare and wellness,electronic skins,the automotive industry,and foldable or rollable displays.Traditional bulk-material-based flexible devices considerably rely on lattice-matched crystal structures and are usually plagued by unavoidable chemical disorders at the interface.Two-dimensional van der Waals materials(2D VdWMs)have exceptional multifunctional properties,including large specific area,dangling-bond-free interface,plane-to-plane van der Waals interactions,and excellent mechanical,electrical,and optical properties.Thus,2D VdWMs have considerable application potential in functional intelligent flexible devices.To utilize the unique properties of 2D VdWMs and their van der Waals heterostructures,new designs and configurations of electronics and optoelectronics have emerged.However,these new designs and configurations do not consider lattice mismatch and process incompatibility issues.In this review,we summarized the recently reported 2D VdWM-based flexible electronic and optoelectronic devices with various functions thoroughly.Moreover,we identified the challenges and opportunities for further applications of 2D VdWM-based flexible electronics and optoelectronics.

Germanium-tin alloys： applications for optoelectronics in mid-infrared spectra

We summarize our work of the optoelectronic devices based on Germanium-tin （GeSn） alloys assisted with the Si3N4liner stressor in mid-infrared （MIR） domains. The device characteristics are thoroughly analyzed by the strain distribution,band structure, and absorption characteristics. Numerical and analytical methods show that with optimal structural pa-rameters, the device performance can be further improved and the wavelength application range can be extended to 2~5 μm in the mid-infrared spectra. It is demonstrated that this proposed strategy provides an effective technique for the strained-GeSn devices in future optical designs, which will be competitive for the optoelectronics applications in mid-infrared wavelength.

Transparent Supercapacitors: From Optical Theories to Optoelectronics Applications

The ever-increasing demand for smart optoelectronics spurs the relentless pursuit of transparent wireless devices as a game-changing technology that can provide unseen visual information behind the electronics.To enable successful operation of the transparent wireless devices,their power sources should be highly transparent in addition to acquiring reliable electrochemical performance.Among various transparent power sources,supercapacitors(SCs)have been extensively investigated as a promising candidate due to their exceptional cyclability,power capability,material diversity,and scalable/low-cost processability.Herein,we describe current status and challenges of transparent SCs,with a focus on their core materials,performance advancements,and integration with application devices.A special attention is devoted to transparent conductive electrodes(TCEs)which act as a keyenabling component in the transparent SCs.Based on fundamental understanding of optical theories and operating principles of transparent materials,we comprehensively discuss materials chemistry,structural design,and fabrication techniques of TCEs.In addition,noteworthy progresses of transparent SCs are briefly overviewed in terms of their architectural design,opto-electrochemical performance,flexibility,form factors,and integration compatibility with transparent flexible/wearable devices of interest.Finally,development direction and outlook of transparent SCs are explored along with their viable roles in future application fields.

Special Issue on Nanotechnology,Optoelectronics and Photonics Technologies

International Conference on Nanotechnology, Optoelectronics and Photonics Technologies （NOPT） is an annual International Conference sponsored by Photonics and Microelectronics Society and Components, Packaging ＆ Manufacturing Society of IACSIT （International Association of Computer Science and Information Technology）,

High-throughput computational material screening of the cycloalkane-based two-dimensional Dion–Jacobson halide perovskites for optoelectronics

Two-dimensional(2D) layered perovskites have emerged as potential alternates to traditional three-dimensional(3D)analogs to solve the stability issue of perovskite solar cells. In recent years, many efforts have been spent on manipulating the interlayer organic spacing cation to improve the photovoltaic properties of Dion–Jacobson(DJ) perovskites. In this work, a serious of cycloalkane(CA) molecules were selected as the organic spacing cation in 2D DJ perovskites, which can widely manipulate the optoelectronic properties of the DJ perovskites. The underlying relationship between the CA interlayer molecules and the crystal structures, thermodynamic stabilities, and electronic properties of 58 DJ perovskites has been investigated by using automatic high-throughput workflow cooperated with density-functional(DFT) calculations.We found that these CA-based DJ perovskites are all thermodynamic stable. The sizes of the cycloalkane molecules can influence the degree of inorganic framework distortion and further tune the bandgaps with a wide range of 0.9–2.1 eV.These findings indicate the cycloalkane molecules are suitable as spacing cation in 2D DJ perovskites and provide a useful guidance in designing novel 2D DJ perovskites for optoelectronic applications.

