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Implementation of data-cube pumpa??probe KPFM on organic solar cells
摘要： An implementation of pump–probe Kelvin probe force microscopy (pp-KPFM) is reported that enables recording the time-resolved surface potential in single-point mode or over a 2D grid. The spectroscopic data are acquired in open z-loop configuration, which simplifies the pp-KPFM operation. The validity of the implementation is probed by measurements using electrical pumping. The dynamical photoresponse of a bulk heterojunction solar cell based on PTB7 and PC71BM is subsequently investigated by recording point-spectroscopy curves as a function of the optical power at the cathode and by mapping 2D time-resolved images of the surface photovoltage of the bare organic active layer.
关键词： Kelvin probe force microscopy (KPFM),time-resolved measurements,bulk heterojunctions,organic photovoltaics,pump–probe configuration,photocarrier dynamics
更新于2025-09-16 10:30:52
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Semiconducting single-walled carbon nanotube/graphene van der Waals junctions for highly sensitive all-carbon hybrid humidity sensors
摘要： Van der Waals (vdW) heterojunctions composed of diverse atomic-thin nanomaterials have great potential as building blocks for innovative nanodevices due to the unique electron coupling effect. However, previous researches have mainly focused on the light-mater interactions and charge transfer process, and the interactions between gas/vapor and vdW heterojunctions still remain to be verified. Herein, we firstly demonstrate the charge transfer based on the interaction between water (H2O) molecules and the all-carbon vdW junctions, which are formed by stacking non-carboxylated (6, 5) single-walled carbon nanotube (SWCNT) on the surface of chemical vapor deposition synthesized graphene. Based on these interaction mechanism and charge transfer process, a proof-of-concept all-carbon vdW junction humidity sensor has been fabricated. The device exhibits good reproducibility and high sensitivity of 24% per 1% RH change in a wide relative humidity range of 5~80 % with short response/recovery time of 198/110 ms. Furthermore, the effect of H2O molecule absorption on the charge transfer dynamics at the SWCNT/graphene vdW junctions has been demonstrated via Raman spectra, giving a novel humidity sensing mechanism. Our finding provides a new strategy to fabricate high performance humidity sensors using vdW heterojuctions as sensing layers.
关键词： humidity sensor,single-walled carbon nanotube,graphene,charge transfer,van der Waals heterojunctions
更新于2025-09-16 10:30:52
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MOCVD Heteroepitaxial β‐Ga <sub/>2</sub> O <sub/>3</sub> and Black Phosphorus Pn Heterojunction for Solar‐Blind Ultraviolet and Infrared Dual‐Band Photodetector
摘要： MOCVD heteroepitaxial β-Ga2O3 and BP pn heterojunction for solar-blind UV and IR dual-band photodetector is proposed and demonstrated for the first time. The device demonstrates a remarkable photoresponse under UV and IR irradiations with a responsivity of 88.5 mA/W and 1.24 mA/W, respectively, an obvious pn heterojunction characteristics, as well as an excellent photoswitch periodicity. Moreover, under different irradiation conditions, the photoelectric properties of β-Ga2O3/BP pn heterojunction, including their photogeneration and photoresponse, are investigated in detail. These results signify that β-Ga2O3/BP pn heterojunction may find potential applications in future UV/IR dual-band detection systems.
关键词： black phosphorus,β-Ga2O3,heterojunctions,UV/IR,photodetector
更新于2025-09-12 10:27:22
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Facile Formation of 2D-3D Heterojunctions on Perovskite Thin Film Surfaces for Efficient Solar Cells
摘要： The interfaces between perovskite and charge transport layers greatly impact the device efficiency and stability of perovskite solar cells (PSCs). Inserting an ultrathin wide bandgap layer between perovskite and hole transport layers (HTL) has recently been shown as an effective strategy to enhance device performance. Herein, a small amount of organic halide salt, N,N’-dimethylethylene-1,2-diammonium iodide, is used to create 2D-3D heterojunctions on MAPbI3 thin film surfaces by facile solution processing. The formation of ultrathin wide bandgap 2D perovskite layer on top of 3D MAPbI3 changes the morphological and photophysical properties of perovskite thin films, effectively reduces the surface defects, and suppresses the charge recombination in the interfaces between perovskite and HTL. As a result, a power conversion efficiency of ~ 20.2%, with an open circuit voltage of 1.14 V, a short-circuit current density of 22.57 mA cm-2, and a fill factor of 0.78, is achieved for PSCs with enhanced stability.
