Low Band Gap Semiconductor Research Articles

Simplified approach to estimate Lorenz number using experimental Seebeck coefficient for non-parabolic band

Reducing lattice thermal conductivity (κL) is one of the most effective ways for improving thermoelectric properties. However, the extraction of κL from the total measured thermal conductivity can be misleading if the Lorenz (L) number is not estimated correctly. κL is obtained using the Wiedemann–Franz law, which estimates the electronic part of thermal conductivity κe = L σT, where σ and T are electrical conductivity and temperature, respectively. κL is then estimated as κL = κT − L σT. For metallic systems, the Lorenz number has a universal value of 2.44 × 10 −8 WΩ K−2 (degenerate limit), but for non-degenerate semiconductors, the value can deviate significantly for acoustic phonon scattering, the most common scattering mechanism for thermoelectric materials above room temperature. Up until now, L is estimated by solving a series of equations derived from Boltzmann transport equations. For the single parabolic band (SPB) model, an equation was proposed to estimate L directly from the experimental Seebeck coefficient. However, using the SPB model will lead to an overestimation of L in the case of low bandgap semiconductors, which results in an underestimation of κL, sometimes even negative κL. In this article, we propose a simpler equation to estimate L for a non-parabolic band. The experimental Seebeck coefficient, bandgap (Eg), and temperature (T) are the main inputs to the equation, which nearly eliminates the need for solving multiple Fermi integrals besides giving accurate values of L.

Utilizing Secondary Bonds Formed by Halogen Substituents: Achieving the Dynamic Transition of Low-Bandgap Semiconductor Polymers from Macromolecules to Small Molecules

Utilizing Secondary Bonds Formed by Halogen Substituents: Achieving the Dynamic Transition of Low-Bandgap Semiconductor Polymers from Macromolecules to Small Molecules

Enhanced photocatalytic hydrogen generation using UiO-66(Zr) MOF with tailored modifications: A review

The utilization of UiO-66 MOF-based photocatalytic materials has achieved significant attention for their potential in hydrogen generation, owing to their remarkable stability and porous crystalline structure. Recent studies have disclosed enhanced light absorption capabilities in UiO-66 through both pre and post-synthetic modifications. These modifications also play a significant role in mitigating the recombination of photogenerated charge carriers by facilitating electron transfer in hybrid or derived materials. Designing of MOF-based modified improved photocatalyst includes, integration with other low band gap semiconductors, incorporation of noble metals as co-catalysts, surface engineering, inclusion of defects or introduction of heteroatom in the framework. MOF-COF hybridization, dye sensitization etc., further reinforced photocatalytic hydrogen yield. The above-mentioned comprehensive investigations have researched into aspects such as morphology, hydrogen generation efficiency, and the underlying mechanisms. It reveals that the creation of heterojunctions at interface channelizes the separation and smooth flow of electrons resulting in suppression of recombination reaction and favorable photocatalytic properties. The synergy between the components often results in enhanced performance. The present article provides a comprehensive review of modified UiO-66 MOF-based materials investigated for photocatalytic hydrogen generation.

Low Bandgap Organic Semiconductors for Photovoltaic Applications

Photovoltaic is one of the best low-cost alternative energy sources. In this paper, organic semiconductors were explored as light harvesters due to their extraordinary properties, but initially, the scientific community focused on synthesizing the large bandgap organic semiconductors, which were unsuitable for photovoltaic applications. Wide bandgap organic semiconductors can capture light only from the UV–Vis region of the solar spectrum, thus showing solar cells’ power conversion efficiency (PCE) of less than 5%. By reducing the bandgap, organic semiconductors can show good compatibility with the air mass (AM) of 1.5 solar spectrums. So, the attention came toward synthesizing low bandgap semiconductors, which led to the enhancement of PCE from 5% to 17%. This review summarizes the overall development of the last 15 years in the field of organic photovoltaic semiconductors. The significant parameters in organic semiconductors are their bandgap, the position of the highest occupied molecular orbital (HOMO), and the lowest unoccupied molecular orbital (LUMO) that can easily be tuned chemically by molecular designing. One of the issues in organic photovoltaic solar devices is the need for absorbers with a narrow bandgap to maximize power conversion efficiencies to a great extent. Moreover, several factors, such as conjugation length, bond length alteration, intermolecular interaction, donor–acceptor charge transfer, planarity, and physical states, are responsible for tuning the bandgap. This review also classifies low bandgap semiconductors based on the core skeleton with their bandgaps, structures, and power conversion efficiencies.

