A cocrystal strategy with a simple preparation process is developed to prepare novel materials for near‐infrared photothermal (PT) conversion and imaging. DBTTF and TCNB are selected as electron ...donor (D) and electron acceptor (A) to self‐assemble into new cocrystals through non‐covalent interactions. The strong D–A interaction leads to a narrow band gap with NIR absorption and that both the ground state and lowest‐lying excited state are charge transfer states. Under the NIR laser illumination, the temperature of the cocrystal sharply increases in a short time with high PT conversion efficiency (η=18.8 %), which is due to the active non‐radiative pathways and inhibition of radiative transition process, as revealed by femtosecond transient absorption spectroscopy. This is the first PT conversion cocrystal, which not only provides insights for the development of novel PT materials, but also paves the way of designing functional materials with appealing applications.
The heat is on: A new cocrystal with NIR photothermal properties is prepared from two small molecules, wherein the strong charge‐transfer interaction leads to active non‐radiative pathways, as revealed by femtosecond transient absorption spectroscopy.
Single-crystal perovskites with excellent photophysical properties are considered to be ideal materials for optoelectronic devices, such as lasers, light-emitting diodes and photodetectors. However, ...the growth of large-scale perovskite single-crystal films (SCFs) with high optical gain by vapor-phase epitaxy remains challenging. Herein, we demonstrated a facile method to fabricate large-scale thin CsPbBr3 SCFs (∼300 nm) on the c-plane sapphire substrate. High temperature is found to be the key parameter to control low reactant concentration and sufficient surface diffusion length for the growth of continuous CsPbBr3 SCFs. Through the comprehensive study of the carrier dynamics, we clarify that the trapped-related exciton recombination has the main effect under low carrier density, while the recombination of excitons and free carriers coexist until free carriers plays the dominate role with increasing carrier density. Furthermore, an extremely low-threshold (∼8 μJ cm–2) amplified spontaneous emission was achieved at room temperature due to the high optical gain up to 1255 cm–1 at a pump power of 20 times threshold (∼20 P th). A microdisk array was prepared using a focused ion beam etching method, and a single-mode laser was achieved on a 3 μm diameter disk with the threshold of 1.6 μJ cm–2. Our experimental results not only present a versatile method to fabricate large-scale SCFs of CsPbBr3 but also supply an arena to boost the optoelectronic applications of CsPbBr3 with high performance.
Lead halide perovskites have recently become a rapidly growing research field due to their great potential in next‐generation solar cells and photonic sources. As a direct bandgap semiconductor, ...perovskites are also promising candidates for low‐threshold and multicolor lasing devices due to their high optical gain, ease of bandgap engineering, large absorption coefficient, and low defect state density. In particular, reduced‐dimensional perovskite structures including nanoplatelets, nanowires, and quantum dots, are crucial for the development of micro‐ or nanosized laser sources for optical chips and high‐resolution imaging, etc. Here, perovskite nanophotonics, in particular the lasing properties of perovskite nanostructures, are discussed. The rapid advances of small lasers based on perovskite nanostructures using both active and passive microcavities are reviewed; these are mainly classified into four sections: thin films, nanoplatelets, nanowires, and quantum dots. Lasing performance in terms of threshold, color‐tunability, spectral coherence, and stability is introduced from both materials and microcavity respects. Fundamental photophysical mechanisms involved in the photoluminescence lasing process, from absorption, emission to gain, are discussed in order to provide insightful understanding lasing properties of different types of perovskites. Finally, some future prospects for perovskite lasing devices are provided.
Recent advances in small lasers based on metal halide perovskites, including thin films, nanoplatelets, nanowires, and quantum dots, are highlighted. The fundamental photophysics, materials fabrication, optical‐cavity design, and device characterization are discussed, toward small high‐performance lasers, with low threshold, wide tunability, high spectral coherence, and good stability.
Perovskite quantum dot lasers Chen, Jie; Du, Wenna; Shi, Jianwei ...
