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Flexible laser display is a critical component for an information output port in next-generation wearable devices. So far, the lack of appropriate display panels capable of providing sustained operation under rigorous mechanical conditions impedes the development of flexible laser displays with high reliability. Owing to the multiple scattering feedback mechanism, random lasers render high mechanical flexibility to withstand deformation, thus making them promising candidates for flexible display planes. However, the inability to obtain pixelated random laser arrays with highly ordered emissive geometries hinders the application of flexible laser displays in the wearable device. Here, for the first time, we demonstrate a mass fabrication strategy of full-color random laser arrays for flexible display panels. The feedback closed loops can be easily fulfilled in the pixels by multiple scatterings to generate durative random lasing. Due to the sustained operation of random laser, the display performance was well-maintained under mechanical deformations, and as a result, a flexible laser display panel was achieved. Our finding will provide a guidance for the development of flexible laser displays and laser illumination devices.

Detecting conformational changes in protein is imperative due to its major role in neurodegenerative disorders. Here, we propose an alternative strategy for monitoring the structural change of proteins based on biological microlasers. Smart responsive protein-based microscale biolasers were constructed by incorporating organic gain medium into the microspheres of silk fibroin via emulsion-solvent evaporation. The lasing characteristic of the biolasers exhibited a sensitive response to the structural transformation of the silk fibroin. With narrowed linewidth, the as-prepared biolasers as sensing signals enable highly sensitive protein conformation detection. These results offer an effective approach to monitoring the protein conformational changes and provide valuable guidance for a better understanding of the relationship between bio-microstructures and their photonic properties.

Metal-organic frameworks (MOFs) have recently emerged as appealing platforms to construct microlasers owing to their compelling characters combining the excellent stability of inorganic materials and processable characters of organic materials. However, MOF microstructures developed thus far are generally composed of multiple edge boundaries due to their crystalline nature, which consequently raises significant scattering losses that are detrimental to lasing performance. In this work, we propose a strategy to overcome the above drawback by designing spherically shaped MOFs microcavities. Such spherical MOF microstructures are constructed by amorphizing MOFs with a topological distortion network through introducing flexible building blocks into the growth environment. With an ultra-smooth surface and excellent circular boundaries, the acquired spherical microcavities possess a Q factor as high as ≈104 and can provide sufficient feedback for high-quality single-mode lasing oscillations. We hope that these results will pave an avenue for the construction of new types of flexible MOF-based photonic components.

Switchable multimode microlasers are of great significance to the development of photonic devices with high integration levels. Herein, we demonstrate an acid/alkaline gas-responsive multimode AIEgen@starch microsphere-based microlaser. The aggregation-induced emission (AIE) active fluorescent dye ASCPI was used as the gain medium in this study. ASCPI was weakly emissive in water but became highly emissive when introduced to a starch microsphere as a guest molecule. The resultant ASCPI@starch microsphere worked well as a typical whispering-gallery-mode microlaser. The laser mode wavelengths were size-dependent. Due to the sensitivity of ASCPI to pH, the output of the microlaser could be switched to a shorter wavelength by acetic acid vapor treatment or a longer wavelength by NH3 vapor treatment. This work will provide useful enlightenment for the rational design of effective switchable lasers using AIE materials with simple preparation procedures.

Lenticular printing technique provides a promising way to realize stereoscopic displays, especially, when microscopic optical structures are integrated into light-emitting materials/devices. Here, we fabricated large-area periodic structures with a spatial resolution at a wavelength scale from hybrid perovskite materials via a space-confined solution growth method. It takes advantages of both high refractive index contrast and high luminescence brightness, which allows the optical modulation on not only the reflection of illumination, but also the light emission from hybrid perovskites. The distributed feedback within these periodic structures significantly improves the degree of polarization and directionality of laser actions while their threshold is also reduced. These findings enable us to present a prototype of lenticular printing laser displays that vary emission colors at different view angles, which may find applications in creating high-resolution and high-contrast holographical images.

Thermally activated delayed-fluorescent (TADF) materials are anticipated to overcome triplet-related losses towards electrically driven organic lasers. Thus far, contributions from triplets to lasing have not yet been experimentally demonstrated owing to the limited knowledge about the excited-state processes. Herein, we experimentally achieve reverse intersystem crossing (RISC)-boosted lasing in organic microspheres with uniformly dispersed TADF emitters. In these materials, triplets are continuously converted to radiative singlets through RISC, giving rise to reduced losses in stimulated emission. The involvement of regenerated singlets in population inversion results in a thermally activated lasing; that is, the lasing intensity increases with increasing temperature, accompanied by accelerated depletion of the excited-state population. Benefiting from the suppression of triplet accumulations by RISC processes, a high-repetition-rate microlaser was achieved.