关键词： Perovskite solar cells,2D-3D heterojunctions,interface engineering,stability,surface passivation
更新于2025-09-12 10:27:22
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Salt‐Assisted Growth of P‐type Cu <sub/>9</sub> S <sub/>5</sub> Nanoflakes for P‐N Heterojunction Photodetectors with High Responsivity
摘要： P-n junctions based on two dimensional (2D) van der Waals (vdW) heterostructure are one of the most promising alternatives in next-generation electronics and optoelectronics. By choosing different 2D transition metal dichalcogenides (TMDCs), the p-n junctions have tailored energy band alignments and exhibit superior performance as photodetectors. The p-n diodes working at reverse bias commonly have high detectivity due to suppressed dark current but suffer from low responsivity resulting from small quantum efficiency. Greater build-in electric field in the depletion layer can improve the quantum efficiency by reducing recombination of charge carriers. Herein, Cu9S5, a novel p-type semiconductor with direct bandgap and high optical absorption coefficient, is synthesized by salt-assisted chemical vapor deposition (CVD) method. The high density of holes in Cu9S5 endows the constructed p-n junction, Cu9S5/MoS2, with strong build-in electric field according to Anderson heterojunction model. Consequently, the Cu9S5/MoS2 p-n heterojunction has low dark current at reverse bias and high photoresponse under illumination due to the efficient charge separation. The Cu9S5/MoS2 photodetector exhibits good photodetectivity of 1.6 × 1012 Jones and photoresponsivity of 76 A W?1 under illumination. This study demonstrates Cu9S5 as a promising p-type semiconductor for high-performance p-n heterojunction diodes.
关键词： Cu9S5,2D metal chalcogenides,photodetectors,van der Waals epitaxy,p-n heterojunctions
更新于2025-09-12 10:27:22
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Deep UV laser at 249 nm based on GaN quantum wells
摘要： In this letter, we report on deep UV laser emitting at 249 nm based on thin GaN quantum wells (QWs) by optical pumping at room temperature. The laser threshold was 190 kW/cm2 that is comparable to state-of-the-art AlGaN QW lasers at similar wavelengths. The laser structure was pseudomorphically grown on a c-plane sapphire substrate by metalorganic chemical vapor deposition, comprising 40 pairs of 4 monolayer (ML) GaN QWs sandwiched by 6 ML AlN quantum barriers (QBs). The low threshold at the wavelength was attributed to large optical and quantum confinement, and high quality of the material, interface, and Fabry-P?rot facet. The emissions below and above the threshold were both dominated by transverse electric polarizations thanks to the valence band characteristics of GaN. This work unambiguously demonstrates the potentials of the binary AlN/GaN heterojunctions for high-performance UV emitters.
关键词： GaN quantum wells,deep UV laser,UV emitters,AlN/GaN heterojunctions,optical pumping
更新于2025-09-12 10:27:22
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A High‐Performance Solution‐Processed Organic Photodetector for Near‐Infrared Sensing
摘要： Sensitive detection of near-infrared (NIR) light enables many important applications in both research and industry. Current organic photodetectors suffer from low NIR sensitivity typically due to early absorption cutoff, low responsivity, and/or large dark/noise current under bias. Herein, organic photodetectors based on a novel ultranarrow-bandgap nonfullerene acceptor, CO1-4Cl, are presented, showcasing a remarkable responsivity over 0.5 A W?1 in the NIR spectral region (920–960 nm), which is the highest among organic photodiodes. By effectively delaying the onset of the space charge limited current and suppressing the shunt leakage current, the optimized devices show a large specific detectivity around 1012 Jones for NIR spectral region up to 1010 nm, close to that of a commercial Si photodiode. The presented photodetectors can also be integrated in photoplethysmography for real-time heart-rate monitoring, suggesting its potential for practical applications.
