Marangoni‐Effect‐Assisted Bar‐Coating Method for High‐Quality Organic Crystals with Compressive and Tensile Strains

Low‐cost solution‐shearing methods are highly desirable for deposition of organic semiconductor crystals over a large area. To enhance the rate of evaporation and deposition, elevated substrate temperature is commonly employed during shearing processes. However, the Marangoni flow induced by a temperature‐dependent surface‐tension gradient near the meniscus line shows negative effects on the deposited crystals and its electrical properties. In the current study, the Marangoni effect to improve the shearing process of 2,7‐dioctyl[1]benzothieno[3,2‐b ][1]benzothiophene for organic field‐effect transistor (OFET) applications is utilized and regulated. By modifying the gradient of surface tension with different combinations of solvents, the mass transport of molecules is much more favorable, which largely enhances the deposition rate, reduces organic crystal thickness, enlarges grain sizes, and improves coverage. The average and highest mobility of OFETs can be increased up to 13.7 and 16 cm² V^?1 s^?1. This method provides a simple deposition approach on a large scale, which allows to further fabricate large‐area circuits, flexible displays, or bioimplantable sensors.     

Direct Growth of Pyramid‐Textured Perovskite Single Crystals: A New Strategy for Enhanced Optoelectronic Performance

Even though there have been a few reports of substrate surface texturing of thin film perovskite solar cells to enhance their light trapping, there has been no direct texturing of the perovskite material, let alone perovskite single crystals (SCs). Herein, a method to prepare a pyramid‐structured perovskite CH₃NH₃PbX₃ (CH₃NH₃⁺ = MA, X = I, Br) SC surface with minimized light reflection and maximized incident light harvesting is reported. Specifically, a hard template is used to directly transfer the pyramidal texture onto the MAPbX₃ SC during its growth. A well‐shaped pyramidal texture is formed on the single‐crystal surface leading to improved light trapping. The textured MAPbBr₃ SC shows good crystallinity, prolonged carrier lifetime, and improved carrier mobility. Furthermore, the photodetector made from the textured SC shows enhanced responsivity of 321 A W^?1 and external quantum efficiency of 7191%, about two times higher than that of a control device. This method may be used to directly fabricate desired textures on general single crystal surfaces.     

Hollow Mesoporous Metal Organic Framework Single Crystals Enabled by Growth Kinetics Control for Enhanced Photocatalysis

The tailored design of hollow mesoporous metal−organic framework (MOF) single crystals to realize the unimpeded mass transport and long-range carrier migration for advanced photoelectric applications is attractive while being a major challenge. Here, a kinetically mediated micelle assembly strategy is presented to synthesize hollow UiO-66(Ce) single crystals in 1,3,5-trimethylbenzene (TMB)-H₂O emulsion system with Pluronic F127/P123 as dual surfactants. This synthesis features the employment of modulator acetic acid, which can coordinate growth kinetics of MOFs, allowing the nucleation of MOF on block polymer micelles and transforming the self-assembly of block polymer/MOF composite monomicelles from water to TMB/H₂O emulsion interface and the growth of MOF from aggregation to oriented attachment, and thus ensuring the formation of hollow mesoporous UiO-66(Ce) single crystals. Moreover, a precise control in cavity diameter from ≈0 to ≈600 nm, mesopore structure from close to radial and dendritic can be achieved by tuning the amount of TMB and the ratio of F127/P123. As a result, the hollow mesoporous UiO-66(Ce) single crystals with large radial mesopores (≈25 nm) and high surface area (≈1061 m2 g) exhibit excellent photocatalytic performance for H₂ generation owing to enhanced permeability and suppressed electron-hole combination.     