Near‐Infrared Active Tri‐nanohybrid for Enhanced Energy Harvesting

AbstractEfficient energy harvesting through full solar spectrum utilization has been considered a promising solution to world energy and environmental issues. In this direction, lead sulphide (PbS) quantum dot (QD) based hybrid materials find greater application due to their near‐infrared (NIR) active photo response. Slower charge injection and inefficient charge separation limit photoactive response of such NIR active low band gap semiconductor like PbS QDs. Moreover, constructing dual charge transfer pathways in a PbS QDs based nanocomposite through the formation of hybrids with suitable materials can be advantageous in suppressing the charge recombination. In this work, we have synthesized a nanocomposite after decorating the PbS‐QDs with semiconducting TiO2 nanoparticles modified with multiwall carbon nanotubes (MWCNT) and thus forming the tri‐hybrid (PbS‐TiO2‐MWCNT) nanocomposites. The enhanced photo‐activities of the tri‐hybrid, as compared to di‐hybrids like PbS‐TiO2, PbS‐MWCNT were confirmed by the steady state, time‐resolved photoluminescence (TRPL) measurements and reactive oxygen species (ROS) generation measurements. Higher ROS generation in the tri‐hybrid has been correlated with a faster interfacial electron transfer due to the dual charge injection pathway of PbS QD to TiO2 and MWCNT. The enhanced activity of the trio‐hybrid has also been analyzed from the first principal calculations in light of an efficient interfacial electron transfer as a result of the dual charge injection pathway. The photoelectrochemical water‐spilling response of the photoanodes in terms of photocurrent density, electrochemical impedance, and Mott–Schottky measurements on PbS‐TiO2 and PbS‐TiO2‐MWCNT photoanodes reveal that a combination of MWCNT and TiO2 exhibits an increase in electrical double layer capacitance, decrease in series resistance and enhancement of carrier density with NIR illumination at the heterojunction. Overall, all the dynamical studies at the interface of the trihybrid‐based photoanodes demonstrate its potential of utilization as a futuristic NIR‐ active photoelectrochemical water‐splitting material.

Colloidal InAs Quantum Dot-Based Infrared Optoelectronics Enabled by Universal Dual-Ligand Passivation.

Solution-processed low-bandgap semiconductors are crucial to next-generation infrared (IR) detection for various applications, such as autonomous driving, virtual reality, recognitions, and quantum communications. In particular, III-V group colloidal quantum dots (CQDs) are interesting as nontoxic bandgap-tunable materials and suitable for IR absorbers; however, the device performance is still lower than that of Pb-based devices. Herein, a universal surface-passivation method of InAs CQDs enabled by intermediate phase transfer (IPT), a preliminary process that exchanges native ligands with aromatic ligands on the CQD surface is presented. IPT yields highly stable CQD ink. In particular, desirable surface ligands with various reactivities can be obtained by dispersing them in green solvents. Furthermore, CQD near-infrared (NIR) photodetectors are demonstrated using solution processes. Careful surface ligand control via IPT is revealed that enables the modulation of surface-mediated photomultiplication, resulting in a notable gain control up to ≈10 with a fast rise/fall response time (≈12/36ns). Considering the figure of merit (FOM), EQE versus response time (or -3dB bandwidth), the optimal CQD photodiode yields one of the highest FOMs among all previously reported solution-processed nontoxic semiconductors comprising organics, perovskites, and CQDs in the NIR wavelength range.

Developments and Challenges Involving Triplet Transfer across Organic/Inorganic Heterojunctions for Singlet Fission and Photon Upconversion.

In this Perspective, we provide an overview of recent advances in harvesting triplets for photovoltaic and photon upconversion applications from two angles. In singlet fission-sensitized solar cells, the triplets are harvested through a low band gap semiconductor such as Si. Recent literature has shown how a thin interlayer or orientation of the singlet fission molecule can successfully lead to triplet transfer. On the other hand, the integration of transition metal dichalcogenides (TMDCs) with suitable organic molecules has shown triplet-triplet annihilation upconversion (TTA-UC) of near-infrared photons. We consider the theoretical aspect of the triplet transfer process between a TMDC and organic semiconductors. We discuss possible bottlenecks that can limit the harvesting of energy from triplets and perspectives to overcome these.

