Search

We present a comprehensive theoretical analysis of intrinsic high-field transport in cuprous halides: CuCl, CuBr, and CuI. Ensemble Monte Carlo transport simulations were performed based on analytical approximations of the multi-valley and three-band electronic structure model. The deformation potentials, extracted from carrier–phonon interaction matrix elements calculated via the Wannier function approach, were employed to determine scattering rates. Our detailed analysis uncovers intriguing transport characteristics based on the complex valence band structures, resulting from spin–orbit coupling and band inversion. Remarkably, the hole mobility in CuI was exceptionally high, reaching up to 193 cm2/V s, while CuCl exhibited unusual temperature dependencies in hole transport. Additionally, the electron mobility in CuI was found to be 254 cm2/V s, indicating a minimal disparity between carrier mobilities, which is advantageous for optoelectronic applications. [ABSTRACT FROM AUTHOR]

Room temperature 6 μm intraband cascade electroluminescence (EL) is demonstrated with lightly n-doped HgTe colloidal quantum dots of ∼8 nm diameter deposited on interdigitated electrodes in a metal–insulator–metal device. With quantum dot films of ∼150 nm thickness made by solid-state-ligand-exchange, the devices emit at 1600 cm−1 (6.25 μm), with a spectral width of 200 cm−1, determined by the overlap of the 1Se–1Pe intraband transition of the quantum dots and the substrate photonic resonance. At the maximum current used of 20 mA, the bias was 30 V, the external quantum efficiency was 2.7%, and the power conversion efficiency was 0.025%. Adding gold nano-antennas between the electrodes broadened the emission and increased the quantum efficiency to 4.4% and the power efficiency to 0.036%. For these films, the doping was about 0.1 electron/dot, the electron mobility was 0.02 cm2 V−1 s−1, and the maximum current density was 0.04 kA cm−2. Higher mobility films made by solution ligand exchange show a 20-fold increase in current density and a 10-fold decrease in EL efficiencies. Electroluminescence with weak doping is interesting for eventually achieving electrically driven stimulated emission, and the requirements for population inversion and lasing are discussed. [ABSTRACT FROM AUTHOR]

The deep-level drain current transient spectroscopy (Id-DLTS) measurements of Al -doped SiC metal–oxide–semiconductor field-effect transistors (MOSFETs) strongly suggest that the reduction in the channel mobility at low temperatures is related to a shallow trap detectable at 70 K. Using the Shockley–Reed–Hall (SRH) theory, the level of this trap has been extracted to be around 0.15 eV below the conduction band minimum of SiC. Density functional theory (DFT) calculations of Al Si N C Al Si and Al Si O C Al Si defect complexes have found one configuration of the Al Si O C Al Si complex, which has a charge transition level within the SRH extracted trap level range. Therefore, we suggest that these Al Si O C Al Si defects are likely candidates for traps responsible for the channel mobility reduction. [ABSTRACT FROM AUTHOR]

We present the results of a new analysis of the literature data on electron mobility μ in dense helium gas aimed at determining the existence of a threshold density for electron self-trapping in gaseous helium as a function of temperature. We have investigated the density dependence of μ and, when available, its dependence on the electric field. The experimental data are favorably rationalized by minimizing the excess free energy of the self-localized states within the optimum fluctuation model. It is shown that the formation of electron bubbles via the self-trapping phenomenon is determined by the delicate balance between the electron thermal energy, the density dependence of the electron energy at the bottom of the conduction band in the gas, and the work necessary to expand the bubble. We show that the self-trapping phenomenon is not limited to low temperatures but occurs at any temperatures for large enough densities. [ABSTRACT FROM AUTHOR]

N-polar InN/In0.61Al0.39N heterostructures are grown directly on sapphire by using metalorganic chemical vapor deposition. The thickness of Mg-doped In0.61Al0.39N is 340 nm, and the root-mean-square surface roughness of 20 nm thick InN is ∼3.2 nm. An optional AlN spike grown at 710 °C for 35 s is used either as an interlayer to separate the InAlN buffer from the InN channel or as a part of InAlN nucleation after sapphire nitridation. High-resolution transmission electron microscopy reveals approximately two monolayers of AlN if used as the interlayer. In this case, the concentration of screw and edge threading dislocations in partially strained InN decreased down to 6.5 × 109 and 38 × 109 cm−2, respectively. More importantly, the interlayer inclusion suppressed remote donor and alloy disorder scatterings, providing, at room temperature, the InN free electron mobility and concentration of 620 cm2/V s and 3 × 1013 cm−2, respectively. On the other hand, omitting the AlN spike by InAlN nucleation led to structural deteriorations while buffer resistivity increased to 1.7 kΩ/□. A current density of ∼12–16 A/mm, breakdown field of ∼75 kV/cm, and electron drift velocity of ∼2 × 107 cm/s were determined in InN by applying 10 ns voltage pulses on fabricated test resistors. [ABSTRACT FROM AUTHOR]

β-(AlxGa1−x)2O3 presents a diverse material characterization exhibiting exceptional electrical and optical properties. Considering the miniaturization of gallium oxide devices, two-dimensional (AlxGa1−x)2O3 alloys, as a critical component in the formation of two-dimensional electron gases, demand an in-depth examination of their carrier transport properties. Herein, we investigate the temperature-dependent carrier mobility and scattering mechanisms of quasi-two-dimensional (2D) (AlxGa1−x)2O3 (x ≤ 5) by solving the Boltzmann transport equation from first-principles. Anisotropic electron mobility of 2D (AlxGa1−x)2O3 is limited to 30−80 cm2/Vs at room temperature, and it finds that the relatively large ion-clamped dielectric tensors (Δɛ) suggest a major scattering role for polar optical phonons. The mobility of 2D (AlxGa1−x)2 is less than that of bulk β-(AlxGa1−x)2O3 and shows no quantum effects attributed to the dangling bonds on the surface. We further demonstrate that the bandgap of 2D (AlxGa1−x)2O3 decreases with the number of layers, and the electron localization function also shows an anisotropy. This work comprehensively interprets the scattering mechanism and unintentional doping intrinsic electron mobility of (AlxGa1−x)2O3 alloys, providing physical elaboration and alternative horizons for experimental synthesis, crystallographic investigations, and power device fabrication of 2D (AlxGa1−x)2O3 atomically thin layered systems. [ABSTRACT FROM AUTHOR]

The Hall electron mobility in sulfur-doped 4H-SiC over a wide range of S concentration was investigated. Sulfur (S) works as a double donor in SiC. The electron concentration in the S + -implanted layers saturates when the S concentration exceeds 1 × 10 18 cm − 3 and the net donor concentration of the S + -implanted layer with S concentration of 1 × 10 19 cm − 3 is 4 × 10 18 cm − 3 , indicating that the solubility or activation limit of S + -implanted SiC is about 2 × 10 18 cm − 3 . The S + -implanted SiC with a S concentration of 1 × 10 18 cm − 3 exhibits an electron mobility of 598 cm 2 /V s, which is more than twice as high as that in N-doped SiC with the same doping concentration (268 cm 2 /V s). The temperature dependence of the electron mobility in S + -implanted SiC is reproduced in the wide temperature range by the calculation of the electron mobility adopting the helium atom model for neutral-impurity scattering. [ABSTRACT FROM AUTHOR]

