Work Function Tuning Research Articles

MXene-Mediated Charge Modulation in Plasmonic Metal-Semiconductor Heterojunctions for Photo-Induced Enhanced Raman Spectroscopy.

The smart integration of nanoparticles with tailored semiconductors, followed by UV illumination prior to Raman measurements, activates photo-induced enhanced Raman spectroscopy (PIERS), enabling ultrasensitive detection. This photo-mediated modulation of charge transfer is a special case of surface-enhanced Raman spectroscopy (SERS), where enhancement is tuned via chemical-interaction-induced charge transfer between the analyte and substrate. Herein, photoinduced charge transfer dynamics are explored by tuning the work function of the supporting material embedding plasmonic nanostructures and creating an interfacial light-mediated charge-transfer system. Using two distinct nanoparticles supported on a two-dimensional material revealed directional charge transport behaviour, reflecting Fermi-level equilibration at heterojunctions. Titanium carbide-based MXene (Ti3C2Tx; Tx = -OH, -F) is introduced as a charge-transfer modulator due to its tunable work function, significantly influencing carrier transport direction and efficiency. Notably, Au-based hybrids exhibit PIERS enhancement upto five orders of magnitude, unlike Ag-based hybrids that show quenching. This confirms that optimized nanoparticle-MXene hybrids facilitate hot electron movement across interfaces, leading to differential PIERS responses. Additionally, density functional theory calculations elucidate electronic structures and photogenerated electron migration. This study provides valuable insights into photo-induced charge transfer, emphasizing its pivotal role in enhancing chemical contributions in SERS, advancing future optical sensing and molecular recognition platforms.

Synthesis and analysis of surface defect induced tuning of band bending and work function of ZnO nanoparticles

Synthesis and analysis of surface defect induced tuning of band bending and work function of ZnO nanoparticles

A homogenous polymer design with widely tunable work functions for high-performance two-dimensional photodetectors

Contact electrodes, which significantly influence the Schottky barrier and interfacial quality with two-dimensional (2D) materials, are key to boosting the performance of 2D photodetectors. However, it is challenging to fabricate electrically conducting films with sufficiently high or low work functions (WF2) in homogenous electrodes for 2D devices due to the fixed WF of traditional metallic and semi-metallic electrodes, which restricts their adaptability for 2D metal-semiconductor-metal (MSM) structured photodetectors. Here, we utilize a homogenous PEDOT:PSS electrode designed with adjustable WF ranging from 5.1 to 3.2 eV in 2D MSM photodetectors, achieving a high rectification ratio of ∼105and superior performance metrics: responsivity up to 1.8 A W-1, anIlight/Idarkof 108, and an ultrafast response time of 3.2 μs. Meanwhile, the excellent transparency of PEDOT:PSS electrode extends the 2D device's response to the near-infrared (NIR) region, overcoming the semiconductor bandgap limitation. The universality of polymer electrode is proven across various 2D photodetectors, and its flexibility enables the creation of durable, wearable 2D devices. This work paves the way for the development of flexible, self-powered photodetectors, heralding a new era of next-generation intelligent interactive systems.

Harnessing Work Function Modulation for Hydrogen Evolution Catalysis in Mesoporous Bimetallic Pt-M Alloys: The Role of Mesopores in Work Function Optimization.

Work function (WF) influences electron transport and intermediates adsorption, enabling charge balance and catalytic optimization for the hydrogen evolution reaction (HER). However, the understanding of the role of mesopores and the relationship between composition and WF in pristine Pt-based alloys remains lacking. Herein, various mesoporous binary Pt-M alloy films (m-Pt-M, M = Pd, Rh, and Ru) with uniform pores and elemental distributions are synthesized, providing an experimental platform to investigate this relationship. It has been demonstrated that the WFs of m-Pt-M catalysts are strongly influenced by their compositions and mesoporous structures, thereby impacting HER activities. Among them, m-Pt-Ru with tailored WF lowers the thermodynamic energy barrier and accelerates the kinetic processes of HER. The mass activity of m-Pt-Ru in alkaline media is 17.8× and 5.1× higher, compared to Pt black and m-Pt, respectively. This work not only provides a simple method for the fabrication of well-defined binary metallic alloy films but also offers experimental insights into the rational design of highly efficient electrocatalysts with tunable WFs.