Spectroscopic Analysis and Study of Charge Transport Properties for Pinacyanol Chloride-Organic Acceptor Complex as Potential Optoelectronics Material

Organic photoconductor, pinacyanol chloride, has been studied with infrared spectroscopy because of its thermal activation energy (Ea) and band gap (Eg = 2Ea) lying in the infrared range. Particularly, pinacyanol chloride and its charge transfer (CT) complexes with chloranil, DDQ, TCNQ and TCNE as organic acceptors are studied in details. The CT complexes are having neither two absorption edges like ternary complex having one donor and two acceptors nor binary type with Lorentzian or Gaussian envelopes. The forbidden gap is direct band gap except chloranil complex due to increase in molecular distance and CT interaction. There is imperfect nesting and partial screening determining the mid-IR envelope, which is qualitatively different from the envelopes in binary systems. There is inverted parabola in some range below this envelope. It is explained how infrared absorption is related with the applications of such organic photoconductors in optoelectronic devices.

Topological Dirac-vortex microcavity laser for robust on-chip optoelectronics

Dirac-vortex microcavity laser based on InAs/InGaAs quantum dots have been experimentally realized on silicon substrate.The topological laser features a large spectral range and high robustness against variations such as cavity size.

Hot-carrier engineering for two-dimensional integrated infrared optoelectronics

Plasmonic hot carrier engineering holds great promise for advanced infrared optoelectronic devices.The process of hot carrier transfer has the potential to surpass the spectral limitations of semiconductors,enabling detection of subbandgap infrared photons.By harvesting hot carriers prior to thermalization,energy dissipation is minimized,leading to highly efficient photoelectric conversion.Distinguished from conventional band-edge carriers,the ultrafast interfacial transfer and ballistic transport of hot carriers present unprecedented opportunities for high-speed photoelectric conversion.However,a complete description on the underlying mechanism of hot-carrier infrared optoelectronic device is still lacking,and the utilization of this strategy for tailoring infrared response is in its early stages.This review aims to provide a comprehensive overview of the generation,transfer and transport dynamics of hot carriers.Basic principles of hot-carrier conversion in heterostructures are discussed in detail.In addition,progresses of two-dimensional(2D)infrared hot-carrier optoelectronic devices are summarized,with a specific emphasis on photodetectors,solar cells,light-emitting devices and novel functionalities through hot-carrier engineering.Furthermore,challenges and prospects of hot-carrier device towards infrared applications are highlighted.

Recent advances in 2D organic−inorganic heterostructures for electronics and optoelectronics

Two‐dimensional(2D)materials show outstanding properties such as dangling bond‐free surfaces,strong in‐plane while weak out‐of‐plane bonding,layer‐dependent electronic structures,and tunable electronic and optoelectronic properties,making them promising for numerous applications.Integrating 2D inorganics with organic materials to make van der Waals heterostructures at the 2D thickness limit has created new platforms for fabricating on‐demand multifunctional devices.To further broaden the limited choices of 2D inorganic‐based heterostructures,a wide range of available 2D organic materials with tunable properties have opened new opportunities for designing large numbers of heterostructures with 2D inorganic materials.This review aims to attract the attention of researchers toward this emerging 2D organic−inorganic field.We first highlight recent progress in organic−inorganic heterostructures and their synthesis and then discuss their potential applications,such as field‐effect transistors,photodetectors,solar cells,and neuromorphic computing devices.In the end,we present a summary of challenges and opportunities in this field.

