Over the last two decades, intensive research efforts have been devoted to the suppressions of photoluminescence (PL) blinking and Auger recombination in metal-chalcogenide nanocrystals (NCs), with ...significant progresses being made only very recently in few specific NC structures. Here we show that nonblinking PL is readily available in the newly synthesized perovskite CsPbI3 NCs and that their Auger recombination of charged excitons is greatly slowed down, as signified by a PL lifetime about twice shorter than that of neutral excitons. Moreover, spectral diffusion is completely absent in single CsPbI3 NCs at the cryogenic temperature, leading to a resolution-limited PL line width of ∼200 μeV.
Here we show that, in single perovskite CsPbI_{3} nanocrystals synthesized from a colloidal approach, a bright-exciton fine-structure splitting as large as hundreds of μeV can be resolved with two ...orthogonally and linearly polarized photoluminescence peaks. This doublet could switch to a single peak when a single CsPbI_{3} nanocrystal is photocharged to eliminate the electron-hole exchange interaction. The above findings have prepared an efficient platform suitable for probing exciton and spin dynamics of semiconductor nanostructures at the visible-wavelength range, from which a variety of practical applications such as in entangled photon-pair source and quantum information processing can be envisioned.
One of the basic assumptions in organic field-effect transistors, the most fundamental device unit in organic electronics, is that charge transport occurs two dimensionally in the first few molecular ...layers near the dielectric interface. Although the mobility of bulk organic semiconductors has increased dramatically, direct probing of intrinsic charge transport in the two-dimensional limit has not been possible due to excessive disorders and traps in ultrathin organic thin films. Here, highly ordered single-crystalline mono- to tetralayer pentacene crystals are realized by van der Waals (vdW) epitaxy on hexagonal BN. We find that the charge transport is dominated by hopping in the first conductive layer, but transforms to bandlike in subsequent layers. Such an abrupt phase transition is attributed to strong modulation of the molecular packing by interfacial vdW interactions, as corroborated by quantitative structural characterization and density functional theory calculations. The structural modulation becomes negligible beyond the second conductive layer, leading to a mobility saturation thickness of only ∼3 nm. Highly ordered organic ultrathin films provide a platform for new physics and device structures (such as heterostructures and quantum wells) that are not possible in conventional bulk crystals.
In patients with cancer, drug tolerance often occurs during the use of chemotherapy drugs, seriously affecting patient prognosis and survival. Therefore, scientists began to study the factors that ...affect chemotherapy drug sensitivity, and the high correlation between Schlafen-11 (SLFN11) and sensitivity to chemical drugs (mainly DNA-damaging agents, DDAs) has received increasing attention since it was discovered through bioinformatics analyses. Regarding the mechanism, SLFN11 may sensitise cells to chemotherapy drugs by preventing DNA damage repair. In recent years, SLFN11 has gradually become a hot research topic, and the results are enriching our understanding of this molecule. Indeed, the biological functions of SLFN11 under normal physiological conditions and in cancer, changes in its expression levels and mechanisms promoting apoptosis within the context of chemotherapeutic interventions have gradually been uncovered. Studies to date provide knowledge and the experimental and theoretical bases underlying SLFN11 and its effects on sensitivity to chemotherapy drugs. This review summarises the existing research on SLFN11 with the aim of achieving a more comprehensive understanding and furthering the development of strategies to target SLFN11 in the treatment of cancer.
Owing to the superior performance of lead-halide perovskites in various optoelectronic devices, their low-dimensional counterparts of quantum-confined nanocrystals (NCs) have started drawing ...intensive research attention. Here we report a systematic study on the optical properties of single FAPbBr3 NCs, which demonstrate high-purity single-photon emission, large absorption cross-section and narrow photoluminescence linewidth. Interestingly, linearly-polarized emission can be partially observed in single FAPbBr3 NCs at the room temperature, the degree of which is significantly enhanced at the cryogenic temperature. The above polarization phenomenon is attributed to the large energy-level splitting of the bright-exciton states, leading to efficient exciton recombination from the lowest state with a 1D dipole moment. This unique feature of linear polarization in the optical emission of single FAPbBr3 NCs has not only provided a deep understanding of their exciton energy-level structures, but also suggested potential polarization-oriented applications such as in photo-detectors, light-emitting diodes and lasers.
•Single perovskite FAPbBr3 nanocrystals shows linearly-polarized photoluminescence.•Linearly-polarized photoluminescence originates from the lowest exciton state with 1D dipole moment.•Structure distortion leads to large energy separations between the bright-exciton states.
