Hole Mobility Research Articles

Semiconducting Properties of Delaminated Titanium Nitride Ti4N3Tx MXene with Gate-Tunable Electrical Conductivity.

MXenes have garnered significant attention due to their atomically thin two-dimensional structure with metallic electronic properties. However, it has not yet been fully achieved to discover semiconducting MXenes to implement them into gate-tunable electronics such as field-effect transistors and phototransistors. Here, a semiconducting Ti4N3Tx MXene synthesized by using a modified oxygen-assisted molten salt etching method under ambient conditions, is reported. The oxygen-rich synthesis environment significantly enhances the etching reaction rate and selectivity of Al from a Ti4AlN3 MAX phase, resulting in well-delaminated and highly crystalline Ti4N3Tx MXene with minimal defects and high content of F and O, which led to its improved hydrophobicity and thermal stability. Notably, the synthesized Ti4N3Tx MXene exhibited p-type semiconducting characteristics, including gate-tunable electrical conductivity, with a current on-off ratio of 5 × 103 and a hole mobility of ∼0.008 cm2 V-1 s-1 at 243 K. The semiconducting property crucial for thin-film transistor applications is evidently associated with the surface terminations and the partial substitution of oxygen in the nitrogen lattice, as corroborated by density functional theory (DFT) calculations. Furthermore, the synthesized Ti4N3Tx exhibits strong light absorption characteristics and photocurrent generation. These findings highlight the delaminated Ti4N3Tx as an emerging two-dimensional semiconducting material for potential electronic and optoelectronic applications.

A Perspective on tellurium-based optoelectronics

Tellurium (Te) has been rediscovered as an appealing p-type van der Waals semiconductor for constructing various advanced devices. Its unique crystal structure of stacking of one-dimensional molecular chains endows it with many intriguing properties including high hole mobilities at room temperature, thickness-dependent bandgap covering short-wave infrared and mid-wave infrared region, thermoelectric properties, and considerable air stability. These attractive features encourage it to be exploited in designing a wide variety of optoelectronics, especially infrared photodetectors. In this Perspective, we highlight the important recent progress of optoelectronics enabled by Te nanostructures, which constitutes the scope of photoconductive, photovoltaic, photothermoelectric photodetectors, large-scale photodetector array, and optoelectronic memory devices. Prior to that, we give a brief overview of basic optoelectronic-related properties of Te to provide readers with the knowledge foundation and imaginative space for subsequent device design. Finally, we provide our personal insight on the challenges and future directions of this field, with the intention to inspire more revolutionary developments in Te-based optoelectronics.

Preparation of Highly-Ordered Tetrabenzorporphyrin Films Controlled by Supramolecular Assemblies and Precursor Approach

The control of the orientation and packing structures of small organic semiconductor molecules is the important issue for the improvement of charge carrier mobilities of organic field effect transistors. Tetrabenzoporphyrin (BP) is one of the promising p-type organic semiconductors but solubility in organic solvents is very low. We have developed a precursor approach, where a spun-cast film of soluble precursor, tetra-bicyclo[2.2.2]octadiene-fused porphyrin (CP), was heated to obtain BP crystalline film by in-situ retro-Diels–Alder reaction. However, the obtained BP film is a polycrystalline film and the field-effect transistors (FETs) hole mobilities were 10-1~10-2 cm2V-1s-1[1]. Recently, we reported the effect of alkyl substituents at 5,15-positions of BP for the control of the molecular arrangement. The best performance of OFET hole mobility of 5,15-disubstituted BP was 4.1 cm2V-1s-1 [2, 3].A supramolecular strategy has attracted attentions as the effective method for the control of molecular arrangement in films. We applied the combination of supramolecular assembling method and the precursor approach to prepare well-ordered BP films. 5,15-Bis(p-dodecylamidephenyl)-CP was deposited on the substrate by drop-casting, spin-coating or dip-coating method, followed by the heating to 200 ºC for 10 min to give the corresponding 5,15-bis(p-dodecylamidephenyl)-BP films. The film morphologies of the BP were compared with 5,15-bis(p-dodecyloxyphenyl)-BP, which doesn’t include amide moieties for hydrogen-bonding, using UV-vis absorption spectroscopy, atomic force microscopy (AFM), X-ray diffraction (XRD) analysis, and p-polarized multiple-angle incidence resolution spectrometry (p-MAIRS) to clarify the effect of amide groups. OFET performance of the BPs will be also discussed to clarify the effect of intermolecular hydrogen bonding interaction.