Considering the strong built-in electric field caused by polarization in wurtzite nitride heterostructures, the energy levels and wave functions of the two-dimensional electrons in AlyGa1−yN back-barrier Al2O3/InxAl1−xN/GaN heterostructures are calculated using the finite element difference method. The dispersion relations and electrostatic potentials of optical phonons are obtained by the transfer matrix method. The electron mobility under optical phonon scattering is studied based on the theory of Lei–Ting force balance equation. The influences of AlyGa1−yN back barrier, ternary mixed crystal effect, and size effect are also analyzed by comparing with the Al2O3/InxAl1−xN/GaN heterostructure without back barrier. It is found that the introduction of a back barrier can attenuate the effect of gate-insulating layer, but enhance the effect of barrier and channel layers on electronic states. Then, the interaction between electrons and optical phonons is weakened, so the electron mobility in AlyGa1−yN back-barrier Al2O3/InxAl1−xN/GaN heterostructure is higher than that in Al2O3/InxAl1−xN/GaN structure under the same conditions. It is also found that using a thinner AlyGa1−yN film with y = 0.25 as the back-barrier layer of Al2O3/InxAl1−xN/GaN heterostructure is more conducive to improving 2DEG mobility. These conclusions can provide references for the preparation of InxAl1−xN/GaN heterojunction devices. [ABSTRACT FROM AUTHOR]

This paper provides a comprehensive study of the impact of the gate recess depth (RD) on the GaN-on-Si MOS-HEMTs DC performances. IDS = f(VGS) and IDS = f(VDS) measurements are conducted at 25 and 150 °C, respectively, in forward and blocking modes. The gate recessed depth (50, 150, and 350 nm) is modulated by adjusting the plasma etching time, which is a critical step for improving the dielectric/GaN interface quality and the gate channel electron mobility. Three distinct regions can be defined separately: the bottom, the sidewall, and the corner region being the junction between the two previous regions. To assess the impact of gate recessed depth (RD) on the several mobilities around the gate cavity first, we applied our previous methodology allowing us to extract the bottom (μbot) and the entire sidewall region mobility (μT), without distinction from the corner. The mobility of the transverse region was found surprisingly to increase with deeper RD. To gain insight into the impact of the RD on this transverse section, a new extraction methodology is proposed to extract separately the gate corner (μcorner) and sidewall (μSW) mobility. These extractions show that the corner mobility is found to be reduced compared to the sidewall one (μcorner < μSW) evidencing the different weighting contributions over the transverse mobility. Moreover, these mobilities are found to be more degraded compared to the bottom one, highlighting the different contributions on the on-state resistance (RON). Indeed, the on-state resistance is lowered with the shallower RD due to the reduced sidewall resistance contribution (lower sidewall length) and despite the incremental contribution of the bottom resistance (larger effective gate length). However, the shallower RD shows an increase in the drain–source leakage current in reason of a lower gate electrostatic control. Technology Computer Aided Design (TCAD) simulations of the three RD morphologies are carried out to validate the experimental trends and the proposed methodology. [ABSTRACT FROM AUTHOR]

The Sn-doping effects on the electrical conduction and optical properties of GaAs(631)A epilayers grown by molecular beam epitaxy were investigated. We found that the conduction type conversion, frequently observed in the doping of layers grown on high-index substrates, is avoided when tin-doping is implemented. The maximum free-carrier concentration (n) obtained in GaAs(631):Sn was 2 × 1019 cm−3, an order of magnitude higher than previously reported for GaAs(631):Si, and within the same order of magnitude for the growth of GaAs(100):Si. The electron mobility was suitable for many optoelectronic applications. Raman spectroscopy showed low lattice disorder in (631) oriented samples, compared with singular (100) samples. The photoluminescence characterization of the samples revealed the blueshift of the optical transitions close to E0 associated with the Moss–Burstein effect for Sn doping. Photoreflectance spectroscopy was used to study the doping properties at the critical points E1 and E1 + Δ1, where the major affectation with n was perceived in the broadening parameter Γ. [ABSTRACT FROM AUTHOR]

We present a comprehensive analysis of the structure–property relationship in small molecule non-fullerene acceptors (NFAs) featuring an acceptor–donor–acceptor configuration employing state-of-the-art quantum chemical computational methods. Our focus lies in the strategic functionalization of halogen groups at the terminal positions of NFAs as an effective means to mitigate non-radiative voltage losses and augment photovoltaic and photophysical properties relevant to organic solar cells. Through photophysical studies, we observe a bathochromic shift in the visible region for all halogen-functionalized NFAs, except type-2, compared to the unmodified compound. Most of these functionalized compounds exhibit exciton binding energies below 0.3 eV and ΔLUMO less than 0.3 eV, indicating their potential as promising candidates for organic solar cells. Selected candidate structures undergo an analysis of charge transport properties using the semi-classical Marcus theory based on hopping transport formalism. Molecular dynamics simulations followed by charge transport simulations reveal an ambipolar nature of charge transport in the investigated NFAs, with equivalent hole and electron mobilities compared to the parent compound. Our findings underscore the crucial role of end-group functionalization in enhancing the photovoltaic and photophysical characteristics of NFAs, ultimately improving the overall performance of organic solar cells. This study advances our understanding of the structure–property relationships in NFAs and provides valuable insights into the design and optimization of organic solar cell materials. [ABSTRACT FROM AUTHOR]

We demonstrated the crystal growth of group-III arsenides (III-As) on GaN via an arsenidation layer and GaN-channel electron mobility transistors (HEMTs) with a regrowth InAs/GaAs source and drain (S/D) region. By annealing under an AsH3 atmosphere, the surface of a GaN (0001) template is arsenided. We grew ⟨ 111 ⟩ oriented InAs and GaAs on arsenided GaN. Silicon-doped n-type InAs with a carrier mobility of over 1500 cm2/V s and a carrier concentration of over 1 × 1019 cm−3 was successfully obtained. The fabrication process and direct-current characteristics of GaN-channel HEMTs with the regrown Si-doped InAs/GaAs S/D region were demonstrated for the first time. A maximum transconductance estimated from transfer characteristics was as high as ∼195 mS/mm for the HEMT with a gate length of 2 μm without passivation, which is comparable to those for the HEMT without any S/D regrowth. The impact of the InAs/GaAs S/D region on the on-resistance of the fabricated HEMTs was estimated to be ∼0.9 Ω mm, which can be reduced by optimizing the device structures and process conditions. These results indicate that the process of GaN arsenidation and III-As regrowth can be used without any device performance degradation. Therefore, further lowering the ohmic contact resistivity and on-resistance of GaN-channel HEMTs is possible by maturing the manufacturing-process technology of III-As-contained GaN-channel HEMTs. [ABSTRACT FROM AUTHOR]

Inquiring the isotopically engineered carrier transport in polar materials remains an open question. Herein, the phonon-limited drift carrier mobility of single-crystal cubic boron nitride is presented using first-principles calculations. Natural c-BN has the predicted electron mobility of 1230 and 760 cm2/V s by solving the iterative Boltzmann transport equation and self-energy relaxation time approximation, respectively. The hole mobility under the Boltzmann transport equation and self-energy relaxation time approximation is 193 and 105 cm2/Vs, respectively. Subsequently, the electron and hole mobilities at the stable isotope levels of boron and nitride are predicted, and nitride isotopes are found to be more effective than boron for carrier mobility. Those carrier mobilities further decrease with increasing temperature due to the strengthened electron–phonon interactions. Moreover, the phonon-assisted indirect optical absorption of c-BN is investigated by considering the contribution of phonons to the indirect electronic inter-band transitions. The predicted imaginary part of the dielectric function is in better agreement with previous experiments. This work aims to understand the role of phonons in determining the carrier mobility and indirect optical absorption of c-BN. [ABSTRACT FROM AUTHOR]

