As a new generation of solution-processable optoelectronic materials, organic-inorganic hybrid halide perovskites have attracted a great deal of interest due to their high and balanced carrier mobility, long carrier diffusion length and large light absorption coefficient. These materials have demonstrated wide applications in solar cell, light-emitting diode, laser, photodetector, catalysis and other fields. Comparing with their polycrystalline film counterpart, perovskite single crystals have low trap density and no grain boundaries and thus are anticipated to possess much better optoelectronic performances. Herein, we review the key progress in the development of organic-inorganic halide perovskite single crystals. Particularly, the crystal growth techniques and applications of these advanced materials are highlighted.作为一种新型的光电材料, 有机-无机杂化钙钛矿以其高光吸收系数、 长扩散长度、 高载流子迁移率等优点为人们所关注. 这类材料在太阳电池、 光电探测器、 发光二极管、 激光器、 催化等诸多领域有极为优秀的表现. 与多晶材料相比, 单晶的低缺陷、 无晶界等特点使其拥有更好的性能. 本文从生长技术和应用两个方面综述了有机-无机杂化钙钛矿单晶的研究进展, 并对该领域的未来发展进行了展望.

•SiO2 honeycomb structure was fabricated by a colloidal crystal templating strategy.•The SiO2 honeycomb structure enhanced both the Voc and FF of the perovskite solar cells.•The intrinsic trade-off between PCE and AVT was smoothed by the SiO2 honeycomb structure.•Solar cells yielded a maximum PCE of 10.3% with relatively high photoactive layer AVT of 38%.Organo-lead-halide perovskite based solar cells have achieved remarkable advancements in power conversion efficiencies (PCEs) in recent years. Given their attractive properties, possible applications for perovskites are wide ranging and among others, particularly appealing for building integrated photovoltaics (BIPVs). In this study, patterned perovskite films were successfully fabricated based on a microsphere lithography SiO2 honeycomb scaffold template, which was derived by a combination of air-water interface self-assembly and O2 plasma etching. These patterned perovskite films exhibited near-neutral-color and tunable semitransparency, which meet the requisites of semitransparent solar cells for BIPVs application. O2 plasma etching of the microsphere template could effectively improve the active layer average visible transmission (AVT), and the existence of the SiO2 nanoscaffold effectively smoothed the internal trade-off of active layer AVT and device PCE. Solar cell devices fabricated with these optimized patterened perovskite films yielded a maximum PCE of 10.3% with relatively high active layer AVT of 38%. This nanoscaffold patterned perovskite opens up a new strategy for design and fabrication of functional photoelectric device based on organo-lead-halide perovskite.

The anisotropy of moisture erosion was observed in CH3NH3PbI3 single crystals. When exposed to moisture, the (001) facet exhibited greater sensitivity to water molecules and showed a faster erosion rate compared to the (100) facet and (112) facet. Structural and chemical origins responsible for anisotropic moisture erosion were elucidated.

Although orthorhombic black phosphorus (BP) single crystals have been successfully synthesized through a chemical vapor transport (CVT) reaction based on a red phosphorus/tin/iodine (RP/Sn/I2) system, the underlying nucleation and growth mechanism is poorly understood during the transformation of RP to BP. Particularly, little is known about the critical state of BP nucleation during the CVT process. Herein, we reveal that the BP nucleation and growth proceed from the crystalline monoclinic violet or Hittorf's phosphorus (HP), which is accurately confirmed via a series of structural and optical experimental identification approaches and supported by quantum chemical studies. We thus propose a step-by-step phase-induced nucleation and growth mechanism for the growth of BP single crystals by using a CVT reaction in a RP/Sn/I2 system. A better understanding of the transformation of RP to BP may pave the way for direct synthesis of phosphorene via a CVT method in the near future.

