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Bilayers of two-dimensional (2D) transition metal chalcogenides (TMDs) such as WSe2 have been attracting increasing attention owing to the intriguing properties involved in the different stacking configurations. The growth of bilayer WSe2 by chemical vapor deposition (CVD) has been facilely obtained without proper control of the stacking configuration. Herein, we report the controlled growth of bilayer WSe2 crystals as large as 30 μm on c-plane sapphire by the CVD method. Combining second harmonic generation (SHG), low-frequency Raman and scanning transmission electron microscopy (STEM), we elucidate the as-grown bilayer WSe2 with a 2H stacking configuration. Atomic force microscope (AFM) measurements reveal that the prominent atomic steps provide the energetically favorable templates to guide the upper layer nuclei formation, resembling the “graphoepitaxial effect” and facilitating the second WSe2 layer following the layer-by-layer growth mode to complete the bilayer growth. Field-effect charge transport measurement performed on bilayer WSe2 yields a hole mobility of up to 40 cm2 V−1 s−1, more than 3× higher than the value achieved in monolayer WSe2-based devices. Our study provides key insights into the growth mechanism of bilayer WSe2 crystals on sapphire and unlocks the opportunity for potential bilayer and multilayer TMD electronic applications.

Conjugated polyaniline can impact the field of water filtration membranes due to its hydrophilic and antibacterial nature, facile and inexpensive synthesis procedure, heat and acid tolerance, and unique doping/dedoping chemistry. However, the gelation effect, its rigid backbone, and the limited hydrophilicity of polyaniline severely restrict the adaptability to membranes and their antifouling performance. This Mini Review summarizes important works of polyaniline-related ultrafiltration membranes, highlighting solutions to conquer engineering obstacles in processing and challenges in enhancing surface hydrophilicity with an emphasis on chemistry. As a pH-responsive polymer convertible to a conductive salt, this classic material should continue to bring unconventional advances into the realm of water filtration membranes.

Heterogeneous integration of robust hydrogel and soft MXene shows multifunctional sensing., Skin-mountable microelectronics are garnering substantial interest for various promising applications including human-machine interfaces, biointegrated devices, and personalized medicine. However, it remains a critical challenge to develop e-skins to mimic the human somatosensory system in full working range. Here, we present a multifunctional e-skin system with a heterostructured configuration that couples vinyl-hybrid-silica nanoparticle (VSNP)–modified polyacrylamide (PAM) hydrogel with two-dimensional (2D) MXene through nano-bridging layers of polypyrrole nanowires (PpyNWs) at the interfaces, featuring high toughness and low hysteresis, in tandem with controlled crack generation and distribution. The multidimensional configurations endow the e-skin with an extraordinary working range (2800%), ultrafast responsiveness (90 ms) and resilience (240 ms), good linearity (800%), tunable sensing mechanisms, and excellent reproducibility. In parallel, this e-skin platform is capable of detecting, quantifying, and remotely monitoring stretching motions in multiple dimensions, tactile pressure, proximity sensing, and variations in temperature and light, establishing a promising platform for next-generation smart flexible electronics.

High-resolution scanning transmission electron microscopy (HR-STEM) with spherical aberration correction enables researchers to peer into two-dimensional (2D) materials and correlate the material properties with those of single atoms. The maximum intensity of corrected electron beam is confined in the area having sub-angstrom size. Meanwhile, the residual threefold astigmatism of the electron probe implies a triangular shape distribution of the intensity, whereas its tails overlap and thus interact with several atomic species simultaneously. The result is the resonant modulation of contrast that interferes the determination of phase transition of 2D materials. Here, we theoretically reveal and experimentally determine the origin of resonant modulation of contrast and its unintended impact on violating the power-law dependence of contrast on coordination modes between transition metal and chalcogenide atoms. The finding illuminates the correlation between atomic contrast, spatially inequivalent chalcogenide orientation, and residual threefold astigmatism on determining the atomic structure of emerging 2D materials.