Highly degenerate n-type CdO with high electron mobility is a promising transparent conducting oxide (TCO) for optoelectronic devices utilizing a spectrum in the Vis-NIR range. In particular, it has been shown that doped CdO thin films can show much superior transparency of >80% in the NIR region compared to conventional transparent conducting oxide (e.g., Sn-doped In2O3) thin films with a similar sheet resistance. However, CdO thin films typically experience rapid degradation in their electron mobilities when exposed to environmental conditions with H2O moisture. Here, we studied the effects of thermal annealing on the environmental stability of In-doped CdO (CdO:In) using a combination of different analytical techniques. CdO:In thin films with different In concentration (0%–8.3%) synthesized by magnetron sputtering were subjected to different post-thermal annealing (PTA) and then aged in different environmental conditions with varying relative humidity (RH) in the range of 0%–85%. Our results reveal that the degradation of CdO:In thin films can be primarily attributed to the oxygen vacancy-related defects at the grain boundaries, which can readily react with the OH− in the moisture. The moisture induced degradation can be mitigated by appropriate PTA at high temperatures (>400 °C) where grain boundary defects, primarily associated with Cd vacancies, can be passivated through hydrogen (H), thus enhancing their environmental stability. The present study provides a comprehensive understanding of the instability mechanisms and defect passivation in transparent conducting CdO:In thin films, which can also be relevant for other wide gap oxides. [ABSTRACT FROM AUTHOR]

The two‐dimensional (2D) monolayer material MoSi2N4 was successfully synthesized in 2020[Hong et al., Science 369, 670, (2020)], exhibiting a plethora of new phenomena and unusual properties, with good stability at room temperature. However, MA2Z4 family monolayer materials involve primarily transition metal substitutions for M atoms. In order to address the research gap on lanthanide and actinide MA2Z4 materials, this work conducts electronic structure calculations on novel 2D MSi2N4 (M = La, Eu) monolayer materials by employing first‐principles methods and CASTEP. High carrier mobility is discovered in the indirect bandgap semiconductor 2D LaSi2N4 monolayer (~5400 cm2 V−1 s−1) and in the spin (spin‐down channel) carrier mobility of the half‐metallic ferromagnetic EuSi2N4 monolayer (~2800 cm2 V−1 s−1). EuSi2N4 monolayer supplements research on spin carrier mobility in half‐metallic ferromagnetic monolayer materials at room temperature and possesses a magnetic moment of 5 μB, which should not be underestimated. Furthermore, due to the unique electronic band structure of EuSi2N4 monolayer (with the spin‐up channel exhibiting metallic properties and the spin‐down channel exhibiting semiconductor properties), it demonstrates a 100% spin polarization rate, presenting significant potential applications in fields such as magnetic storage, magnetic sensing, and spintronics. [ABSTRACT FROM AUTHOR]

This study explored eight novel and highly stable monolayer configurations: C 3 X 2 (X = N, P, As, Sb, and Bi) and C 3 XY (X = P and As, Y As and Sb) by analyzing their electronic, optical, and photocatalytic properties based on first-principles density functional theory. The findings indicated that the C 3 X 2 monolayers, except for C 3 Bi 2 , exhibit indirect band gap semiconductor properties, and their band gaps are 1.497, 1.862, 2.272, 1.448, and 1.561 eV, respectively. Notably, only C 3 P 2 and C 3 As 2 fulfilled the prerequisites for photocatalytic water splitting, boast high electron mobility (up to ∼103 cm2/Vs), strong absorption in the visible light range, and high solar-to-hydrogen (STH) efficiency (30.16% for C 3 P 2 and 23.05% for C 3 As 2). Moreover, the Janus C 3 PAs, C 3 PSb, and C 3 AsSb monolayers exhibited indirect band gaps ranging from 1.616 to 2.070 eV and satisfied the band structure criteria for photocatalytic water splitting. These three Janus monolayers outperformed C 3 X 2 in terms of optical absorption, carrier mobility, and STH efficiency owing to their inherent electric fields. The STH efficiency of C 3 PSb and C 3 AsSb reach 31.26% and 29.17%, respectively, with electron mobility reaching up to 4642.01 and 11902.64 cm2/Vs, respectively, indicating their exceptional potential for photocatalytic water splitting. • We theoretically proposed eight novel and stable structures: C 3 X 2 (X = N, P, As, Sb, Bi) and C 3 XY (X = P, As; Y As, Sb). • Monolayer C 3 P 2 and C 3 As 2 exhibit strain-tunable photocatalytic water-splitting capabilities. • Compared with non-Janus C 3 X 2 , C 3 XY has better photocatalytic water splitting performance due to its built-in electric field. [ABSTRACT FROM AUTHOR]

Borophene, a boron analogue of graphene, is typically metallic, while all bulk boron phases are insulating. Here, we predict by first‐principles calculations that recently synthesized bilayer borophene, being suggested to be composed of two stacked v1/12 sheets, is a semiconductor with a bandgap of 1.13 eV, almost the same as that of silicon. It is shown that the stacking mode between two boron sheets as well as the density and pattern of the interlayer boron‐boron (B─B) bonds are the key factors for opening the bandgap in the otherwise metallic boron sheet. Moreover, the bilayer borophene exhibits electron mobility of 878.6 cm2 V−1 s−1 and a significantly higher optical absorption coefficient in the visible region than silicon. These excellent electronic and optical properties hosted in a two atom‐thick space, together with high thermal and mechanical stability, position the bilayer borophene as a promising nanomaterial for maintaining the miniaturization of electronics. [ABSTRACT FROM AUTHOR]

To address the high‐cost issue that impedes the large‐scale fabrication and industrialization of organic solar cells (OSCs), it is crucial to design low‐cost photovoltaic materials with simplified synthesis procedures. In this study, a novel fully non‐fused acceptor, ATVT‐BO, featuring a triisopropylbenzene‐substituted (E)‐1,2‐di(thiophen‐2‐yl)ethene (TVT) unit as the central core is designed and synthesized. A control acceptor, A4T‐BO, with the same alkyl chains but a bithiophene central core, is also synthesized for comparison. Theoretical calculations and practical measurements reveal that compared to A4T‐BO, the insertion of an ethylene bond in ATVT‐BO enhances the molecular planarity and reduces the aromaticity, leading to enhanced π‐electron delocalization and thus improved electron mobility and a red‐shifted optical absorption spectrum. The 3D molecular packing mode of ATVT‐BO, characterized by tight intermolecular interactions, also promotes efficient charge transport in OSCs. Consequently, when paired with the low‐cost polymer PTVT‐T, featuring an ester‐substituted TVT structure, as the photoactive layer, the PTVT‐T:ATVT‐BO‐based device achieves a remarkable power conversion efficiency of 14.8%, distinctly higher than that of PTVT‐T:A4T‐BO‐based cell. The result highlights the significant potential of TVT units in creating both low‐cost polymer donors and fully non‐fused acceptors, which opens up new possibilities for designing low‐cost photoactive materials in OSCs. [ABSTRACT FROM AUTHOR]