High‐Color‐Rendering and High‐Efficiency White Organic Light‐Emitting Devices Based on Double‐Doped Organic Single Crystals

Organic single crystals with much higher carrier mobility and stability compared to the amorphous organic materials have shown great potential in electronic and optoelectronic devices. However, their applications in white organic light‐emitting devices (WOLEDs), especially the three‐color‐strategy WOLEDs, have been hindered by the difficulties in fabricating complicated device structures. Here, double‐doped white‐emission organic single crystals are used as the active layers for the first time in the three‐color‐strategy WOLEDs by co‐doping the red and green dopants into blue host crystals. Precise control of the dopant concentration in the double‐doped crystals results in moderately partial energy transfer from the blue donor to the green and red dopants, and thereafter, simultaneous RGB emissions with balanced emission intensity. The highest color‐rendering index (CRI) and efficiency, to the best of the authors' knowledge, are obtained for the crystal‐based WOLEDs. The CRI of the WOLEDs varies between 80 and 89 with the increase of the driving current, and the luminance and current efficiency reach up to 793 cd m^?2 and 0.89 cd A^?1, respectively. The demonstration of the present three‐color organic single‐crystal‐based WOLED promotes the development of the single crystals in optoelectronics.     

Solutal-Marangoni-Flow-Mediated Growth of Patterned Highly Crystalline Organic Semiconductor Thin Film Via Gap-Controlled Bar Coating

Application-oriented patterned growth of organic semiconductor (OSC) thin films with single crystalline domains is crucial for fabricating sophisticated high-performance organic-electronic and optoelectronic devices; however, fabricating these patterned nanometer-thick crystals in a simple, fast, and effective manner is a difficult task with a roll-to-roll printing process. Here, a simple bar-coating approach to form an array of single-crystal-like OSC thin-film patterns at a rate of a few millimeters per second is introduced. To this end, the processing parameters of a gap-controlled bar-coating method is optimized, including coating speed, crystal nucleation, and solution fluidics, which allow a high degree of morphological control of bar-coated OSC films in an area of several centimeters. In particular, it is demonstrated that the solutal-Marangoni flow induced by a suitable solvent additive can considerably improve molecular mass transport and induce favorable vertical phase separation. Thus, organic transistors based on the OSC patterns fabricated with the additive-assisted bar coating show a field-effect mobility of up to 20 cm² V⁻¹ s⁻¹ and superior operational stability. The proposed bar coating method will facilitate an industry-level application of organic electronics.     

Recent Progress on Synthesis,Intrinsic Properties and Optoelectronic Applications of Perovskite Single Crystals

Metal halide perovskite have shown great potential for applications in photovoltaics, light-emitting diodes and photon detectors, mainly owing to their superb optoelectronic properties, low-cost raw materials and facile fabrication process. Although, polycrystalline perovskite thin-films have been actively investigated for preparing various optoelectronic devices, the presence of detrimental defects at grain boundaries, serious ion migration and limited stability unfortunately hinder their device performance and practical application. As a contrast, perovskite single crystals (SCs) exhibit no grain boundaries, much lower trap density and much improved stability, hence providing a more attractive choice for not only optoelectronic device applications but also fundamental research. In this review, recent progress in the growth methods of perovskite SCs is summarized, followed by giving a detailed introduction of the intrinsic properties of perovskite SCs including optical properties, defects, charge carrier dynamics, ion migration and stability. On these base, the applications of perovskite SCs in various optoelectronic devices like solar cells, photodetectors, and radiation detectors are discussed, where the relationship between the composition, device architecture and device performance is highlighted. Finally, a tentative discussion on the current challenges and future opportunities in the development of perovskite SCs and optoelectronic devices is presented.     

Azeotropic Binary Solvent Mixtures for Preparation of Organic Single Crystals

Here, a new approach is introduced to prepare large single crystals of π‐conjugated organic molecules from solution. Utilizing the concept of azeotropism, single crystals of tri‐isopropylsilylethynyl pentacene (TIPS‐PEN) with dimensions up to millimeters are facilely self‐assembled from homogeneous solutions comprising two solvents with opposing polarities and a positive azeotropic point. At solvent compositions close to the azeotropic point, an abrupt transition of morphology from polycrystalline thin‐films to large single crystals is found. How to adjust the initial ratio of the binary solvents so that the change in solvent composition during evaporation favors the specific H‐aggregation and promotes an efficient self‐assembly of TIPS‐PEN is explained. The charge‐carrier (hole) mobilities are substantially enhanced by a factor of 4 from the morphology of thin‐films to large single crystals used as active layer in field‐effect transistors. Additionally, this approach is extended to other π–π stacked organic molecules to elucidate its broad applicability.     