V.T., J.-H.F., and M.-H.C. are indebted to the support from the King Abdullah University of Science and Technology (KAUST) Office of Sponsored Research (OSR) under Award No: OSR-2018-CARF/CCF-3079. V.T. acknowledged the financial support from KAUST Catalysis Center (KCC). Characterization and fabrication of HER electrodes in this work were performed as User Proposals (#5067 and #5424) at the Molecular Foundry, Lawrence Berkeley National Lab, supported by the Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. Raman spectroscopy was performed at the Joint Center for Artificial Photosynthesis, a DOE Energy Innovation Hub, supported through the Office of Science of the U.S. Department of Energy under Award Number DE-SC0004993. A.Y.L. and J.K. also acknowledge the support from the KAUST under contract (OSR- 2015-CRG4-2634) and the support from U.S. Army Research Office through the MIT Institute for Soldier Nanotechnologies (Grant No. 023674). N.J.M and J.A.K acknowledge support from the U.S. Department of Energy, Office of Science under Award Number DE-SC0015894 and by a U.S. Department of Energy Office of Science Graduate Student Research (SCGSR) award. V.T. expresses his gratitude to Dr. Chang-Ming Jiang, Dr. Pin Lu, Wu Zhan, Vipawee Limsakoune, and Teresa L. Chen for the fruitful discussion in DROPS mechanisms and assistance in instrumentation. This work was performed, in part, at the Center for Integrated Nanotechnologies, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International, Inc., for the U.S. DOE’s National Nuclear Security Administration under contract DE-NA-0003525. The views expressed in the article do not necessarily represent the views of the U.S. DOE or the United States Government

Advanced beyond-silicon electronic technology requires both channel materials and also ultralow-resistance contacts to be discovered

Metallic molybdenum disulfide (MoS2), e.g., 1T phase, is touted as a highly promising material for energy storage that already displays a great capacitive performance. However, due to its tendency to aggregate and restack, it remains a formidable challenge to assemble a high-performance electrode without scrambling the intrinsic structure. Here, we report an electrohydrodynamic-assisted fabrication of 3D crumpled MoS2 (c-MoS2) and its formation of an additive-free stable ink for scalable inkjet printing. The 3D c-MoS2 powders exhibited a high concentration of metallic 1T phase and an ultrathin structure. The aggregation-resistant properties of the 3D crumpled particles endow the electrodes with open space for electrolyte ion transport. Importantly, we experimentally discovered and theoretically validated that 3D 1T c-MoS2 enables an extended electrochemical stable working potential range and enhanced capacitive performance in a bivalent magnesium-ion aqueous electrolyte. With reduced graphene oxide (rGO) as the positive electrode material, we inkjet-printed 96 rigid asymmetric micro-supercapacitors (AMSCs) on a 4-in. Si/SiO2 wafer and 100 flexible AMSCs on photo paper. These AMSCs exhibited a wide stable working voltage of 1.75 V and excellent capacitance retention of 96% over 20 000 cycles for a single device. Our work highlights the promise of 3D layered materials as well-dispersed functional materials for large-scale printed flexible energy storage devices.

Two-dimensional transition metal dichalcogenide nanoribbons are touted as the future extreme device downscaling for advanced logic and memory devices but remain a formidable synthetic challenge. Here, we demonstrate a ledge-directed epitaxy (LDE) of dense arrays of continuous, self-aligned, monolayer and single-crystalline MoS

The optoelectronic properties of atomically thin transition-metal dichalcogenides are strongly correlated with the presence of defects in the materials, which are not necessarily detrimental for certain applications. For instance, defects can lead to an enhanced photoconduction, a complicated process involving charge generation and recombination in the time domain and carrier transport in the spatial domain. Here, we report the simultaneous spatial and temporal photoconductivity imaging in two types of WS2 monolayers by laser-illuminated microwave impedance microscopy. The diffusion length and carrier lifetime were directly extracted from the spatial profile and temporal relaxation of microwave signals respectively. Time-resolved experiments indicate that the critical process for photo-excited carriers is the escape of holes from trap states, which prolongs the apparent lifetime of mobile electrons in the conduction band. As a result, counterintuitively, the photoconductivity is stronger in CVD samples than exfoliated monolayers with a lower defect density. Our work reveals the intrinsic time and length scales of electrical response to photo-excitation in van der Waals materials, which is essential for their applications in novel optoelectronic devices., 21 pages, 4 figures

