Two-dimensional (2D) organic-inorganic perovskites have recently attracted increasing attention due to their great environmental stability, remarkable quantum confinement effect and layered characteristic. Heterostructures consisting of 2D layered perovskites are expected to exhibit new physical phenomena inaccessible to the single 2D perovskites and can greatly extend their functionalities for novel electronic and optoelectronic applications. Herein, we develop a novel solution method to synthesize (C 4 H 9 NH 3 ) 2 PbI 4 /(C 4 H 9 NH 3 )(CH 3 NH 3 )Pb 2 I 7 single-crystals with the centimeter size, high phase purity, controllable junction depth, high crystalline quality and great stability for highly narrow dual-band photodetectors. On the basis of the different lattice constant, solubility and growth rate between (C 4 H 9 NH 3 ) 2 PbI 4 and (C 4 H 9 NH 3 )(CH 3 NH 3 )Pb 2 I 7 , the newly designed synthesis method allows to first grow the (C 4 H 9 NH 3 ) 2 PbI 4 guided by the self-assembled layer of the organic cations at the water-air interface and subsequently the (C 4 H 9 NH 3 )(CH 3 NH 3 )Pb 2 I 7 layer is formed via diffusion process. Such growth process provides an efficient away for us to readily obtain the (C 4 H 9 NH 3 ) 2 PbI 4 /(C 4 H 9 NH 3 )(CH 3 NH 3 )Pb 2 I 7 single-crystals with various thickness and junction depth by controlling the concentration, reaction 2 temperature and time. The formation of heterostructures has been verified by X-ray diffraction, cross-section photoluminescence and reflection spectroscopy with the estimated junction width below 70 nm. Photodetectors based on such heterostructural single crystal plates exhibit extremely low dark current (∼10 −12 A), high on/off current ratio (∼10 3 ), and highly narrow dual-band spectral response with a full-width at half-maximum of 20 nm at 540 nm and 34 nm at 610 nm due to the high crystalline quality of the synthesized heterostructures and extremely large resistance in the out-of-plane direction leading to the efficient control of photogenerated carrier collection. In particular, the synthetic strategy is general for other 2D perovskites and the narrow dual-band spectral response with all full-width at half-maximum <40 nm can be continuously tuned from red to blue by properly changing the halide compositions. Our findings not only provide an efficient synthetic approach with great simplicity to create 2D perovskite based heterostructural single crystals for investigating the physical processes in those heterostructures, but also offer an alternative strategy to achieve optical-filterless narrow dual-band photodetectors in the entire visible range for multicolor optical sensing.

2D layered halide perovskites have attracted significant attention. Apart from the linear optical properties, it is also intriguing to explore the nonlinear optics of 2D layered halide perovskites and their heterostructures. Previous nonlinear optical (NLO) studies of 2D perovskites primarily focus on the thin films or microplates. Herein, the NLO properties of (n‐C4H9NH3)2PbI4/(n‐C4H9NH3)2(CH3NH3)Pb2I7 heterostructures with centimeter size are systematically studied. The NLO properties can be continuously tuned by changing the thickness. A giant two‐photon absorption (2PA) coefficient up to 44 cm MW−1 is obtained for the heterostructures with a total thickness of 20 µm based on the nonlinear transmittance measurement. Additionally, strong multiphoton‐induced photoluminescence is observed in the heterostructures. It is proposed that the giant 2PA coefficient might arise from the small thickness (≈1 µm) of (n‐C4H9NH3)2(CH3NH3)Pb2I7 layer and possibly the nonradiative energy transfer between the different constituting layers within the heterostructures through an antenna‐like effect. Finally, benefiting from the giant 2PA coefficient, direct detection of 980 nm light is demonstrated with a responsivity of 10−7 A W−1 in the heterostructures. The findings suggest the promising applications of 2D perovskite heterostructures in the infrared photodetection and some other nonlinear absorption related optoelectronic devices.

All‐inorganic lead halide perovskites have gained wide attention as a class of promising material for both fundamental investigations and optoelectronic applications due to their excellent optical properties. They simultaneously possess relatively high refractive index and high exciton binding energy exceeding 100 meV, making them possess high emission efficiency at room temperature and thus promise a coherent light source. High‐quality all‐inorganic lead halide perovskite microcrystal arrays exhibiting ultralow‐threshold single‐mode lasing would find promising applications in the on‐chip integration of photonic and electronic circuits. However, currently it is still challenging to synthesize high‐quality all‐inorganic perovskite arrays. Here, the seeds‐assisted space‐confined growth of all‐inorganic perovskite arrays is reported for ultralow‐threshold single‐mode lasing. The naturally vapor‐phase‐grown submicron plates possess high crystal quality, exhibiting an ultralow lasing threshold of ≈0.22 µJ cm–2 among reported perovskite‐based lasing. Benefiting from the space‐confined effect, the as‐grown samples have small lateral size (submicron) leading to the single whispering‐gallery mode (WGM) lasing. Importantly, the method can successfully synthesize high‐quality CsPbI3 submicron plate arrays and demonstrate single‐mode lasing in those submicron plate arrays. The study provides a convenient and effective route to controllably grow all‐inorganic submicron plate arrays for ultralow‐threshold single‐WGM lasing.

Two-dimensional (2D) perovskites have recently attracted intensive interest for their great stability against moisture, oxygen, and illumination compared with their three-dimensional (3D) counterparts. However, their incompatibility with a typical lithography process makes it difficult to fabricate integrated device arrays and extract basic optical and electronic parameters from individual devices. Here, we develop a combination of solution synthesis and a gas-solid-phase intercalation strategy to achieve hexagonal-shaped 2D perovskite microplates and arrays for functional optoelectronics. The 2D perovskite microplates were achieved by first synthesizing the lead iodide (PbI) microplates from an aqueous solution and then following with intercalation via the vapor transport method. This method further allows us to synthesize arrays of 2D perovskite microplates and create individual 2D perovskite microplate-based photodetectors. In particular, chlorine (Cl) can be efficiently incorporated into the microplates, resulting in significantly improved performance of the 2D perovskite microplate-based photodetectors.

The diversification of data types and the explosive increase of data size in the information era continuously required to miniaturize the memory devices with high data storage capability. Atomically thin two-dimensional (2D) transition metal dichalcogenides (TMDs) are promising candidates for flexible and transparent electronic and optoelectronic devices with high integration density. Multistate memory devices based on TMDs could possess high data storage capability with a large integration density and thus exhibit great potential applications in the field of data storage. Here, we report the multistate data storage based on multilayer tungsten diselenide (WSe2) transistors by interface engineering. The multiple resistance states of the WSe2 transistors are achieved by applying different gate voltage pulses, and the switching ratio of the memory can be as large as 105 with high cycling endurance. The water and oxygen molecules (H2O/O2) trapped at the interface between the SiO2 substrate and WSe2 introduce the trap states and thus the large hysteresis of the transfer curves, which leads to the multistate data storage. In addition, the laminated Au thin film electrodes make the contact interface between the electrodes and WSe2 free of dangling bond and Fermi level pinning, thus giving rise to the excellent performance of memory devices. Importantly, the interface trap states can be easily controlled by a simple oxygen plasma treatment of the SiO2 substrate, and subsequently, the performance of the multistate memory devices can be manipulated. Our findings provide a simple and efficient strategy to engineer the interface states for the multistate data storage applications and would motivate more investigations on the trap state-associated applications.