Micro/nanoscale photonic barcodes based on multicolor luminescent segmented heterojunctions hold potential for applications in information security. However, such multicolor heterojunctions reported thus far are exclusively based on static luminescent signals, thus restricting their application in advanced confidential information protection. Reported here is a strategy to design responsive photonic barcodes with heterobimetallic (Tb3+ /Eu3+ ) metal-organic framework multicolor heterostructures. The spatial colors could be precisely controlled by thermally manipulating the energy-transfer process between the two lanthanides, thus achieving responsive covert photonic barcodes. Also demonstrated is that spatially resolved responsive barcodes with multi-responsive features could be created in a single heterostructure. These findings offer unique opportunities to purposely design highly integrated responsive microstructures and smart devices toward advanced anti-counterfeiting applications.

Miniaturized lasers with high spectral purity and wide wavelength tunability are crucial for various photonic applications. Here we propose a strategy to realize broadband-tunable single-mode lasing based on a photoisomerization-activated intramolecular charge-transfer (ICT) process in coupled polymer microdisk cavities. The photoisomerizable molecules doped in the polymer microdisks can be quantitatively transformed into a kind of laser dye with strong ICT character by photoexcitation. The gain region was tailored over a wide range through the self-modulation of the optically activated ICT isomers. Meanwhile, the resonant modes shifted with the photoisomerization because of a change in the effective refractive index of the polymer microdisk cavity. Based on the synergetic modulation of the optical gain and microcavity, we realized the broadband tuning of the single-mode laser. These results offer a promising route to fabricate broadband-tunable microlasers towards practical photonic integrations.

A universal approach is demonstrated for realizing dual-wavelength lasing in organic core-shell structured microlaser arrays, which show great promise in serving as all-color laser display panels. By alternately printing hydrophilic and hydrophobic laser dye solutions on preprocessed substrates, precisely patterned core-shell heterostructure arrays were obtained. The spatially separated core and shell independently function as optical resonators to support dual-wavelength tunable lasing in each heterostructure. Such a general method enables to flexibly control the lasing wavelength of the core-shell microlasers across a wide spectral range by systematically designing the gain media. Using as-prepared microlaser arrays as display panels, full-color laser displays were achieved with a color gamut much larger than that of standard RGB space. These results provide insights for design concepts and device construction for novel optoelectronic applications.

2D anisotropic transport of photons/electrons is crucial for constructing ultracompact on-chip circuits. To date, the photons in organic 2D crystals usually exhibit the isotropic propagation, and the anisotropic behaviors have not yet been fully demonstrated. Now, an orientation-controlled photon-dipole interaction strategy was proposed to rationally realize the anisotropic and isotropic 2D photon transport in two co-crystal polymorph microplates. The monoclinic microplate adopts a nearly horizontal transition dipole moment (TDM) orientation in 2D plane, exhibiting anisotropic photon-dipole interactions and thus distinct re-absorption waveguide losses for different 2D directions. By contrast, the triclinic plate with a vertical TDM orientation, shows 2D isotropic photon-dipole interactions and thus the same re-absorption losses along different directions. Based on this anisotropy, a directional signal outcoupler was designed for the directional transmission of the real signals.

Herein, we demonstrated a steric-hindrance-controlled laser switch in pure metal-organic framework (MOF) microcrystals. The well-faceted MOF microwires with aggregation-induced emission (AIE) lumnogens as linkers function as typical Fabry-Pérot microlasers. The steric hindrance around the AIE linkers can be reduced by the loss of guest molecules, which lead to the enhanced rotation of linkers with red-shifted gain behavior. On this basis, the gain region was readily switched through changing the steric hindrance via the desorption/adsorption of guests. As a result, the reversible switching of the dual-wavelength lasing from MOF microwires was achieved. The results provide a promising route to the development of versatile micro-/nanolasers with desired applications.