The highly prevalent and virulent disease in the Western Hemisphere Coccidioidomycosis, also known as Valley Fever, can cause serious illness such as severe pneumonia with respiratory failure. It can also take on a disseminated form where the infection spreads throughout the body. Thus, a serious impetus exists to develop effective detection of the disease that can also operate in a rapid and high-throughput fashion. Here, we report the assembly of a highly sensitive biosensor using reduced graphene oxide (rGO) with Coccidioides(cocci) antibodies as the target analytes. The facile design made possible by the scalable microcontact printing (μCP) surface patterning technique which enables rapid, ultrasensitive detection. It provides a wide linear range and sub picomolar (2.5 pg/ml) detection, while also delivering high selectivity and reproducibility. This work demonstrates an important advancement in the development of a sensitive label-free rGO biosensor for Coccidioidomycosis detection. This result also provides the potential application of direct pathogen diagnosis for the future biosensor development.

This work was supported by the Taiwan Ministry of Science and Technology (Grant No. MOST 108-2112-M-005-012-MY3 and 109-2112-M-005-013-MY3), and also supported in part by the National Natural Science Foundation of China under Grant No. 61974070 and 61874074, 1311 Talent Plan, and Start-Up Fund from Nanjing University of Posts and Telecommunications under Grant No. NY219003, and Shenzhen Peacock Plan (Grant No. KQTD2016053112042971).

In article number 2100215, Soohyung Park, Sylke Blumstengel, Norbert Koch, and co‐workers demonstrate a key mechanism for opto‐electronic properties enhancement of an organic/inorganic van der Waals semiconductor heterostructure in the 2D limit. A straddling type‐I energy level alignment enables sub‐picosecond resonance energy transfer from organic molecules to a 2D inorganic semiconductor monolayer, with enhanced luminescence yield from the inorganic component. [Image: see text]

Electronic charge rearrangement between components of a heterostructure is the fundamental principle to reach the electronic ground state. It is acknowledged that the density of states distribution of the components governs the amount of charge transfer, but a notable dependence on temperature has not yet been considered, particularly for weakly interacting systems. Here, we experimentally observe that the amount of ground state charge transfer in a van der Waals heterostructure formed by monolayer MoS2 sandwiched between graphite and a molecular electron acceptor layer increases by a factor of three when going from 7 K to room temperature. State-of-the-art electronic structure calculations of the full heterostructure that account for nuclear thermal fluctuations reveal intra-component electron-phonon coupling and inter-component electronic coupling as the key factors determining the amount of charge transfer. This conclusion is rationalized by a model applicable to multi-component van der Waals heterostructures.

Surface functionalization of nanoscale materials has a significant impact on their properties. We have demonstrated the effect of different passivating ligands on the crystal phase of organometal halide perovskite quantum dots (PQDs). Using static and dynamic spectroscopy, we studied phase transitions in CH3NH3PbBr3 PQDs ligated with either octylaminebromide (P-OABr) or 3-aminopropyl triethoxysilane (P-APTES). Around 140 K, P-OABr underwent a structural phase transition from tetragonal to orthorhombic, established by the emergence of a higher energy band in the photoluminescence (PL) spectrum. This was not observed in P-APTES, despite cooling down to 20 K. Additionally, time-resolved and excitation power-dependent PL, as well as Raman spectroscopy over a range of 300-20 K, revealed that recombination rates and types of charge carriers involved are significantly different in P-APTES and P-OABr. Our findings highlight how aspects of PQD phase stabilization are linked to nanoscale morphology and the crystal phase diagram.

In this report, we present a study of using nitrogen-doped graphene as the air electrode of low temperature solid oxide fuel cells (LT-SOFCs) operating at 350 °C or lower. Three graphene derivatives were prepared through hydrothermal reactions and their electrochemical performance and material properties were characterized in the temperature range of 225–350 °C in atmospheric air. Nitrogen-doped graphene was found to exhibit a decent air electrode performance comparable to a porous Pt electrode aged for 8 h at 350 °C, but only for a limited time. After ∼10 h of operation at 350 °C, the electrode performance degraded significantly due to carbon oxidation. However, alternative routes of synthesizing/doping graphene derivatives are expected to improve the viability of using these materials as a practical high temperature air electrode.

