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Bandgap tunable Zn3-3Mg3N2 alloy for earth-abundant solar absorber
摘要： Zn3-3xMg3xN2 alloy layers with x ≤ 0.3 can be epitaxially grown at a temperature as low as 140 oC. The bandgap (Eg) of Zn3-3xMg3xN2 widens from 1.2 to 2.1 eV with increasing x. The Eg value of 1.4 eV is obtained at x = 0.18, and the x = 0.18 film has a large absorption coefficient (104-105 cm-1) in the visible region. The Zn3-3xMg3xN2 with Eg = 1.4 eV shows n-type conductivity with a reasonably high electron mobility of 47 cm2 V-1 s-1. Therefore, Zn3-3xMg3xN2 is a candidate for an earth-abundant solar absorber that can be fabricated at low temperatures.
关键词： Nitride alloy,Bandgap tunability,Photovoltaic semiconductors,Sputtering
更新于2025-09-23 15:21:01
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Sputtered p-type Cu <sub/>x</sub> Zn <sub/>1-x</sub> S back contact to CdTe solar cells
摘要： As thin film cadmium telluride (CdTe) solar cells gain prominence, one particular challenge is optimizing contacts and their interfaces to transfer charge without losses in efficiency. Back contact recombination is still significant and will prevent CdTe solar technology from reaching its full potential in device efficiency, and transparent back contacts have not been developed for bifacial solar technology or multijunction solar cells. To address these challenges, this study investigates sputtered CuxZn1-xS as a p-type semi-transparent back contact material to thin film polycrystalline CdTe solar cells, at Cu concentrations x = 0.30, 0.45 and 0.60. This material is selected for its high hole conductivity (160 to 2,120 S cm-1), wide optical band gap (2.25 to 2.75 eV), and variable ionization potential (approximately 6 to 7 eV) that can be aligned to that of CdTe. We report that without device optimization, CdTe solar cells with these CuxZn1-xS back contacts perform as well as control cells with standard ZnTe:Cu back contacts. We observe no reduction in external quantum efficiency, low contact barrier heights of approximately 0.3 eV, and carrier lifetimes on par with those of baseline CdTe. These cells are relatively stable over one year in air, with VOC and efficiency of the x = 0.30 cell decreasing by only 1% and 3%, respectively. Using SEM and STEM to investigate the CuxZn1-xS?CdTe interface, we demonstrate that the CuxZn1-xS layer segregates into a bilayer of Cu-Te-S and Zn-Cd-S, and thermodynamic reaction calculations support these findings. Despite its bilayer formation, the back contact still functions well. This investigation explains some of the physical mechanisms governing the device stack, inspires future work to understand interfacial chemistry and charge transfer, and elicits optimization to achieve higher efficiency CdTe cells.
关键词： solar cell back contact design,transparent semiconductors,copper zinc sulfide,solar cell interfaces,CdTe photovoltaics
更新于2025-09-23 15:21:01
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Growth mechanisms of F4-TCNQ on inorganic substrates and nanostructures
摘要： The organic semiconductor tetrafluorotetracyanoquinodimethane (F4-TCNQ) is a promising candidate for the doping of organic semiconductors, two-dimensional materials and inorganic compounds, such as ZnO, and also to enhance the charge carrier injection at contacts in organic electronics. In order to evaluate its applicability as a functionalization material or as an electrically active part in devices, we present a systematic study on the growth mode of F4-TCNQ beyond the first few monolayers on different inorganic substrates that cover a broad variety regarding their physical, chemical and morphological surface properties. The materials used are silicon, silicon carbide, graphene on silicon, sapphire, nanocrystalline diamond, as well as gallium nitride (GaN) layers and nanowire arrays. While the surface termination influences the shape and morphology of the islands of F4-TCNQ which form on all substrates investigated, no significant dependence of the growth mode on the substrate doping type and concentration is observed. GaN nanowires are found to act as nucleation sites for F4-TCNQ islands and to be covered by few monolayers of F4-TCNQ forming a closed coaxial shell. In conclusion, F4-TCNQ is identified to nucleate via Stranski-Krastanov growth consisting of monolayers and islands of different size and shape. The findings in this work provide basic growth information for the implementation of F4-TCNQ as functionalization material for nanowire-based applications.
