Multi-Layer Palladium Diselenide as a Contact Material for Two-Dimensional Tungsten Diselenide Field-Effect Transistors

Our researchers were involved in the research of electrical interfaces to two-dimensional semiconductors. The outcome of collaboration was a surprising finding, which was published in Nanomaterials. The two-dimensional semiconductor material under research was tungsten diselenide (WSe2), which has emerged as a promising ambipolar semiconductor material for field-effect transistors (FETs) due to its unique electronic properties, including a sizeable band gap, high carrier mobility, and remarkable on–off ratio. However, engineering the contacts to WSe2 remains an issue, and high contact barriers prevent the utilization of the full performance in electronic applications. Furthermore, it could be possible to tune the contacts to WSe2 for effective electron or hole injection and consequently pin the threshold voltage to either conduction or valence band. This would be the way to achieve complementary metal–oxide–semiconductor devices without doping of the channel material.This study investigates the behaviour of two-dimensional WSe2 field-effect transistors with multi-layer palladium diselenide (PdSe2) as a contact material. We demonstrate that PdSe2 contacts favour hole injection while preserving the ambipolar nature of the channel material. This consequently yields high-performance p-type WSe2 devices with PdSe2 van der Waals contacts. Further, we explore the tunability of the contact interface by selective laser alteration of the WSe2 under the contacts, enabling pinning of the threshold voltage to the valence band of WSe2, yielding pure p-type operation of the devices. See more in Nanomaterials.

Posted in Research | Leave a comment

The role of graphene topography in initial stages of pentacene layer growth

Using atomic force microscopy, we probed growth of pentacene molecules on graphene that was fabricated by chemical vapor deposition (CVD) and transferred onto 300 nm-thick SiO2 substrates. We observe that the folds on CVD graphene act as a potential barrier for the surface transport of pentacene molecules.  They are oriented either parallel or perpendicular to the folds, they are also predominantly oriented along the symmetry axes of graphene. Orientation of pentacene islands on graphene evaporated at room temperature has a wide distribution. On the contrary, most of the pentacene islands evaporated at 60°C are oriented at 30° with respect to the fold direction. In addition, we interpret the 3D growth of pentacene islands on graphene in terms of reduced polar components of surface energy on graphene investigated with contact angle measurements. The results were published in ACS Omega.

Posted in Research | Leave a comment

Time-of-flight photoconductivity investigation of high charge carrier mobility in Ti3C2Tx MXenes thin-film

We measured record-high charge mobility in randomly oriented multilayered network of two-dimensional (2D) Ti3C2Tx (where Tx is the surface termination and corresponds to O, OH and F) was studied using time-of-flight photoconductivity (TOFP) method, which is highly sensitive to the distribution of charge carrier velocities. We prepared samples comprising Ti3C2Tx with thickness of 12 nm or 6-monolayers. MXene flakes of size up to 16 μm were randomly deposited on the surface by spin-coating from water solution. Using TOFP, we have measured electron mobility that reached values up to 279 cm2/Vs and increase with electric-field in a Poole-Frenkel manner. These values are approximately 50 times higher than previously reported field-effect mobility. Interestingly, our zero-electricfield extrapolate approaches electron mobility measured using terahertz absorption method, which represents intra-flake transport. Our data suggest that macroscopic charge transport is governed by two distinct mechanisms. The high mobility values are characteristic for the intra-flake charge transport via the manifold of delocalized states. On the other hand, the observed Poole-Frenkel dependence of charge carrier mobility on the electric field is typical for the disordered materials and suggest the existence of an important contribution of inter-flake hopping to the overall charge transport. Results were published in

Posted in Research | Leave a comment

PhD position in experimental study of Electro-optical properties of 2D heterostructures including organic semiconductors

We are seeking a talented PhD student to join our team and experimentaly investigate the electro-optical properties of 2D heterostructures and organic semiconductors. The ideal candidate will have a strong background in solid state physics and intuition to perform experimental research. The successful candidate will be responsible for developing and implementing advanced techniques for characterizing the properties of these materials, as well as for designing and conducting experiments to gain deeper insights into their behavior. The candidate will learn how to prepare 2D heterostructures including organic semiconductors and study their applicability by preparing novel electronic components, organic thin film transistors, photodetectors, organic solar cells, memory components, energy-harvesting components, and bio-mimetic components e.g. biosensors. The selected candidate will be immediately employed and involved in the experimental research in Laboratory for Organic Matter Physics.