Synthesis and Characterization of Epitaxially-Fused Quantum Dot Superlattices at the Single Grain Limit

Epitaxially-fused superlattices of colloidal quantum dots (QD epi-SLs) may exhibit electronic minibands and high-mobility charge transport, but doing so requires epi-SLs with extremely high degrees of spatial and chemical (compositional) uniformity. In this talk, I will discuss both our efforts to understand and improve the epi-SL formation process, as well as recent charge transport studies on single epi-SL grains.Epi-SLs are synthesized from a parent SL structure, typically composed of QDs with long insulating ligands. Over the past several years, we have developed insight into the physical and chemical mechanisms by which this parent SL structure is converted into an epi-SL. I will present detailed, multi-model structural characterization of the SL structures, which unveils the astonishing choreographic process by which millions of QDs rotate and translate, in concert, to form the epi-SL.This structural transformation is initiated by chemical changes to the QD ligand layer, usually through manual introduction of liquids into the SL film. Mechanistic studies into this ligand-exchange process reveal a multi-step chemical sequence that initiates with a simple acid-base reaction. We exploit this insight to fabricate epi-SLs by means of photochemical triggering (using ultraviolet illumination) rather than alternative “hands-on” techniques which suffer from poor experimental control and pronounced chemical inhomogeneity and structural damage in the films. The use of light to trigger the SL conversion process enables much finer control in both the temporal and spatial domains, opening the door to much larger-area SL films and direct photopatterning of epi-SLs.In the latter portion of the talk, I will present recent work charge transport studies in individual, highly-ordered PbSe QD epi-SL grains. One technical challenge in making these devices is the inherent mismatch in using traditional microfabrication techniques to make single-grained devices of air-sensitive materials. Here, we demonstrate the air-free fabrication of microscale field-effect transistors (μ-FETs) with channels consisting of single PbSe QD epi-SL grains (~ 1 -10 µm grain sizes) and analyze charge transport phenomena in these samples. The devices exhibit p-channel or ambipolar transport with a hole mobility as high as 3.5 cm2 V–1 s–1 at 290 K and 6.5 cm2 V–1 s–1 at 170–220 K, one order of magnitude larger than that of previous QD solids.

(Invited) Dynamic Relaxation of Charge Carrier Mobilities in Organic Photovoltaics

A non-fullerene small molecular acceptor (NFA) is a prominent molecule that shows moderate electron mobility and a narrow bandgap complementary to middle-bandgap p-type conjugated polymers, which leads to great improvement in the performance of organic photovoltaic (OPV) cells. However, little is known about the relaxation of charge carriers, which is key to efficient charge transport. Herein, we report simultaneous time-of-flight (TOF) and time-resolved microwave conductivity (TRMC) measurements[1] employing benzodithiophene-based polymer (PBDB-T):soluble C70-fullerere (PCBM) and PBDB-T:NFA (ITIC or Y6) blends, as benchmark systems[2, 3]. In addition to the conventional TOF mobilities, relaxation of the hole and electron mobility was evaluated by TRMC under an external electric field. Although PBDB-T:ITIC exhibited much faster relaxation than PBDB-T:PCBM, the relaxation in PBDB-T:Y6 was considerably moderate. This is consistent with the energetic disorder estimated from the photoabsorption onset. Interestingly, the slower relaxation of the electrons compared to the holes in PBDB-T:Y6 is in line with the preferred normal device structure. Our work deepens the understanding of the energetics of polymer:NFA blends and offers a basis for achieving efficient NFA properties.Reference[1] Y. Shimata, A. Saeki, J. Phys. Chem. C 121 (2017) 18351.[2] F. Hamada, A. Saeki, ChemSusChem 14 (2021) 3528.[3] S. Li, F. Hamada, R. Nishikubo, A. Saeki, Sustainable Energy Fuels 6 (2022) 756.

