Possible charge ordering and anomalous transport in graphene/graphene quantum dot heterostructure

[Abstract] Observations of superconductivity and charge density waves (CDW) in graphene have been elusive thus far due to weak electron–phonon coupling (EPC) interactions. Here, we report a unique observation of anomalous transport and multiple charge ordering phases at high temperatures (T1 ∼ 213K, T2 ∼ 325K) in a 0D−2D van der Waals (vdW) heterostructure comprising of single layer graphene (SLG) and functionalized (amine) graphene quantum dots (GQD). The presence of functionalized GQD contributed to charge transfer with shifting of the Dirac point ∼ 0.05 eV above the Fermi level (ab initio simulations) and carrier density n ∼ −0.3 × 1012 cm−2 confirming p-doping in SLG and two-fold increase in EPC interaction was achieved. Moreover, we elucidate the interplay between electron–electron and electron–phonon interactions to substantiate high temperature EPC driven charge ordering in the heterostructure through analyses of magnetotransport and weak anti-localization (WAL) ramework. Our results provide impetus to investigate strongly correlated phenomena such as CDW and superconducting phase transitions in novel graphene based heterostructures.R R would like to acknowledge funding by European Regional Development Fund-Project 'MSCAfellow2@MUNI' (No. CZ.02.2.69/0.0/0.0/18070/0009846). I J G would like to thank for the support of the Operational Program Research, Development and Education Project 'MSCAfellow4@MUNI' (CZ.02.2.69/0.0/0.0/20079/0017045) and the Spanish Ministry of Universities for Beatriz Galindo (BG22/000147) and Maria Zambrano funding (RSU.UDC.MZ09 [RSU.UDC.MZ11]) transferred by the European Union Next Generation EU. We acknowledge CzechNanoLab Research Infrastructure supported by MEYS CR (LM2023051) to carry out this research. The computational results presented have been achieved using the Vienna Scientific Cluster (VSC). The authors would like to acknowledge Sumit Mandal, Vidyasagar College, Calcutta University, Subhajit Saha from the Department of Renewable energy, Maulana Abul Kalam Azad University, West Bengal, India and Jan Michalička, CEITEC Brno University of Technology, Brno 61200, Czechia for helpful discussions during this work.Česká republika. Ministerstvo školství, mládeže a tělovýchovy České republiky; LM202305

Enhancing Performances of Hybrid Perovskite Light Emitting Diodes with Thickness Controlled PMMA Interlayer

status: publishe

Size Tunable Cesium Antimony Chloride Perovskite Nanowires and Nanorods

All-inorganic perovskite nanocrystals are emergent alternative of organolead halide perovskites. Cesium antimony halide (Cs₃Sb₂X₉, X = Cl, Br, I) all-inorganic perovskites nanocrystals possessing analogous electronic configuration to the organolead halide perovskites are promising materials for optoelectronic applications. We report on a colloidal route to synthesis uniform Cs₃Sb₂Cl₉ perovskite nanowires with lengths up to several microns. We have synthesized aspect ratio controlled nanorods with the same ∼20 nm diameter of nanowires by tuning the precursors and ligands in the reaction. The crystallinity of the nanocrystals is significantly altered from the pristine bulk trigonal and orthorhombic phases owing to the one-dimensional shape of the nanocrystals. Rietveld refinement carefully separates out orthorhombic phase from the trigonal phase revealing a coexistence of both the phases in a minor and major ratio in the nanocrystals. The functionality in the form of fast photodetector demonstrates Cs₃Sb₂Cl₉ nanocrystals as promising materials for optoelectronic applications

Demonstration of Ultrarapid Interfacial Formation of 1D Fullerene Nanorods with Photovoltaic Properties

We demonstrate ultrarapid interfacial formation of one-dimensional (1D) single-crystalline fullerene C₆₀ nanorods at room temperature in 5 s. The nanorods of ∼11 μm in length and ∼215 nm in diameter are developed in a hexagonal close-pack crystal structure, contrary to the cubic crystal structure of pristine C₆₀. Vibrational and electronic spectroscopy provide strong evidence that the nanorods are a van der Waals solid, as evidenced from the preservation of the electronic structure of the C₆₀ molecules within the rods. Steady state optical spectroscopy reveals a dominance of charge transfer excitonic transitions in the nanorods. A significant enhancement of photogenerated charge carriers is observed in the nanorods in comparison to pristine C₆₀, revealing the effect of shape on the photovoltaic properties. Due to their ultrarapid, large-scale, room-temperature synthesis with single-crystalline structure and excellent optoelectronic properties, the nanorods are expected to be promising for photosensitive devices applications