The effect of the CH3NH3PbClxI3-x perovskite layer thickness and grain size on its electrophysical and optical properties

Lead halide perovskite CH3NH3PbClxI3-x thin films are widely used as photoactive layers in perovskite solar cells. CH3NH3PbClxI3-x is a low band gap semiconductor with a broad absorption spectrum and a high conductivity showing excellent compatibility with exciting hole and electron selective layers in terms of electronic energy alignment, which provide efficient charge generation, separation and transport in perovskite solar cells. In this paper, CH3NH3PbClxI3-x layers were deposited on the TiO2 surface by one step spin-coating technique from a methylammonium iodide (MAI) and lead chloride (PbCl2) solution. To prepare the perovskite solution, PbCl2 (Sigma-Aldrich) 230 mg of PbCl2 and 394 mg of MAI were dissolved in 1 ml of N, N-Dimethylformamide (Sigma-Aldrich) solvent. As expected, the elevation of the spin-coating rate resulted in CH3NH3PbClxI3-x thickness reduction, which should lead to a decrease in the R3 resistance in CH3NH3PbClxI3-x. However, the impedance spectroscopy revealed that with thickness reduction from 955 nm to 753 nm, the R3 resistance of CH3NH3PbClxI3-x declines from about 2590 Ώ to 2258 Ώ reaching the minimum value at 505 nm. The further decrease in CH3NH3PbClxI3-x thickness increased CH3NH3PbClxI3-x film resistance. The study of CH3NH3PbClxI3-x absorbance and luminescence spectra showed that the change in CH3NH3PbClxI3-x defect density occurred, which explains the decrease in CH3NH3PbClxI3-x resistance. According to the absorbance and luminescence spectroscopy study, the CH3NH3PbClxI3-x thickness reduction led to a decrease in the density of interstitial CH3NH3PbClxI3-x+ defects. CH3NH3PbClxI3-x+ species form deep levels trapping free electrons and as a result, increasing CH3NH3PbClxI3-x resistance. The PSCs based on a 505 nm thick CH3NH3PbClxI3-x layer showed the highest performance with the improved short current density and fill factor. The champion device had a power conversion efficiency of 9.92 %.

Self‐sacrificial Templated Synthesis of Fe/N Co‐doping TiO2 for Enhanced CO2 Photocatalytic Reduction

AbstractAs a green photocatalyst, TiO2 has been widely used in adsorption, desorption and redox reactions, but the wide energy band and moderate visible light absorption have greatly inhibited its applications in photocatalysis. The effective method of enhancing the performance of catalysts is the development of heterojunction and metal‐nonmetal co‐doping. Herein, Fe−N co‐doped TiO2 heterojunction photocatalysts (FexTi@C) were successfully synthesized by calcining a self‐sacrificial template (NH2−MIL‐125(Ti)) injected with Fe3+ solution. X‐ray diffraction (XRD), transmission electron microscopy (TEM), X‐ray photoelectron spectroscopy (XPS), N2 adsorption/desorption analysis, and photoelectrochemical tests were used to characterize FexTi@C, showing multiple rutile/anatase TiO2 heterojunction structure, low bandgap, and significant absorption in visible light. In addition, the Ti−O−Fe tetrahedra and more oxygen vacancies were provided since the doped N is from the pristine MOF and the radii of Fe3+ and Ti4+ are similar, which improved the photocatalytic efficiency of CO2 reduction to CH4, especially the Fe0.8Ti@C reached 7.8‐fold and 10.2‐fold CH4 yield increase compared with the original TiMOF template and the undoped Ti@C, respectively. This work presents a simple method for the fabrication of low bandgap semiconductors, and also makes a new attempt at the synergistic effect between the in‐situ elements and valence bonds of MOF‐derived catalysts.

Structural, electronic and thermoelectric properties of SnTe with dilute co-doping of Ag and Cu

The low bandgap semiconductor, SnTe is receiving significant attention as a thermoelectric material because of its low toxicity and environment-friendly nature. In this study, we report the effect of co-doping dilute concentrations of Ag and Cu ions in SnTe that suppresses the Sn vacancies leading to optimized thermoelectric properties. Samples of nominal chemical composition Sn1.03–2xAgxCuxTe (x = 0, 0.01, 0.02, 0.04) were prepared by the solid-state route. The Rietveld refinement of powder XRD of these compounds showed a fcc (Fm3¯m) structure with no other impurity phases. Diffuse reflectance IR spectroscopy showed an increase in the bandgap upon Ag-Cu co-doping in SnTe, associated with valence band convergence. Electronic band structure calculations confirmed an increase in the bandgap along with a reduction in the energy difference between light and heavy valence bands having maxima at the L and Σ points. Partial density of states (P-DOS) calculations showed that Ag-Cu doping in SnTe does not contribute towards the formation of resonant energy levels. The Seebeck coefficient S of the Sn1.01Ag0.01Cu0.01Te reached a maximum value of ∼ 95 μV/K at 783 K, compared to 86 μV/K of pure SnTe. The power factor increased with the doping concentration, reaching ∼ 10.8 μWK−2cm−1 at 783 K for x = 0.04. The lattice thermal conductivity κL decreased on Ag-Cu co-doping, with κL = 0.44 Wm−1K−1 above 750 K for x = 0.04, which is close to the Cahill model. The combination of higher power factor and reduced lattice thermal conductivity in the Ag-Cu co-doped samples resulted in enhanced ZT = 0.24–0.29 at 773 K.