(Invited) An Unsymmetrical 5,15-Disubstituted Tetrabenzoporphyrin: Effect of Molecular Symmetry on the Packing Structure and Charge Transporting Property

One of the key issues in the development of organic field-effect transistor (OFET) materials is the improvement of charge mobility. Since charge mobility depends on intermolecular interactions in solid state, it is important to control the crystal structure. In the current mainstream OFET materials, such as acenes and heteroacenes, which have one-dimensionally (1D) extended polycyclic aromatic frameworks, the effect of substitution on the crystal structure has been intensively studied. On the other hand, some bulky (trialkylsilyl)ethynyl-substituted derivatives such as 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene) have been known to afford brickwork packing. In comparison, two-dimensionally (2D) extended π-conjugated molecules tend to form a sandwich herringbone, a co-facial herringbone, and a 1D columnar structure, due to their enhanced π−π interaction. The molecular design strategy to control the crystal structure of two-dimensional (2D) π-extended organic semi-conductors has not been intensively explored.We synthesized an unsymmetric tetrabenzoporphyrin derivative (TIPS-Ph-BP) to demonstrate the effect of molecular symmetry on crystal packing.1 An unsymmetric structure would make 2D π-stacking more stable than a one-dimensional (1D) columnar structure to counteract steric and electronic imbalance in the crystal. TIPS-Ph-BP formed an antiparallel slipped π-stacking and 2D herringbone-like structure as expected, but, it formed a dimeric herringbone packing consisting of slipped π-stacking in an antiparallel manner in the crystal. OFETs using TIPS-Ph-BP achieved the maximum hole mobility of 0.71 cm2 V-1 s-1 due to the partially 2D packing structure.Although TIPS-Ph-BP gave dimeric herringbone packing, this strategy could be used to control the crystal structures of various 2D extended π-conjugated systems. Further modification of the porphyrin substituents is ongoing. Reference K. Miyazaki, K. Matsuo, H. Hayashi, M. Yamauchi, N. Aratani, H. Yamada, Org. Lett. 2023, 25, 7354-7358

Theoretical Study on Optoelectronic Properties of 1,4-Dithiazole-5,10-dihydrophenazine and Its B ← N-Fused Derivatives.

Recently, Liu et al. reported 1,4-dithiazole-5,10-dihydrophenazine (DTDHP) and its B ← N-fused derivative (DTHDHP-BF2), which were expected to show excellent optoelectronic properties (Angew. Chem. Int. Ed. 2022, 61, e202205893). However, their charge-transport performance and luminescence emission mechanisms have not been revealed. In this work, we used density functional theory (DFT) calculations to investigate the optoelectronic properties of DTDHP and DTHDHP-BF2 and analyzed the influence of the introduction of -BF2 on the basic parameters governing charge transport and injection in detail. Our calculation results showed that adding -BF2 could stabilize the frontier molecular orbitals and decrease the reorganization energies associated with electron transport due to the formation of B ← N bonds, and the intermolecular electronic couplings are greatly enhanced owing to the strong intermolecular F···H interactions. Based on the master equation coupled with the Marcus-Hush electron transfer theory, we theoretically predicted the charge transport properties of DTDHP and DTHDHP-BF2. The optimum hole mobility (3.87 cm2 V-1 S-1) and electron mobility (1.52 cm2 V-1 S-1) of DTHDHP-BF2 are, respectively, 3 and 9 times as high as the corresponding optimum values of compound DTDHP. Moreover, the assignments of multiple fluorescence bands in the experiment were confirmed by time-dependent density functional theory (TDDFT) calculations. The simulated emission spectra indicate that the experimental fluorescence maxima at 687 nm originates from the S1 → S0 transition of the double proton transfer phototautomer (T2H) of DTDHP, and the shoulder peak at ∼660 nm may be related to the excited-state single-proton transfer phototautomer (T1H); for DTHDHP-BF2, the experimental fluorescence maxima at 687 nm should be attributed to normal Stokes shifted emission, and the shifted fluorescence with a peak at 751 nm originates from the emission of the photodissociation product of DTHDHP-BF2.