Pb(In1/2Nb1/2)O3–PbZrO–Pb(Mg1/3Nb2/3)O3–PbTiO3 (PIN–PZ–PMN–PT) quaternary system relaxor ferroelectric materials possess a high ferroelectric phase transition temperature (TFE–FE > 120 °C) due to the enhanced A–B repulsion intensity in the ABO3 lattice caused by the incorporation of In3+ and Zr4+ cations. Due to these additions, excellent piezoelectric property (d33[001]* = 1820 pm V−1) at room temperature and good thermal stability were observed in the PIN–PZ–PMN–PT single crystals. Strong frequency dispersion (frequency ∼0.1–100 kHz) and small short-range correlation length (〈ξ〉 ∼ 118 nm) of polar nanoregions (PNRs) illustrate the high degree of relaxor nature of these quaternary-system single crystals in comparison with the PMN–0.2PT relaxor single crystal (〈ξ〉 ∼ 210 nm). The high relaxor nature is speculated to be caused by In3+ and Zr4+ cations and is considered one of the main reasons for the excellent piezoresponse of the PIN–PZ–PMN–PT single crystal. Moreover, PNRs with orthorhombic 〈011〉 polarization might have a modulation effect on the (011) surface, leading to the anisotropic nanodomain structures. A lower free energy for domain switching on the (011) surface was needed than that on the (001) surface, which was confirmed by the piezoresponse hysteresis loops and local domain poling behavior studies.

Single crystal reflects the intrinsic physical properties of a material, and single crystals with high-crystalline quality are highly desired for the acquisition of high-performance devices. We found that large single crystals of perovskite CH3NH3PbI3(Cl) could be grown rapidly from chlorine-containing solutions. Within 5 days, CH3NH3PbI3(Cl) single crystal as large as 20 mm × 18 mm × 6 mm was harvested. As a most important index to evaluate the crystalline quality, the full width at half-maximum (fwhm) in the high-resolution X-ray rocking curve (HR-XRC) of as-grown CH3NH3PbI3(Cl) single crystal was measured as 20 arcsec, which is far superior to so far reported CH3NH3PbI3 single crystals (∼1338 arcsec). The unparalleled crystalline quality delivered a low trap-state density of down to 7.6 × 108 cm–3, high carrier mobility of 167 ± 35 cm2 V–1 s–1, and long transient photovoltaic carrier lifetime of 449 ± 76 μs. The improvement in the crystalline quality, together with the rapid growth rate and excellent carrier transport property, provides state-of-the-art single crystalline hybrid perovskite materials for high-performance optoelectronic devices.

Organolead halide perovskites have attracted extensive attention as light harvesting materials for optoelectronic devices due to their high charge carrier mobility, high photoconversion efficiency, and long charge diffusion length. In this study, we present the first self-powered organolead halide perovskite single crystal photodetector driven by a triboelectric nanogenerator (TENG). A high-performance planar photodetector showing a responsivity of 7.92 A W−1 to white light under a bias of 4 V was fabricated on the (100) facet of a bulk CH3NH3PbI3 perovskite single crystal. Furthermore, we demonstrate a cost-effective approach to the fabrication of a drum-shaped TENG by using two used digital versatile discs (DVDs), which could generate a high output of up to 200 V and 55 μA. By integrating the CH3NH3PbI3 single crystal photodetector with the TENG, the self-powered device exhibited a large responsivity of 196 V (mW cm−2)−1 and a wide detection range from 10 μW cm−2 to 100 mW cm−2. These results provide a new strategy for driving the organolead halide perovskite photodetector with the energy harvested from the environment rather than an external power supply.

Methylammonium lead iodide perovskite (MAPbI3) has made a re-entry into the literature nowadays for its extraordinary characteristics, such as high absorption of light, long carrier diffusion length, high carrier mobility, low trap-state density, low surface recombination velocity and ease of attainment. Here, we report a self-powered photodetector based on a CH3NH3PbI3 single crystal by employing asymmetric Au–Al electrodes. The key issue of this photodetector was the metal–semiconductor contacts, owing to the Schottky junction between them. By setting the channel length between the Au–Al electrodes to 30 μm for sufficient electron–hole pair separation and transportation, the device showed good performance under 1 sun illumination. The short-circuit photocurrent density and open-circuit voltage were 6.86 mA cm−2 and 0.7 V, respectively. The photocurrent was almost 2 orders of magnitude larger than that based on a perovskite polycrystalline film with a similar device structure. More importantly, the device could detect the lowest noticeable incident power density down to 1 × 10−8 W cm−2. Under this weak light intensity, the responsivity was as high as 0.24 A W−1 without any bias. The photoresponse also had a broadband ranging from 375 nm to 808 nm accompanied by a fast response speed.