关键词： GaN nanowires,surface functionalization,growth mode,organic semiconductors,organic electronics,surface doping,F4-TCNQ
更新于2025-09-23 15:21:01
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Layer-by-layer assembled synthesis of hollow yolk-shell CdSa??graphene nanocomposites and their high photocatalytic activity and photostability
摘要： Herein, we successfully synthesized, for the first time, a diameter of 340 nm hollow yolk-shell type CdS–graphene composite photocatalyst with a hollow core and an independent void space with 5~10 nm between hollow CdS core and graphene (GR) shell with the thickness of about 2 nm (denoted as hollow CdS@@GR), by the bottom-up method using the template-guided layer-by-layer self-assembly process. The formation mechanism of hollow CdS@@GR nanocomposites was proposed. Due to the unique hollow structure that can absorb more light, more dye, and catalyst molecules and the synergistic effect between hollow CdS core and GR shell with void space, hollow CdS@@GR showed enhanced photocatalytic performance. In addition, GR shell can effectively protect CdS from photocorrosion, and even after five repeated runs, the recycled nanocomposites exhibited superior stability. Moreover, we also proposed the possible photocatalytic mechanism of such nanostructures based on free radical capturing experiments and fluorescent probe technique. The design and fabrication of the hollow yolk-shell structured nanocomposites will provide a new potential route for other stable and efficient photocatalysts to satisfy versatile solar energy conversion.
关键词： Graphene,CdS,Hollow yolk-shell type,Stability,Nanocomposites,Semiconductors
更新于2025-09-23 15:21:01
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Ambient air-processed mesoscopic solar cells based on methylammonium and phenethylammonium quasi-2D/3D perovskites
摘要： The instability of perovskite solar cells under ambient conditions leads many scientific groups to produce their solar cell devices under controllable, yet, expensive conditions. In this work, a mesoscopic solar cell device produced under ambient air/temperature conditions and relatively high humidity is presented. The active material is based on methylamine, phenethylamine, lead(II) iodide and lead(II) chloride. Furthermore, a bis(trifluoromethane)sulfonimide lithium (Li-TFSI) salt layer was used as a dopant onto mesoscopic TiO2, while the hole-transport material used was the popular poly(3-hexylthiophene-2,5-diyl) (P3HT) polymer. All layers were deposited by simple spin coating technique, while the whole process took place under 40–60% relative humidity–ambient conditions. The sequential deposited perovskite layer was built by a 3D mixed halide (CH3NH3)3PbI3Cl2 layer on top of a mixed 3D/Quasi-2D perovskite (CH3NH3)3PbI3Cl2–(C8H9NH3)2(CH3NH3)2Pb3I10 layer. These specific perovskites were used to take advantage of the well-known power conversion efficiency (PCE) of the mixed halide perovskite based on methylamine, and the proven reproducibility and stability of the phenethylamine-based perovskites, especially under non-controllable conditions. The champion mesoscopic device presented a PCE of 13.22%, with short circuit current density (JSC) of 23.67 mA/cm2, open circuit voltage (VOC) of 1034 mV and fill factor (FF) 0.54.
关键词： Mesoscopic structure,Methylamine–phenethylamine mixed cations,Hybrid organic–inorganic semiconductors,Ambient conditions,Perovskites,Mesoporous solar cells
更新于2025-09-23 15:21:01
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Role of Sb on the vertical-alignment of type-II strain-coupled InAs/GaAsSb multi quantum dots structures
摘要： The implementation of GaAs0.8Sb0.2 as CL to obtain type-II strain-coupled InAs MQD structures has been examined and compared to similar structures without Sb or without strain coupling. First, it has been demonstrated that capping with GaAsSb prevents the formation of In-rich agglomerations that hampered the QD formation as it has been observed in the sample without Sb. Instead, it promotes the vertical alignment (VA) of almost all QDs with a high density of QD columns. Second, there is a preferential Sb accumulation over the dots together with an undulation of the growth front, contrary to the observed in the uncoupled structure. In case of a deficient covering of GaAsSb, as occurs for giant QDs, In-rich agglomerations may develop. Each VAQD column consists of a sequence of alternating quantum blocks of pyramid-shaped In(Ga)As separated by GaAsSb blocks that rest over them. These Sb-rich blocks are not homogeneous accumulating around the pyramidal apex like a collar. Between the columns, there is an impoverishment of In and Sb compared to the uncoupled sample. These columns can behave as self-aligned nanowires with type II band alignment between self-assembled InAs and GaAsSb quantum blocks that opens new opportunities for novel devices.