Molecular engineering push-pull structural versatility in the triphenylamine-thienodioxine-based hole transporting materials for high-performance organic and perovskite solar cells

This study proposes a push-pull molecular engineering approach to fabricate versatile hole-transporting materials (HTMs) for photovoltaic cells. Herein, we introduce a D-π-A strategy for fabricating four highly functional small molecules of thienodioxine core-based HTMs (CJ06C1 to CJ06C4), via core functionalization with diversified electron-withdrawing acceptor moieties. The engineered HTMs are evaluated by employing quantum calculations to analyze the structure-property relationships from optoelectronic, electrochemical, and solvability attributes. The findings reveal that acceptor-integrated HTMs unveil excellent band alignment with active perovskite layer with deeper HOMO energy levels (-4.96 eV to 5.02 eV), transparency in the visible portion λmaxabs<521, which entail appropriate photophysical attributes. In comparison to the reference HTM (CJ06), the acceptor-integrated HTMs have exhibited potentially higher hole mobility rate, accredited to smaller hole reorganization energies (0.15 eV to 0.21 eV), greater transfer integral values (0.26 eV to 0.31 eV) and greater hole hopping rates (1.08×1028 S−1 to 3.70×1028 S−1). The electron-excitation investigation exhibited stronger electronic coupling, smaller hole-electron spatial overlapping, and higher charge transference length (19.42 Å to 21.14 Å) in the fabricated HTMs. Thus ensued a significant upsurge in intrinsic charge transference (74.22–99.74 %) and lower exciton binding energies, leading to easy charge dissociation and low recombination chances compared to the parent HTM (CJ06C1). Moreover, the findings from dipole moments (12.56 D to 13.05 D) and solvation-free energy (-91.08 kJ/mol) to −108.1 kJ/mol),imply easier processability and aptness for film formation. Overall, this study ensures the efficiency of thienodioxine core functionalization with acceptor moieties for fabricating state-of-the-art HTMs. The promising attributes of fabricated HTMs pave the way for forthcoming perovskite solar cells.

Liquid phase exfoliation of few-layer borophene with high hole mobility for low-power electronic devices

Borophene, the two-dimensional allotrope of boron, has garnered significant interest in recent years due to its exceptional electronic, mechanical, and optical properties. In this work, an environment-friendly green approach has been utilized to synthesize p-type borophene, which consists of few layers as evidenced by electron and atomic force microscopic images. The Raman analysis indicated that these borophene layers possess β12 and χ3 phases. The photoemission spectra of these samples exhibit single exponential decay with a long lifetime of 7.2 µsec, showcasing its potential as a phosphorescent material in optoelectronics and quantum technologies. The photo-sensing capability of borophene was investigated by fabricating a Si/SiO2/Borophene/Ti/Pt photo-detector, which achieved an external quantum efficiency of 31 %, maximum photo responsivity of 200 mAW−1 and detectivity of 8.7x1011 Jones. Hall effect van der Pauw measurements revealed the p-type conductivity of the borophene film, along with a high hole mobility of 931.44 cm2V-1s−1 and a charge carrier density of 2 x 1012 cm−3, rendering these layers suitable for high-speed and low power electronic devices. This work emphasizes the importance of novel 2D materials like borophene with exceptional optoelectronic characteristics for developing future low-power electronic devices with remarkable performance.

Giant Enhancement of Hole Mobility for 4H-Silicon Carbide through Suppressing Interband Electron-Phonon Scattering.

4H-silicon carbide (4H-SiC) possesses a high Baliga figure of merit, making it a promising material for power electronics. However, its applications are limited by low hole mobility. Herein, we found that the hole mobility of 4H-SiC is mainly limited by the strong interband electron-phonon scattering using mode-level first-principles calculations. Our research indicates that applying compressive strain can reverse the sign of crystal-field splitting and change the ordering of electron bands close to the valence band maximum. Therefore, the interband electron-phonon scattering is severely suppressed and the electron group velocity is significantly increased. The out-of-plane hole mobility of 4H-SiC can be greatly enhanced by ∼200% with 2% uniaxial compressive strain applied. This work provides new insights into the electron transport mechanisms in semiconductors and suggests a strategy to improve hole mobility that could be applied to other semiconductors with hexagonal crystalline geometries.

Endless Dirac nodal lines and high mobility in kagome semimetal Ni3In2Se2 : a theoretical and experimental study