Work Function Tuning in Strain Induced Double Gated Junctionless Transistor: A Device to Circuit Performance Study for Sub-20nm Nodes

Work Function Tuning in Strain Induced Double Gated Junctionless Transistor: A Device to Circuit Performance Study for Sub-20nm Nodes

Achieving tunable work function in MoO thin films: A key to low-cost, high-performance organic electronics

Achieving tunable work function in MoO thin films: A key to low-cost, high-performance organic electronics

Work function tuning of directly grown multi-layer graphene on silicon by PECVD and fabrication of Ag/ITO/Gr/n-Si/Ag solar cell

Work function tuning of directly grown multi-layer graphene on silicon by PECVD and fabrication of Ag/ITO/Gr/n-Si/Ag solar cell

Rare Earth Single Atoms Steering Hydrogen Spillover Over Pd/WO3 Toward High‐Efficiency H2 Sensor at Near Room Temperature

Abstract Metal oxide semiconductor (MOS) supported Pd materials are potential candidates for H2 sensors, while effective H2 detection at near room temperature remains a great challenge owing to the difficulty of hydrogen migration from Pd at low temperature. Herein, guided by theoretical calculations, rare earth single atoms doping Pd nanoparticles supported on WO3 nanorods with tunable work function differences (ΔФ) and oxygen vacancies are precisely developed to improve H2 sensing performances. The resultant Ce‐Pd/WO3 presents the highest response of 31.3 toward 50 ppm H2, showing 6 times improvement over the Pd/WO3, which realizes the trace and fast detection of H2. Density functional theory results reveal that the energy barrier of hydrogen migration and the formation energy of oxygen vacancy decrease after introducing rare earth single atoms, and Ce‐Pd/WO3 with the lowest ΔФ exhibits the most facile hydrogen spillover and desorption. The in situ spectra characterization and hydrogen spillover experiments further demonstrate the highly improved hydrogen migration over the Ce‐Pd/WO3. Significantly, the real‐time monitoring application of the Ce‐Pd/WO3 device for hydrogen leak (0.1 V/V%) in Al‐air batteries is also verified. This work can shed light on the development of a high‐efficiency H2 sensor via the precise modulation of work functions.

Work Function Engineering of Copper Sulfides for 2D Electronics

Achieving ideal metal/semiconductor junctions remains a critical challenge in advancing 2D electronics. While current approaches often rely on clean van der Waals contact interfaces to mitigate Fermi‐level pinning, they offer limited tunability in achieving precise energy level alignment with 2D semiconductors. In this work, a wide range of work function modulation in copper sulfide (Cu2−xS, 0 ≤ X < 1) electrode materials is proposed that can be achieved through an air‐ambient sulfurization process. Depending on the concentration of sulfur atoms, the Cu2−xS electrode showed considerable modulation in work function from 5.10 to 4.15 eV (ΔΦ = 950 meV). The continuous tunable work function of Cu2−xS electrodes enables the ideal junction interface with ohmic contact properties of both n‐type and p‐type transition metal dichalcogenides materials. Our efficient work function engineering strategy provides an innovative way to design 2D electronics for the development of integrated electronics devices.