Wafer-Scale Growth of Aligned C60 Single Crystals via Solution-Phase Epitaxy for High-Performance Transistors

Fullerene (C₆₀) single crystals with exceptionally low defects and nearly perfect translational symmetry make them appealing in achieving high-performance n-type organic transistors. However, because of its natural 0D structure, control over continuous crystallization of C₆₀ over a large area is extremely challenging. Here, the authors report a solution-phase epitaxial approach for wafer-scale growth of continuously aligned C₆₀ single crystals. This method enables the rational control of the density of nucleation event at meniscus front by confining the size and shape of meniscus with a microchannel template. In this case, a single nucleus as seed crystal can be formed at the front of meniscus, and then epitaxial growth from the seed crystal occurs with continuous retreat of the meniscus. As a result, highly uniform C₆₀ single-crystal array with ultralow defect density is obtained on 2-inch substrate. Organic field-effect transistors made from the C₆₀ single-crystal array show a high average electron mobility of 2.17 cm² V⁻¹ s⁻¹, along with a maximum mobility of 5.09 cm² V⁻¹ s⁻¹, which is much superior to the C₆₀ polycrystalline film-based devices. This strategy opens new opportunities for the scalable fabrication of high-performance integrated devices based on organic crystals.     

Highly Efficient Organic THz Generator Pumped at Near‐Infrared: Quinolinium Single Crystals

A novel highly efficient ionic electro‐optic quinolinium single crystals for THz wave applications is reported. Acentric quinolinium derivatives, HMQ‐T (2‐(4‐hydroxy‐3‐methoxystyryl)‐1‐methylquinolinium 4‐methylbenzenesulfonate) and HMQ‐MBS (2‐(4‐hydroxy‐3‐methoxystyryl)‐1‐methylquinolinium 4‐methoxybenzenesulfonate) exhibit high order parameters cos³θ_p = 0.92 and cos³θ_p = 1.0, respectively, as well as a large macroscopic optical nonlinearity, which is in the range of the benchmark stilbazolium DAST (N,N‐dimethylamino‐N’‐methylstilbazolium 4‐methylbenzenesulfonate) and phenolic polyene OH1 (2‐(3‐(4‐hydroxystyryl)‐5,5‐dimethylcyclohex‐2‐enylidene)malononitrile) crystals. As‐grown unpolished bulk HMQ‐T crystals with a side length of about 6 mm and thickness of 0.56 mm exhibit 3.1 times higher THz generation efficiency than 0.37 mm thick OH1 crystals and about 8.4 times higher than 1 mm thick inorganic standard ZnTe crystals at the near‐infrared fundamental wavelength of 836 nm. Therefore, HMQ crystals with high order parameter obviously have a very high potential for high power THz‐wave generation and its applications.     

Interfacial Pyro-Phototronic Effect: A Universal Approach for Enhancement of Self-Powered Photodetection Based on Perovskites with Centrosymmetry

Utilizing the pyro-phototronic effect presents a potent approach to augment the efficacy of self-powered photodetectors (PDs) that rely on metal halide perovskites (MHPs). Nevertheless, the pyro-phototronic effect has thus far been restricted to perovskites possessing a non-centrosymmetric crystal structure, limiting their scope of application. This study introduces a universal interfacial pyro-phototronic effect (IPPE) strategy to MHP single crystals with centrosymmetry. The utilization of heterojunctions or Schottky junctions has resulted in the observation of typical four-stage photoresponses with rapid speed, thereby significantly enhancing the performance of self-powered PDs and expanding the spectral response range. The contact conditions, such as the choice of metals and surface smoothness, have an important impact on IPPE. The IPPE approach is a versatile technique that can be employed to fabricate self-powered PDs based on diverse 3D and 2D perovskites. This study broadens the utilization of the pyro-phototronic phenomenon in centrosymmetric perovskites, which offer advantages in producing optoelectronic devices with superior performance.     

