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Manipulating the Phase Distributions and Carrier Transfers in Hybrid Quasi-Two-Dimensional Perovskite Films
摘要： Quasi two-dimensional perovskites are promising alternatives to conventional three-dimensional perovskites because of their high stability and easy tunability. However, controlling the phase distribution according to device architecture remains a major challenge. Here, the manipulation of phase purity and vertical distribution proven by ultrafast transient absorption spectroscopy, and their effect on device characteristics are reported. By adding ethyl acetate as antisolvent, the growth direction of the perovskite film is flipped. CH3NH3Cl and dimethyl sulfoxide are used to slow the growth rate of the crystal, which gives better phase purity. The direction of carrier transfer is tuned accordingly. It is found that solar cell performance is more sensitive to phase purity relative to vertical distribution. These findings are of importance for the applications of quasi-2D perovskites in different types of devices that require to change phase purity and vertical distribution.
关键词： solar cells,carrier transfer,vertical distribution,phase purity,quasi-2D perovskite
更新于2025-11-19 16:56:35
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CdSe/CdMnS Nanoplatelets with Bilayer Core and Magnetically Doped Shell Exhibit Switchable Excitonic Circular Polarization: Implications for Lasers and Light-Emitting Diodes
摘要： We utilized time-resolved photoluminescence (TRPL) spectroscopy to study the excitonic circular polarization (PX) from CdSe/CdMnS core/shell nanoplatelets (NPLs) with a bilayer core. This allows an extensive study of the emission dynamics as a function of magnetic ?eld, temperature, doping concentration, and excitation wavelength. In the presence of an external magnetic ?eld, pulsed excitation below the shell gap results in near-zero excitonic circular polarization PX at all time delays. In contrast, pulsed excitation with photon energy larger than the shell gap results in a rapid (100 ps) buildup of the excitonic circular polarization which subsequently remains constant at a level of up to 40%. We propose a model to describe the dynamics which takes into account the exchange interaction between carrier and magnetic ion (Mn) spins. The studied system exhibits a fast switchable excitonic circular polarization, implying possible applications in lasers and light emitting diodes.
关键词： spd exchange interaction,quasi-2D,time-resolved photoluminescence,nanoplatelets,magneto-optical switch
更新于2025-09-23 15:21:01
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Boosting the Efficiency and Curtailing the Efficiency Roll-off in Green Perovskite Light-Emitting Diodes via Incorporating Ytterbium as Cathode Interface Layer
摘要： Perovskite light-emitting diodes (PeLEDs) exhibit high external quantum efficiencies (EQEs), emerging as a next-generation technology for lighting and display applications. Nevertheless, they suffer from severe efficiency roll-off at high luminance, particularly in case of blue and green emissions, which is one of the major bottlenecks in their industrial applications. Here, we attack this problem using a rare-earth metal, Yb, as cathode interface layer (CIL) for green PeLEDs. By adopting a new device configuration of ITO/TFB/FA-based Quasi-2D Perovskite/TPBi/Yb/Ag, we achieved a peak current efficiency (CE) of 22.3 cd/A with a corresponding EQE of 5.28% and a high maximum luminance of 19,160 cd/m2. Importantly, the maximum CE of 22 cd/A at 2,000 cd/m2 slightly decreased to 16.8 cd/A at 5,000 cd/m2 and maintained a still decent value of 12 cd/A at a very high luminance of 10,000 cd/m2, exhibiting a remarkably low efficiency roll-off. Our Yb-incorporated devices significantly outperformed the PeLEDs containing conventional CILs, including Mg and Liq, in terms of peak efficiency, efficiency roll-off and operational lifetime. We attribute this encouraging performance to barrier-free, efficient electron injection enabled by the low work function of Yb (2.6 eV) which led to a high electron current, nearly approaching the hole current in hole-dominant PeLEDs, as confirmed by the single-carrier device measurements. In addition, we also present Yb-incorporated PeLEDs containing Cs-based Quasi-2D perovskite as the emissive layer which displayed an impressive CE of 51.3 cd/A with a corresponding EQE of 16.4% and a maximum luminance of 14,240 cd/m2, and still demonstrated a reduced efficiency roll-off comparing to that of the Liq-based equivalent. These results unveil the inspiring prospects of Yb as an efficient CIL for PeLEDs towards high efficiency with reduced efficiency roll-off.