Structural, electronic, magnetic and optical properties of Cu4Mn2Te4 have been reported earlier by the authors, and here, the transport properties of the same are discussed along with the band structure investigation of the neodymium-doped cubic material LMO (LiMn2O4), namely LiMn 1. 7 5 Nd 0. 2 5 O4 compound, under spin polarized schemes through the First Principles calculations. The Full Potential-Linearized Augumented Plane Wave Method (FP-LAPW) method is adopted to investigate the electronic structures based on the framework of Density Functional Theory (DFT). Exchange potentials are treated using the Generalized Gradient Approximations (GGA). Cohesive energy calculations reveal that the ferromagnetic phase of LiMn 1. 7 5 Nd 0. 2 5 O4 and the antiferromagnetic phase of Cu4Mn2Te4 exhibits a stable phase. Of these, FM-LiMn 1. 7 5 Nd 0. 2 5 O4 shows a semi-metallic-like behavior in spin-up channel and metallic behavior in spin-down channel whereas antiferromagnetic Cu4Mn2Te4 exhibits a band gap in both spin-up and spin-down channels. Dirac points are identified at −0.0625 eV in the band structure plot of FM-LiMn 1. 7 5 Nd 0. 2 5 O4 at its high symmetry points Γ and W which is an indication of high electron mobility at ambient condition. The presence of flat and dispersive bands around the Fermi energy level is an indication of high thermopower, and it is present in both the compounds FM-LiMn 1. 7 5 Nd 0. 2 5 O4 and AFM-Cu4Mn2Te4. From the present computations, at 300 K, a power factor range of ( S 2 σ scaled by relaxation time in μ W/msK2) 1. 7 5 × 1 0 2 0 ↑ and 9. 3 7 × 1 0 2 1 ↓ is obtained for ferromagnetic LiMn 1. 7 5 Nd 0. 2 5 O4 compounds at up and down spins, respectively. A typical power factor (μ Wm − 1 s − 1 K − 2 ) of 4. 7 9 × 1 0 1 5 ↑ and 2. 9 7 × 1 0 1 8 ↓ is obtained for antiferromagnetic Cu4Mn2Te4 at 325 K required for good thermoelectric performance. [ABSTRACT FROM AUTHOR]

In this study we investigate a relatively new material for terahertz (THz) photoconductive antennas (PCAs): GaAs epitaxial films grown on (111)A-oriented semi-insulated GaAs substrates and doped with Si. GaAs:Si (111)A films with the required high resistance without postgrowth annealing have been grown by molecular-beam epitaxy. The Si doping of (111)A-oriented GaAs was expected to lead to the formation of acceptors that facilitate the activation of As Ga + traps. The relaxation times of nonequilibrium charge carriers in the films were measured in pump-probe experiment, and, finally, the electron mobility was estimated from the carrier lifetime and current–voltage characteristics measured under pulsed pumping by Ti:sapphire femtosecond laser. Dipole and bow-tie PCAs were fabricated, and the THz emission spectra and the total THz emission power were measured with varying applied voltage and optical excitation power. The properties of GaAs:Si (111)A films and the PCAs based on them are compared with LTG-GaAs (100) and (111)A-oriented films. [ABSTRACT FROM AUTHOR]

Two-dimensional materials have excellent electronic and optical properties, suggesting absolute advantages in nanodevices. In this work, a new two-dimensional material with a puckered structure, a C2B6 monolayer, is proposed. The material presents dynamic and thermal stability calculated by first-principle simulations. Interestingly, the C2B6 monolayer possesses semiconductor behavior with an ultra-narrow bandgap of approximately 0.671 eV by HSE06 functional. Meanwhile, the hole in the C2B6 monolayer shows ultrahigh mobility at approximately 6,342 cm2⋅V−1⋅s−1 in decent transport directions, which is larger than traditional transition metal dichalcogenides materials. More importantly, the pronounced anisotropy of mobility of the electrons and holes can separate the photogenerated charges, suggesting the applications for photocatalytic, photovoltaic and optical and cold chain electronic devices. Then, the novel properties of the light absorption characteristic are obtained, and the anisotropic photocurrent implies the C2B6 monolayer can be used as a potential photoelectric device. Our results provide theoretical guidance for the design and application of two-dimensional materials. [ABSTRACT FROM AUTHOR]

High‐mobility emissive n‐type polymer semiconductors (HMEN‐CPs) are essential for organic optoelectronic devices. However, due to the lack of highly electron‐deficient building blocks with excellent physicochemical properties and the molecular design trade‐offs, the development of HMEN‐CPs has significantly lagged behind that of p‐type counterparts. Here, a new electron‐deficient acceptor, TFBVDPP is developed, by integrating the efficient carrier‐transporting diketopyrrolopyrrole and intense light‐emitting phenylene‐vinylene into a single molecule system. A series of all‐acceptor‐type polymers are synthesized by Pd‐catalyzed Suzuki polycondensation. The introduction of a vinyl bridge induces intra‐/intermolecular non‐covalent interactions, significantly narrowing the optical bandgap while enhancing coplanarity and crystallinity of the conjugated backbone, thus one of the polymers P1 exhibits ideal ambipolar transports with hole and electron mobilities reaching 4.6 and 3.7 cm2 V−1 s−1, respectively. Additionally, by directly homopolymerizing TFBVDPP, the non‐radiative transition is effectively suppressed, maintaining high electron transport while enhancing emission. This system shows excellent unipolar electron mobility (µe) and high quantum yield (Φ), achieving a record Φ · µe value exceeding 10−2 cm2 V−1 s−1, which is at least three orders of magnitude higher than the reported values. This study provides a new approach for developing HMEN‐CPs, and demonstrates their great potential in advancing organic optoelectronic technologies. [ABSTRACT FROM AUTHOR]

The unbalanced electron‐hole mobility is the major bottleneck for boosting the photovoltaic performance of organic solar cells. In this study, 2D n‐type inorganic semiconductor material tin sulfide (SnS) is prepared and introduced into the PM6:Y6 bulk heterojunction organic solar cells to improve photovoltaic performance. The incorporation of SnS promotes Y6 crystallization, and renders the face‐on orientation of Y6 molecules dominant. The improved active layer morphology suppresses carrier recombination and strengthens the electron transport. The electron mobility increases significantly from 4.71 × 10−4 cm2 V−1 s−1 to 7.61 × 10−4 cm2 V−1 s−1 with the hole/electron mobilities (µh/µe) value reducing from 1.67 to 1.11. With enhanced and balanced carrier mobility, the open‐circuit voltage, short‐circuit current density and fill factor of the SnS‐doped PM6:Y6 organic solar cells are improved simultaneously, and the power conversion efficiency is boosted from 16.66 to 18.50%. Additionally, the SnS doped devices exhibit better thermal and storage stability. The improved photovoltaic performance is further verified in PM6:L8‐BO and D18:Y6 based organic solar cells. This work demonstrates that n‐type SnS dopant is an efficient and universal method to improve photovoltaic performance of non‐fullerene organic solar cells. [ABSTRACT FROM AUTHOR]

Flexible perovskite solar cells (PSCs) have received great attention due to their low weight, high power ratio, and potential applications in wearable electronic products. The efficiency and stability of flexible PSCs are directly affected by the carrier extraction and transport capabilities of electron transport layer. Herein, efficient flexible PSCs are prepared through incorporating 2,5‐Furandicarboxylic acid (FDCA) multifunctional intermediate layer between tin oxide (SnO2) and perovskite, which can effectively eliminate defects at the interfacial to increase the electron mobility of the SnO2 layer, modify the surface of SnO2 to shift the conduction band upward to improve interface charge extraction, passivate the buried interface of perovskite to induce larger perovskite crystal growth, and establish a bridge between SnO2 and perovskite to improve charge collection efficiency. As a result, the rigid PSCs with FDCA display a champion power conversion efficiency (PCE) of 24.53% with a high open circuit voltage (VOC) of 1.204 V. Furthermore, the flexible device with FDCA achieves a high PCE of 22.10%, and preserve 90% of its initial PCE after aging for 500 h at ambient condition without encapsulation, and maintain 81% of its original PCE after 10,000 bending cycles. [ABSTRACT FROM AUTHOR]

