Solution-processed metal halide perovskites have been recognized as one of the most promising semiconductors, with applications in light-emitting diodes (LEDs), solar cells and lasers. Various additives have been widely used in perovskite precursor solutions, aiming to improve the formed perovskite film quality through passivating defects and controlling the crystallinity. The additive’s role of defect passivation has been intensively investigated, while a deep understanding of how additives influence the crystallization process of perovskites is lacking. Here, we reveal a general additive-assisted crystal formation pathway for FAPbI3 perovskite with vertical orientation, by tracking the chemical interaction in the precursor solution and crystallographic evolution during the film formation process. The resulting understanding motivates us to use a new additive with multi-functional groups, 2-(2-(2-Aminoethoxy)ethoxy)acetic acid, which can facilitate the orientated growth of perovskite and passivate defects, leading to perovskite layer with high crystallinity and low defect density and thereby record-high performance NIR perovskite LEDs (~800 nm emission peak, a peak external quantum efficiency of 22.2% with enhanced stability).
Solution-processed metal-halide perovskites are emerging as one of the most promising materials for displays, lighting and energy generation. Currently, the best-performing perovskite optoelectronic devices are based on lead halides and the lead toxicity severely restricts their practical applications. Moreover, efficient white electroluminescence from broadband-emission metal halides remains a challenge. Here we demonstrate efficient and bright lead-free LEDs based on cesium copper halides enabled by introducing an organic additive (Tween, polyethylene glycol sorbitan monooleate) into the precursor solutions. We find the additive can reduce the trap states, enhancing the photoluminescence quantum efficiency of the metal halide films, and increase the surface potential, facilitating the hole injection and transport in the LEDs. Consequently, we achieve warm-white LEDs reaching an external quantum efficiency of 3.1% and a luminance of 1570 cd m−2 at a low voltage of 5.4 V, showing great promise of lead-free metal halides for solution-processed white LED applications.
Metal halide perovskite light-emitting diodes (LEDs) have achieved great progress in recent years. However, bright and spectrally stable blue perovskite LED remains a significant challenge. Three-dimensional mixed-halide perovskites have potential to achieve high brightness electroluminescence, but their emission spectra are unstable as a result of halide phase separation. Here, we reveal that there is already heterogeneous distribution of halides in the as-deposited perovskite films, which can trace back to the nonuniform mixture of halides in the precursors. By simply introducing cationic surfactants to improve the homogeneity of the halides in the precursor solution, we can overcome the phase segregation issue and obtain spectrally stable single-phase blue-emitting perovskites. We demonstrate efficient blue perovskite LEDs with high brightness, e.g., luminous efficacy of 4.7, 2.9, and 0.4 lm W-1 and luminance of over 37,000, 9,300, and 1,300 cd m-2 for sky blue, blue, and deep blue with Commission Internationale de l’Eclairage (CIE) coordinates of (0.068, 0.268), (0.091, 0.165), and (0.129, 0.061), respectively, suggesting real promise of perovskites for LED applications.
Here, ferric oxide-loaded
metal–organic framework (FeTCPP/Fe2O3 MOF) nanorice was designed and constructed by
the liquid diffusion method. The introduction of iron metal nodes
and the loading of Fe2O3 can effectively catalyze
the Fenton reaction to produce hydroxyl radicals (•OH) and overcome the hypoxic environment of tumor tissue by generating
oxygen. The monodispersity and porosity of the porphyrin photosensitizers
in the MOF structure exposed more active sites, which promoted energy
exchange between porphyrin molecules and oxygen molecules for photodynamic
therapy (PDT) treatment. Therefore, the generated hydroxyl radicals
and singlet oxygen (1O2) can synergistically
act on tumor cells to achieve the purpose of improving tumor therapy.
Then the erythrocyte membrane was camouflaged to enhance blood circulation
and tissue residence time in the body, and finally, the targeted molecule
AS1411 aptamer was modified to achieve the high enrichment of MOF
photosensitizers on a tumor domain. As a result, the MOF nanorice
camouflaged by the erythrocyte membrane can effectively reduce side
effects and improve the therapeutic effect of PDT and chemo-dynamic
therapy (CDT). The study not only improved the efficacy of PDT and
CDT in essence from the MOF nanorice but also used the camouflage
method to further concentrate FeTCPP/Fe2O3 on
the tumor sites, achieving the goal of multiple gains. These results
will provide theoretical and practical directions for the development
of tumor-targeted MOF nanomaterials.
Density functional theory calculations were carried out to investigate the effect of oligomer length, halogen substitution, and heteroatom substitution on the organic field-effect transistor (OFET) performance of a series of oligothienoacenes (1-5 for oligothienoacene with thiophene units' number from two to six). Compounds 1-5 are revealed to act only as p-type semiconductors due to their very high electron injection barrier relative to the work function potential of Au source-drain electrodes. Heteroatom substitution of the thiophene sulfur atom in particular with boron in the fused-ring thiophene oligomer 5 was revealed to elevate the HOMO energy level and lower the LUMO energy level and therefore lower both the hole and electron injection barriers. However, halogen substitution cannot effectively improve the electron injection barrier, but significantly increased the reorganization energy, therefore leading to decreased transfer mobility. The appropriate ionization potential and electron affinity, balanced charge injection barrier for both hole and electron relative to the work function potential of Au source-drain electrodes, low hole and electron reorganization energy, and good intrinsic transfer mobility for both hole and electron of both the boron-substituted hexathienoacenes 5BH and 5BH-2F-a make these two compounds good potential semiconductors for ambipolar OFET devices, with calculated intrinsic charge-transfer mobilities achieving 3.74 and 5.07 cm 2 V -1 s -1 for hole and 4.77 and 5.76 cm 2 V -1 s -1 for electron, respectively. The high intrinsic mobilities of 5BH and 5BH-2F-a are rationalized in terms of their frontier orbitals, molecular structure variation upon oxidation and reduction, and electron coupling between two neighboring molecules. All the results indicate that heteroatom substitution of sulfur atoms in oligothienoacenes is a rational way toward good ambipolar OFET semiconducting materials.
Efficient and stable
red perovskite light-emitting diodes (PeLEDs)
are important for realizing full-color display and lighting. Red PeLEDs
can be achieved either by mixed-halide or low-dimensional perovskites.
However, the device performance, especially the brightness, is still
low owing to phase separation or poor charge transport issues. Here,
we demonstrate red PeLEDs based on three-dimensional (3D) mixed-halide
perovskites where the defects are passivated by using 5-aminovaleric
acid. The red PeLEDs with an emission peak at 690 nm exhibit an external
quantum efficiency of 8.7% and a luminance of 1408 cd m–2. A maximum luminance of 8547 cd m–2 can be further
achieved as tuning the emission peak to 662 nm, representing the highest
brightness of red PeLEDs. Moreover, those LEDs exhibit a half-life
of up to 8 h under a high constant current density of 100 mA cm–2, which is over 10 times improvement compared to literature
results.
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