弛豫铁电单晶热释电探测器读出电路的设计

以(1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3(PMN-xPT或PMNT)(PMN-xPT,或PMN-PT)为代表的弛豫铁电单晶具有非常高的热释电系数、比较低的热扩散系数、比较稳定的化学性能,是一种综合性能优异的热释电材料.利用弛豫铁电单晶可以制备出高性能的红外光传感器,针对用这种新型热释电材料制成的红外...     

Water-Surface-Mediated Precise Patterning of Organic Single-Crystalline Films via Double-Blade Coating for High-Performance Organic Transistors

Application-oriented growth of patterned organic semiconductor (OSC) thin films with a single domain is a nonnegotiable requirement for the manufacturing of high-performance organic electronic devices. However, the prevalent selective-wetting patterning method remains a challenge in controlling the density of nucleation events in microscale spaces, resulting in thin films with high grain boundary density and no preferential orientation spherulites. Herein, a simple double-blade-coating printing technique using a combination of wetting-patterned substrates to produce an array of highly crystalline OSC thin films is developed. Specifically, the approach confines the OSC crystallization on a molecular-flat water surface in specific areas, enabling a significant reduction in the number of nuclei. Consequently, patterned 2,7-dioctyl[1]benzothieno[3,2-b] benzothiophene (C₈-BTBT) thin films comprising single-crystal domains are achieved with an exceptionally high yield of 62.5%. The organic field-effect transistor array developed from such patterns of C₈-BTBT single-crystalline films exhibits an excellent average mobility of 11.5 cm² V⁻¹ s⁻¹ which is 12.5-fold higher compared to that of the reference sample fabricated via conventional single-blade coating. It is believed that this approach can be widely applied to other soluble organic materials, thereby opening up opportunities for fabricating multicomponent integrated electronics.     

用于振动能收集器的弛豫铁电单晶切型研究

弛豫铁电单晶具有优越的压电性能和良好的温度适应性,在压电器件领域具有良好的应用前景。但是由于其复杂的工程化畴组态和各向异性,在器件设计过程中必须要考虑切型问题。该文从物联网电源的需求出发,以弛豫铁电单晶应用于振动能收集器为例,构造了以输出电压为考核目标的优化切型判据;利用基于欧拉旋转定理的张量计算方法计算分析了沿其赝立方结构的[001]、[011]和[111]极化的铌镁酸铅-钛酸铅单晶适用于振动能收集器的优化切型;分析了3种切型对切角误差的敏感性;最后给出了优化切型下的相关物理性能张量。     

Organic Ionic Plastic Crystals as Hole Transporting Layer for Stable and Efficient Perovskite Solar Cells

Organic ionic plastic crystals (OIPCs) are synthesized through a simple metal‐free, cost‐effective approach. The strategized synchronization of electron‐rich phenoxazine with benzimidazolium iodide (OIPC‐I) and bromide (OIPC‐Br) salts lead to enhanced hole mobility and conductivity of OIPCs which is suitable for an efficient alternative to conventional organic hole transporting materials (HTMs) for stable perovskite solar cells (PSCs). The fabricated PSCs with OIPC‐I as hole transporting layer yielded a power conversion efficiency of 15.0% and 18.1% without and with additive (Li salt) respectively, which are comparable with spiro‐OMeTAD based devices prepared under similar conditions. Furthermore, the PSCs with OIPCs show good stability compared to the spiro‐OMeTAD with or without additives. Here, first time benzimidazolium‐based OIPCs have been used as an alternative organic HTM for perovskite solar cells, which opens a window for the design of effective OIPCs for highly efficient PSCs with long‐term stability.     