A perovskite single crystal of the quaternary system PIN–PZ–PMN–PT, with rhombohedral (R) symmetry (3m) and a size of 10 × 10 × 6 mm3, was successfully grown by a slow cooling method, which had a high rhombohedral-to-tetragonal (T) ferroelectric (FE) phase transition temperature (TR–T = 129 °C). The introduction of In3+ and Zr4+ enhanced the repulsion intensity between Pb2+ and B-site cations in the ABO3 lattice and increased the energy difference ΔET–R, resulting in an improved FE phase transition temperature compared to the PMN–PT binary system single crystals. The evolution of domain configuration induced by both electric field and temperature was studied for the [001]C PIN–PZ–PMN–PT single crystal by using a polarized light microscope. Star porphyritic domains with short-range order before poling and stripe domains with long-range order after poling were observed, respectively, confirming the typical relaxor domain configurations of the R phase. Fine domain walls induced by temperature for the poled [001]C sample were responsible for the high piezoelectric property. Furthermore, minor ferroelectric property variations (ΔPmax < 6%, ΔPr < 10%) were observed at the temperature range from 20 °C to 140 °C, indicating the good thermal stability of the quaternary system PIN–PZ–PMN–PT single crystal.

Photodetectors capable of detecting two or more bands simultaneously with a single system have attracted extensive attentions because of their critical applications in image sensing, communication, and so on. Here, we demonstrate a self-powered ultrabroadband photodetector monolithically integrated on a 0.72Pb(Mg1/3Nb2/3)O3–0.28PbTiO3 (PMN–28PT) single crystal. By combining the optothermal and pyroelectric effect, the multifunctional PMN–28PT single crystal can response to a wide wavelength range from UV to terahertz (THz). At room temperature, the photodetector could generate a pyroelectric current under the intermittent illumination of incident light in absence of external bias. A systematic study of the photoresponse was investigated. The pyroelectric current shows an almost linear relationship to illumination intensity. Benefiting from the excellent pyroelectric property of PMN–28PT single crystal and the optimized device architecture, the device exhibited a dramatic improvement in operation frequency up to 3 kHz without any obvious degradation in sensitivity. Such a self-powered photodetector with ultrabroadband response may open a window for the novel application of ferroelectric materials in optoelectronics.Keywords: ferroelectric; photodetector; pyroelectric; self-powered; ultrabroadband;

Quantitative characterization of the mechanical properties of a polystyrene (PS) monolayer colloidal crystal (MCC) annealed with solvent vapor has been performed for the first time by means of atomic force microscopy nanoindentation. The results showed that both the compressive and bending elastic modulus of PS MCC increased with the prolongation of annealing time from initial to 13 min. When the annealing time reached 15 min or even more, the PS MCC almost deformed to a planar film, and the elastic modulus of the PS MCC presented a drastic increase. These results provide a basis for tailoring the mechanical properties of a polymer colloidal monolayer via solvent vapor annealing. Such self-supported and high-mechanical-strength colloidal monolayers can be transferred to other surfaces for potential and promising applications in the bottom-up fabrication of highly ordered nanostructured materials such as nano dot arrays, photonic crystals, and many others.

We demonstrate an integrated module of self-powered ferroelectric transistor memory based on the combination of a ferroelectric FET and a triboelectric nanogenerator (TENG). The novel TENG was made of a self-assembled polystyrene nanosphere array and a poly(vinylidene fluoride) porous film. Owing to this unique structure, it exhibits an outstanding performance with an output voltage as high as 220 V per cycle. Meanwhile, the arch-shaped TENG is shown to be able to pole a bulk ferroelectric 0.65Pb(Mg1/3Nb2/3)O3–0.35PbTiO3 (PMN-PT) single crystal directly. Based on this effect, a bottom gate ferroelectric FET was fabricated using pentacene as the channel material and a PMN-PT single crystal as the gate insulator. Systematic tests illustrate that the ON/OFF current ratio of this transistor memory element is approximately 103. More importantly, we demonstrate the feasibility to switch the polarization state of this FET gate insulator, namely the stored information, by finger tapping the TENG with a designed circuit. These results may open up a novel application of TENGs in the field of self-powered memory systems.