Low-cost and stable SFX-based semiconductor materials in organic optoelectronics

In the progress of realizing the commercialization of organic optoelectronic materials,the four basic coherent factors are stability,cost,performance,and processability,all which determine the results of device applications.Spiro[fluorene-9,9′-xanthene](SFX)has been becoming the robust building-block that fulfilling the practical requirements due to its key features of non-planarity,one-pot facile availability,well-defined quality assurance as well as performance behaviors.In this review,we introduce the SFX and its analogues,including synthesis,molecular design,device performance,and structure-property relationship,in the applications of organic light-emitting diodes(OLEDs),organic photovoltaics,perovskite solar cells(PSCs)and others.Furthermore,emitters or hosts for OLED and hole transport materials for PSCs are highlighted at the level of molecular configuration and film morphology.Tracing the thread from intrinsic photoelectric properties,molecular packing to optoelectronic application,the advantage of stability and low-cost of SFX-based materials are illuminated,and an outlook is given providing orientation for bring SFX into the fields of catalysis and energy chemistry in view of its binary conjugation and three-dimensional configuration.

Defect engineering of two-dimensional materials towards nextgeneration electronics and optoelectronics

The ultrathin body of two-dimensional(2D)materials provides potential for next-generation electronics and optoelectronics.The unavoidable atomic defects substantially determine the physical properties of atomic-level thin 2D materials,thus enabling new functionalities that are impossible in three-dimensional semiconductors.Therefore,rational design of atomic defects provides an alternative approach to modulate the physical properties of 2D materials.In this review,we summarize the recent progress of defect engineering in 2D materials,particularly in device performance enhancement.Firstly,the common defects in 2D materials and approaches for generating and repairing defects,including synthesis and post-growth treatments,are systematically introduced.The correlations between defects and optical,electronic,and magnetic properties of 2D materials are then highlighted.Subsequently,defect engineering for high performance electronics and optoelectronics is emphasized.At last,we provide our perspective on challenges and opportunities in defect engineering of 2D materials.

Metal Halide Perovskite for next-generation optoelectronics:progresses and prospects

Metal halide perovskites(MHPs),emerging as innovative and promising semiconductor materials with prominent optoelectronic properties,has been pioneering a new era of light management(ranging from emission,absorption,modulation,to transmission)for next-generation optoelectronic technology.Notably,the exploration of fundamental characteristics of MHPs and their devices is the main research theme during the past decade,while in the next decade,it will be primarily critical to promote their implantation in the next-generation optoelectronics.In this review,we first retrospect the historical research milestones of MHPs and their optoelectronic devices.Thereafter,we introduce the origin of the unique optoelectronic features of MHPs,based on which we highlight the tunability of these features via regulating the phase,dimensionality,composition,and geometry of MHPs.Then,we show that owing to the convenient property control of MHPs,various optoelectronic devices with target performance can be designed.At last,we emphasize on the revolutionary applications of MHPs-based devices on the existing optoelectronic systems.This review demonstrates the key role of MHPs played in the development of modern optoelectronics,which is expected to inspire the novel research directions of MHPs and promote the widespread applications of MHPs in the next-generation optoelectronics.

The rise of two-dimensional tellurium for next-generation electronics and optoelectronics

Single-element two-dimensional(2D)tellurium(Te)which possesses an unusual quasi-one-dimensional atomic chain structure is a new member in 2D materials family.2D Te possesses high carrier mobility,wide tunable bandgap,strong light-matter interaction,better environmental stability,and strong anisotropy,making Te exhibit tremendous application potential in next-generation electronic and optoelectronic devices.However,as an emerging 2D material,the research on fundamental property and device application of Te is still in its infancy.Hence,this review summarizes the most recent research progresses about the new star 2D Te and discusses its future development direction.Firstly,the structural features,basic physical properties,and various preparation methods of 2D Te are systemically introduced.Then,we emphatically summarize the booming development of 2D Te-based electronic and optoelectronic devices including field effect transistors,photodetectors and van der Waals heterostructure photodiodes.Finally,the future challenges,opportunities,and development directions of 2D Te-based electronic and optoelectronic devices are prospected.