Vacuum Processability of Self-Assembled Monolayers and Their Chemical Interaction with Perovskite Interfaces

Self-assembled monolayers (SAMs) have gained significant attention as an interfacial engineering strategy for perovskite solar cells (PSCs) due to their efficient charge transport ability and work function tunability. While solution-based methods such as dip-coating and spin-coating are widely used for SAM deposition, challenges such as non-uniform coverage, solvent contamination, and limited control over molecular orientation hinder their scalability and reproducibility. In contrast, vacuum deposition techniques, including thermal evaporation, overcome these limitations by enabling the formation of highly uniform materials with precise control over thickness and molecular arrangement. Importantly, the chemical interactions between SAM materials and perovskite layers, including coordination bonding with Pb2+ ions, play an important role in passivating surface defects, modulating energy levels, and promoting uniform perovskite crystallization. These interactions not only enhance wettability but also improve the overall quality and stability of perovskite films. This review highlights the advantages of vacuum-deposited SAMs, promoting strong chemical interactions with perovskite layers and improving interfacial properties critical for scalable applications.

On-Surface Reactions of Electronically Active Self-Assembled Monolayers for Electrode Work Function Tuning

On-Surface Reactions of Electronically Active Self-Assembled Monolayers for Electrode Work Function Tuning

Exploiting Bis-Sulfonimide Featuring Multiple d-pπ Bonds to Construct Interlayers for Organic Solar Cells.

Herein, bis-sulfonimide (BSI), characterized by multiple d-pπ bonds rather than typical p-pπ bonds, is unprecedently utilized as a general and extendable building block to develop a series of multifunctional cathode interlayer materials (CIMs) for organic solar cells (OSCs). An illustrative CIM, BSIz-TT-PDI, demonstrates favorable alcohol processability, superior work function tunability, appropriate energy levels, strong self-doping effect, and decent crystallinity. These attributes contribute to its high conductivity exceeding 5×10-3 S/cm, as well as precise optimization of the interfacial connection between the active layer and metal cathode. Therefore, BSIz-TT-PDI-based OSCs delivers an outstanding efficiency of 18.08 % using PM6:Y6 active layer while retaining 84 % of its initial performance after tracking at the maximum power point under continuous illumination for 1100 hours. Additionally, the devices maintain over 94 % of the optimal performance across a film thickness range of BSIz-TT-PDI from 5 to 90 nm. Moreover, BSIz-TT-PDI exhibits high compatibility with various active layers, enabling a record efficiency of 19.80 % with the PM6:BTP-eC9:L8-BO active layer. This work not only introduces a new library of water/alcohol-soluble n-type semiconductors containing BSI, while also pioneers the creation of thickness-insensitive CIMs for stable and efficient OSCs by integrating electron-withdrawing components with d-pπ bonds.

Exploiting Bis‐Sulfonimide Featuring Multiple d–pπ Bonds to Construct Interlayers for Organic Solar Cells

Abstract Herein, bis‐sulfonimide (BSI), characterized by multiple d‐pπ bonds rather than typical p‐pπ bonds, is unprecedently utilized as a general and extendable building block to develop a series of multifunctional cathode interlayer materials (CIMs) for organic solar cells (OSCs). An illustrative CIM, BSIz‐TT‐PDI, demonstrates favorable alcohol processability, superior work function tunability, appropriate energy levels, strong self‐doping effect, and decent crystallinity. These attributes contribute to its high conductivity exceeding 5×10−3 S/cm, as well as precise optimization of the interfacial connection between the active layer and metal cathode. Therefore, BSIz‐TT‐PDI‐based OSCs delivers an outstanding efficiency of 18.08 % using PM6:Y6 active layer while retaining 84 % of its initial performance after tracking at the maximum power point under continuous illumination for 1100 hours. Additionally, the devices maintain over 94 % of the optimal performance across a film thickness range of BSIz‐TT‐PDI from 5 to 90 nm. Moreover, BSIz‐TT‐PDI exhibits high compatibility with various active layers, enabling a record efficiency of 19.80 % with the PM6:BTP‐eC9:L8‐BO active layer. This work not only introduces a new library of water/alcohol‐soluble n‐type semiconductors containing BSI, while also pioneers the creation of thickness‐insensitive CIMs for stable and efficient OSCs by integrating electron‐withdrawing components with d‐pπ bonds.