Possible charge ordering and anomalous transport in graphene/graphene quantum dot heterostructure

Observations of superconductivity and charge density waves (CDW) in graphene have been elusive thus far due to weak electron-phonon coupling (EPC) interactions. Here, we report a unique observation of anomalous transport and multiple charge ordering phases at high temperatures ( T1 ∼ 213K , T2 ∼ 325K ) in a 0D−2D van der Waals (vdW) heterostructure comprising of single layer graphene (SLG) and functionalized (amine) graphene quantum dots (GQD). The presence of functionalized GQD contributed to charge transfer with shifting of the Dirac point ∼ 0.05 eV above the Fermi level (ab initio simulations) and carrier density n ∼ − 0.3 × 1012 cm−2 confirming p-doping in SLG and two-fold increase in EPC interaction was achieved. Moreover, we elucidate the interplay between electron-electron and electron-phonon interactions to substantiate high temperature EPC driven charge ordering in the heterostructure through analyses of magnetotransport and weak anti-localization (WAL) framework. Our results provide impetus to investigate strongly correlated phenomena such as CDW and superconducting phase transitions in novel graphene based heterostructures.</p

Transparent, Flexible Silicon Nanostructured Wire Networks with Seamless Junctions for High-Performance Photodetector Applications

Optically transparent photodetectors are crucial in next-generation optoelectronic applications including smart windows and transparent image sensors. Designing photodetectors with high transparency, photoresponsivity, and robust mechanical flexibility remains a significant challenge, as is managing the inevitable trade-off between high transparency and strong photoresponse. Here we report a scalable method to produce flexible crystalline Si nanostructured wire (NW) networks fabricated from silicon-on-insulator (SOI) with seamless junctions and highly responsive porous Si segments that combine to deliver exceptional performance. These networks show high transparency (∼92% at 550 nm), broadband photodetection (350 to 950 nm) with excellent responsivity (25 A/W), optical response time (0.58 ms), and mechanical flexibility (1000 cycles). Temperature-dependent photocurrent measurements indicate the presence of localized electronic states in the porous Si segments, which play a crucial role in light harvesting and photocarrier generation. The scalable low-cost approach based on SOI has the potential to deliver new classes of flexible optoelectronic devices, including next-generation photodetectors and solar cells

Narrow bandgap silver mercury telluride alloy semiconductor nanocrystal for self-powered midwavelength-infrared photodiode

Abstract Infrared colloidal quantum dots (CQDs) have been of interest due to their low-cost fabrication and facile wavelength tunability for various infrared optoelectronic applications. Recently, the mid-wavelength infrared (MWIR) quantum dot sensor has been successfully realized by forming a photodiode via a post-chemical treatment method. Controlling the doping density of the quantum dot solid and engineering the device structure require an extremely sophisticated technique, which hinders consistent doping density and restricts further development in understanding the fundamental photophysics and manufacturing process. Here, we report an air-stable and highly reproducible MWIR CQDs photodiode by incorporating synthesized p-doped Ag-HgTe colloidal nanocrystals (NCs). The Ag-HgTe alloy NCs allow clearly defined p-doped QDs layers, leading to uniform dopant distribution and the ease of engineering device fabrication. By optimizing the doping density, we achieved an average noise equivalent temperature difference of below 10 mK at 78 K with the self-powered MWIR photodiode sensor

Supramolecular Aggregates of Tetraphenylethene-Cored AIEgen toward Mechanoluminescent and Electroluminescent Devices

Luminescent materials possessing both the mechanoluminescence (MCL) and electroluminescence (EL) properties are the quest for sensing and optoelectronic applications. We report on the synthesis of a new tailor-made luminogen, 1,2-bis­(4-(1-([1,1′-biphenyl]-4-yl)-2,2-diphenylvinyl)­phenyl)-1,2-diphenylethene (<b>TPE 5</b>), using Suzuki coupling reaction with high yield. An aggregation-induced emission (AIE) active complex <b>TPE 5</b> forms supramolecular spherical aggregates at the air–water interface of a Langmuir trough. As a consequence, a large enhancement of luminescence is obtained from the mono- and multilayer Langmuir–Blodgett films of <b>TPE 5</b> owing to the AIE effect. The luminogen <b>TPE 5</b> exhibits a reversible MCL response, displaying photoluminescence switching due to change in the crystalline states under external stimuli. The unique feature of luminescence enhancement upon aggregate formation is utilized for the fabrication of light-emitting diodes with low threshold voltage using supramolecular aggregates as the active layer. This work demonstrates an efficient strategy for obtaining controlled supramolecular aggregates of AIEgen with a potential in the dual applications of MCL and EL