Assembly of functional carboxymethyl cellulose/polyethylene oxide/anatase TiO_(2) nanocomposites and tuning the dielectric relaxation, optical, and photoluminescence performances

Nanocomposite films consisting of carboxymethyl cellulose,polyethylene oxide(CMC/PEO),and anatase titanium diox-ide(TO)were produced by the use of sol-gel and solution casting techniques.TiO2 nanocrystals were effectively incorporated into CMC/PEO polymers,as shown by X-ray diffraction(XRD)and attenuated total reflectance fourier transform infrared(ATR-FTIR)analysis.The roughness growth is at high levels of TO nanocrystals(TO NCs),which means increasing active sites and defects in CMC/PEO.In differential scanning calorimetry(DSC)thermograms,the change in glass transition temperature(Tg)val-ues verifies that the polymer blend interacts with TO NCs.The increment proportions of TO NCs have a notable impact on the dielectric performances of the nanocomposites,as observed.The electrical properties of the CMC/PEO/TO nanocomposite undergo significant changes.The nanocomposite films exhibit a red alteration in the absorption edge as the concentration of TO NCs increases in the polymer blend.The decline in the energy gap is readily apparent as the weight percentage of TO NCs increases.The photoluminescence(PL)emission spectra indicate that the sites of the luminescence peak maximums show slight variation;peaks get wider,while their intensities decrease dramatically as the concentration of TO increases.These nanocomposite materials show potential for multifunctional applications including optoelectronics,antireflection coatings,pho-tocatalysis,light emitting diodes,and solid polymer electrolytes.

Optoelectronic Synapses Based on MXene/Violet Phosphorus van der Waals Heterojunctions for Visual‑Olfactory Crossmodal Perception

The crossmodal interaction of different senses,which is an important basis for learning and memory in the human brain,is highly desired to be mimicked at the device level for developing neuromorphic crossmodal perception,but related researches are scarce.Here,we demonstrate an optoelectronic synapse for vision-olfactory crossmodal perception based on MXene/violet phosphorus(VP)van der Waals heterojunctions.Benefiting from the efficient separation and transport of photogenerated carriers facilitated by conductive MXene,the photoelectric responsivity of VP is dramatically enhanced by 7 orders of magnitude,reaching up to 7.7 A W^(−1).Excited by ultraviolet light,multiple synaptic functions,including excitatory postsynaptic currents,pairedpulse facilitation,short/long-term plasticity and“learning-experience”behavior,were demonstrated with a low power consumption.Furthermore,the proposed optoelectronic synapse exhibits distinct synaptic behaviors in different gas environments,enabling it to simulate the interaction of visual and olfactory information for crossmodal perception.This work demonstrates the great potential of VP in optoelectronics and provides a promising platform for applications such as virtual reality and neurorobotics.

Environmental engineering of transition metal dichalcogenide optoelectronics

The explosion of interest in two-dimensional van der Waals materials has been in many ways driven by their layered geometry. This feature makes possible numerous avenues for assembling and ma- nipulating the optical and electronic properties of these materials. In the specific case of monolayer transition metal dichalcogenide semiconductors, the direct band gap combined with the flexibility for manipulation of layers has made this class of materials promising for optoelectronics. Here, we review the properties of these layered materials and the various means of engineering these properties for optoeleetronics. We summarize approaches for control that modify their structural and chemical en- vironment, and we give particular detail on the integration of these materials into engineered optical fields to control their optical characteristics. This combination of controllability from their layered surface structure and photonic environment provide an expansive landscape for novel optoelectronic phenomena.