Wearable and portable self-powered units have stimulated considerable attention in both the scientific and technological realms. However, their innovative development is still limited by inefficient bulky connections between functional modules, incompatible energy storage systems with poor cycling stability, and real safety concerns. Herein, we demonstrate a flexible solar-charging integrated unit based on the design of printed magnesium ion aqueous asymmetric supercapacitors. This power unit exhibits excellent mechanical robustness, high photo-charging cycling stability (98.7% capacitance retention after 100 cycles), excellent overall energy conversion and storage efficiency (ηoverall = 17.57%), and outstanding input current tolerance. In addition, the Mg ion quasi-solid-state asymmetric supercapacitors show high energy density up to 13.1 mWh cm−3 via pseudocapacitive ion storage as investigated by an operando X-ray diffraction technique. The findings pave a practical route toward the design of future self-powered systems affording favorable safety, long life, and high energy., Wearable self-powered electronics receive considerable attention, but development is hindered by bulky designs, energy storage systems, and safety issues. Here the authors demonstrate a flexible solar-charging integrated unit based on printed magnesium ion aqueous asymmetric supercapacitors.

Tuning the Fermi level (EF) in two-dimensional transition metal dichalcogenide (TMDC) semiconductors is crucial for optimizing their application in (opto-)electronic devices. Doping by molecular electron acceptors and donors has been suggested as a promising method to achieve EF-adjustment. Here, we demonstrate that the charge transfer (CT) mechanism between TMDC and molecular dopant depends critically on the electrical nature of the substrate as well as its electronic coupling with the TMDC. Using angle-resolved ultraviolet and X-ray photoelectron spectroscopy, we reveal three fundamentally different, substrate-dependent CT mechanisms between the molecular electron acceptor 1,3,4,5,7,8-hexafluoro-tetracyano-naphthoquinodimethane (F6TCNNQ) and a MoS2 monolayer. Our results demonstrate that any substrate that acts as charge reservoir for dopant molecules can prohibit factual doping of a TMDC monolayer. On the other hand, the three different CT mechanisms can be exploited for the design of advanced heterostructures, exhibiting tailored electronic properties in (opto-)electronic devices based on two-dimensional semiconductors. Doping of 2D semiconductors by electron acceptor or donor molecules has been suggested as a method to optimize their properties for electronic devices. Here, the authors identify three distinct charge transfer mechanisms that depend on the substrate and yield different doping efficiencies.

The facile synthesis of hierarchically functional, catalytically active, and electrochemically stable nanostructures holds a tremendous promise for catalyzing the efficient and durable oxygen evolution reaction (OER) and yet remains a formidable challenge. Herein, we report the scalable production of core-shell nanostructures composed of carbon-coated cobalt diphosphide nanosheets, C@CoP

The application of liquid-exfoliated 2D transition metal disulfides (TMDs) as the hole transport layers (HTLs) in nonfullerene-based organic solar cells is reported. It is shown that solution processing of few-layer WS

Memristive devices have been extensively demonstrated for applications in nonvolatile memory, computer logic, and biological synapses. Precise control of the conducting paths associated with the resistance switching in memristive devices is critical for optimizing their performances including ON/OFF ratios. Here, gate tunability and multidirectional switching can be implemented in memristors for modulating the conducting paths using hexagonal α-In2 Se3 , a semiconducting van der Waals ferroelectric material. The planar memristor based on in-plane (IP) polarization of α-In2 Se3 exhibits a pronounced switchable photocurrent, as well as gate tunability of the channel conductance, ferroelectric polarization, and resistance-switching ratio. The integration of vertical α-In2 Se3 memristors based on out-of-plane (OOP) polarization is demonstrated with a device density of 7.1 × 109 in.-2 and a resistance-switching ratio of well over 103 . A multidirectionally operated α-In2 Se3 memristor is also proposed, enabling the control of the OOP (or IP) resistance state directly by an IP (or OOP) programming pulse, which has not been achieved in other reported memristors. The remarkable behavior and diverse functionalities of these ferroelectric α-In2 Se3 memristors suggest opportunities for future logic circuits and complex neuromorphic computing.