Temperature-dependent domain configurations were studied for both unpoled and poled [110]C-oriented 0.63Pb(Mg1/3Nb2/3)O3–0.37PbTiO3 (PMN–0.37PT) single crystals by polarized light microscopy (PLM). Combining the dielectric properties and the domain configurations upon heating, it was found that the temperature-induced phase transition in the unpoled [110]C-oriented PMN–0.37PT single crystal followed the tetragonal (T) → cubic (C) sequence. However, under an electric (E) field of 10 kV cm−1 along the [110]C direction, a single domain orthorhombic (O) phase was induced. The E field-dependent domain structures were observed in situ under PLM, which verified that the T phase turned to O phase when an E field of 10 kV cm−1 was applied along the [110]C direction. Upon subsequent heating, the phase transition followed the O → T → C sequence. The O–T discontinuous phase transition led to a remarkable change in the dielectric coefficient and strain with increasing temperature. The strain at 45 °C (0.148%) was 2.2 times larger than that at room temperature (0.068%), accompanied by a tremendous piezoelectric coefficient ( ~1645 pm V−1).

•A facile strategy for rapid patterning of curved colloid surfaces is developed.•The colloid surfaces can be made both entirely and partially nanostructured.•Nonsolvent induced phase separation is firstly used for patterning colloid surface.We have designed an effective strategy for producing nanostructures on the polymer colloid surfaces within few minutes. The poly(N-vinylpyrrolidone) (PVP)-stabilized polystyrene colloid latex dispersed in ethanol was exposed to a nonsolvent medium of PVP and nanometric droplets formed on the polymer colloid surfaces within few minutes. Surface wettability of the polymer colloids with nanoprotrusions experienced a significant change as compared with the smooth polymer colloids. The formation mechanism was ascribed to the precipitation of PVP phase due to the nonsolvent induced phase separation. To further confirm the proposed mechanism, the material components included in the polymer colloid lattices before the nanostructuration process and surface compositions on the nanostructured polymer colloid surfaces were characterized using gel permeation chromatography (GPC) and time-of-flight secondary ion mass spectrometry (TOF-SIMS) respectively. This new strategy provides an alternative and promising method for patterning curved polymer surfaces. The polymer colloids with different surface textures would be ideal for use as model systems in biomedical research such as targets in phagocytosis and platforms of drug delivery.

0–3 type composites based on pre-poled Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 (PIN–PMN–PT) ceramic and poly-vinylidene fluoride (PVDF) have been fabricated. The dielectric and piezoelectric properties of the 0–3 composites were studied as a function of ceramic volume fraction. The results showed that the dielectric constant εr and piezoelectric strain constant d33 were enhanced with an increase of ceramic volume fraction. The composites possessed lower acoustic impedance and better flexibility comparing to the PIN–PMN–PT ceramic with the same composition, but their acoustic impedance Z and elastic stiffness coefficient C33 presented an abnormal decrease trend when a high volume fraction of ceramic (>80 %) was loaded in the composites. Since the Curie temperature of the PIN–PMN–PT ceramic reinforcement phase was much higher than the melting point of PVDF, pre-poled ceramic phase could keep its polarization during the subsequent complex processing. By comparing the dielectric and piezoelectric properties of composites using pre-poled ceramic with those using virgin one, it was found that pre-polarization of the PIN–PMN–PT reinforcement phase could improve the performance of these 0–3 type ceramic/polymer composites.

A graphene/patterned ZnO (G/PZO) nanorod array composite was successfully fabricated by using the colloidal nanosphere monolayer templating strategy. Compared with graphene/compact ZnO (G/CZO) nanorod arrays, the G/PZO nanorod array composite exhibited a highly efficient and stable field emission with a low turn-on field. The field emission had a strong dependence on the density and the inter-distance of the emitters. By changing the diameter of polystyrene (PS) colloidal nanospheres, optimal emitter inter-distance was obtained. Graphene supported on ZnO nanorod arrays, patterned by an 886 nm PS colloidal nanosphere monolayer, displayed the best field emission with a turn-on electric field of only 6.4 V μm−1 and the field enhancement factor β was 1158. The K point in the Fowler–Nordheim plot demonstrated the electron tunneling mechanism took place in this composite material. The cyclic experiment showed that the field emission of the G/PZO nanorod array composite was of high stability.

