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Perovskite nanocrystals (NCs), such as MAPbX3 (MA+ = methylammonium; X = Cl, Br, or I), have received attention owing to their excellent optoelectronic properties and ease of integrating with flexible substrates. Lanthanide ion doping is widely used as an effective strategy to enhance the optoelectronic performance of perovskite NCs. However, incorporating the lanthanide dopant and ensuring the emission stability of the perovskite NCs in high‐performance optoelectronic devices remains a major challenge. Herein, the synthesis of Eu2+‐doped MAPbBr3 NCs within the channels of SBA‐15 is presented to improve their stability. The doped MAPbBr3 NC@SBA‐15 composites exhibit significantly improved stability than that of undoped MAPbBr3 NCs. The doped MAPbBr3 NC@SBA‐15 composites exhibit moderate PL quantum yields and excellent stability under ambient conditions and UV irradiation. In addition, the MAEu0.3Pb0.7Br3 NC@SBA‐15 composite applied in white‐light‐emitting diodes (WLEDs) achieves a color rendering index of 73.5. Moreover, MAEu0.3Pb0.7Br3 NC@SBA‐15 can be combined with styrene‐ethylene‐butylene‐styrene to fabricate a flexible direct X‐ray detector, realizing a high sensitivity of 7592.2 µC Gyair−1 cm−2 and a low detection limit of <77 nGyair s−1; this is an outstanding value for a NC‐based flexible direct X‐ray detector. This work serves as a guide for the design of perovskite NCs for both WLEDs and flexible X‐ray detectors. [ABSTRACT FROM AUTHOR]

We report a strategy for the self-assembly of zeolitic imidazolate framework-8 (ZIF-8) particles induced by the evaporation of a methanol–water mixture. This strategy effectively suppresses the coffee ring effect, facilitates the rapid assembly of ZIF-8 particles, and improves the orientation and optical properties of self-assembled superstructures. [ABSTRACT FROM AUTHOR]

The development of metal‐halide perovskite nanocrystals (NCs) that yield bright and stable emission is of great importance. Previous reported perovskite NCs are mostly based on APbX3‐type family fabricated via ligand‐ or surfactant‐assisted chemical approaches. However, realizing bright and stable emission remains a challenge because of desorption of ligands/surfactants during long‐term operation. Herein, Ruddlesden–Popper (RP)‐type (A)2(MA)n‐1PbnBr3n+1 NCs with size less than Bohr radius stabilized in mesoporous silica scaffold, which are prepared in situ via physical approach at low temperature are introduced. The RP NCs in mesoporous silica exhibit the formation of spatially and electronically separated quantum wells, efficient energy funneling between different n phases for bright emission (photoluminescence quantum yields of ≈99%), high irradiation stability (T70 = 110 days), and long‐term stability (T90 = 110 days). These RP NCs have broad potential for bright light‐emitting diodes, high‐resolution PL imaging, and waterproof inks. Importantly, for the first time, stretchable perovskite X‐ray scintillator is demonstrated with excellent X‐ray imaging with resolution greater than 14 line pairs mm−1. These findings offer a paradigm to motivate future research toward stable and efficient perovskite optoelectronics. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) metal halide perovskites have shown great potential in high performance optoelectronic applications due to their intrinsic quantum well structure, enhanced moisture- and photo-stability. Unfortunately, there is still no effective method to produce large-size 2D hybrid perovskite single crystals, and consequently there is lack of research on its optoelectronic applications. Herein, we report the utilization of a controlled evaporation process to grow well-defined large-size (＞200 mm2) 2D (PEA)2PbBr4 (C6H5CH2CH2NH3+, PEA+) single crystals. Upon careful examination of the crystal growth kinetics, it was found that the optimum temperature for the growth of (PEA)2PbBr4 single crystal wafer was 23 ± 0.5 °C. The wafers that were harvested showed high mu-tau (μτ) product, superior environmental stability and irradiation resistance. Furthermore, an array of planar-type UV photodetectors were designed and fabricated with extremely low dark current (∼10−13 A), large ON/OFF current ratio (∼105), very high specific detectivity (∼1013 cm Hz1/2 W−1) and fast response rate (∼0.4 ms). All the above performance data are among the best achieved compared to those of the state-of-the-art materials including ZnO, TiO2 and GaN in the field. It makes us believe that the availability of these materials may pave the way for ultrafast optical computing and optical communications. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) AA' n-1 M n X 3n+1 type halide perovskites incorporating straight-chain symmetric diammonium cations define a new type of structure, but their optoelectronic properties are largely unexplored. Reported here is the synthesis of a centimeter-sized AA' n-1 M n X 3n+1 type perovskite, BDAPbI 4 (BDA=NH 3 C 4 H 8 NH 3 ), single crystal and its charge-transport properties under X-ray excitation. The crystal shows a staggered configuration of the [PbI 6 ] 4- layers, a band gap of 2.37 eV, and a low trap density of 3.1×10 9  cm -3 . The single-crystal X-ray detector exhibits an excellent sensitivity of 242 μC Gy air -1  cm -2 under the 10 V bias (0.31 V μm -1 ), a detection limit as low as 430 nGy air  s -1 , ultrastable response current, a stable baseline with the lowest dark current drift of 6.06×10 -9  nA cm -1  s -1  V -1 , and rapid response time of τ rise =7.3 ms and τ fall =22.5 ms. These crystals are promising candidates for the next generation of optoelectronic devices., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

By fine-tuning the crystal nucleation and growth process, a low-temperature-gradient crystallization method is developed to fabricate high-quality perovskite CH 3 NH 3 PbBr 3 single crystals with high carrier mobility of 81 ± 5 cm 2 V -1 s -1 (>3 times larger than their thin film counterpart), long carrier lifetime of 899 ± 127 ns (>5 times larger than their thin film counterpart), and ultralow trap state density of 6.2 ± 2.7 × 10 9 cm -3 (even four orders of magnitude lower than that of single-crystalline silicon wafers). In fact, they are better than perovskite single crystals reported in prior work: their application in photosensors gives superior detectivity as high as 6 × 10 13 Jones, ≈10-100 times better than commercial sensors made of silicon and InGaAs. Meanwhile, the response speed is as fast as 40 µs, ≈3 orders of magnitude faster than their thin film devices. A large-area (≈1300 mm 2 ) imaging assembly composed of a 729-pixel sensor array is further designed and constructed, showing excellent imaging capability thanks to its superior quality and uniformity. This opens a new possibility to use the high-quality perovskite single-crystal-based devices for more advanced imaging sensors., (© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)