Kagome-lattice crystal is crucial in quantum materials research, exhibiting unique transport properties due to its rich band structure and the presence of nodal lines and rings. Here, we investigate the electronic transport properties and perform first-principles calculations for Ni3In2Se2kagome topological semimetal. First-principles calculations of the band structure without the inclusion of spin-orbit coupling (SOC) shows that three bands are crossing the Fermi level (EF), indicating the semi-metallic nature. With SOC, the band structure reveals a gap opening of the order of 10 meV.Z2index calculations suggest the topologically nontrivial natures (ν0;ν1ν2ν3) = (1;111) both without and with SOC. Our detailed calculations also indicate six endless Dirac nodal lines and two nodal rings with aπ-Berry phase in the absence of SOC. The temperature-dependent resistivity is dominated by two scattering mechanisms:s-dinterband scattering occurs below 50 K, while electron-phonon (e-p) scattering is observed above 50 K. The magnetoresistance (MR) curve aligns with the theory of extended Kohler's rule, suggesting multiple scattering origins and temperature-dependent carrier densities. A maximum MR of 120% at 2 K and 9 T, with a maximum estimated mobility of approximately 3000 cm2V-1s-1are observed. Ni3In2Se2is an electron-hole compensated topological semimetal, as we have carrier density of electron (ne) and hole (nh) arene≈nh, estimated from Hall effect data fitted to a two-band model. Consequently, there is an increase in the mobility of electrons and holes, leading to a higher carrier mobility and a comparatively higher MR. The quantum interference effect leading to the two dimensional (2D) weak antilocalization effect (-σxx∝ln(B)) manifests as the diffusion of nodal line fermions in the 2D poloidal plane and the associated encircling Berry flux of nodal-line fermions.

Wafer-scale Te thin film with high hole mobility and piezoelectric coefficients

p-type semiconductors are significant for integrated nanoelectronics. Tellurium (Te), a mono-elemental material, is a p-type semiconductor with high mobility. Its outstanding performance renders it widely applicable in the fields of electronics and optoelectronics. However, the wafer-scale fabrication of Te thin films is challenging. In this study, we reported an ion-bean sputtered Te thin film and investigated the effects of annealing temperatures. Annealing-induced crystallization kinetics were assessed through Raman spectroscopy, x-ray diffraction, and atomic force microscopy. After annealing, the film's conductivity increased from 10−5 to 10−4 S and mobility from 18 to 53 cm2 V−1 s−1. Dual AC resonance tracking switching spectroscopy piezoelectric force microscopy is used to investigate piezo/ferroelectric properties. The coercive voltages are −2 and 4 V respectively, and the effective piezoelectric coefficient (d33) is 40 pm/V. Butterfly and phase-switching loops demonstrate its possible ferroelectricity. The Te thin film has potential applications in optoelectronics, nonvolatile memory devices, and neuromorphic computation.

Single-Layer InGeS: Robust direct Bandgap, super high electron Mobility, long-lived Carriers, and Ohmic contact for Next-Generation Field-Effect transistors

Two-dimensional (2D) materials holding appropriate bandgaps, high carrier mobility, and long carrier lifetime require to be urgently explored as electronic devices such as field effect transistors (FETs) become more and more miniaturized. Herein, single-layer (SL) InGeS is thoroughly investigated using first-principles calculations. Theoretical results confirm SL InGeS has nice thermal and dynamical stability at 300 K. SL InGeS holds a direct bandgap of 1.28 eV by HSE06, and its electrons and holes are inherently located at different atomic regions. In the visible range, SL InGeS displays a maximum optical absorption of ∼ 5 × 105 cm−1, surpassing that of most known 2D materials. Furthermore, SL InGeS possesses high electron mobility (∼11100 cm2 V−1 s−1) and relatively low hole mobility (∼1000 cm2 V−1 s−1), and its carrier lifetime is as long as 4.99 ns. In addition, an Ohmic contact is designed in the graphene/InGeS heterojunction, implying small current resistance. In brief, all these scientific findings promise SL InGeS is a hopeful candidate in ultrathin FET devices.

Achievable hole concentration at room temperature as a function of Mg concentration for MOCVD-grown p-GaN after sufficient annealing

Relationship between the hole concentration at room temperature and the Mg doping concentration in p-GaN grown by MOCVD after sufficient annealing was studied in this paper. Different annealing conditions were applied to obtain sufficient activation for p-GaN samples with different Mg doping ranges. Hole concentration, resistivity and mobility were characterized by room-temperature Hall measurements. The Mg doping concentration and the residual impurities such as H, C, O and Si were measured by secondary ion mass spectroscopy, confirming negligible compensations by the impurities. The hole concentration, resistivity and mobility data are presented as a function of Mg concentration, and are compared with literature data. The appropriate curve relating the Mg doping concentration to the hole concentration is derived using a charge neutrality equation and the ionized-acceptor-density [ ] (cm−3) dependent ionization energy of Mg acceptor was determined as = 184 − 2.66 × 10−5 × [ ]1/3 meV.