•Solvent vapor annealing enables the transformation of a colloidal PC into a PC heterostructure.•Such a heterostructure is free of interface imperfection since it is a direct descendant of the original colloidal crystal.•A wide photonic band gap is demonstrated along the crystallographic [1 1 1] direction in these PC heterostructures.We describe the transformation of a colloidal photonic crystal into a photonic crystal heterostructure. It was achieved by annealing a polystyrene multilayer colloidal photonic crystal partially immersed in water using a solvent vapor. The floating polystyrene colloidal photonic crystal was divided into two parts by the liquid level, which can be manipulated by the addition of ethanol into the water. The top part protruding out of the water experienced a uniform lattice stretching upon exposure to the solvent vapor. The bottom part that stayed immersed in the water remained unaffected due to the protection by the water. The inconsistent behaviors of the two parts resulted in the formation of a colloidal photonic crystal heterostructure. Such a heterostructure was free of interface imperfection since it was a direct descendant of the original colloidal crystal. Meanwhile, optical measurements demonstrated the presence of a wider photonic band gap along the crystallographic [1 1 1] direction in these photonic crystal heterostructures compared with the original colloidal photonic crystals.

Three-dimensional finite-difference time-domain simulation (FDTD), using both a single sphere model and a period model, were performed to study the size effect of colloidal spheres on the ordered pore array generated by spherical-lens photolithography (SLP). The size of the spheres ranged from just above the exposure wavelength to micron scale. A complex pattern consisting of a large and six surrounding tiny circular pores was obtained when the size of colloidal spheres increased to 2 μm, which was much different from the reported sole circular pore. The validation of simulation based on the period model was further verified by the experimental results. Large-area and ordered sexfoil pore arrays were observed when using 2 μm colloidal spheres monolayer as a microlens array. The slight difference between the simulation and the experiment results was attributed to the bleaching of the exposed photoresist. Sexfoil-shaped patterns have enriched the morphology of pore arrays generated by SLP, which may find applications in various technologically important areas.Keywords: colloidal crystal; FDTD simulation; sexfoil pore arrays; spherical-lens photolithography

Hexagonal crown-capped ZnO micro rods were successfully prepared by a facile low-temperature hydrothermal method. The as-prepared ZnO micro rods are 4.4–5.2 μm in length and 2.4–3.6 μm in diameter, possessing a single-crystal hexagonal structure. The morphology evolution and structure changes were tracked during hydrothermal growth by field-emission scanning electron microscopy and X-ray diffraction, respectively. A three-stage growth mechanism of the hexagonal crown-capped ZnO micro rods was proposed and further verified by a growth solution renewal experiment. The room-temperature photoluminescence (PL) spectrum of the hexagonal crowns exhibits a strong UV emission at about 382 nm. The temperature dependent PL results indicate that the UV emission originates from the radiative free-exciton recombination.

A series of novel Ce3+ singly doped and Ce3+/Mn2+ co-doped color-tunable KBaY(BO3)2 phosphors were synthesized by a high-temperature solid-state reaction, and the crystal structures and luminescence properties were investigated in detail. The crystallographic cation sites occupancy of the doping Ce3+ and Mn2+ ions for KBaY(BO3)2: Ce3+, Mn2+ samples were analyzed by the Rietveld refinement method. It was demonstrated that Ce3+ and Mn2+ ions can both enter into the two types of cation sites in the KBaY(BO3)2 crystal lattice, with a slight tendency of occupancy for Ce3+ on Y3+ ion sites and Mn2+ on the Ba2+/K+ ion sites. By controlling Mn2+ ions content with a fixed Ce3+ concentration, the emission color of the phosphor varied from blue (0.160, 0.150) to pink-white (0.348, 0.272) and eventually to orange (0.490, 0.372). The critical energy transfer distance calculated by the concentration quenching theory was 16.52 Å and the energy transfer from Ce3+ to Mn2+ took place via a resonance-type dipole–dipole mechanism. By combining the single-phase KBa0.97Y0.97(BO3)2: 0.01Ce3+, 0.05Mn2+ phosphor with an n-UV 370 nm InGaN chip, a phosphor-converted white LED lamp was successfully fabricated, producing a white light with a warm correlated color temperature of 4710 K and color coordinates of (0.347, 0.307).