  • Preparation of 2D heterostructures including organic semiconductors;
  • Develop and implement advanced techniques for characterizing the electro-optical properties of 2D heterostructures;
  • Design and conduct experiments to investigate the behavior of these materials under different conditions;
  • Analyse data and interpret results to gain insights into the fundamental properties of these materials;
  • Collaborate with other researchers to advance our understanding of 2D heterostructures and their potential applications;
    • Publish research findings in leading scientific journals and present work at national and international conferences.

For more check this link:

Posted in Research | Leave a comment

Nanoscopic Roughness Characterization of Chitosan with Buried Graphene Oxide for Fuel Cell Application

Direct alkaline ethanol fuel cells are showing promising improvements. In this brief communication, we have presented atomic force microscopy of fuel cell membranes, enhanced with graphene-oxide nanoparticles. More in

Posted in Research | Leave a comment

Influence of P3HT:PCBM Ratio on Thermal and Transport Properties of Bulk Heterojunction Solar Cells

Our researchers were measuring the performance of organic solar cells in order to validate a novel experimental method, which can be used to study the non-radiative recombination processes. In details, the influence of P3HT:PCBM ratio on thermal and transport properties of solar cells were determined by photothermal beam deflection spectrometry, which is advantageous tool for nondestructively study of bulk heterojunction layers of organic solar cells. P3HT:PCBM layers of different P3HT:PCBM ratios were deposited on top of PEDOT:PSS/ITO layers which were included in organic bulk-heterojunction solar cells. The thermal diffusivity, energy gap and charge carrier lifetime were measured at different illumination conditions and with a different P3HT:PCBM ratios. As expected, it was found that the energy band gap depends on the P3HT:PCBM ratio. Thermal diffusivity is decreasing, while charge carrier lifetime is increasing with PCBM concentration. Energy band gap was found to be independent on illumination intensity, while thermal diffusivity was increasing and carrier lifetime was decreasing with illumination intensity. The carrier lifetime exhibits qualitatively similar dependence on the PCBM concentration when compared to the open-circuit voltage of operating solar cells under AM1.5 illumination. BDS and standard I-V measurement yielded comparable results arguing that the former is suitable for characterization of organic solar cells. Results were published in

Posted in Research | Leave a comment

Conjugated Polymer Mesocrystals with Structural and Optoelectronic Coherence and Anisotropy in Three Dimensions

We measured record high charge mobility in a mm-sized organic semiconductors. Semiconducting mesocrystalline bulk polymer specimens that exhibit nearintrinsic properties using channel-die pressing are demonstrated. A predominant edge-on orientation is obtained for poly(3-hexylthiophene-2,5-diyl) (P3HT) throughout 2 mm-thick/wide samples. This persistent mesocrystalline arrangement at macroscopic scales allows reliable evaluation of the electronic charge transport anisotropy along all three crystallographic axes, with high mobilities found along the π-stacking. Indeed, charge-carrier mobilities of up to 2.3 cm2/Vs are measured along the π-stack, which are some of the highest mobilities reported for polymers at low charge-carrier densities (drop-cast films display mobilities of maximum ≈10−3 cm2/Vs). The structural coherence also leads to an unusually well-defined photoluminescence line-shape characteristic of an H-aggregate (measured from the surface perpendicular to the materials flow), rather than the typical HJ-aggregate feature usually found for P3HT. The approach is widely applicable: to electrical conductors and materials used in n-type devices, such as poly{[N,N′-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)2,6-diyl]-alt-5,5′-(2,2′-bithiophene)} (N2200) where the mesocrystalline structure leads to high electron transport along the polymer backbones (≈1.3 cm2/Vs). This versatility and the broad applicability of channel-die pressing signifies its promise as a straightforward, readily scalable method to fabricate bulk semiconducting polymer structures at macroscopic scales with properties typically accessible only by the tedious growth of single crystals. More in