关键词： high responsivity,bulk heterojunctions,photodetectors,organic photodiodes,near-infrared
更新于2025-09-12 10:27:22
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Direct Synthesis of a Self‐Assembled WSe <sub/>2</sub> /MoS <sub/>2</sub> Heterostructure Array and its Optoelectrical Properties
摘要： Functional van der Waals heterojunctions of transition metal dichalcogenides are emerging as a potential candidate for the basis of next-generation logic devices and optoelectronics. However, the complexity of synthesis processes so far has delayed the successful integration of the heterostructure device array within a large scale, which is necessary for practical applications. Here, a direct synthesis method is introduced to fabricate an array of self-assembled WSe2/MoS2 heterostructures through facile solution-based directional precipitation. By manipulating the internal convection flow (i.e., Marangoni flow) of the solution, the WSe2 wires are selectively stacked over the MoS2 wires at a specific angle, which enables the formation of parallel- and cross-aligned heterostructures. The realized WSe2/MoS2-based p–n heterojunction shows not only high rectification (ideality factor: 1.18) but also promising optoelectrical properties with a high responsivity of 5.39 A W?1 and response speed of 16 μs. As a feasible application, a WSe2/MoS2-based photodiode array (10 × 10) is demonstrated, which proves that the photosensing system can detect the position and intensity of an external light source. The solution-based growth of hierarchical structures with various alignments could offer a method for the further development of large-area electronic and optoelectronic applications.
关键词： transition-metal dichalcogenides,p–n junctions,Marangoni flow,photodetectors,heterojunctions
更新于2025-09-11 14:15:04
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Efficient Polymer Solar Cells Based on New Random Copolymers with Porphyrin‐Incorporated Side Chains
摘要： Two new wide bandgap block copolymers (PL1 and PL2) with porphyrin-incorporated side chains are designed and used as electron donors for solution-processed bulk heterojunction polymer solar cells. The photophysical, electrochemical, and photovoltaic properties, charge transport mobility and film morphology of these two block copolymers are investigated. Detailed investigations reveal that the different alkyl groups and electron-withdrawing substituents on the porphyrin pendant units have significant influence on the polymer solubility, absorption energy level, band gap, and charge separation in the bulk-heterojunction thin films, and thus the overall photovoltaic performances. Organic photovoltaic devices derived from these copolymers and ([6,6]-phenyl-C71-butyric acid methyl ester) (PC71BM) acceptor show the best power conversion efficiencies of 5.83% and 7.14%, respectively. These results show that the inclusion of a certain proportion of side chain porphyrin group as a pendant in the traditional donor-acceptor (D-A) type polymer can broaden the molecular absorption range and become a full-color absorbing molecule. The size of the porphyrin pendant also has an obvious effect on the properties of the molecule.
关键词： block copolymers,organic photovoltaics,polymer solar cells,bulk heterojunctions,porphyrin
更新于2025-09-11 14:15:04
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BiOBr/Ag6Si2O7 heterojunctions for enhancing visible light catalytic degradation performances with a sequential selectivity enabled by dual synergistic effects
摘要： Efficient separation of photogenerated electron-hole pairs is always one of the key factors boosting visible light photodegradation efficiency. Till now, there are few reports on the synergistic competitive consumption of photogenerated active species and the synergistic adsorption of organic contaminants to promote the performance of a designed heterojunction. Herein, we design and construct a novel BiOBr/Ag6Si2O7 heterojunction with the dual synergistic effects towards methylene blue (MB) and methyl orange (MO). The dual synergistic effects could avoid the combination of photogenerated h+/e? pairs, improve the adsorption efficiency, and even regulate the photodegradation efficiency. Thus, for an aqueous mixture of MB and MO, the BiOBr/Ag6Si2O7 photocatalyst exhibits largely improved adsorption capacities of the dyes by a multi-layer adsorption mode. Moreover, the photocatalyst could further promote the photodegradation rate of MO while slow that of MB due to the competitive consumption of photogenerated active species, showing a sequential selectivity phenomenon. Thanks to the dual synergistic effects, the adsorption capacity of MO increases 1379% higher than that of neat MO solution, and the photodegradation time decrease from 30 to 12 min with a rate constant of 0.22 min?1, 38% higher than that of neat MO solution.
关键词： BiOBr,Silver silicates,Visible light photodegradation,Heterojunctions,Photocatalysts
更新于2025-09-11 14:15:04