Theoretical study of the non-parabolicity and size effects on the diamagnetic susceptibility of donor impurity in Si, HgS and GaAs cylindrical quantum dot and quantum disk: applied magnetic field influence is considered

ABSTRACT Through this work, we have investigated the influence of the conduction band non-parabolicity (NP) and magnetic field on the diamagnetic susceptibility for a confined shallow donor impurity in a homogeneous cylindrical quantum dot (CQD) and quantum disk (QDisk); the size effect has been considered. Our calculations have been performed using the variational method which consists of the choice of a trial wave function. The Schrodinger equation has been solved within the effective-mass approximation considering the infinite height potential barrier. The numerical calculations are performed taking into account different semiconductor materials (i.e. Si, HgS and GaAs). Our results reveal that both the size and conduction band NP have a significant impact on the behaviour of the diamagnetic susceptibility for both studied systems (i.e. CQD and QDisk). It has been also noticed that, for both CQD and QDisk, the NP increases the diamagnetic susceptibility (). Furthermore, this effect is remarkable for low band gap semiconductors, especially in large QD (weak radial confinement). However, it is much more important in HgS due to its narrow band gap compared to Si and GaAs materials.

Deposition and Characterization of Heterostructures Based on Doped Ferrocene for Film-Device Applications

Novel heterostructures based on ferrocenium hexafluorophosphate (FcPF6), 2,6-dihydroxyanthraquinone (DHAQ) or 2,6-diaminoanthraquinone (DAAQ), zinc phthalocyanine (ZnPc) and nylon 11 were deposited by the high-vacuum thermal evaporation (HVTE) technique. Morphological and mechanical characterizations of these organic heterostructures FcPF6:DHAQ/nylon(ZnPc) and FcPF6:DAAQ/nylon(ZnPc) were carried out. Subsequently, corresponding optical parameters were calculated. The heterostructure with FcPF6:DHAQ presented the lowest optical band gap and fundamental band gap at 1.55 eV and 2.45 eV, respectively. The nylon(ZnPc) layer favors the optical behavior and places these heterostructures within organic low-bandgap semiconductor range. Additionally, devices were fabricated, and their electrical behavior was evaluated. The ITO/FcPF6:DHAQ/nylon(ZnPc)/Ag device exhibits ohmic behavior, and the ITO/FcPF6:DAAQ/nylon(ZnPc)/Ag device exhibits ohmic behavior at low voltages, but at V ≥ 5 V, its behavior changes to Space Charge Limited Current (SCLC). This device carries a maximum current of 0.02 A, three orders of magnitude higher than the current carried by the device with the DHAQ. The SCLC conduction mechanism showed a hole mobility of 9.27 × 10−8 (cm2)/Vs, the concentration of thermally excited holes of 3.01 × 1023 m−3, and trap concentration of 3.93 × 1021 m−3. FcPF6:DHAQ/nylon(ZnPc) and FcPF6:DAAQ/nylon(ZnPc) are potential candidates for organic devices as an emitter layer and active layer, respectively.

Preparation of mesoporous poly(fullerene oxide) framework by thermal [3 + 2] cycloadditions and its application as a semiconductor photocatalyst

We report the formation of an interconnected, three-dimensional, mesoporous polymeric fullerene oxide framework via thermal [3 + 2] cyclo-additions of monomeric C60 and fullerene oxides (C60On), formed upon thermal decomposition of C60Br24, causing the eliminations of bromine atoms in an oxygen atmosphere at an elevated temperature of 200 °C. The newly formed mesoporous fullerene oxide framework is found to be a low bandgap semiconductor capable of acting as a photocatalyst similar to graphitic C3N4. The sunlight-assisted photocatalytic degradation of the methylene blue dye is demonstrated. To have a better understanding of the mechanism of the [3 + 2] cyclo-additions of monomeric C60 and fullerene oxides, a theoretical investigation has been carried out and the energetics of the reaction C60O + C60 → C120O is calculated.