To confirm the existence of the carrier multiplication (CM) effect and estimate its generation efficiency of multiple excitons in semiconductor nanocrystals (NCs), it is imperative to completely ...exclude the false contribution of charged excitons from the measured CM signal. Here we place single CdSe NCs above an aluminum film and successfully resolve their UV-excited photoluminescence (PL) time trajectories where the true and false CM signals are contained in the blinking "on" and "off" levels, respectively. By analyzing the PL dynamics of the on-level photons, an average CM efficiency of ∼20.2% can be reliably estimated when the UV photon energy is ∼2.46 times the NC energy gap.
The pure blue light‐emitting diodes (LEDs) play a key role in the application of solid display and illumination. Most of pure blue LEDs reported so far, are based on semiconductor quantum dots and ...metal complex, involving heavy metal elements. Here, the fabrication of O, N co‐doped carbon dots (CDs) by a hydrothermal method from perylene‐3,4,9,10‐tetracarboxylic dianhydride and 2,3‐diaminophenazine is shown. These CDs show strong photoluminescence (PL) emission peaked at 447 nm (in ethanol) with absolute PL quantum yields of 88.9%. They are then doped into poly(vinyl carbazole) to form the active emission layer in the pure blue CDs LEDs. The electroluminescence emission of these CDs LEDs is centered at 452 nm with Commission Internationale d'Eclairage (CIE) coordinates of (0.14, 0.10). Moreover, the pure blue CDs LEDs show a high external quantum efficiency of 2.114%, high brightness of 648 cd m–2, long half‐lifetime (T50) of 200 h, and a favorable current efficiency of 2.2 cd A−1. This work opens a new way to develop cost‐effective, environmental‐friendly, and high‐efficient metal‐free pure blue LEDs.
The electroluminescence emission of these CDs LEDs is centered at 452 nm with CIE coordinates of (0.14, 0.10). Moreover, the pure blue CDs LEDs show a high EQE of 2.114%, high brightness of 648 cd m−2, T50 of 200 h, and a favorable current efficiency of 2.2 cd A−1.
Van der Waals （vdW） heterojunctions based on two-dimensional （2D） atomic crystals have been extensively studied in recent years. Herein, we show that both vertical and lateral vdW heterojunctions can ...be realized with layered molecular crystals using a two-step physical vapor transport （PVT） process. Both types of heterojunctions show clean and sharp interfaces without phase mixing under atomic force microscopy （AFM）. They also exhibit a strong interfacial built-in electric field similar to that of their inorganic counterparts. These heterojunctions have greater potential for device applications than individual materials. The lateral heterojunction （LHJ） devices show rectifying characteristics due to the asymmetric energy barrier for holes at the interface, while the vertical heterojunction （VHJ） devices behave like metal-insulator-semiconductor tunnel junctions, with pronounced negative differential conductance （NDC）. Our work extends the concept of vdW heterojunctions to molecular materials, which can be generalized to other layered organic semiconductors （OSCs） to obtain new device functionalities.
In this work, we report a strong photoluminescence (PL) enhancement of monolayer MoS2 under different treatments. We find that by simple ambient annealing treatment in the range of 200 °C to 400 °C, ...the PL emission can be greatly enhanced by a factor up to two orders of magnitude. This enhancement can be attributed to two factors: first, the formation of Mo-O bonds during ambient exposure introduces an effective p-doping in the MoS2 layer; second, localized electrons formed around Mo-O bonds related defective sites where the electrons can be effectively localized with higher binding energy resulting in efficient radiative excitons recombination. Time resolved PL decay measurement showed that longer lifetime of the treated sample consistent with the higher quantum efficiency in PL. These results give more insights to understand the luminescence properties of the MoS2.
Exciton polaritons (EPs) are half‐light, half‐matter quasiparticles formed due to the coupling between photons and excitons in semiconductors. Their uniqueness lies at the strong light–matter ...interactions and long‐distance transport, thus promising for many novel applications in photonics, information, and quantum technologies. Recently, EPs in group‐VI transition‐metal dichalcogenides (TMDs) have attracted a lot of research interest due to their room‐temperature stability, long‐distance propagation, and controllability through electric gating, valley‐selective optical pumping, and precise thickness control. In this progress report, recent studies of EPs in TMDs are reviewed, highlighting their key properties and functionalities, and then discussing the potential directions for future research.
Exciton polaritons (EPs) in group‐VI transition‐metal dichalcogenides (TMDs) have attracted a lot of research interest in the 2D materials and photonics communities in the past few years. Here, recent studies of EPs in TMDs, highlighting their key properties and functionalities are reviewed, and the potential directions for future research are discussed.
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