Enhanced electrical performance in graphene field-effect transistors through post-annealing of high-k HfLaO gate dielectrics

High-k gate dielectrics have attracted a great deal of attention in the investigation of transistors due to their unique properties such as superior gate controllability. However, their integration into graphene field-effect transistors (GFETs) remains problematic and the physical mechanisms governing the performance of these devices are still not fully understood. In this study, the effects of post-annealing on GFETs utilizing the high-k HfLaO ternary oxide as the gate dielectric were comprehensively investigated. The HfLaO film was deposited on top of graphene by magnetron sputtering, and the device performance with various post-annealing temperatures was conducted. It was found that post-annealing temperature can effectively increase the dielectric constant through balancing the oxygen-vacancy defects and moisture absorption. Both the surface morphology of HfLaO and performance of GFETs were investigated, and the fabricated GFETs exhibit notable electrical performance enhancements. Specifically, GFETs with a 200 °C post-annealed HfLaO gate dielectric demonstrate the optimal device performance, featuring a minimal Dirac point voltage (VDirac) of 1.1 V and a minimal hysteresis (ΔVDirac) of 0.5 V. The extracted hole and electron mobilities are 4012 and 1366 cm2/V · s, respectively, nearly one order of magnitude higher than that of GFETs with as-deposited HfLaO. This work outperforms other existing GFETs utilizing high-k gate dielectric and chemical vapor deposition grown graphene in terms of both carrier mobility and on–off ratio. It is also noted that the excessive post-annealing temperature can negatively impact the GFET performance through introducing oxygen vacancies, increasing the surface roughness, lowering the breakdown voltage, and inducing recrystallization.

Effect of Sb2S3 sacrificial layer thickness on structural, optical and electrical properties of CuSbS2 films and investigation of diode parameters of CuSbS2/CdS heterojunctions

The ternary copper chalcogenides CuSbS2 (CAS) is found to have appealing optical and photovoltaic properties to be used as absorber layer in thin film solar cells. However, the difficulty to grow good quality CuSbS2 layer of micrometer thickness by chemical bath deposition method holds a big challenge. In this work, we reported the effect of incorporating Sb2S3 sacrificial layer of different thickness on structural, optical and electrical properties of CAS films. The X-ray diffraction results and Raman spectroscopic analysis confirm the formation of single-phase orthorhombic crystal structure for CuSbS2. The increase of Sb content in CAS films with the increase in deposition time of Sb2S3 layer has been reflected in the change in relative intensity ratio of characteristic Raman peaks as well as in diffraction peak profiles. The magnitude of defect states in terms of Urbach energy is decreased drastically by increasing Sb percentage in the films. A clear improvement in electrical properties of CAS films is observed with the decrease in Cu/Sb ratio. The carrier density is increased by one order of magnitude from 1016 to 1017 cm−3 and hole mobility increases from 1.14 to 4.87 cm2/Vs. The impact of Sb concentration on Scottky diode parameters of CAS/CdS heterojunction was studied by using thermionic emission model. Both the ideality factor and series resistance are decreased with the increase in Sb content. The J-V measurements reveal that the integration of Sb2S3 sacrificial layer improves the PV parameters such as fill factor, open circuit voltage, photocurrent and efficiency. The overall improvement in diode parameters can be ascribed to decrease in defect states, better film quality, absorber layer thickness and improved stoichiometry of CAS films.

A universal hole transport layer for efficient organic solar cells processed by blade coating

Doctor-blade coating technology is a roll-to-roll compatible high-throughput thin film fabrication route. In this work, doctor-blading was applied for fabricating organic solar cells (OSCs) using a polyoxometalates material phosphomolybdic acid (PMA) as a hole transport layer (HTL). Compared to PEDOT:PSS, PMA-based devices demonstrate lower trap-assisted recombination, higher hole mobility, prolonged charge carrier lifetime and faster charge collection. With PM6:Y6 as active layer, PMA-based device delivered a high power conversion efficiency (PCE) of 17.79 % with a boosted short-circuit current density (JSC) value of 28.08 mA/cm2, which is one of the best performances for PM6:Y6-based solar cells through doctor-blading process. In addition, the performance improvement was observed in both conventional and inverted structured devices with various donor: acceptor combinations. These results indicate the high universality of PMA for printable processing and its prospect in preparation of the industrial production of OSCs.