Organic electrochemical transistors (OECTs) are of great interest owing to their potential applications in bioelectronics and neuromorphic systems. However, n‐type OECTs suffer from poor stability and facile degradation, mainly due to the oxygen reduction reactions in organic mixed ionic‐electronic conductors during device operation. In this study, a small‐molecule passivation strategy is introduced to greatly improve the stability of poly(benzobisimidazobenzophenanthroline) (BBL)‐based n‐type OECTs. 6,6‐Phenyl‐C61‐butyric acid methyl ester (PCBM) is spin‐coated onto the BBL layer to form a smooth and hydrophobic passivation layer, which effectively inhibits the oxygen reduction reactions while enabling ion permeation in aqueous electrolytes. Consequently, the OECTs employing the PCBM/BBL bilayers with an optimized PCBM thickness exhibit significantly improved operational stability at various electrolyte conditions (0.1 m NaCl or NaOH) and over a wide gate‐voltage sweep range (from −0.7 to 0.7 V). Owing to the high electron mobility of PCBM, the carrier mobility and switching speed of the PCBM/BBL OECTs are also improved compared with those of the pristine BBL OECTs. This study demonstrates the beneficial effects of simple surface passivation in organic mixed ionic‐electronic conductors and provides valuable insights for the design of high‐performance and stable OECTs for more specialized and advanced applications. [ABSTRACT FROM AUTHOR]

Exciton diffusion and carrier transport are two critical factors that determine the efficiency of organic photovoltaics (OPVs). However, the relationship between these two factors has not been extensively studied. Designing non‐fullerene acceptors (NFAs) with efficient diffusion coefficients and high electronic transmittance is a key area of focus. In this study, materials for bulk‐heterojunction (BHJ) and quasiplanar‐heterojunction (Q‐PHJ) devices are synthesized to validate the desired differences in crystallinity. The single crystal of BOBO4Cl‐βδ demonstrated the most compact packing structure, with an improved planar configuration and closer π···π distances, resulting in higher electron mobility and superior exciton diffusion coefficient. Consequently, BOBO4Cl‐βδ‐based devices achieved a power conversion efficiency (PCE) of 17.38% in Q‐PHJ, compared to a lower PCE of 14.75% in BHJ devices. Furthermore, incorporating BOBO4Cl‐βδ into the D18/L8‐BO Q‐PHJ system increased the PCE from 17.98% to 18.81%, one of the highest values recorded for Q‐PHJ devices. This improvement is attributed to strong crystallinity of BOBO4Cl‐βδ, which enhances the packing arrangement and improves the exciton diffusion coefficient. Our work highlights the importance of molecular design with tunable exciton diffusion and carrier transport for BHJ and Q‐PHJ OPV architectures and reveals the relationship between them, which contributes to the achievement of high‐performance NFAs. [ABSTRACT FROM AUTHOR]

Composites consisting of two nano-or molecular-scale components tend to exhibit newer properties or characterizations compared to the matrix material. However, they are extremely limited in thermoelectricity due to the difficulty of achieving an extremely homogeneous distribution of the material on such a small scale. In this paper, we successfully prepared a series of composite thermoelectric materials of Sr 0.9 La 0.1 Ti 0.85 Nb 0.15 O 3 /carbon nanotubes (CNTs, with contents of 0.5, 1.5, 2.5, and 5.0 wt%). Highly homogeneous dispersion of CNTs was observed in the strontium titanate oxide (SrTiO 3) matrix prepared via high-temperature and high-pressure (HPHT) synthesis due to the interaction between SrTiO 3 and multi-walled CNTs. The experimental results showed that CNTs were uniformly dispersed in the composite powders synthesized using the HPHT method. Meanwhile, the electrical conductivity increased linearly with the increase in the CNTs content. The power factor reached 684 μWm−1K−2 at 973K with 2.5 wt% CNTs composite concentration. This considerable enhancement is attributed to the increase in the charge carrier concentration as well as the higher electron mobility. In addition, the lattice thermal conductivity was suppressed due to enhanced Umklapp scattering. This ultimately leads to a thermoelectric figure of merit, zT , of 0.33 at 973 K. This work opens a new window on the thermoelectric properties of nanocomposite SrTiO 3 -based thermoelectric materials. [ABSTRACT FROM AUTHOR]

The heterojunctions based transition metal carbide (MXenes) provides new possibilities for achieving high-performance photodetector. The electronic, mechanical, optical, and photocatalytic properties of the Hf 2 CO 2 -based heterojunctions are calculated based on first-principles calculations, and the photocurrent (I ph) and extinction ratio (ER) are calculated based on quantum transport simulations. The Hf 2 CO 2 /Sc 2 CF 2 , Hf 2 CO 2 /Zr 2 CO 2 , and Hf 2 CO 2 /Sc 2 CCl 2 heterojunctions are ionic semiconductors with indirect bandgap. The Hf 2 CO 2 /Sc 2 CF 2 heterojunction exhibits high solar to hydrogen efficiency (η STH) of 40.14 % and applying biaxial strain can effectively modulate the η STH of the Hf 2 CO 2 /Zr 2 CO 2 heterojunction. The Hf 2 CO 2 /Zr 2 CO 2 heterojunction has low overpotentials (ηHER) of 0.19 V and exhibits high electron mobility. The photodetector based on the Hf 2 CO 2 /Zr 2 CO 2 heterojunction exhibits high I ph , and the photodetector based on the Hf 2 CO 2 /Sc 2 CF 2 heterojunction has large ER and sensitivity to infrared and ultraviolet polarized light. The I ph and ER are significant increase by bending the photodetector. Our research indicates the potential applications of the Hf 2 CO 2 -based heterojunctions in photocatalytic water splitting and photodetector. [Display omitted] [ABSTRACT FROM AUTHOR]

The metal‐organic vapor phase epitaxy (MOVPE) method faces several challenges when used for the growth of N‐polar GaN on foreign substrates, including the presence of a rough surface morphology characterized by step bunching or hexagonal hillocks. In this study, it is aimed to address these issues by establishing optimal growth conditions for the MOVPE method, enabling the growth of N‐polar GaN/Al0.9Ga0.1N/AlN heterostructures with a smooth surface morphology on a vicinal sapphire substrate. The formation of 2D electron gas (2DEG) in N‐polar GaN/AlGaN/AlN prepared using MOVPE is discussed. Additionally, in the study, the impact of growth conditions, such as temperature and V/III ratio, on the electrical properties of N‐polar GaN is investigated. In the results, it is revealed that growth at lower temperatures and a V/III ratio of 30 000 effectively suppresses 3D growth. Moreover, an increase in the V/III ratio correlates with a decrease in residual impurity concentrations (C and H); hence, electron mobility improves. Moreover, the N‐polar GaN/AlGaN/AlN field‐effect transistor, grown under optimized conditions, exhibits a higher maximum drain–source current (IDmax). In these results, possibilities are broadened for the high performance of N‐polar GaN channel high‐electron‐mobility transistors through MOVPE. [ABSTRACT FROM AUTHOR]

Recently, N‐polar GaN/AlGaN/AlN high‐electron‐mobility transistors (HEMTs) have been demonstrated using molecular beam epitaxy (MBE). However, the MBE method is not suitable for mass production because of the need for ultrahigh vacuum, small chamber size, and long deposition time. This study fabricates N‐polar GaN‐ or AlGaN‐channel HEMTs on AlN with polarization directions opposite to those of Ga‐polar GaN‐based HEMTs without any cap layer and demonstrates field‐effect transistor static characteristics. In this article, the focus is on the crystal quality of the underlying layer and the effect of crystalline quality on electrical properties is investigated. The crystalline quality of the twist component of the N‐polar AlN layer is improved by combining the Al‐polar tiny‐pit layer and polarity inversion from Al‐ to N‐polar. Finally, it is shown that the crystalline quality of the twist component is a crucial factor for improving the electron mobility of the N‐polar GaN channel and simultaneously increasing IDS. [ABSTRACT FROM AUTHOR]