A comparative study on binary polymer blends comprising rigid planar low-bandgap semiconductor and flexible coil-type insulator

A polymer blend is an essential member of a class of materials analogous to metal alloys, in which two polymers are blended together to create a noble material with different physical properties. Not only the physicochemical properties of each polymer but also their relative interaction and miscibility are a key to eliciting novel materials properties. Here, we investigated the effects of blending a flexible coil-type insulating polymer on the charge transport characteristics of rigid planar semiconducting polymers. To this end, we systematically controlled the blending ratio of the commercial insulating polymer, polystyrene, and one of two different diketopyrrolopyrrole-based donor-acceptor alternating copolymers, and characterized the electrical, microstructural, and morphological properties of the semiconductor–insulator polymer blend films. We found that the electrical properties of the films are strongly correlated with the polymer blend ratio and the resulting films’ vertical segregation and crystalline structures and that hole transport and electron transport alter differently with the polymer backbone structure and blend ratio. These results are expected to be greatly helpful in optimizing the semiconductor–insulator polymer ink formulations for potential use in printed electronics.

In Situ Growth of PbS Nanoparticles without Organic Linker on ZnO Nanostructures via Successive Ionic Layer Adsorption and Reaction (SILAR)

The process of effective solar energy harvesting and conversion requires efficient photon absorption, followed by charge generation and separation, then electron transfer. Nanostructured materials have been considered as potential building blocks for the development of future generations of solar cells. Much attention has been given to wide-bandgap semiconductor nanowires, combined and sensitized with low-bandgap semiconductors effectively attached to the nanowires for low-cost and highly efficient solar cells. Here, the in situ growth of lead sulfide (PbS) nanoparticles on the surface of zinc oxide (ZnO) nanowires grown by the Successive Ionic Layer Adsorption and Reaction (SILAR) technique is presented for different numbers of cycles. The morphology and structure of PbS nanoparticles are confirmed by Scanning Electron Microscopy (SEM), revealing the decoration of the nanowires with the PbS nanoparticles, Transmission Electron Microscopy (TEM) and HR-TEM, showing the tight attachment of PbS nanoparticles on the surface of the ZnO nanowires. The Selected Area Electron Diffraction (SAED) confirms the crystallization of the PbS. Photoluminescence spectra show a broad and more intense deep-level emission band.

A Transparent, High-Performance, and Stable Sb2 S3 Photoanode Enabled by Heterojunction Engineering with Conjugated Polycarbazole Frameworks for Unbiased Photoelectrochemical Overall Water Splitting Devices.

Developing low-cost, high-performance, and durable photoanodes is essential in solar-driven photoelectrochemical (PEC) energy conversion. Sb2 S3 is a low-bandgap (≈1.7eV) n-type semiconductor with a maximum theoretical solar conversion efficiency of ≈28% for PEC water splitting. However, bulk Sb2 S3 exhibits opaque characteristics and suffers from severe photocorrosion, and thus the use of Sb2 S3 as a photoanode material remains underexploited. This study describes the design and fabrication of a transparent Sb2 S3 -based photoanode by conformably depositing a thin layer of conjugated polycarbazole frameworks (CPF-TCzB) onto the Sb2 S3 film. This structural design creates a type-II heterojunction between the CPF-TCzB and the Sb2 S3 with a suitable band-edge energy offset, thereby, greatly enhancing the charge separation efficiency. The CPF-TCzB/Sb2 S3 hybrid photoanode exhibits a remarkable photocurrent density of 10.1mAcm-2 at 1.23V vs reversible hydrogen electrode. Moreover, the thin CPF-TCzB overlayer effectively inhibits photocorrosion of the Sb2 S3 and enables long-term operation for at least 100h with ≈10% loss in photocurrent density. Furthermore, a standalone unbiased PEC tandem device comprising a CPF-TCzB/Sb2 S3 photoanode and a back-illuminated Si photocathode can achieve a record solar-to-hydrogen conversion efficiency of 5.21%, representing the most efficient PEC water splitting device of its kind.