InfoMat,
January 2020, Letnik:
2, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Owing to the excellent properties of perovskite quantum dots (QDs), such as an easy synthesis process, high photoluminescence quantum yields, high defect tolerance, and tunable bandgap with different ...elements, laser actions have been widely conducted. Over the past few years, several approaches have been used for successfully creating perovskite QD lasers. In this review, we summarize the progress of perovskite QD lasers from the aspects of laser theory, characteristics and applications of QD lasers, advantages of perovskite materials for lasers, factors influencing the QD laser threshold, two‐photon pumped QD lasers, and perovskite QD laser stability. At the same time, aiming at existing problems, possible solutions and prospects are presented.
The graph shows a 3D perovskite quantum dots lasing behavior under light pump. The perovskite quantum dots hold an ABX3 structure. With light pumping, the quantum dots achieved optical gain through biexciton state and emit coherent photons.
Plasmonic nanolaser holds great potential in breaking down the diffraction limit of conventional optics to the deep sub‐wavelength regime and in ultrafast lasing dynamics. However, plasmonic laser ...devices are constrained in practical applications due to their high cost and high thresholds. All‐inorganic cesium lead halide perovskites are promising solutions for their excellent optical gain properties and high emission efficiency. In this work, high‐quality single‐crystalline CsPbBr3 perovskite nanowires (NWs) are synthesized by chemical vapor deposition method. The plasmonic lasing is achieved from the CsPbBr3 nanowire based plasmonic devices with lasing threshold down to ≈6.5 µJ cm−2 at room temperature. The highly polarized emission parallel to nanowire axis and polarization‐sensitive pump response confirm the plasmonic characteristic in these devices. Furthermore, time‐resolved photoluminescence study suggests that the radiative recombination lifetime of CsPbBr3 NW is shortened by a factor of ≈6.14 due to Purcell effect. The lasing threshold of plasmonic device increases along with the nanowire length, indicating greater potential in small size and integration in plasmonic device than its photonic counterparts. The results not only provide a solution to fabricate low‐cost nanowire based plasmonic lasers, but also advocate the prospect of all‐inorganic perovskite nanowires as promising candidates in plasmonic‐based devices.
Plasmonic nanolaser holds great potential in breaking down the diffraction limit of conventional optics to deep sub‐wavelength regime. Herein, all‐inorganic CsPbBr3 nanowire based plasmonic lasers are demonstrated at room tempearutre with threshold ≈6.5 µJ cm−2. The lasing threshold of plasmonic device increases along with the nanowire length, indicating greater potential in plasmonic integration device than its photonic couterparts.
Recently, inorganic–organic perovskite nanowires with strong photon confinement and isotropy have attracted considerable attention for advanced applications in optoelectronic devices from lasers and ...photodetectors to transistors. Moreover, their high exciton oscillation strength and binding energy make them very promising for polariton devices in the strong light–matter interaction region. This study presents the strong exciton–photon coupling in hybrid inorganic–organic CH3NH3PbBr3 micro/nanowire cavities at room temperature. Clear anticrossing feature is observed by using remote excitation photoluminescence emission spectroscopy with vacuum Rabi splitting energy up to 390 meV. The observed vacuum Rabi splitting energy of up to ≈390 meV (0.32 × 3.66 µm2) is attributed to large oscillator strength and photon confinement in reduced dimension of the micro/nanowire based Fabry–Pérot cavities. With increasing pump fluence, the exciton–photon coupling is weakened because of carrier screening effect, which leads to the occurrence of photonic lasing instead of polariton lasing. The demonstrated strong exciton–photon coupling in perovskite micro/nanowire cavities is significant for the development of high performance polariton‐based incoherent and coherent light sources, nonlinear optics, and slow light applications.
Strong exciton–photon coupling in hybrid inorganic–organic CH3NH3PbBr3 micro/nanowire cavities at room temperature is presented. By using remote excited emission spectroscopy, anticrossing with vacuum Rabi splitting energy up to ≈390 meV is observed. With increasing pump fluence, the exciton–photon coupling is weakened, which leads to photonic lasing insted of polariton lasing.