•High-quality colloidal masks for nanosphere lithography application were prepared.•The method combined the colloidal self-assembly with the chemical vapor deposition.•The interstice size in the colloidal masks could be finely tuned.Nanosphere lithography (NSL), which utilizes self-assembled monolayer colloidal crystal (MCC) as a mask to fabricate ordered nanostructures over large areas, is a high through-put and low-cost method. In this work, polystyrene (PS) MCC with tunable interstice size is prepared by a combination of self-assembly of PS nanospheres at the air–water interface and chemical vapor deposition (CVD) of siloxane polymers. Water vapor around the MCC reacts with the silicon tetrachloride (SiCl4) steam introduced by nitrogen carrier gas to form siloxane polymers. Consequently, it induces the formation of a siloxane polymers layer coating on the surface of each PS sphere, which results in the shrinkage of the interstice between neighboring PS spheres. In this way, the deformation of colloidal spheres during thermal annealing could be avoided. Accordingly, extra cracks arising from the constraint of spheres deformation on a rigid substrate are eliminated. Furthermore, the interstice size of the colloidal mask can be precisely controlled by manipulating the CVD conditions. In addition, the colloidal mask could be transferred onto any kind of substrates including rigid, flexible, flat, or curved solid substrates after CVD coating. The method provides a facile approach to the fabrication of interstice-size-tunable, high-quality colloidal masks for NSL application.

•A strategy is developed for fabrication of hierarchically ordered structures.•Only two steps are required by colloidal self-assembly and solvent vapor annealing.•The hierarchical structures show fine antireflection properties at 1100 nm–1800 nm.A facile strategy for fabricating hierarchically micro- and nano-scale ordered features as antireflection coating is developed. Compared to conventional lithographic techniques, this process exhibits the advantages of low cost and high efficiency. Only two fabrication steps are required by combining colloidal crystal self-assembly with solvent vapor annealing at the air/water interface. These special hierarchically ordered arrays demonstrate fine structure-enhanced antireflection properties in the near-infrared spectral region ranging from 1100 nm to 1800 nm, which may be highly valuable for designing many optoelectronic devices.

Here we demonstrate a facile approach to the fabrication of transferrable and high-quality latex colloidal masks with tunable interstice size for nanosphere lithography (NSL). A polystyrene (PS) monolayer colloidal crystal (MCC) was first prepared via an air–water interface self-assembly method and subsequently transferred onto the surface of water in a hydrothermal reactor. Thermal annealing of the PS colloidal monolayer floating at the water surface under a temperature higher than the glass-transition temperature of polystyrene caused deformation of the PS spheres, leading to the shrinkage of the interstice. By manipulating the diameter of the colloidal spheres and the thermal annealing process, flexible control in size, shape and spacing of the interstice in a colloidal mask was achieved, which would facilitate the broad use of NSL to study the size-, shape-, and period-dependent optical, magnetic, electronic, and catalytic properties of nanoparticle arrays.

The confined self-assembly of asymmetric diblock copolymer polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) within an array of silica nanobowls prepared using a colloidal spheres templating technique is investigated. By manipulation of the nanobowl size, block copolymer (BCP) thickness, and interfacial interaction, a rich variety of ordered BCP nanostructures not accessible in the bulk system or under other confinements are obtained, resulting in hierarchically ordered nanostructures.