The epitaxial growth of heavily Ge‐doped GaN films using pulsed sputtering deposition (PSD) on AlN (0001)/sapphire substrates is presented and the correlations among their structural, electrical, and optical properties are investigated. High‐quality Ge‐doped PSD‐GaN films are grown with electron concentrations of 0.33–4.4 × 1020 cm−3. Notably, cathode luminescence spectra reveal the absence of defect‐induced emissions associated with Ga vacancies (2.3–2.4 eV), consistent with the high electron mobilities of the films. As the electron concentration increases, the optical bandgap also increases. This correlation can be explained by combining the theoretical formulas for the Burstein–Moss shift and the bandgap renormalization effects. Remarkably, the optical bandgap reaches 3.84 eV at 4.4 × 1020 cm−3 carrier concentration, marking the highest value reported for the optical bandgap of GaN. These results indicate the potential of heavy Ge doping in GaN via PSD for applications in highly transparent conductive layers and tunneling junctions within GaN‐based optoelectronic devices. [ABSTRACT FROM AUTHOR]

The failure process caused by overvoltage stress in cascode GaN–field effect transistors (FETs) is discussed through single unclamped inductive switching (UIS) waveforms, burst UIS waveforms, and capacitance–voltage characteristic shifts. One of the critical disadvantages of GaN–high electron mobility transistors (HEMTs) is their lack of UIS withstand capability, primarily because there is no mechanism for removing holes generated by avalanche breakdown. The device failure is observed at the drain voltage peak in the single UIS, and sudden and random breaks are observed in the burst UIS even with the same overvoltage stress. Both hole and electron traps after the burst UIS are observed, and the failure position is at the chip edge. From these results, it is verified that cascode GaN–FETs are broken due to time‐dependent dielectric breakdown of passivation films. [ABSTRACT FROM AUTHOR]

Indium phosphide (InP) is widely utilized in the fields of electronics and photovoltaics due to its high electron mobility and high photoelectric conversion efficiency. Strain engineering has been extensively employed in semiconductor devices to adjust physical properties and enhance material performance. In the present work, the band structure and electronic effective mass of InP under different strains are investigated by ab initio calculations. The results show that InP consistently exhibits a direct bandgap under different strains. Both uniaxial strain and biaxial tensile strain exhibit linear effects on the change in bandgap values. However, the bandgap of InP is significantly influenced by uniaxial compressive strain and biaxial tensile strain, respectively. The study of the InP bandgap under different hydrostatic pressures reveals that InP becomes metallic when the pressure is less than −7 GPa. Furthermore, strain also leads to changes in effective mass and the anisotropy of electron mobility. The studies of electronic properties under different strain types are of great significance for broadening the application of InP devices. [ABSTRACT FROM AUTHOR]

Indium phosphide (InP) is an excellent material used in space electronic devices due to its direct band gap, high electron mobility, and high radiation resistance. Displacement damage in InP, such as vacancies, interstitials, and clusters, induced by cosmic particles can lead to the serious degradation of InP devices. In this work, the analytical bond order potential of InP is modified with the short-range repulsive potential, and the hybrid potential is verified for its reliability to simulate the atomic cascade collisions. By using molecular dynamics simulations with the modified potential, the primary damage defects evolution of InP caused by 1–10 keV primary knock-on atoms (PKAs) are studied. The effects of electronic energy loss are also considered in our research. The results show that the addition of electronic stopping loss reduces the number of point defects and weakens the damage regions. The reduction rates of point defects caused by electronic energy loss at the stable state are 32.2% and 27.4% for 10 keV In-PKA and P-PKA, respectively. In addition, the effects of electronic energy loss can lead to an extreme decline in the number of medium clusters, cause large clusters to vanish, and make the small clusters dominant damage products in InP. These findings are helpful to explain the radiation-induced damage mechanism of InP and expand the application of InP devices. [ABSTRACT FROM AUTHOR]

In polarizable materials, electronic charge carriers interact with the surrounding ions, leading to quasiparticle behavior. The resulting polarons play a central role in many materials properties including electrical transport, interaction with light, surface reactivity, and magnetoresistance, and polarons are typically investigated indirectly through these macroscopic characteristics. Here, noncontact atomic force microscopy (nc-AFM) is used to directly image polarons in Fe2O3 at the single quasiparticle limit. A combination of Kelvin probe force microscopy (KPFM) and kinetic Monte Carlo (KMC) simulations shows that the mobility of electron polarons can be markedly increased by Ti doping. Density functional theory (DFT) calculations indicate that a transition from polaronic to metastable free-carrier states can play a key role in migration of electron polarons. In contrast, hole polarons are significantly less mobile, and their hopping is hampered further by trapping centers. [ABSTRACT FROM AUTHOR]

The investigation of aluminum gallium nitride/gallium nitride high electron mobility transistor (AlGaN/GaN HEMT) devices with a dual‐metal gate (DMG) structure encompasses both electrical and thermal characteristics. As efforts to enhance heat dissipation progress, there is a concurrent exploration of novel semiconductor materials boasting high thermal conductivity, like boron arsenide and phosphide. Combining these materials into a model and measuring their interface achieves efficient energy transport. Minimizing the self‐heating impact in AlGaN/GaN HEMTs is essential for enhancing device efficiency. This research exposes the heterogenous combination of boron arsenide and phosphide cooling substrates with metals, GaN semiconductors and HEMT. In this research, the autoencoder deep neural network techniques in GaN HEMT for self‐heat reduction is driven by the ability to effectively analyze and model the thermal behavior of the device. Autoencoders learn complex relationships within temperature data and identify patterns associated with self‐heating. By leveraging these learned representations, the deep neural network optimizes control strategies to mitigate self‐heating effects in GaN HEMT devices, ultimately contributing to improved thermal management and enhanced overall performance. In this research, the use of genetic algorithms in GaN HEMT aims to optimize device parameters systematically, to minimize self‐heating effects and enhance overall thermal performance. The structure also enhances electron mobility within the channel. Results show DMG structures, exhibiting higher saturation output currents and transconductance despite self‐heating. The DMG exhibits a maximum gm value of 0.164 S/mm, which is 10% higher significantly enhancing GaN‐based HEMTs for improved reliability and efficiency in various applications. [ABSTRACT FROM AUTHOR]

In this proposed work focuses to overcome the traditional doping challenges in L-shaped tunnel field transistors by using charge plasma (CP) concept and increase current conduction by forming heterogeneous junction (SiC-Si-SiC). Silicon carbide is used for the material for Source and Drain. The concept of charge plasma is implemented in the source and drain regions by implementing different work functions and to improve current conduction the source and drain regions is made of Silicon Carbide and the channel is made of Silicon which forms heterojunction which creates horizontal tensile strain and vertical compressive strain in the channel region which increases electron mobility mainly for low-power semiconductor applications. The performance of device parameters like the transfer characteristics subthreshold swing, output characteristics have been described. Analysis of Threshold Voltage, drain current and ION/IOFF ratio have been carried for CP based L-TFET. Sentaurus Technology Computer Aided Design (TCAD) has been used to evaluate and analyze the device for the CP-based TFET. The device was simulated in the Sentaurus TCAD in which the certain parameters are evaluated in which certain models such as, Slotboom model is applied to consider the impact of doping concentrations on energy bandgap narrowing in the source/drain (S/D) regions. Also, Fermi statistics and Shockley-Read-Hall recombination models are used. The inclusion of charge plasma and SiC in the device improves the electron mobility and current conduction is improved with less leakage current and can be used for low power applications such as inverter, memory devices. [ABSTRACT FROM AUTHOR]