Transparent and Conductive Polyimide-Ionene Hybrid Interlayers for High Performance and Cost-Effective Semitransparent Organic Solar Cells.

The contradiction between high transmittance and favorable conductivity poses a great challenge in developing effective cathode interlayer (CIL) materials with sufficient thickness tolerance, which hinders the further advancement of organic solar cells (OSCs). Herein, a completely new class of alcohol processable polyimide-ionene hybrids (PIIHs) is proposed by melding pyromellitic diimide (PMD) subunits into imidazolium-based ionenes backbone covalently. These PIIHs, named PMD-DI and PMD-PD, boast high transparency, suitable energy levels, and decent conductivity. A higher PMD content endows PMD-PD with improved work function tunability, electrical properties, and crystallinity, enabling PMD-PD as CIL material with excellent thickness-insensitive characteristics, while simultaneously improving device stability significantly. Furthermore, PMD-PD also exhibits good compatibility with various electrodes and active layers, offering solar cell efficiencies of up to 19.91% and 19.29% with Ag and Cu cathodes, respectively. More importantly, the application of PMD-PD can improve the performance of semi-transparent OSCs without losing transmittance, thereby drastically enhancing the light utilization efficiency to 4.04% with an ultrathin, low-cost Cu cathode, that competes with leading optical modulation-free semitransparent OSCs with expensive Ag cathodes. This work opens a pathway to realize transparent and conductive interlayers by strategic molecular design, leading to highly efficient, stable, and cost-effective OSCs suitable for diverse applications.

Work function tuning of thermally evaporated V2Ox films using UV-Ozone treatment and its influence on V2Ox/c-Si(n) solar cells

Work function tuning of thermally evaporated V2Ox films using UV-Ozone treatment and its influence on V2Ox/c-Si(n) solar cells

Concurrent Interface Passivation and Contact Work Function Tuning in Organic Self‐Aligned Gate Transistors and Complementary Circuits Using Phosphonic Acid Self‐Assembled Monolayers

Abstract The self‐aligned gate (SAG) transistor architecture is attractive for electronic circuit applications due to its enabling attributes, including low parasitic capacitances and higher frequency operation. However, SAG transistors often rely on complex manufacturing, which limits their practical utilization. Herein, we overcome this bottleneck and demonstrate organic SAG transistors in which the self‐aligned source/drain (S/D) electrodes are separated by the gate (G) terminal with sub‐20 nm gaps. The SAG architecture eliminates parasitic overlaps while minimizing access resistance for the injected carriers. Moreover, precise work function engineering of the self‐aligned Au S/D contacts is demonstrated using phosphonic acid (PA) self‐assembled monolayers (SAMs) functionalized directly onto Au. Analysis of the Au surface corroborated by Density Functional Theory calculations and scanning tunneling microscopy reveal the unexpected formation of PA SAMs directly onto Au for the first time. Combining different organic semiconductors with appropriate SAMs enables the development of hole and electron‐transporting SAG transistors with enhanced performance. Integrating the n‐ and p‐channel transistors yields complementary logic circuitry with high gain and noise margins, showcasing the effectiveness of this approach. The work highlights the enormous potential of combining the SAG transistor platform with work function modifying PA SAMs to develop printed electronics with improved functionality.