A Photocatalytic Hydrolysis and Degradation of Toxic Dyes by Using Plasmonic Metal–Semiconductor Heterostructures: A Review

Converting solar energy to chemical energy through a photocatalytic reaction is an efficient technique for obtaining a clean and affordable source of energy. The main problem with solar photocatalysts is the recombination of charge carriers and the large band gap of the photocatalysts. The plasmonic noble metal coupled with a semiconductor can give a unique synergetic effect and has emerged as the leading material for the photocatalytic reaction. The LSPR generation by these kinds of materials has proved to be very efficient in the photocatalytic hydrolysis of the hydrogen-rich compound, photocatalytic water splitting, and photocatalytic degradation of organic dyes. A noble metal coupled with a low bandgap semiconductor result in an ideal photocatalyst. Here, both the noble metal and semiconductor can absorb visible light. They tend to produce an electron–hole pair and prevent the recombination of the generated electron–hole pair, which ultimately reacts with the chemicals in the surrounding area, resulting in an enhanced photocatalytic reaction. The enhanced photocatalytic activity credit could be given to the shared effect of the strong SPR and the effective separation of photogenerated electrons and holes supported by noble metal particles. The study of plasmonic metal nanoparticles onto semiconductors has recently accelerated. It has emerged as a favourable technique to master the constraint of traditional photocatalysts and stimulate photocatalytic activity. This review work focuses on three main objectives: providing a brief explanation of plasmonic dynamics, understanding the synthesis procedure and examining the main features of the plasmonic metal nanostructure that dominate its photocatalytic activity, comparing the reported literature of some plasmonic photocatalysts on the hydrolysis of ammonia borane and dye water treatment, providing a detailed description of the four primary operations of the plasmonic energy transfer, and the study of prospects and future of plasmonic nanostructures.

Local structure and electron density distribution analysis of tin(II) sulfide using pair distribution function and maximum entropy method

Abstract Tin(II) sulfide (SnS) is a low symmetric orthorhombic double-layered dual bandgap semiconductor. It is low cost, toxic-free and highly abundant on Earth, with multifunctional optical, electronic, magnetic and light conversion applications when doped adequately with impurity. These physical properties can be understood only by the complete understanding of microstructural properties like average structure, electron density distribution inside the unit cell, bonding nature and local structure. In this work, the average and local structure, along with the electron density distribution of a nano crystallite sized single-phase sample of tin(II) sulfide is elucidated with the help of precise X-ray intensity data. The average structural information was extracted using Rietveld refinement analysis and the visual mapping of 3D, 2D and 1D electron density distribution inside the unit cell and its numerical contribution using maximum entropy method (MEM). The bonding between the first inter and intra bonding between Sn and S atoms is 2.65,105 Å and 3.2689 Å with mid bond electron density 0.907 e/Å3 and 0.1688 e/Å3 respectively. The inter-atomic correlations of 1st, 2nd and 3rd nearest neighbour atoms, their bond length, and the crystallite size are reported from pair distribution function (PDF) analysis using low Q-XRD data (Q ∼ 6.5 Å−1). The PDF analysis shows that the first and second nearest Sn–S bonding distance is 2.6064 Å and 3.4402 Å, first is between the Sn and S atoms of the same layer and the other between the Sn and S atoms of the adjacent layers respectively.

Application of SWSFET in Image Segmentation

Image segmentation is a fundamental image processing technique to extract the required information from an image. The core element of any integrated circuit (IC) chip for signal processing is the metal oxide semiconductor field effect transistor (MOSFET). There are various limitations of MOSFET in sub-nm process technology. This work introduces the application of a new type of MOSFET, which is known as the spatial wave function switched field effect transistor (SWSFET), in the image processing application. The channel in a SWSFET is comprised of various low bandgap semiconductor layers. The charge carriers move across various channels and generate current through different drain terminals. The SWSFET is used to design a window detector which is applied in image segmentation.

Module-Patterned Polymerization towards Crystalline 2D sp2 -Carbon Covalent Organic Framework Semiconductors.

Despite rapid progress over the past decade, most polycondensation systems even upon a small structural variation of the building units eventually result in amorphous polymers other than the desired crystalline covalent organic frameworks. This synthetic dilemma is a central and challenging issue of the field. Here we report a novel approach based on module-patterned polymerization to enable efficient and designed synthesis of crystalline porous polymeric frameworks. This strategy features a wide applicability to allow the use of various knots of different structures, enables polycondensation with diverse linkers, and develops a diversity of novel crystalline 2D polymers and frameworks, as demonstrated by using the C=C bond-formation polycondensation reaction. The new sp2 -carbon frameworks are highly emissive and enable up-conversion luminescence, offer low band gap semiconductors with tunable band structures, and achieve ultrahigh charge mobilities close to theoretically predicted maxima.