A Facile Method for the Growth of Organic Semiconductor Single Crystal Arrays on Polymer Dielectric toward Flexible Field‐Effect Transistors

Polymer dielectrics with intrinsic mechanical flexibility are considered as a key component for flexible organic field‐effect transistors (OFETs). However, it remains a challenge to fabricate highly aligned organic semiconductor single crystal (OSSC) arrays on the polymer dielectrics. Herein, for the first time, a facile and universal strategy, polar surface‐confined crystallization (PSCC), is proposed to grow highly aligned OSSC arrays on poly(4‐vinylphenol) (PVP) dielectric layer. The surface polarity of PVP is altered periodically with oxygen‐plasma treatment, enabling the preferential nucleation of organic crystals on the strong‐polarity regions. Moreover, a geometrical confinement effect of the patterned regions can also prevent multiple nucleation and misaligned molecular packing, enabling the highly aligned growth of OSSC arrays with uniform morphology and unitary crystallographic orientation. Using 2,7‐dioctyl[1]benzothieno[3,2‐b]benzothiophene (C8‐BTBT) as an example, highly aligned C8‐BTBT single crystal arrays with uniform molecular packing and crystal orientation are successfully fabricated on the PVP layer, which can guarantee their uniform electrical properties. OFETs made from the C8‐BTBT single crystal arrays on flexible substrates exhibit a mobility as high as 2.25 cm² V^?1 s^?1, which has surpassed the C8‐BTBT polycrystalline film‐based flexible devices. This work paves the way toward the fabrication of highly aligned OSSCs on polymer dielectrics for high‐performance, flexible organic devices.     

Ultra‐Thin Layered Ternary Single Crystals [Sn(SxSe1−x)2] with Bandgap Engineering for High Performance Phototransistors on Versatile Substrates

2D ternary semiconductor single crystals, an emerging class of new materials, have attracted significant interest recently owing to their great potential for academic interest and practical application. In addition to other types of metal dichalcogenides, 2D tin dichalcogenides are also important layered compounds with similar capabilities. Yet, multi‐elemental single crystals enable to assist multiple degrees of freedom for dominant physical properties via ratio alteration. This study reports the growth of single crystals Se‐doped SnS₂ or SnSSe alloys, and demonstrates their capability for the fabrication of phototransistors with high performance. Based on exfoliation from bulk high quality single crystals, this study establishes the characteristics of few‐layered SnSSe in structural, optical, and electrical properties. Moreover, few‐layered SnSSe phototransistors are fabricated on both rigid (SiO₂/Si) and versatile polyethylene terephthalate substrates and their optoelectronic properties are examined. SnSSe as a phototransistor is demonstrated to exhibit a high photoresponsivity of about 6000 A W^?1 with ultra‐high photogain ≈8.8 × 10⁵, fast response time ≈9 ms, and specific detectivity (D*) ≈8.2 × 10¹² J. These unique features are much higher than those of recently published phototransistors configured with other few‐layered 2D single crystals, making ultrathin SnSSe a highly qualified candidate for next‐generation optoelectronic applications.     

Hierarchically Organized Superstructure Emerging from the Exquisite Association of Inorganic Crystals,Organic Polymers,and Dyes: A Model Approach Towards Suprabiomineral Materials

We report a novel hierarchically organized superstructure emerging from an exquisite association of inorganic crystals, organic polymers, and dyes. The resultant K₂SO₄/poly(acrylic acid) composite includes five different tiers from the nanoscopic to the macroscopic. An additional new tier leading to functionality is formed by the incorporation of organic dyes that are organized in a nanospace. The emergent superstructure and properties are designed through changes in polymer concentration. The multiple roles of the polymer realize the generation of the architecture at each size scale. This model approach should be widely applicable to other systems, allowing for the preparation of innovative materials by an appropriate combination of crystals, polymers, and functional molecules.