The escalating interest in 2D nanoflakes‐based group‐IVA metal chalcogenides is attributed to their noteworthy properties, such as high electron mobility, exceptional chemical stability, and applicability across diverse scientific disciplines such as sensing, energy storage applications, supercapacitors, and lithium‐ion batteries. This study introduces an innovative self‐powered photodetector based on 2D metal chalcogenide nanoflakes (SnS2 and SnSe2) formed into nanoflowers on a silicon substrate through the hydrothermal method. The amalgamation of the light‐induced pyroelectric effect into the SnS2 photodetector achieves impressive enhancement ratios of 353%, 425%, 351%, 662%, and 153% in photoresponsivity and detectivity compared to the photovoltaic effect at 365, 456, 532, 632, and 850 nm, respectively, at zero bias. The SnSe2 photodetector achieved responsivity values of 14, 82, 36, 4, and 28 mA W−1 at the corresponding wavelengths in self‐powered mode. The SnSe2 device exhibits superior photosensitivity of 30792%, 55692%, 28803%, 9678%, and 68587% at the corresponding wavelengths, under zero bias. In addition, the photocurrent response caused by the photovoltaic‐pyroelectric effect is thoroughly defined, and the impacts of light wavelength, power intensity, and bias voltage are studied. This study presents a cutting‐edge self‐powered broadband photodetector utilizing pyroelectric materials and opens possibilities for designing high‐performance, fast photodetectors based on the pyro‐phototronic effect. [ABSTRACT FROM AUTHOR]

Exceptional interlayer coupling of organic–inorganic vdWHs is paramount for enhancing electron mobility. Herein, we report a novel transfer-free method to fabricate MoSe2/Ni3(HITP)2 vdWHs. The MOF film promotes interfacial charge transfer, leading to a threefold increase in electron mobility. This work provides a platform for developing high-performance optoelectronic devices. [ABSTRACT FROM AUTHOR]

In this study, a novel GaP/SiH heterostructure was successfully predicted and constructed. Subsequently, an in-depth and systematic investigation was conducted to explore its structural, electronic, transport and optical properties. The calculated structural performance results revealed that the GaP/SiH heterostructure was a typical type-II van der Waals heterostructure, exhibiting excellent energy stability, mechanical stability and thermodynamic stability. In particular, the formation of the GaP/SiH heterostructure significantly reduced the bandgap of the materials to 2.24eV, and the type-II energy band arrangement effectively suppressed the recombination of photogenerated carriers. Furthermore, the biaxial and vertical strains could finely modulate the electronic structure of the GaP/SiH heterojunction. The electron mobility of the GaP/SiH heterostructure was measured to be 1573.91 cm2 V⁻1 s⁻1, indicating its superior charge carrier transport capabilities. Meanwhile, the GaP/SiH heterostructure also exhibited excellent optical absorption performance in the visible and UV region up to 2.34 × 106 cm−1. Thus, the GaP/SiH heterostructure will be a strong candidate for photocatalytic applications due to its excellent light absorption properties, electrical properties, and stability. • Predicted high-mobility Type-II GaP/SiH heterostructure for photocatalytic. • Type-II band alignment in GaP/SiH for enhanced carrier recombination suppression. • Tunable electronic structure of GaP/SiH heterojunction via strain engineering. • Optimized band gap and absorption for GaP/SiH in photocatalytic applications. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) without hole transport layer (HTL) based on organic and inorganic metal halide perovskite have received vast consideration in recent years. For predigestion of device structure and construction process, the exclusion of the HTL is a marvelous way. By detaching the HTL part of the devices, we could reduce the cost and complexity of the structures. Currently, a novel 2D material named Ti3C2 MXene with high electron mobility, excellent metallic conductivity and functionalized surface groups applied for tuning the energy offsets has been reported to be added in the perovskite absorber layer, leading to a remarkable power conversion efficiency (PCE) improvement. In this work, the role of MXenes in controlling the work function of the involved layers to modify the band alignment towards better performance of the cells is explained. Two HTL free structures of FTO/mTiO2/cTiO2/MAPbI3/Spiro-OMeTAD/Au named as HFRC, and FTO/mTiO2+MXene/cTiO2+MXene/MXene/MAPbI3+MXene/Spiro-OMeTAD/Au named as HFMC were simulated by SCAPS-1D software to study the response of the photovoltaic devices and obtain the highest possible efficiency considering the physics behind. To the best of our knowledge, this is the first time such structures and the results of the current simulation are studied that may be used as a guideline for other practical purposes. We present a modeling procedure that optimizes the thickness of the involved layers and specifies the optimum level of the doping concentration. We also show that by optimizing the work function of the back contact, the device performance witnesses a significant improvement, proving the considerable role of the back contact in these cells. The simulated HTL-free devices illustrate attainably PCEs of about 20.32% and 21.04% for the cells without and with MXene, under AM 1.5G illumination and absorption up to 760 (nm). [ABSTRACT FROM AUTHOR]

Strain engineering is an effective method to tune the physical properties of materials. In this work, we found that applying 5% biaxial compression to monolayer boron sulfur can simultaneously induce a band order reversal of valence bands and valley engineering of conduction bands. This change significantly enhances the room temperature intrinsic mobility, boosting it from 2 to 260 cm2 V−1 s−1 for holes and 63 to 543 cm2 V−1 s−1 for electrons. The high hole mobility surpasses that of bulk GaN and silicon. We further demonstrate that the valence band order reversal not only lifts the px/y state above the pz states, giving to a more dispersive highest valence band, and thus smaller electron scattering channels and hole effective mass, but also shifts the stronger σz bonding to weaker π-bonding characteristics, resulting in smaller electron–phonon coupling strength. Those combined effects results in a substantial increase in hole mobility. [ABSTRACT FROM AUTHOR]

As a promising 2D material, bismuth oxyselenide (Bi2O2Se) has demonstrated significant potential to overcome existing technical barriers in various electronic device applications due to its unique physical properties like high symmetry, adjustable electronic structure, and ultra-high electron mobility. However, the rapid growth of Bi2O2Se films down to a few atomic layers with precise control remains a significant challenge. In this work, the growth of two-dimensional (2D) Bi2O2Se thin films by the pulsed laser deposition (PLD) method is systematically investigated. By controlling temperature, oxygen pressure, laser energy density, and laser emission frequency, we finally prepare atomically thin and flat Bi2O2Se (001) thin films on the (001) surface of SrTiO3. Importantly, we provide a fundamental and unique perspective toward understanding the growth process of atomically thin and flat Bi2O2Se films, and the growth process primarily proceeds in four steps. Moreover, the combined results of the crystallinity quality, surface morphology, and the chemical states demonstrate the PLD-growth of high-quality Bi2O2Se films in a controllable and fast mode. [ABSTRACT FROM AUTHOR]

For the first time, we present the detailed synthesis, photophysical, electrochemical, host–guest and charge transport properties of spiro[fluorene-9,9′-xanthene] (SFX) and carbazole macrocycle SPS-NR-02. The electron and hole transport values measured using the space charge limited current (SCLC) method resulted in ambipolar charge transport with an electron to hole mobility ratio of 0.39. [ABSTRACT FROM AUTHOR]