Nanosphere lithography (NSL) has been regarded as an inexpensive, inherently parallel, high-throughput, materials-general approach to the fabrication of nanoparticle arrays. However, the order of the resulting nanoparticle array is essentially dependent on the quality of the colloidal monolayer mask. Furthermore, the lateral feature size of the nanoparticles created using NSL is coupled with the diameter of the colloidal spheres, which makes it inconvenient for studying the size-dependent properties of nanoparticles. In this work, we demonstrate a facile approach to the fabrication of a large-area, transferrable, high-quality latex colloidal mask for nanosphere lithography. The approach is based on a combination of the air/water interface self-assembly method and the solvent-vapor-annealing technique. It enables the fabrication of colloidal masks with a higher crystalline integrity compared to those produced by other strategies. By manipulating the diameter of the colloidal spheres and precisely tuning the solvent-vapor-annealing process, flexible control of the size, shape, and spacing of the interstice in a colloidal mask can be realized, which may facilitate the broad use of NSL in studying the size-, shape-, and period-dependent optical, magnetic, electronic, and catalytic properties of nanomaterials.

A simple, fast, and cost-effective co-self-assembly approach to fabricate large-area two-dimensional (2D) binary colloidal crystals has been developed. By manipulating the size ratio and number ratio of the two monodisperse polystyrene latexes, a variety of binary colloidal crystal monolayers with different structures were successfully prepared. The co-self-assembly mechanism of the 2D binary colloidal crystals at the air−water interface was investigated. It was found that the glass slide and the ethanol involved in this work had played significant roles as buffer storage and spreading agent, respectively.Keywords: air−water interface; binary colloidal crystals; self-assembly

•Novel rare-earth borate KBaTbB2O6 was synthesized using a conventional solid-state reaction method.•The crystal structure of KBaTbB2O6 has been determined by the Rietveld analysis.•Tunable emission in red wavelength range was realized by controlling Eu3+ ions content.Novel rare-earth borate KBaTbB2O6 was synthesized using a conventional solid-state reaction method. The crystal structure of KBaTbB2O6 has been determined by the Rietveld analysis, which demonstrates that the final chemical composition is K0.46Ba0.54Tb0.49BO3 and KBaTbB2O6 is isomorphous with KBaY(BO3)2 and crystallizes in the planar trigonal [BO3]3− group R-3 m with lattice parameters of a=5.4562(4) Å, c=17.8629(2) Å, and Z=3. Tunable emission in red wavelength range was realized by doping and controlling Eu3+ ions content into KBaTbB2O6. The critical energy transfer distance calculated by the concentration quenching theory was 6.64 Å and the energy transfer from Tb3+ to Eu3+ took place via a resonance-type mechanism.

Here we demonstrate a facile approach to the fabrication of transferrable and high-quality latex colloidal masks with tunable interstice size for nanosphere lithography (NSL). A polystyrene (PS) monolayer colloidal crystal (MCC) was first prepared via an air–water interface self-assembly method and subsequently transferred onto the surface of water in a hydrothermal reactor. Thermal annealing of the PS colloidal monolayer floating at the water surface under a temperature higher than the glass-transition temperature of polystyrene caused deformation of the PS spheres, leading to the shrinkage of the interstice. By manipulating the diameter of the colloidal spheres and the thermal annealing process, flexible control in size, shape and spacing of the interstice in a colloidal mask was achieved, which would facilitate the broad use of NSL to study the size-, shape-, and period-dependent optical, magnetic, electronic, and catalytic properties of nanoparticle arrays.

A graphene/patterned ZnO (G/PZO) nanorod array composite was successfully fabricated by using the colloidal nanosphere monolayer templating strategy. Compared with graphene/compact ZnO (G/CZO) nanorod arrays, the G/PZO nanorod array composite exhibited a highly efficient and stable field emission with a low turn-on field. The field emission had a strong dependence on the density and the inter-distance of the emitters. By changing the diameter of polystyrene (PS) colloidal nanospheres, optimal emitter inter-distance was obtained. Graphene supported on ZnO nanorod arrays, patterned by an 886 nm PS colloidal nanosphere monolayer, displayed the best field emission with a turn-on electric field of only 6.4 V μm−1 and the field enhancement factor β was 1158. The K point in the Fowler–Nordheim plot demonstrated the electron tunneling mechanism took place in this composite material. The cyclic experiment showed that the field emission of the G/PZO nanorod array composite was of high stability.

