Atomically thin transition metal dichalcogenides (TMDCs) have intriguing nanoscale properties like high charge mobility, photosensitivity, layer‐thickness‐dependent bandgap, and mechanical ...flexibility, which are all appealing for the development of next generation optoelectronic, catalytic, and sensory devices. Their atomically thin thickness, however, renders TMDCs poor absorptivity. Here, bilayer MoS2 is combined with core‐only CdSe QDs and core/shell CdSe/ZnS QDs to obtain hybrids with increased light harvesting and exhibiting interfacial charge transfer (CT) and nonradiative energy transfer (NET), respectively. Field‐effect transistors based on these hybrids and their responses to varying laser power and applied gate voltage are investigated with scanning photocurrent microscopy (SPCM) in view of their potential utilization in light harvesting and photodetector applications. CdSe–MoS2 hybrids are found to exhibit encouraging properties for photodetectors, like high responsivity and fast on/off response under low light exposure while CdSe/ZnS–MoS2 hybrids show enhanced charge carrier generation with increased light exposure, thus suitable for photovoltaics. While distinguishing optically between CT and NET in QD–TMDCs is nontrivial, it is found that they can be differentiated by SPCM as these two processes exhibit distinctive light‐intensity dependencies: CT causes a photogating effect, decreasing the photocurrent response with increasing light power while NET increases the photocurrent response with increasing light power, opposite to CT case.
Photocurrent imaging is used to discriminate between charge transfer (CT) and nonradiative energy transfer (NET) in quantum dot‐bilayer MoS2 hybrid field effect transistors, as these two processes exhibit distinctive light‐intensity dependencies: CT causes a photogating effect, decreasing the photocurrent response with the increasing light power while NET increases the photocurrent response with increasing light power, opposite to CT case.
Despite numerous organic semiconducting materials synthesized for organic photovoltaics in the past decade, fullerenes are widely used as electron acceptors in highly efficient bulk-heterojunction ...solar cells. None of the non-fullerene bulk heterojunction solar cells have achieved efficiencies as high as fullerene-based solar cells. Design principles for fullerene-free acceptors remain unclear in the field. Here we report examples of helical molecular semiconductors as electron acceptors that are on par with fullerene derivatives in efficient solar cells. We achieved an 8.3% power conversion efficiency in a solar cell, which is a record high for non-fullerene bulk heterojunctions. Femtosecond transient absorption spectroscopy revealed both electron and hole transfer processes at the donor-acceptor interfaces. Atomic force microscopy reveals a mesh-like network of acceptors with pores that are tens of nanometres in diameter for efficient exciton separation and charge transport. This study describes a new motif for designing highly efficient acceptors for organic solar cells.
Despite the promise of simple manufacturing via an entirely solution-based process at low temperature (<100 °C), the planar-type inverted perovskite solar cells (PeSCs) based on methylammonium lead ...tri-iodide (MAPbI 3 ) still suffer from a notorious instability problem under operational conditions. Here, we found that the operational stability of PeSCs with MAPbI 3 is significantly related to a high density of ionic defects and correlated amorphous regions at the interface between the electron transport layer and the MAPbI 3 film. By recrystallizing the surface of the MAPbI 3 layer, we fabricate defect-free stoichiometric MAPbI 3 crystals and demonstrated burn-in loss-free and intrinsically stable inverted MAPbI 3 PeSCs. The inverted MAPbI 3 PeSCs exhibited a power conversion efficiency (PCE) of 18.8% and maintained over 80% and 90% of their initial PCEs even after 1000 hours of real operation (under AM 1.5G irradiation) and continuous heating conditions (at 85 °C in the dark), respectively. Our work demonstrates that the MAPbI 3 layer under ionic defect-free conditions is ‘intrinsically’ stable under operational conditions.
Mixed matrix materials (MMMs) hold great potential for membrane gas separations by merging nanofillers with unique nanostructures and polymers with excellent processability. In situ growth of the ...nanofillers is adapted to mitigate interfacial incompatibility to avoid the selectivity loss. Surprisingly, functional polymers have not been exploited to co‐grow the nanofillers for membrane applications. Herein, in situ synergistic growth of crystalline zeolite imidazole framework‐8 (ZIF‐8) in polybenzimidazole (PBI), creating highly porous structures with high gas permeability, is demonstrated. More importantly, PBI contains benzimidazole groups (similar to the precursor for ZIF‐8, i.e., 2‐methylimidazole) and induces the formation of amorphous ZIFs, enhancing interfacial compatibility and creating highly size‐discriminating bottlenecks. For instance, the formation of 15 mass% ZIF‐8 in PBI improves H2 permeability and H2/CO2 selectivity by ≈100% at 35 °C, breaking the permeability/selectivity tradeoff. This work unveils a new platform of MMMs comprising functional polymer‐incorporated amorphous ZIFs with hierarchical nanostructures for various applications.
In situ growth of ZIFs in polybenzimidazole (PBI) generates bimodal free volumes from tightly packed amorphous ZIF‐8 (induced by PBI) and highly porous crystalline ZIF‐8. Such hierarchical nanostructures improve H2 permeability and H2/CO2 selectivity simultaneously, overcoming the permeability/selectivity tradeoff. The study unveils an important yet often neglected role of functional polymers in designing mixed matrix materials for various applications.
Polymer–inorganic hybrid nanocomposites exhibit enhanced material properties, combining the advantages of both their organic and inorganic subcomponents. Extensive research is being carried out to ...functionalize polymers towards various improved physicochemical characteristics such as electrical, optical, and mechanical properties for various applications. Vapor-phase material infiltration is an emerging hybridization route, derived from atomic layer deposition, which facilitates uniform incorporation of inorganic entities into a polymer matrix, leading to novel applications in fields such as microelectronics, energy storage, smart coatings, and smart fabrics. In this article, recent advances in employing vapor-phase material infiltration as a hybridization and nanopatterning technique for various application avenues are reviewed.