Fullerene derivatives are extensively employed in inverted perovskite solar cells due to their excellent electron extraction capabilities. However, [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) agglomerates easily in solution and exhibits a relatively low ionization barrier, increasing charge recombination losses and charge accumulation in the interface. Here, tetramethylthiuram disulfide (TMDS) is introduced into the PCBM solution to induce the formation of reducing sulfur radicals through UV light irradiation, allowing for n doping of the PCBM material. The resulting modified PCBM layer exhibits enhanced conductivity and electron mobility, significantly suppressing charge recombination. As a result, the resulting devices incorporating TMDS achieve a champion efficiency of 26.10% (certified 25.39%) and 24.06% at a larger area (1.0 cm2) with negligible hysteresis. More importantly, the optimized devices retain 95% and 90% of their initial efficiency after 1090 h under damp heat testing (85 °C and 85% relative humidity) and after 1271 h under maximum power point-tracking conditions, respectively. Fullerene derivatives tend to increase charge recombination losses and charge accumulation at the interface in inverted perovskite solar cells. Here, authors introduce tetramethylthiuram disulfide to induce formation of sulfur radicals for n-doping, achieving efficiency of 26.1% in stable devices. [ABSTRACT FROM AUTHOR]

The study of charge transfer in thin film solar cells made of several layers is of high importance since they may lose their energy via the recombination process at the interfaces, specifically at the interface of the electron transport layer (ETL) and perovskite. Titanium dioxide (TiO2) is mostly used as an ETL in perovskite solar cells due to its many advantages. However, TiO2 has some disadvantages, such as low electron mobility compared to the perovskite layer and electron trap states on its top at the interface. These effects cause the accumulation of carriers at the ETL/perovskite interface then the non-radiative recombination will be enhanced, which is considered as one of the significant losses in the Perovskite Solar Cells (PSCs). In this work, a new technique is taken for more optimal ETL doping. We fabricated the ETL layers with graded doping of platinum quantum dots (Pt QDs), in which Pt QDs concentration is high at the ETL/Perovskite interface and zero at the FTO/ETL interface. This strategy not only suppresses the recombination at the ETL/perovskite interface and subsequently enhances the device efficiency from 12.92 to 14.36% but also improves the stability of the PSCs. [ABSTRACT FROM AUTHOR]

Light‐emitting diodes (LEDs) based on perovskite quantum dots (QDs), abbreviated as P‐QLEDs have been regarded as significantly crucial emitters for lighting and displays. Efficient and stable P‐QLEDs still lack ideal electron transport materials (ETM), which could efficiently block hole, transport electron, reduce interface non‐radiative recombination and possess high thermal stability. Here, we report 2,4,6‐Tris(3′‐(pyridine‐3‐yl) biphenyl‐3‐yl)‐1,3,5‐triazine (TmPPPyTz, 3P) with strong electron‐withdrawing moieties of pyridine and triazine to modulate the performance of P‐QLEDs. Compared with commonly used 1,3,5‐Tris(1‐phenyl‐1H‐benzimidazol‐2‐yl)benzene (TPBi), the pyridine in 3P have a strong interaction with perovskites, which can effectively suppress the interface non‐radiative recombination caused by the Pb2+ defects on the surface of QDs. In addition, 3P have deep highest occupied molecular orbital (HOMO) (enhancing hole‐blocking properties), matched lowest unoccupied molecular orbital (LUMO) and excellent electron mobility (enhancing electron transport properties), realizing the carrier balance and maximizing the exciton recombination. Furthermore, high thermal resistance of 3P obviously improves the stability of QDs under variable temperature, continuous UV illumination, and electric field excitation. Resultantly, the P‐QLEDs using the 3P as ETM achieved an outstanding performance with a champion EQE of 30.2 % and an operational lifetime T50 of 3220 hours at an initial luminance of 100 cd m−2, which is 151 % and about 11‐fold improvement compared to control devices (EQE=20 %, T50=297 hours), respectively. These results provide a new concept for constructing the efficient and stable P‐QLEDs from the perspective of selective ETM. [ABSTRACT FROM AUTHOR]

Zinc and Manganese vanadates are highly regarded as potential photoanode materials for photoelectrochemical (PEC) water splitting due to their limited bandgap, varying optical and electrical characteristics based on their composition, and robust nature. To advance the practical use these materials, it is essential to creating precisely composed and structured Zinc and Manganese vanadates to enhance their overall effectiveness. In this work, we employed various morphologies, such as nanobelt flower like Zinc vanadate (ZV), nano-needle like Manganese vanadate (MV), a composite with ZV and MV, and a ZV-MV@CNF ternary composition. These novel morphologies grown on ITO substrate using a simple, hydrothermal approach without using any seed layer. The structural, surface, and optical examinations confirmed that the ZV-MV@CNF catalyst had superior visible light absorption, accelerated charge transfer, heterojunction interface between ZV and MV, and increased electron mobility, leading to outstanding photoelectrochemical performance. The photocurrent density of the ZV-MV@CNF photoanode reached 6.59 mA cm−2 at 1 V versus Ag/AgCl in a 0.25 M KOH solution under the illumination light. These results are ∼3.00, 3.52, and 1.28 times greater than the pristine ZV, MV, and ZV-MV, respectively. The fine-tuned ZV, MV, ZV-MV, and ZV-MV@CNF electrodes showed applied bias photon to current efficiency (ABPE) values of 0.09 %, 0.06 %, 0.14 %, and 0.18 %, respectively. The improved photoelectrochemical behavior of the ZV-MV@CNF electrode is credited to the excellent light absorption, and the remarkable catalytic and charge transport capabilities of CNFs. Therefore, these experimental results and characterization analysis suggested that advanced hierarchical nanostructures hold significant promise for water splitting applications. [ABSTRACT FROM AUTHOR]

Strain engineering is a widely used technique for enhancing the mobility of charge carriers in semiconductors, but its effect is not fully understood. In this work, we perform first-principles calculations to explore the variations of the mobility of electrons and holes in silicon upon deformation by uniaxial strain up to 2% in the [100] crystal direction. We compute the π11 and π12 electron piezoresistances based on the low-strain change of resistivity with temperature in the range 200 K to 400 K, in excellent agreement with experiment. We also predict them for holes which were only measured at room temperature. Remarkably, for electrons in the transverse direction, we predict a minimum room-temperature mobility about 1200 cm2 V−1 s−1 at 0.3% uniaxial tensile strain while we observe a monotonous increase of the longitudinal transport, reaching a value of 2200 cm2 V−1 s−1 at high strain. We confirm these findings experimentally using four-point bending measurements, establishing the reliability of our first-principles calculations. For holes, we find that the transport is almost unaffected by strain up to 0.3% uniaxial tensile strain and then rises significantly, more than doubling at 2% strain. Our findings open new perspectives to boost the mobility by applying a stress in the [100] direction. This is particularly interesting for holes for which shear strain was thought for a long time to be the only way to enhance the mobility. [ABSTRACT FROM AUTHOR]

La10−xNdxSi6O27 (x = 0, 0.1, 0.2, 0.3) was synthesized via planetary grinding, and dense ceramic discs were prepared using SPS technology. The structure, microstructure, density, open porosity, total conductivity and electronic conductivity of the samples were measured and analyzed, respectively. La10−xNdxSi6O27 is characterized by a hexagonal apatite structure. The elements in the sample are distributed in a uniform manner and the content is consistent with the stoichiometry. The total conductivity of La10−xNdxSi6O27 exhibits an increase with the incorporation of Nd3+ content in the doped samples of x = 0.1, 0.2, and 0.3. The total conductivity of La9.7Nd0.3Si6O27 is the highest, reaching 5.39 × 10−3 S cm−1 at 850 °C. The electron mobility of the sample is less than 1%, which is suitable for use as a solid electrolyte. [ABSTRACT FROM AUTHOR]