关键词： GaAsSb capping layer,III-V semiconductors alloys,Transmission electron microscopy,Composition distribution,Vertical aligned quantum dots
更新于2025-09-23 15:21:01
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Type-II heterojunction constructed by Ag2S-coupled ZnO microspheres with visible light-responsive antibacterial activity
摘要： ZnO nanorods-assembled microspheres were photosensitized with a layer of low bandgap Ag2S nanoparticles on the branched nanorods to get a type-II core/shell heterojunction (ZnO@Ag2S). The heterojunction with unique band configuration exhibited better visible light-responsive antibacterial activity than pure ZnO, which is attributed to the inhibition of photocarrier recombination and efficient charge separation and transfer. Scavenger test confirmed that the photoinactivation of bacteria was directed by the (cid:1) radicals and photogenerated holes. The growth of Gram-negative bacteria was more effectively restrained by ZnO@Ag2S than that of Gram-positive bacteria and fungi because of structural difference of cell walls.
关键词： ZnO@Ag2S,Composite materials,Mechanism,Semiconductors,Photocatalytic activity
更新于2025-09-23 15:21:01
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Photovoltaic-Driven SiC MOSFET Circuit Breaker with Latching and Current Limiting Capability
摘要： This paper introduces a Solid State Circuit Breaker with Latching and Current Limiting capabilities for DC distribution systems. The proposed circuit uses very few electronic parts and it is fully analog. A SiC N-MOSFET driven by a photovoltaic driver and a maximum current detector circuit are the core elements of the system. This work details circuit operation under different conditions and includes experimental validation at 1 kVdc. Wide versatility, highly configurable, and very fast response, less than 1 μs in the case of short-circuit, are the most remarkable outcomes.
关键词： SiC MOSFET,Solid State Circuit Breaker (SSCB),fault current limiter,WBG semiconductors,DC power distribution
更新于2025-09-23 15:21:01
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Polariton condensation in photonic crystals with high molecular orientation
摘要： We study Frenkel exciton-polariton Bose–Einstein condensation in a two-dimensional defect-free triangular photonic crystal with an organic semiconductor active medium containing bound excitons with dipole moments oriented perpendicular to the layers. We ?nd photonic Bloch modes of the structure and consider their strong coupling regime with the excitonic component. Using the Gross– Pitaevskii equation for exciton polaritons and the Boltzmann equation for the external exciton reservoir, we demonstrate the formation of condensate at the points in reciprocal space where photon group velocity equals zero. Further, we demonstrate condensation at non-zero momentum states for transverse magnetic-polarized photons in the case of a system with incoherent pumping, and show that the condensation threshold varies for different points in the reciprocal space, controlled by detuning.
关键词： organic semiconductors,photonic crystalls,photonics,exciton polaritons,Bose–Einstein condensate
更新于2025-09-23 15:21:01
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Efficiency of Charge-Transfer Doping in Organic Semiconductors Probed with Quantitative Microwave and Direct-Current Conductance
摘要： Although molecular charge-transfer doping is widely used to manipulate carrier density in organic semiconductors, only a small fraction of charge carriers typically escape the Coulomb potential of dopant counterions to contribute to electrical conductivity. Here, we utilize microwave and direct-current (DC) measurements of electrical conductivity to demonstrate that a high percentage of charge carriers in redox-doped semiconducting single-walled carbon nanotube (s-SWCNT) networks is delocalized as a free carrier density in the π-electron system (estimated as >46% at high doping densities). The microwave and four-point probe conductivities of hole-doped s-SWCNT films quantitatively match over almost 4 orders of magnitude in conductance, indicating that both measurements are dominated by the same population of delocalized carriers. We address the relevance of this surprising one-to-one correspondence by discussing the degree to which local environmental parameters (e.g., tube?tube junctions, the relative Coulombic stabilization, and local bonding environment) may impact magnitudes of each transport measurement.
关键词： microwave conductivity,organic semiconductors,single-walled carbon nanotube,charge-transfer doping,DC conductivity
更新于2025-09-23 15:21:01