Noble metal nanoparticles are extensively used for sensitizing metal oxide chemical sensors through the catalytic spillover mechanism. However, due to earth-scarcity and high cost of noble metals, ...finding replacements presents a great economic benefit. Besides, high temperature and harsh environment sensor applications demand material stability under conditions approaching thermal and chemical stability limits of noble metals. In this study, we employed thermally stable perovskite-type La0.8Sr0.2FeO3 (LSFO) nanoparticle surface decoration on Ga2O3 nanorod array gas sensors and discovered an order of magnitude enhanced sensitivity to carbon monoxide at 500 °C. The LSFO nanoparticle catalysts was of comparable performance to that achieved by Pt nanoparticles, with a much lower weight loading than Pt. Detailed electron microscopy and X-ray photoelectron spectroscopy studies suggested the LSFO nanoparticle sensitization effect is attributed to a spillover-like effect associated with the gas-LSFO-Ga2O3 triple-interfaces that spread the negatively charged surface oxygen ions from LSFO nanoparticles surfaces over to β-Ga2O3 nanorod surfaces with faster surface CO oxidation reactions.
Nanoparticles (NPs) at high loadings are often used in mixed matrix membranes (MMMs) to improve gas separation properties, but they can lead to defects and poor processability that impede membrane ...fabrication. Herein, it is demonstrated that branched nanorods (NRs) with controlled aspect ratios can significantly reduce the required loading to achieve superior gas separation properties while maintaining excellent processability, as demonstrated by the dispersion of palladium (Pd) NRs in polybenzimidazole for H2/CO2 separation. Increasing the aspect ratio from 1 for NPs to 40 for NRs decreases the percolation threshold volume fraction by a factor of 30, from 0.35 to 0.011. An MMM with percolated networks formed by Pd NRs at a volume fraction of 0.039 exhibits H2 permeability of 110 Barrer and H2/CO2 selectivity of 31 when challenged with simulated syngas at 200 °C, surpassing Robeson's upper bound. This work highlights the advantage of NRs over NPs and nanowires and shows that right‐sizing nanofillers in MMMs is critical to construct highly sieving pathways at minimal loadings. This work paves the way for this general feature to be applied across materials systems for a variety of chemical separations.
Nanorods with suitable aspect ratios are ideal for constructing percolated networks in polymers with low loadings and easiness to fabricate defect‐free membranes, compared with nanoparticles and nanowires. This work demonstrates mixed matrix materials containing Pd‐percolated networks enabled by 3.9 vol% Pd branched nanorods, achieving H2/CO2 separation properties superior to state‐of‐the‐art membrane materials and surpassing the upper bound.
We report the synthesis of a tellurophene‐containing low‐bandgap polymer, PDPPTe2T, by microwave‐assisted palladium‐catalyzed ipso‐arylative polymerization of ...2,5‐bis(α‐hydroxy‐α,α‐diphenyl)methyltellurophene with a diketopyrrolopyrrole (DPP) monomer. Compared with the corresponding thiophene analog, PDPPTe2T absorbs light of longer wavelengths and has a smaller bandgap. Bulk heterojunction solar cells prepared from PDPPTe2T and PC71BM show PCE values of up to 4.4 %. External quantum efficiency measurements show that PDPPTe2T produces photocurrent at wavelengths up to 1 µm. DFT calculations suggest that the atomic substitution from sulfur to tellurium increases electronic coupling to decrease the length of the carbon–carbon bonds between the tellurophene and thiophene rings, which results in the red‐shift in absorption upon substitution of tellurium for sulfur.
Telluric rings: The tellurophene‐containing low‐bandgap polymer PDPPTe2T, prepared by microwave‐assisted ipso‐arylative polymerization, exhibited red‐shifted absorption spectra compared to the thiophene analogue. Bulk heterojunction solar‐cell devices from PDPPTe2T and PC71BM reach a power conversion efficiency of 4.4 % and produce photocurrent at wavelengths up to 1 μm.
Controlling crystallization and grain growth is crucial for realizing highly efficient hybrid perovskite solar cells (PSCs). In this work, enhanced PSC photovoltaic performance and stability by ...accelerating perovskite crystallization and grain growth via 2D hexagonal boron nitride (hBN) nanosheet additives incorporated into the active perovskite layer are demonstrated. In situ X‐ray scattering and infrared thermal imaging during the perovskite annealing process revealed the highly thermally conductive hBN nanosheets promoted the phase conversion and grain growth in the perovskite layer by facilitating a more rapid and spatially uniform temperature rise within the perovskite film. Complementary structural, physicochemical, and electrical characterizations further showed that the hBN nanosheets formed a physical barrier at the perovskite grain boundaries and the interfaces with charge transport layers, passivating defects, and retarding ion migration. As a result, the power conversion efficiency of the PSC is improved from 17.4% to 19.8%, along with enhanced device stability, retaining ≈90% of the initial efficiency even after 500 h ambient air storage. The results not only highlight 2D hBN as an effective additive for PSCs but also suggest enhanced thermal transport as one of the pathways for improved PSC performance by 2D material additives in general.
In situ synchrotron X‐ray scattering and real‐time thermal imaging for the first time unraveled the effects of the thermally conductive additive, hexagonal boron nitride nanosheets, on enhancing the crystallization kinetics in organic‐inorganic hybrid perovskites and the associated solar cell performance and stability.
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