Surface plasmon polaritons (SPPs) are crucial for the development of next generation information and communication technologies. However, the ohmic losses inherent to all plasmonic devices seriously limit their practical application in on-chip photonic communications. Here, loss compensation of SPPs and their application in photonic logic processing was demonstrated in rationally designed organic/silver nanowire heterostructures. The heterostructures were synthesized by inserting silver nanowires (AgNWs) into crystalline organic microwires, which served as a microscale optical gain medium. These heterostructures with large organic/metal interfacial areas ensured the efficient energy transfer from excitons to SPPs. Gain for subwavelength SPPs in the heterostructure was achieved through stimulated emission of strongly confined SPPs. Furthermore, cascade gain was performed to realize basic nanoscale photonic devices, such as Boolean logic units. The results would pave an alternative avenue to incorporating SPP-enhanced devices into hybrid photonic circuitry.

Porous organic frameworks have emerged as the promising platforms to construct tunable microlasers. Most of these microlasers are achieved from metal-organic frameworks via meticulously accommodating the laser dyes with the sacrifice of the pore space, yet they often suffer from the obstacles of either relatively limited gain concentration or sophisticated fabrication techniques. Herein, we reported on the first hydrogen-bonded organic framework (HOF) microlasers with color-tunable performance based on conformation-dependent stimulated emissions. Two types of HOF microcrystals with the same gain lumnogen as the building block were synthesized via a temperature-controlled self-assembly method. The distinct frameworks offer different conformations of the gain building block, which lead to great impacts on their conjugation degrees and excited-state processes, resulting in remarkably distinct emission colors (blue and green). Accordingly, blue/green-color lasing actions were achieved in these two types of HOFs based on well-faceted assembled wire-like cavities. These results offer a deep insight on the exploitation of HOF-based miniaturized lasers with desired nanophotonics performances.

Exciton–polariton Bose–Einstein condensation (EP BEC) is of crucial importance for the development of coherent light sources and optical logic elements, as it creates a new state of matter with coherent nature and nonlinear behaviors. The demand for room temperature EP BEC has driven the development of organic polaritons because of the large binding energies of Frenkel excitons in organic materials. However, the reliance on external high-finesse microcavities for organic EP BEC results in poor compactness and integrability of devices, which restricts their practical applications in on-chip integration. Here, we demonstrate room temperature EP BEC in organic single-crystal microribbon natural cavities. The regularly shaped microribbons serve as waveguide Fabry–Pérot microcavities, in which efficient strong coupling between Frenkel excitons and photons leads to the generation of EPs at room temperature. The large exciton–photon coupling strength due to high exciton densities facilitates the achievement of EP BEC. Taking advantages of interactions in EP condensates and dimension confinement effects, we demonstrate the realization of controllable output of coherent light from the microribbons. We hope that the results will provide a useful enlightenment for using organic single crystals to construct miniaturized polaritonic devices., The use of room temperature exciton–polariton Bose–Einstein condensation is limited by the need for external high-finesse microcavities. The authors generate room temperature EPs with single-crystal microribbons as waveguide Fabry–Pérot microcavities, and demonstrate controllable output of coherent light.

Near-infrared (NIR) microlasers play a significant role in telecommunication and biomedical tissue imaging. However, it remains a big challenge to realize NIR microlasers because of the difficulty in preparing highly efficient NIR luminescent materials and perfect optical resonators. Here, we propose a molecular design strategy to creatively realize the first spiropyrane (SP)-based NIR microlasers with low threshold from self-assembled microsphercial caps. The tetraphenylethylene (TPE) moiety with a highly twisted conformation provides a large free volume to facilitate the photoisomerization process of SP and enhance NIR emission of merocyanine in the solid state. Moreover, self-assembled TPE-SP microsphercial caps simultaneously serve as gain media and resonant microcavities, providing optical gain and feedback for NIR laser oscillations with a low threshold (3.68 μJ/cm

[K(dibenzo-18-crown-6)]+ (KC) cations are used for cocrystallization with manganese halides, producing isostructural single crystals of organic–inorganic hybrid complexes, [K(dibenzo-18-crown-6)]2M...

Micro/nanoscale multicolor barcodes with unique identifiability and a small footprint play significant roles in applications such as multiplexed labeling and tracking systems. Now, a strategy is reported to design multicolor photonic barcodes based on 1D Ln-MOF multiblock heterostructures, where the domain-controlled emissive colors and different block lengths constitute the fingerprint of a corresponding heterostructure. The excellent heteroepitaxial growth characteristics of MOFs enable the effective modulation of the coding structures, thereby remarkably increasing the encoding capacity. The as-prepared multicolor barcodes enable an efficient authentication and exhibit great potential in fulfilling the functions of anti-counterfeiting, information security, and so on. The results will pave an avenue to novel hybrid MOFs for optical data recording and security labels.