2D transition metal dichalcogenide (TMD) layered materials are promising for future electronic and optoelectronic applications. The realization of large-area electronics and circuits strongly relies on wafer-scale, selective growth of quality 2D TMDs. Here, a scalable method, namely, metal-guided selective growth (MGSG), is reported. The success of control over the transition-metal-precursor vapor pressure, the first concurrent growth of two dissimilar monolayer TMDs, is demonstrated in conjunction with lateral or vertical TMD heterojunctions at precisely desired locations over the entire wafer in a single chemical vapor deposition (VCD) process. Owing to the location selectivity, MGSG allows the growth of p- and n-type TMDs with spatial homogeneity and uniform electrical performance for circuit applications. As a demonstration, the first bottom-up complementary metal-oxide-semiconductor inverter based on p-type WSe2 and n-type MoSe2 is achieved, which exhibits a high and reproducible voltage gain of 23 with little dependence on position.

The photoelectrochemical (PEC) approach is attractive as a promising route for the nitrogen reduction reaction (NRR) toward ammonia (NH3 ) synthesis. However, the challenges in synergistic management of optical, electrical, and catalytic properties have limited the efficiency of PEC NRR devices. Herein, to enhance light-harvesting, carrier separation/transport, and the catalytic reactions, a concept of decoupling light-harvesting and electrocatalysis by employing a cascade n+ np+ -Si photocathode is implemented. Such a decoupling design not only abolishes the parasitic light blocking but also concurrently improves the optical and electrical properties of the n+ np+ -Si photocathode without compromising the efficiency. Experimental and density functional theory studies reveal that the porous architecture and N-vacancies promote N2 adsorption of the Au/porous carbon nitride (PCN) catalyst. Impressively, an n+ np+ -Si photocathode integrating the Au/PCN catalyst exhibits an outstanding PEC NRR performance with maximum Faradaic efficiency (FE) of 61.8% and NH3 production yield of 13.8 µg h-1 cm-2 at -0.10 V versus reversible hydrogen electrode (RHE), which is the highest FE at low applied potential ever reported for the PEC NRR.

High refractive index and broad absorption spectrum theoretically make perovskites ideal for luminescent solar concentrators. Monte Carlo simulations show that perovskites perform better than CdSe/CdTe quantum dots.

We report our results of developing perovskite thin films with high coverage, improved uniformity and preserved crystalline continuity in a single pass deposition. This approach, inspired by the natural phenomena of tears of wine, works by regulating the hydrodynamics of the material comprising of droplets during spray-pyrolysis. In contrast to conventional spray-pyrolysis where droplets dry independently and form a rough morphology, the use of binary solvent system creates localized surface tension gradients that initiate Marangoni flows, thus directing the incoming droplets to spontaneously undergo coalescing, merging and spreading into a continuous wet films before drying. By systematically exploring the dynamics of spreading and drying, we achieve spray-coated perovskite photovoltaics with power conversion efficiency of 14.2%, a near two-fold improvement than that of the spray-pyrolysis counterpart. Of particular significance is the fact that the single pass deposition technique unveils novel inroads in efficient management of lead consumption during deposition.

The research presented here was supported by the King Abdullah University of Science and Technology (KAUST) Office of Sponsored Research (OSR) under Award No: CRF-2015-2634-CRG4 and CRF-2016-2996-CRG5. J. H. H. thanks the financial support from City University of Hong Kong.