关键词： electron injection,ytterbium,quasi-2D,perovskite light-emitting diodes,stability,cathode interface layer,efficiency roll-off
更新于2025-09-23 15:21:01
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Nona??Conjugated Polymer Based on Polyethylene Backbone as Dopanta??Free Holea??Transporting Material for Efficient and Stable Inverted Quasia??2D Perovskite Solar Cells
摘要： Novel non-conjugated polymer based on polyethylene backbone, PVCz-OMeTPA with suitable energy levels, good hole mobility as well as excellent film-forming ability assisting the formation of high-quality perovskite films, is developed as efficient dopant-free hole-transporting materials (HTMs) for inverted quasi-2D perovskite solar cells (PSCs). Quasi-2D PSCs using ultra-thin, dopant-free PVCz-OMeTPA as HTM exhibited excellent power conversion efficiency of 17.22% and long-term environmental stability.
关键词： low-cost,quasi-2D perovskite solar cells,main-chain non-conjugated polymer,dopant-free hole-transporting materials
更新于2025-09-23 15:21:01
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Nona??Preheating Processed Quasia??2D Perovskites for Efficient and Stable Solar Cells
摘要： Although the hot-casting (HC) technique is prevalent in developing preferred crystal orientation of quasi-2D perovskite films, the difficulty of accurately controlling the thermal homogeneity of substrate is unfavorable for the reproducibility of device fabrication. Herein, a facile and effective non-preheating (NP) film-casting method is proposed to realize highly oriented quasi-2D perovskite films by replacing the butylammonium (BA+) spacer partially with methylammonium (MA+) cation as (BA)2?x(MA)3+xPb4I13 (x = 0, 0.2, 0.4, and 0.6). At the optimal x-value of 0.4, the resultant quasi-2D perovskite film possesses highly orientated crystals, associated with a dense morphology and uniform grain-size distribution. Consequently, the (BA)1.6(MA)3.4Pb4I13-based solar cells yield champion efficiencies of 15.44% with NP processing and 16.29% with HC processing, respectively. As expected, the HC-processed device shows a poor performance reproducibility compared with that of the NP film-casting method. Moreover, the unsealed device (x = 0.4) displays a better moisture stability with respect to the x = 0 stored in a 65% ± 5% relative humility chamber.
关键词： solar cells,crystal orientation,quasi-2D perovskites,film casting
更新于2025-09-23 15:19:57
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Phase control of quasi-2D perovskites and improved light-emitting performance by excess organic cations and nanoparticle intercalation
摘要： The optoelectronic properties of quasi-two-dimensional organic–inorganic hybrid perovskites can be tuned by controlling the formation of Ruddlesden–Popper type phases, which enables diverse device applications such as photovoltaics and light-emitting diodes (LEDs). Herein, the influence of excess organic cations on the phase formation of (PEA)2MAn?1PbnBr3n+1 is systematically investigated with various mixing ratios to discover the phase distribution beneficial for light-emitting diodes. It is found that PEA cations exceeding Pb ions in molar ratio are required to produce small-n phases in the films with a strong photoluminescence, while excess MA cations enable the formation of more large-n phases. Low electrical conductivity inherent to the properties of quasi-2D perovskites is further lowered by the introduction of excess organic cations. This is overcome by the intercalation of zinc oxide (ZnO) nanoparticles (NPs) into the blocking layers composed of PEA cations. Importantly, these metal oxide NPs also modulate the phase distribution, enabling the realization of bright green quasi-2D perovskites with a better stability and a maximum luminance of nearly 60 000 cd m?2, which is the highest brightness compared to the so far reported quasi-2D perovskite LEDs incorporating organic cations.
关键词： phase control,excess organic cations,nanoparticle intercalation,light-emitting diodes,quasi-2D perovskites
更新于2025-09-19 17:15:36
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Understanding the Defect Properties of Quasi-2D Halide Perovskites for Photovoltaic Applications
摘要： Quasi-2D halide perovskites have emerged as one of the most promising photovoltaic materials owing to their excellent stability, yet the device power conversion efficiency (PCE) is far from satisfactory. Beside of crystal orientation related carrier transport, defects in absorbers also play a crucial role in device performance, which receives limited attention in the 2D perovskite field. Herein we systematically profiled the defects states in 2D perovskite film by the temperature-dependent admittance spectroscopy (AS), light-intensity-dependent VOC, space-charge-limited-circuit (SCLC), and photoluminescence measurements. It is revealed that the Quasi-2D perovskite films suffer from severe defects as compared to the 3D counterparts in terms of both trap energy levels and trap densities. Consequently, nonradiative recombination of photogenerated carriers is much greater in the corresponding devices, wherein the monomolecular recombination is dominant. These findings substantially benefit a deeper understanding of the nature of 2D perovskite materials, which promotes the further design of 2D perovskite solar cells.