Organolead halide perovskites have attracted extensive attention as light harvesting materials for optoelectronic devices due to their high charge carrier mobility, high photoconversion efficiency, and long charge diffusion length. In this study, we present the first self-powered organolead halide perovskite single crystal photodetector driven by a triboelectric nanogenerator (TENG). A high-performance planar photodetector showing a responsivity of 7.92 A W−1 to white light under a bias of 4 V was fabricated on the (100) facet of a bulk CH3NH3PbI3 perovskite single crystal. Furthermore, we demonstrate a cost-effective approach to the fabrication of a drum-shaped TENG by using two used digital versatile discs (DVDs), which could generate a high output of up to 200 V and 55 μA. By integrating the CH3NH3PbI3 single crystal photodetector with the TENG, the self-powered device exhibited a large responsivity of 196 V (mW cm−2)−1 and a wide detection range from 10 μW cm−2 to 100 mW cm−2. These results provide a new strategy for driving the organolead halide perovskite photodetector with the energy harvested from the environment rather than an external power supply.

Highly efficient blue-emitting NaBa4(AlB4O9)2X3 (X = Cl, Br):Eu2+ phosphors (NBAC:Eu2+ and NBAB:Eu2+) were prepared by solid-state reaction. Two different crystallographic cation sites of Eu2+ ion occupancy were confirmed by Rietveld structural refinement, photoluminescence spectroscopy and measurement of fluorescence decay lifetimes. The NBAC:Eu2+ and NBAB:Eu2+ phosphors exhibited broad excitation ranging from 250 to 420 nm, both of which overlapped well with the emission of n-UV LED chips. Under 365 nm excitation, intense asymmetric blue emission bands were obtained for NBAC:Eu2+ and NBAB:Eu2+, peaking around 429 and 437 nm, respectively. The optimal Eu2+ doping concentration in both NBAC:xEu2+ and NBAB:xEu2+ was determined to be the same (10 mol%). The concentration quenching mechanism turned out to be electric dipole–dipole interactions. The NBAB:0.1Eu2+ and NBAC:0.1Eu2+ phosphors presented superior blue-emitting properties to the commercially available BAM:Eu2+ blue phosphor. The optimized NBAB:0.1Eu2+ and NBAC:0.1Eu2+ exhibited high external quantum efficiencies of 98.7% and 74.7% of the commercially available compound BaMgAl10O17:Eu2+ (BAM:Eu2+), respectively, while the NBAB:0.1Eu2+ phosphor demonstrated a very narrow band (FWHM ≤ 33 nm) and an ultra-high color purity of 99.58%. These results suggest that NBAB:Eu2+ and NBAC:Eu2+ can serve as promising blue-emitting candidates for n-UV pumped white LEDs.

Pb(In1/2Nb1/2)O3–PbZrO–Pb(Mg1/3Nb2/3)O3–PbTiO3 (PIN–PZ–PMN–PT) quaternary system relaxor ferroelectric materials possess a high ferroelectric phase transition temperature (TFE–FE > 120 °C) due to the enhanced A–B repulsion intensity in the ABO3 lattice caused by the incorporation of In3+ and Zr4+ cations. Due to these additions, excellent piezoelectric property (d33[001]* = 1820 pm V−1) at room temperature and good thermal stability were observed in the PIN–PZ–PMN–PT single crystals. Strong frequency dispersion (frequency ∼0.1–100 kHz) and small short-range correlation length (〈ξ〉 ∼ 118 nm) of polar nanoregions (PNRs) illustrate the high degree of relaxor nature of these quaternary-system single crystals in comparison with the PMN–0.2PT relaxor single crystal (〈ξ〉 ∼ 210 nm). The high relaxor nature is speculated to be caused by In3+ and Zr4+ cations and is considered one of the main reasons for the excellent piezoresponse of the PIN–PZ–PMN–PT single crystal. Moreover, PNRs with orthorhombic 〈011〉 polarization might have a modulation effect on the (011) surface, leading to the anisotropic nanodomain structures. A lower free energy for domain switching on the (011) surface was needed than that on the (001) surface, which was confirmed by the piezoresponse hysteresis loops and local domain poling behavior studies.