Posted in Research | Leave a comment

Solution-Processed Graphene–Nanographene van der Waals Heterostructures for Photodetectors with Efficient and Ultralong Charge Separation

Our group has been involved in an interesting study of the photoconductivity of solution-processed nanographene ad-layers. Sensitization of graphene with inorganic semiconducting nanostructures has been demonstrated as a powerful strategy to boost its optoelectronic performance. However, the limited tunability of optical properties and toxicity of metal cations in the inorganic sensitizers prohibits their widespread applications, and the in-depth understanding of the essential interfacial charge-transfer process within such hybrid systems remains elusive. Here, we design and develop high-quality nanographene (NG) dispersions with a large-scale production using high-shear mixing exfoliation. The physisorption of these NG molecules onto graphene gives rise to the formation of graphene−NG van der Waals heterostructures (VDWHs), characterized by strong interlayer coupling through π−π interactions. As a proof of concept, photodetectors fabricated on the basis of such VDWHs show ultrahigh responsivity up to 4.5 × 107 A/W and a specific detectivity reaching 4.6 × 1013 Jones, being competitive with the highest values obtained for graphene-based photodetectors. The outstanding device characteristics are attributed to the efficient transfer of photogenerated holes from NGs to graphene and the long-lived charge separation at graphene−NG interfaces (beyond 1 ns), as elucidated by ultrafast terahertz (THz) spectroscopy. These results demonstrate the great potential of such graphene−NG VDWHs as prototypical building blocks for high-performance, low-toxicity optoelectronics. The study is published in

Posted in Research | Leave a comment


Our team has an open position for a PhD candidate. Highlights:

  • State-of-the-art lab 
  • Network of world-renowned researches 
  • Full funding 
  • Top career opportunity
  • International team

Candidate will get strong experience in the area of fabrication and characterization of charge transport and electronic properties of two-dimensional materials such as graphene or graphene-related materials, and/or electronic charge transport characterization of thin films of advanced high-mobility organic semiconductors. The selected candidate will become a member of Laboratory of Organic Matter Physics (


2D heterostructures, organic semiconductors, sensors, FET, photodetectors, neuromorphic devices, time-of-flight photoconductivy, SNOM and AFM, photolithography, clean room.

The position is available immediately. 

Cordially invited to contact us here.

Posted in Research | Leave a comment

Multiresponsive Nonvolatile Memories Based on Optically Switchable Ferroelectric Organic Field‐Effect Transistors

Our group was involved in research of novel type of organic transistors. Organic transistors are key elements for flexible, wearable, and biocompatible logic applications. Multiresponsivity is highly sought‐after in organic electronics to enable sophisticated operations and functions. Such a challenge can be pursued by integrating more components in a single device, each one responding to a specific external stimulus. Here, the first multiresponsive organic device based on a photochromic–ferroelectric organic field‐effect transistor, which is capable of operating as nonvolatile memory with 11 bit memory storage capacity in a single device, is reported. The memory elements can be written and erased independently by means of light or an electric field, with accurate control over the readout signal, excellent repeatability, fast response, and high retention time. Such a proof of concept paves the way toward enhanced functional complexity in optoelectronics via the interfacing of multiple components in a single device, in a fully integrated low‐cost technology compatible with flexible substrates. These findings were published in Advanced Materials.

Posted in Uncategorized | Leave a comment