关键词： carrier recombination,Quasi-2D halide perovskites,defects properties,photovoltaic materials,solar cells
更新于2025-09-19 17:13:59
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Solar-blind deep-ultraviolet photodetectors based on solution-synthesized quasi-2D Te nanosheets
摘要： Solar-blind deep ultraviolet (DUV) photodetectors with high responsivity (R) and fast response speed are crucial for practical applications in astrophysical analysis, environmental pollution monitoring, and communication. Recently, 2D tellurium has emerged as a potential optoelectronic material because of its excellent photoelectric properties. In this study, solar-blind DUV photodetectors are demonstrated based on solution-synthesized and air-stable quasi-2D Te nanosheets (Te NSs). An R of 6.5×104 A/W at 261 nm and an external quantum efficiency (EQE) of higher than 2.26×106% were obtained, which are highest among most other 2D material-based solar-blind DUV photodetectors. Moreover, the photoelectric performance of the quasi-2D Te-based photodetector exhibited good stability even after ambient exposure for 90 days without any encapsulation. These results indicate that quasi-2D Te NSs provide a viable approach for developing solar-blind DUV photodetectors with ultrahigh R and EQE.
关键词： FET,photodetector,solar-blind deep ultraviolet,quasi-2D Te nanosheets
更新于2025-09-19 17:13:59
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Pulsed Laser Deposition Assisted van der Waals Epitaxial Large Area Quasi‐2D ZnO Single‐Crystal Plates on Fluorophlogopite Mica
摘要： There are still challenges in growth of transferable large area orientated ultrathin high-melting-point metal oxide single crystals with conventional methods. Herein, a new pathway to produce high quality single-crystal ZnO nanoplates with more than 400 μm crystal size is revealed by using the van der Waals epitaxy (vdWE) combined with pulsed laser deposition (PLD) method on fluorophlogopite mica. The quasi-2D ZnO plates as thin as 5 nm on fluorophlogopite mica without transition layer are achieved, showing an excellent thickness and orientation control while maintaining the excellent crystalline. ZnO nanoplates grown on conducting graphite and insulating hexagonal boron nitride (h-BN) 2D substrates are also obtained through PLD assisted vdWE. The transfer of 15 nm thick quasi-2D ZnO plates with 8 mm × 8 mm area onto a SiO2/Si substrate is successfully demonstrated. Based on the ZnO nanoplates, semitransparent self-powered ultraviolet (UV) photodetectors and light-emitting diodes centered at 400 nm UV region are demonstrated. This research highlights that the PLD assisted vdWE method is a fascinating way to fabricate high coverage ultrathin 2D ZnO plates with precisely thickness control for optoelectronic applications and may have enormous inspiration for other 2D nanomaterials growth.
关键词： pulsed laser deposition,van der Waals epitaxy,quasi-2D,ZnO single-crystal plate
更新于2025-09-19 17:13:59
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Nonconfinement Structure Revealed in Dion–Jacobson Type Quasi‐2D Perovskite Expedites Interlayer Charge Transport
摘要： Dion–Jacobson (DJ) type 2D perovskites with a single organic cation layer exhibit a narrower distance between two adjacent inorganic layers compared to the corresponding Ruddlesden–Popper perovskites, which facilitates interlayer charge transport. However, the internal crystal structures in 2D DJ perovskites remain elusive. Herein, in a p-xylylenediamine (PDMA)-based DJ perovskite bearing bifunctional NH3+ spacer, the compression from confinement structure (inorganic layer number, n = 1, 2) to nonconfinement structure (n > 3) with the decrease of PDMA molar ratio is unraveled. Remarkably, the nonconfined perovskite displays shorter spacing between 2D quantum wells, which results in a lower exciton binding energy and hence promotes exciton dissociation. The significantly diminishing quantum confinement promotes interlayer charge transport leading to a maximum photovoltaic efficiency of ≈11%. Additionally, the tighter interlayer packing arising from the squeezing of inorganic octahedra gives rise to enhanced ambient stability.
关键词： exciton,planar perovskite solar cells,nonconfinement structures,Dion–Jacobson,quasi-2D perovskite
更新于2025-09-19 17:13:59