Rationally constructing an interlayer to suppress the lithium polysulfide (LiPS) shuttling but allow fast transport of Li-ions is of great significance for high-density Li–S batteries. Despite numerous nanomaterials have been explored, an effective approach to fabricate an ideal interlayer is still elusive. Herein, we developed a new electropolymerization strategy to grow in-situ a polycarbazole-type interlayer with a number of merits to boost the reversible capacity. Firstly, the membrane is microporous but compact with uniform 0.82 nm nanochannels that can effectively suppress the diffusion of polysulfide species. Secondly, using the CNT (700 nm) as conductive substrate, the electropolymerized membrane is ultrathin (60 nm), which facilitates fast transport of lithium ions and rate performance. Thirdly, the membrane is electron conductive (23 S m−1) that benefits the charge transfer and redox reaction. Li–S batteries configured with such an UCCM type of interlayer have showed enhanced sulfur utilization by threefold, with a reversible capacity of 920 mA h g−1 after 600 cycles at 0.2 C, and a high areal density of 10 mAh cm−2 at 11.2 mg cm−2 sulfur loading. A safer lithium-ion sulfur full-cell with lithiated graphite anode demonstrated a stable capacity over 4 mAh cm−2 under a low electrolyte/sulfur ratio of ~10 μL mg−1.

© OSA 2018. Strong enhancement of exciton binding has been observed in valence-excitons in the optical regime of 2D materials. We report direct observation of long-lived core-exciton states in transition metal dichalcogenides by attosecond transient absorption spectroscopy in the XUV.

Authors acknowledge L. J. Cote, F. Kim, K. Sohn and J. Huang for providing additional experimental results discussed in this review. R. Cruz-Silva thanks the support from the Exotic Nanocarbons Project, Japan Regional Innovation Strategy by the Excellence, JST. T. H. Han acknowledges the Basic Science Research Program by National Research Foundation of Korea (NRF 2014R1A1A1008196). V. C. Tung acknowledges the support by the Office of Science, Basic Energy Sciences, of the U.S. Department of Energy (No. DE-AC02-05CH11231) and ACS Petroleum Funds Doctoral New Investigator (PRF# 54717-DN110).

The structurally robust nature of nanocarbon allotropes, e.g., semiconducting single-walled carbon nanotubes (SWCNTs) and C{sub 60}s, makes them tantalizing candidates for thermally stable and mechanically flexible photovoltaic applications. However, C{sub 60}s rapidly dissociate away from the basal of SWCNTs under thermal stimuli as a result of weak intermolecular forces that “lock up” the binary assemblies. Here, we explore use of graphene nanoribbons (GNRs) as geometrically tailored protecting layers to suppress the unwanted dissociation of C{sub 60}s. The underlying mechanisms are explained using a combination of molecular dynamics simulations and transition state theory, revealing the temperature dependent disassociation of C{sub 60}s from the SWCNT basal plane. Our strategy provides fundamental guidelines for integrating all-carbon based nano-p/n junctions with optimized structural and thermal stability. External quantum efficiency and output current–voltage characteristics are used to experimentally quantify the effectiveness of GNR membranes under high temperature annealing. Further, the resulting C{sub 60}:SWCNT:GNR ternary composites display excellent mechanical stability, even after iterative bending tests. - Graphical abstract: The incorporation of solvent resistant, mechanically flexible and electrically addressable 2-D soft graphene nanoribbons facilitates the assembly of photoconductive carbon nano-p/n junctions for thermally stable and flexible photovoltaic cells.

In this paper, we report that a kind of perylene diimide derivative with bulky rigid substituents, 1,7-bis(p-tert-butylphenoxy)-N,N′-dicyclohexyl-perylene-3,4,9,10-tetracarboxylic diimide (TBPCHPDI) possesses both high electron mobility (1.8 cm2 V−1s−1) and high fluorescence quantum yield (0.32) in the solid state. Through X-ray diffraction (XRD), UV–Vis absorption and fluorescence spectra, and differential scanning calorimetry (DSC) measurements, it is demonstrated that the above phenomenon can be ascribed to the unique crystal structure of TBPCHPDI: due to steric hindrance of bulky rigid substituents, the intermolecular π–π actions are neglectable, providing high luminescence efficiency; in the mean time, the spacing between perylene chromophores is still very short (3.47 A), which is favorable for the hopping transportation of charge carrier from one molecule to neighboring molecule. Therefore, our finding would help design and synthesize novel organic semiconductive materials with potential applications in electrically pumped lasers which require high emission efficiency when large current density is applied.