Transparent OLED displays for selective bidirectional viewing using ZnO/Yb:Ag cathode with highly smooth and low-barrier surface

Transparent organic light-emitting diode (TrOLED) displays represent cutting-edge technology posed to significantly enhance user experience. This study addresses two pivotal challenges in TrOLED development. Firstly, we focus on the innovation of transparent cathodes, a fundamental component in TrOLEDs, by introducing a ZnO/Yb:Ag cathode. This cathode employs a combination of seed layer and metal doping techniques to achieve a highly uniform surface morphology and a low surface energy barrier. The optimized Yb:Ag cathode on ZnO, with a mere thickness of 15 nm, exhibits remarkable properties: an extremely low surface roughness of 0.52 nm, sheet resistance of 11.6 Ω ϒ−1, an optical transmittance of 86.7% at 510 nm, and tunable work function (here, optimized to be 3.86 eV), ensuring superior electron injection capability. Secondly, we propose a novel TrOLED pixel structure that features selective bidirectional viewing, allowing different types of information to be selectively displayed on each side while preserving overall transparency and minimizing pixel complexity. This design innovation distinguishes itself from conventional TrOLEDs that display images on only one side. The bidirectional TrOLED design not only enhances openness and esthetic appeal but also holds promise for diverse applications across various user environments.

Tunable Work Function and Surface Energy in Titanium Nitride (TiN) Thin Films through Quantum Well States.

High work function metals are crucial in various semiconductor applications. Titanium nitride (TiN) is particularly noteworthy as a high work function material in metal gate structures, which significantly enhances the transistor performance and reliability in advanced semiconductor devices. In this study, we employ first-principles calculations to demonstrate that the TiN work function oscillates with thickness due to the quantum well state effect. Furthermore, we investigate the termination and surface dependence of the work function across different crystallographic orientations. We show that the work function can be enhanced to up to 8.04 eV for TiN(111) with N-termination at five monolayers (5 MLs). Our findings provide valuable insights for fine-tuning the high work function of TiN.

2D MXenes: Synthesis, Properties, and Applications in Silicon-Based Optoelectronic Devices.

MXenes, a rapidly emerging class of 2D transition metal carbides, nitrides, and carbonitrides, have attracted significant attention for their outstanding properties, including high electrical conductivity, tunable work function, and solution processability. These characteristics have made MXenes highly versatile and widely adopted in the next generation of optoelectronic devices, such as perovskite and organic solar cells. However, their integration into silicon-based optoelectronic devices remains relatively underexplored, despite silicon's dominance in the semiconductor industry. In this review, a timely summary of the recent progress in utilizing Ti-based MXenes, particularly Ti3C2Tx, in silicon-based optoelectronic devices is provided. The composition, synthesis methods, and key properties of MXenes that contribute to their potential for enhanced device performance are focused on. Furthermore, the latest advancements in MXene applications in silicon-based solar cells and photodetectors are discussed from fundamental and applied perspectives. Finally, the key challenges and future opportunities for the integration of MXenes in silicon-based optoelectronic devices are outlined.

Integer Charge Transfer Model-PTCDA on MgO(001)/Ag(001) Probing the Transition from Single to Double Integer Charge Transfer.

For weakly interacting adsorbate/substrate systems, the integer charge transfer (ICT) model describes how charge transfer across interfaces depends on the substrate work function. In particular, work function regimes where no charge transfer occurs (vacuum level alignment) can be distinguished from regions where integer charge transfer by electron tunneling from substrate to adsorbate or vice versa takes place (Fermi level pinning). While the formation of singly integer charged molecular anions and cations of organic semiconductors on various substrates has been well described by this model, the double integer charging regime has so far remained unexplored and experimentally elusive. Here, we extend the integer charge transfer model to the transition from single to double integer charging. This was made possible by combining a molecular adsorbate with high electron affinity (Perylenetetracarboxylic-dianhydride (PTCDA)) with a substrate with tunable work function (ultrathin MgO(001) films on Ag(001)). Our results, obtained with scanning tunneling microscopy (STM), photoemission spectroscopy (PES), work function measurements and density function theory (DFT) calculations, show that after completing the single negative charging of all molecules in a PTCDA monolayer in the first Fermi level pinning regime, the system transitions to a vacuum level alignment regime for singly charged molecules when the substrate work function is reduced, and finally enters the second Fermi level pinning regime at very low substrate work function, in which the molecules become doubly negatively charged.