The monolithic incorporation of electrical and optical components is critically important for achieving high-speed on-chip signal processing, but yet hard to satisfy the explosive growth in the demands on bandwidth and information density. Three-dimensional (3D) circuits, which are desirable for their improved performance in data handling, are ideal candidates to simultaneously promise high-capacity computing with improved speed and energy efficiency. In such highly integrated circuits, however, the selective electrical modulation of light signals is still difficult to achieve owing to the lack of controllable integration of micro-scale optical functional devices and modulation units. In this work, we demonstrate an electrically modulated microlaser module on a 3D-integrated microsystem composed of a dye-doped polymeric microcavity and an underneath microscale electrical heating circuit. The lasing mode was modulated based on electrical heating-assisted thermo-optic response of the polymeric matrices, which were further fabricated into coupled microdisks, yielding wavelength-tunable single-mode microlasers with selective electrical modulation. On this basis, a prototype of electrically controlled microlaser module with reduced signal cross-talk was achieved. The results will provide a useful enlightenment for the rational design of novel tunable optical devices with more complicated functionalities under far-field regulation, paving the way for the on-chip optoelectronic integration.

Organic polymorphs with tunable luminescence are crucial in developing organic luminescent materials, but the regulation of molecular packing modes and intermolecular interactions in organic crystals remains a challenge. Here, we report three triphenylamine–benzothiazole (TZ) compounds by systematically changing the substituents, resulting in different crystal emission characteristics. The polymorphs of blue emission (TZ-1B) and cyan emission (TZ-1C) crystals are obtained by controlling the crystallization conditions, however, we could not obtain organic polymorphs of TZ-2 or TZ-3 in various solvent systems. By molecular systems and detailed single crystal analysis, it is found that appropriate substituents play a key role in manipulating the intermolecular interactions and the molecular packing modes to affect the optical properties of organic crystals. Moreover, TZ-1C exhibits blue-shifted mechanochromism, while TZ-1B does not. More importantly, TZ-1B exhibits a lasing emission at 454 nm with a low threshold and a high cavity quality factor. TZ-1C exhibits amplified spontaneous emission (ASE) at 462 nm. Thus, the molecular systems provide a reasonably potent molecular strategy to understand the molecular packing structure–fluorescence property relationship.

The controlled construction of organic heterostructured architectures derived from molecules with similar nucleation thresholds and concentrations has been rare and remains a great challenge. Herein, we report a sequential epitaxial growth to synthesize dual-color-emitting organic heterostructures with 9,10-bis(phenylethynyl)anthracene (BPEA) microwire trunks and tris-(8-hydroxyquinoline)aluminium (Alq3) microstructure branches by an anti-solvent induced sequential crystallization strategy. During the epitaxial growth process, the hydrogen-bonding interactions of the anti-solvent and solvent cause a large change in the solubility and crystallization rate of BPEA and Alq3 molecules in the mixed system, which facilitates sequential crystallization of organic molecule pairs with similar nucleation thresholds and concentrations into desired heterostructures by manipulating the synergism of anti-solvents and solvents. The Förster resonant energy transfer process in heterostructures could be modulated by varying the structure of heterostructures, such as the shape, amount and angles of the branches. The present synthesis strategy provides a unique insight into the detailed formation mechanism of complex organic heterostructures, further guiding the construction of more functional heterostructure materials.

Organic cocrystals with unique energy-level structures are potentially a new class of materials for the development of versatile solid-state lasers. However, till now, the stimulated emission in cocrystal materials remains a big challenge possibly because of the nonradiative charge-transfer (CT) transitions. Here, for the first time, we report organic cocrystal microlasers constructed by simultaneously tailoring the energy levels and cavity structures based on the intermolecular halogen-bonding interactions. The intermolecular interactions triggered different self-assembly processes, resulting in distinct types of high-quality resonant microcavities. More importantly, the halogen-bonding interactions alleviated intermolecular CT and thus brought about a favorable four-level energy structure for the population inversion and tunable lasing in the cocrystals.

In this work, we demonstrate a stimulated emission-controlled photonic transistor on a single organic triblock nanowire composed of alternate energy donor and acceptor. The population of acceptor excitons was engineered by energy transfer to achieve enhanced fluorescence, which was further amplified by the stimulated emission of the donor and the optical feedback in the nanowire microcavities, yielding a remarkable nonlinear amplification of the acceptor emission. On this basis, a prototype of photonic transistor with high nonlinear gain at very low pump energy was achieved. The results will provide a useful enlightenment for the rational design of novel all-optical switches with desired performances.