The application of liquid-exfoliated 2D transition metal disulfides (TMDs) as the hole transport layers (HTLs) in nonfullerene-based organic solar cells is reported. It is shown that solution processing of few-layer WS2 or MoS2 suspensions directly onto transparent indium tin oxide (ITO) electrodes changes their work function without the need for any further treatment. HTLs comprising WS2 are found to exhibit higher uniformity on ITO than those of MoS2 and consistently yield solar cells with superior power conversion efficiency (PCE), improved fill factor (FF), enhanced short-circuit current (JSC ), and lower series resistance than devices based on poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) and MoS2 . Cells based on the ternary bulk-heterojunction PBDB-T-2F:Y6:PC71 BM with WS2 as the HTL exhibit the highest PCE of 17%, with an FF of 78%, open-circuit voltage of 0.84 V, and a JSC of 26 mA cm-2 . Analysis of the cells' optical and carrier recombination characteristics indicates that the enhanced performance is most likely attributed to a combination of favorable photonic structure and reduced bimolecular recombination losses in WS2 -based cells. The achieved PCE is the highest reported to date for organic solar cells comprised of 2D charge transport interlayers and highlights the potential of TMDs as inexpensive HTLs for high-efficiency organic photovoltaics.

Light and soil condition has significant effect on the quality of plants cultivated. However, there are limited studies conducted on this research area, specifically on the Amaranthus Cruentus (red amaranth) microgreens. Therefore, this research project aims to investigate the influence of light and soil condition on red amaranth microgreens growth as well as its antioxidants contents. Microgreens were grown under different soil condition with the same light condition, and vice versa. The stem length, root length, fresh weight and dry weight of microgreens were measured. The antioxidants and mineral content were also analysed. This paper concludes that neutral pH and loose soil is the best soil condition for cultivating microgreens. Black soil produced microgreens with 1.89 and 2.60-fold higher in terms of stem length, and 1.50 and 2.13-fold higher in terms of fresh weight than those cultivated in orange and tallow soil respectively. Compost can be added to soil to improve its quality. In terms of lighting condition, sunlight provided the best light source for yielding high quality microgreens, reducing the growth time of microgreens from 11 days to 8 days. Red+blue and white artificial light can also be used to substitute sunlight as they yielded similar quality.

Because of the consumption of fossil fuel, CO2 emission, a product of burning fossil fuel, causes the global warming. Electrochemical CO2 reduction reaction (eCO2RR) provides a solution that allows to reduce the carbon emission and produce useful products. Among those CO2 reduction products, formic acid is one of the most attractive candidates because it has higher volumetric capacity of H2 (53 g H2/L) and can release H2 by catalyst under room temperature, which makes it a promising energy carrier.[1] Also, it is feasible to transport since it is nonflammable and stable under room temperature. Among the materials for eCO2RR, bismuth has better selectivity toward formate production (Faraday efficiency > 80%).[2] However, production rate, partial current density toward formate, of those catalyst remained low. One of the approach to boost the production rate is to increase the surface area of catalyst. By creating the porous structure, surface area of catalyst will be increased and thus enhances the production rate of formate. In this work, we successfully synthesized sponge-liked bismuth by chemical vapor deposition (CVD) method for eCO2RR. As results, it shows an excellent current density (28 mA/cm2) and faraday efficiency toward formate (95%) in moderate applied potential -1.05 V (vs. reversible hydrogen electrode (RHE)) under low catalyst loading. Furthermore, Comparing to electroplating bismuth, sponge-liked bismuth have double current density under same electroactive surface area. [1] Eppinger, J. and K.W. Huang, Formic Acid as a Hydrogen Energy Carrier . Acs Energy Letters, 2017. 2(1): p. 188-195. [2] Larrazabal, G.O., A.J. Martin, and J. Perez-Ramirez, Building Blocks for High Performance in Electrocatalytic CO2 Reduction: Materials, Optimization Strategies, and Device Engineering. J Phys Chem Lett, 2017. 8(16): p. 3933-3944.