This paper addresses the challenges of data sparsity and personalization limitations inherent in current recommendation systems when processing extensive academic paper datasets. To overcome these ...issues, the present work introduces an innovative recommendation model that integrates the wealth of structured information from knowledge graphs and refines the amalgamation of temporal and relational data. By applying attention mechanisms and neural network technologies, the model thoroughly explores the text characteristics of papers and the evolving patterns of user behaviors. Additionally, the model elevates the accuracy and personalization of recommendations by meticulously examining citation patterns among papers and the networks of author collaboration. The experimental findings show that the present model surpasses baseline models on all evaluation metrics, thereby enhancing the precision and personalization of academic paper recommendations.
Exciton transport in two-dimensional Ruddlesden-Popper perovskite plays a pivotal role for their optoelectronic performance. However, a clear photophysical picture of exciton transport is still ...lacking due to strong confinement effects and intricate exciton-phonon interactions in an organic-inorganic hybrid lattice. Herein, we present a systematical study on exciton transport in (BA)
(MA)
Pb
I
Ruddlesden-Popper perovskites using time-resolved photoluminescence microscopy. We reveal that the free exciton mobilities in exfoliated thin flakes can be improved from around 8 cm
V
s
to 280 cm
V
s
by anchoring the soft butyl ammonium cation with a polymethyl methacrylate network at the surface. The mobility of the latter is close to the theoretical limit of Mott-Ioffe-Regel criterion. Combining optical measurements and theoretical studies, it is unveiled that the polymethyl methacrylate network significantly improve the lattice rigidity resulting in the decrease of deformation potential scattering and lattice fluctuation at the surface few layers. Our work elucidates the origin of high exciton mobility in Ruddlesden-Popper perovskites and opens up avenues to regulate exciton transport in two-dimensional materials.
The realization of low-energy-consumption lasers based on atomically thin two-dimensional (2D) transition metal dichalcogenides (TMDCs) is crucial for the development of optical communications, ...flexible displays, and lasers on the chip level. However, among the as-demonstrated TMDC-based lasers so far, the gain materials are mainly achieved by a mechanical exfoliation approach accompanied by poor reproducibility and controllability. In this work, we report a controllable design for generating large-scale lasing from chemical vapor deposition (CVD)-derived high-quality monolayer MoS2 film. Strong continuous-wave optically driven whispering-gallery-mode lasing is achieved in a wide temperature range from 77 to 400 K. The eminent lasing performances result from the strong spatial confinement of carriers and the enhanced efficiency of spontaneous emission owing to the lensing and screening effects of silica microsphere cavities. These findings not only advance the fundamental understanding of 2D lasing effects but also provide solutions to fabricate low-cost, scalable, and integratable TMDC-based lasers.
Perovskite materials, especially metal halide perovskites, exhibit excellent properties, such as large optical coefficients, high carrier mobilities, long carrier lifetimes, tunable resistivities, ...large X-ray attenuation coefficients, and simple processing techniques. In recent decades, perovskites have attracted significant attention in the photoelectric field due to their versatile utility in solar cells, light-emitting diodes, photodetectors, X/γ-ray detectors, and lasing. However, the wide applicability of perovskites highly depends on the quality of perovskite crystals and films. Thus far, several perovskite growth technologies and methods have emerged. Therefore, this review classified and summarized the main methods that have been employed to achieve perovskite growth in recent years, including the solution temperature-lowering (STL) method, inverse temperature crystallization (ITC), anti-solvent vapor-assisted crystallization (AVC), spin coating, and chemical vapor deposition (CVD). Through analysis and summary, it has been determined that the STL, ITC, and AVC methods are mainly used to grow high-quality perovskite single crystals. While the spin-coating method has a significant advantage in the preparation of perovskite films, the CVD method is propitious in the fabrication of a variety of morphologies of micro/nano perovskite materials. We hope that this review can be a comprehensive reference for scientific researchers to prepare perovskite-related materials.
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