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2001834 (1 of 8) mobility, and low cost, make this emergent technology very promising. [1-9] Recently, near-infrared and green PeLEDs with external quantum efficiency (EQE) over 20% were reported, [10-13] signifying that we are one step closer to the practical application of PeLEDs in lighting and displays. Several metrics are generally used to assess the performance of PeLEDs. EQE and lifetime are of particular importance among them. Besides, brightness is an intuitive criterion for visible LEDs. [14-16] Most of the previous studies have not yet matched these three metrics simultaneously. For example, the green PeLED with the to-date record-high EQE of 20.3%, the record of PeLEDs so far, had a maximal luminance of 14 000 cd m −2 and 46 h lifetime (measured at continual mode of 100 cd m −2); [11] while for the most stable green PeLED to date (lifetime 250 h measured at initial brightness of 100 cd m −2), the EQE and luminance were 10.5% and 16 436 cd m −2 , respectively. [17] Critical factors that affect the PeLEDs lifetime include the materials stability, the intrinsic defects in perovskites, and most importantly, ion migration within devices. [18-21] Stable perovskites with high luminescence are essential to achieve PeLEDs with both high stability and efficiency. Hybrid organicinorganic perovskites degrade quickly against the heat and environmental moisture. All-inorganic perovskites usually have higher stability, but their PLQY is generally unsatisfactory because of the relatively low film quality. [22] The nonuniform morphology of perovskite films and the high density of defect states are detrimental to the electroluminescence (EL) emission. Intrinsic defects can mediate charge-carrier trapping thus leading to nonradiative recombination loss, which is harmful to the device performance. For efficient PeLEDs with high stability, many efforts have been devoted to reduce the trap states in perovskite films. Introducing large organic ligands is a widely adopted approach, as it can passivate defects and achieve a relatively high film quality by stabilizing the perovskite surfaces or facilitating the formation of low-dimensional perovskites. [13,23-27] Through optimal composition and phase engineering, Yang et al. achieved an EQE of 14.36% and an improved stability for green PeLEDs with quasi-2D perovskites. [27] Meanwhile, Xu et al. demonstrated a highly efficient and stable PeLEDs through the rational design of passivation molecules. [13] The improved stability results from a combination of reduced Joule heating caused by the high efficiency and the suppression of ion migration due to reduced defect density.

Blue-emitting materials and their light-emitting diodes (LEDs) are always challenging in lighting and display applications. Recently, perovskite LEDs (PeLEDs) with efficient and stable green/red emission have made great progress, where external quantum efficiency (EQE) over 20% has been reached. However, it is still a big challenge to realize stable blue PeLEDs with high efficiency mainly because of the poor film quality and unreasonable device structure. Herein, a cocktail strategy, that is, multication (Cs/Rb/FA/PEA/K)­Pb­(Cl/Br)3, is demonstrated to improve both the efficiency and stability of blue PeLEDs. Combined with the “insulator–perovskite–insulator” structure, PeLEDs based on a multication (Cs/Rb/FA/PEA/K)­Pb­(Cl/Br)3 perovskite film show maximum EQE of 2.01% and maximum luminance of 4015 cd/m2 at 484 nm. More importantly, the device exhibits robust durability, and its half-lifetime is over 300 min under continuous operation. The multication strategy could open up a new avenue for the design of new blue-emitting materials for high-performing PeLEDs.

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The energy level alignment and carrier mobility of the charge transport layer are of crucial importance for electron extraction and transport in planar heterojunction perovskite solar cells (PSCs).

Gene therapy with small interfering RNA (siRNA) has been proved to be a promising technology to treat various diseases by hampering the production of target proteins. However, developing a delivery system that has high efficiency in transporting siRNA without obvious side effects remains a challenge. Herein, we designed a new survivin siRNA delivery system based on polyethyleneimine functionalized black phosphorus (BP) nanosheets which could suppress tumor growth by silencing survivin expression. Combined with the photothermal properties of the BP nanosheets, the presented delivery system shows excellent therapy efficiency for tumors. Therefore, the BP-based delivery system would be a promising tool for future clinical applications.

With the development of biotechnology, the detection of cancer biomarkers has been a promising approach for cancer diagnosis and therapy. Herein, we reported a DNA octahedron-based fluorescence nanoprobe, which was capable of detecting and imaging of two kinds of tumor-related mRNAs in living cells simultaneously. The DNA nanoprobe was constructed of eight single-stranded DNAs, in which two oligonucleotides (recognition sequences) were modified with quenchers (BHQ2 and BHQ3) and the adjacent sequences were modified with fluorophores (Cy3 and Cy5), respectively. In the presence of targets, the recognition sequences could dissociate from the nanoprobe skeleton by strand displacement reaction and the fluorescence was recovered accordingly. With the modification of AS1411 aptamer, the nanoprobe could internalize cancer cells more efficiently and distinguish cancer cells from normal cells. In addition, the nanoprobe exhibited good stability, biocompatibility, selectivity, and responded quickly to the targets as well. The DNA nanoprobe was designed in the formation of octahedron and may provide an inspiration for multidetection of cancer biomarkers based on the DNA nanotechnology.

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