Constructed black phosphorus quantum dots/BiVO4 Z-scheme heterojunction catalysis for efficient Rhodamine b degradation and DFT study

Black phosphorus (BP) is highly regarded in photocatalysis for its bandgap thickness dependency, high hole mobility, and broad visible light absorption. This study introduces a simple hydrothermal method to construct a BP QDs/BiVO4 direct Z-scheme heterojunction. The composite’s crystal structure, morphology, and photochemical properties were comprehensively characterized. The photocatalytic activity was evaluated using Rhodamine B (RhB) degradation under visible light. Notably, BP QDs0.12%/BiVO4 exhibited exceptional performance, achieving a 95.4 % RhB degradation after 100 min, three times higher than BiVO4 alone. The direct Z-scheme heterojunction played a pivotal role in facilitating O2− and h+ involvement in the degradation process. The interfacial interaction between BP QDs and BiVO4 significantly enhanced BiVO4′s visible light absorption, preserving its strong oxidation–reduction capacity. This enhancement was further corroborated by DFT simulation calculations. Overall, this study presents a novel approach for constructing efficient Z-scheme photocatalysts based on BP QDs, laying a solid foundation for their application in the field of photocatalytic degradation.

Effect of Alkyl Side Chains in BDT and 2D‐BDT Small‐Molecules as Donor Materials for Vacuum‐Processed Organic Photovoltaic Devices

Nine molecules based on benzo[1,2‐b:4,5‐b′]dithiophene (BDT) and 2D‐BDT derivatives are studied as donor materials in organic photovoltaic (OPV) devices fabricated by thermal evaporation, aiming to understand how different alkyl lateral substituents affect the molecular packing, the charge transport, and, subsequently, the device performance. Synthesis of the molecules is followed by a comprehensive characterization using thermal and differential scanning calorimetry analyses, which confirm their thermal stability and suitability for vacuum‐processed OPV devices. Thermal analysis also demonstrates a strong correlation between the melting point reduction of the molecules and the disorder caused by the alkyl chains. As the synthesized molecules present similar optical properties, the differences in the device performance are caused by the different substituents. BDT derivatives with low melting point temperatures produce reduced current density, hole mobility, and overall device performance, which are attributed to poor molecular packing. Additionally, energy‐dispersive X‐ray spectroscopy analysis suggests phase separation with fullerene, further impacting the efficiency of the devices. The findings indicate that the photovoltaic performance of BDT‐based molecules can be modulated by avoiding aliphatic substituents, providing a strategy for the design of more efficient materials, with thermal evaporation as an ideal method to evaluate and decouple molecular packing from solubility.

Ge quantum well channel P-MOSFET for 2.45 GHz wireless weak energy harvesting

Wireless energy harvesting is an important application of microwave wireless energy transmission system, but due to the weak energy of RF signals in the 2.45 GHz band, its rectification efficiency is not ideal. As one of the core rectifier components of wireless weak energy harvesting system, the performance of MOSFET determines the rectification efficiency of the system, and its optimized design to improve the rectification efficiency is an important direction of current research in the field. In view of this, this paper proposes and designs Ge quantum well channel PMOS for wireless weak energy harvesting at 2.45 GHz, aiming to improve the rectification efficiency of wireless weak energy harvesting systems. Starting from adjusting the structural physical parameters of the MOS tubes, the absolute value of the threshold voltage is reduced in the weak energy density region, which in turn improves the rectification efficiency of the device. Then, the novel diode connection with the introduction of substrate bias effect is compared with the conventional connection using an ADS simulation circuit, and the simulation results show that the leakage current is smaller and the rectification efficiency is higher under the novel connection. On this basis, a Ge quantum well channel PMOS device is proposed. Compared with the Ge surface channel, the hole mobility of the quantum well channel will be greatly improved, and its rectification efficiency can also be improved. The device is connected to the rectifier circuit with a novel connection and simulated using Silvaco's Mixedmode module. The results show that the rectification efficiencies of the Ge quantum well channel MOS reach 13.53 % and 32 % at low input powers of −20.34 dBm and −6.28 dBm, respectively, which are 3.3 and 1.14 times higher than those of the conventional surface channel MOS.