All-carbon based photovoltaics comprised of n-type fullerenes (C60s) and p-type single walled carbon nanotubes (SWCNTs) have potential for light harvesting and storage because of their advantageous carrier transport properties and improved mechanical/chemical stability. However, fullerenes tend to slip away from the graphitic basal plane due to the weak van der Waals force between dissimilar graphitic allotropes. Here, we report that the stability of these structures can be enhanced by wrapping them with graphene nanoribbons. We have developed molecular dynamic simulations of C60-coated, graphene nanoribbon-wrapped SWCNTs to systematically explore the relationship between nanoribbon morphology and wrapping behavior. Theoretical modeling shows that the competition between the van der Waals and bending energies of graphene nanoribbons affects both the wrapping process and the structure of the final assembly. Simulation predictions are corroborated by experimental evidence, both revealing the significant potential for stabilizing all-carbon active layers using graphene nanoribbons with optimized geometry.

Nanocarbon-based photovoltaics offer a promising new architecture for the next generation of solar cells. We demonstrate that a key factor determining the efficiency of single-walled carbon nanotube (SWCNT)/fullerene devices is the chirality of the SWCNT. This is shown via current density vs voltage measurements of nanocarbon devices prepared with (9,7), (7,6) and (6,5) SWCNTs, as well as density-functional theory (DFT) density of states calculations of C60 adsorbed onto the corresponding SWCNTs. The trends in efficiency are rationalized in terms of the relative energies of the fullerene and SWCNT conduction band energy levels.

We have developed an electrospraying technique inspired from Marangoni flow seen in nature. We demonstrate our ability to synthesise highly crystalline uniform perovskite thin films with enhanced coverage and high absorption. Due to a difference in the vapour pressure of DMSO and NMP, a gradient force is developed that helps in propagating the incoming precursor droplet to coalesce and merge with other droplets thus inducing a dynamic self-assembly within the thin film. This results in thin films with high uniformity and good morphological and topological characteristics, that collectivelty resulted in a respectable PCE of greater than 14%. Optical studies are conducted in parallel to better understand the energy phase space of perovskite crystals. The high temperature tetragonal phase showed a high recombination rate of 180 ns, ideal for photovoltaic performances, while the low temperature measurements reveal considerable complexity in spectral and dynamic properties that demand further invesgtiation.

Over the past decade, advances in material synthesis and interfacial engineering have produced more efficient polymer solar cells with improved absorption of the solar irradiation and charge carrier transport that have led to continuously increased power conversion efficiencies (PCE), recently surpassing 8%.[1] In parallel to the material design and engineering in the active layer, novel organic photovoltaic architectures have emerged. A representative example is tandem photovoltaics in which subcells are stacked along the optical path to increase optical absorption.[2–5] When the subcells are connected in series, the ideal open-circuit voltage (VOC) is equivalent to the sum of the VOCs of the individual subcells. PCE enhancement is most significant when high-efficiency polymers with complementary absorption profiles are stacked. Central to the construction of tandem devices is the interconnect layer that spatially separates but electrically connects the two subcells. Ideal candidates for interconnect layers require (a) high optical transparency over the entire solar spectrum; (b) sufficient vertical conductivity; (c) complete coverage to avoid intermixing of the two subcells; (d) low surface roughness to avoid interrupting the deposition of neighboring subcells; and (e) appropriate energetics to facilitate efficient charge recombination. For solution-processable interconnect materials, there are additional challenges such as orthogonal solubility, chemical and mechanical stability, and so on. Thus far, the conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is predominantly used as a component in solution-processable interconnect layers.[3–7] However, low transmittance of PEDOT:PSS in the red to near infrared (NIR) region results in a loss of available solar flux, which could adversely affect the overall photocurrent. In addition, PEDOT:PSS could also react with some common interfacial materials such as metal oxides, thus degrading the quality of interfaces over time.[6] Recently, graphene oxide (GO) was found to be capable of replacing PEDOT:PSS as a hole transporting layer in polymer solar cells.[8,9] Since GO is an insulating soft carbon sheet[10,11] with thickness of around 1 nm and lateral dimension extends readily into tens of micrometers, an effective GO modifying layer needs to have as small thickness