Synthesis of novel mesoscopic semiconductor architectures continually generates new photonic knowledge and applications. However, it remains a great challenge to synthesize semiconductor microcrystals with smoothly curved surfaces owing to the crystal growth anisotropy. Here, a superkinetic crystal growth method is developed to synthesize 2D oval organic semiconductor microcrystals. The solid source dispersion induces an exceptionally large molecular supersaturation for vapor deposition, which breaks the crystal growth anisotropy. The synthesized stadium-shaped organic semiconductor microcrystals naturally constitute fully chaotic optical microresonators. They support low-threshold lasing on high-quality-factor scar modes localized near the stadium boundary and directional laser emission assisted by the chaotic modes. These results will reshape the understanding of the crystal growth theory and provide valuable guidance for crystalline photonic materials design.

MOF-based one-dimensional materials have received increasing attention in the nanophotonics field, but it is still difficult in the flexible shape evolution of MOF micro/nanocrystals for desired optical functionalities due to the susceptible solvothermal growth process. Herein, we report on the well-controlled shape evolution of pure-MOF microcrystals with optical waveguide and lasing performances based on a bottom-up and top-down synergistic method. The MOF microcrystals from solvothermal synthesis (bottom-up) enable the evolution from microrods via microtubes to nanowires through a chelating agent-assisted etching process (top-down). The three types of MOF 1D-microstructures with high crystallinity and smooth surfaces all exhibit efficient optical waveguide performance. Furthermore, MOF nanowire with lowest propagation loss served as low-threshold pure-MOF nanolasers with Fabry-Perot resonance. These results advance the fundamental understanding on the controlled MOF evolution mechanism, and offer a valuable route for the development of pure-MOF-based photonic components with desired functionalities.

Information encryption and decryption have attracted particular attention; however, the applications are frequently restricted by limited coding capacity due to the indistinguishable broad photoluminescence band of conventional stimuli-responsive fluorescent materials. Here, we present a concept of confidential information encryption with photoresponsive liquid crystal (LC) lasing materials, which were used to fabricate ordered microlaser arrays through a microtemplate-assisted inkjet printing method. LC microlasers exhibit narrow-bandwidth single-mode emissions, and the wavelength of LC microlasers was reversibly modulated based on the optical isomerization of the chiral dopant in LCs. On this basis, we demonstrate phototunable information authentication on LC microlaser arrays using the wavelength of LC microlasers as primary codes. These results provide enlightenment for the implementation of microlaser-based cryptographic primitives for information encryption and anticounterfeiting applications.

Halide perovskites have shown tremendous potential for next-generation flat-panel laser displays due to their remarkable optoelectronic properties and outstanding material processability; however, the lack of a general approach for the fast growth of perovskite laser arrays capable of electrical operations impedes actualization of their display applications. Herein, a universal and robust wettability-guided screen-printing technique is reported for the rapid growth of large-scale multicolor perovskite microdisk laser arrays, which can serve as laser display panels and further be used to realize current-driven displays. The perovskite microlasers are precisely defined with controlled physical dimensions and spatial locations by such a printing strategy, and each perovskite microlaser serves as a pixel of a display panel. Moreover, the screen-printing procedure is highly compatible with light-emitting diode (LED) device architectures, which is favorable for the mass production of micro-LED arrays. On this basis, a prototype of a current-driven display is demonstrated with desired functionalities. The outstanding performance and feasible fabrication of screen-printed perovskite microlaser arrays embedded in LEDs provide deep insights into the concepts and device architectures of electrically driven laser display technology.

Organic materials are an important class of gain media for fabricating miniaturized lasers because they combine fabrication simplicity with wide spectral coverage and tunability. However, progress toward near-infrared (NIR) organic solid-state lasers has been limited because of serious nonradiative processes originating from the severe intermolecular interaction in the condensed state. Here, we develop a strategy to realize room-temperature NIR microscale lasers through encapsulating organic dyes into the cavities of metal-organic frameworks (MOFs). The spatial confinement of the dye molecules within the MOF pores contributes to suppressing the multiple nonradiative processes (i.e., aggregation-caused quenching and exciton-exciton annihilation). This results in a much higher radiative efficiency and thus much easier population inversion and low-threshold NIR lasing. Furthermore, the lasing wavelength can be further expanded based on the tailorable energy levels of the dye molecules. The results will provide useful enlightenment for the development of miniaturized NIR laser sources for new photonic applications.

Modern high-security cryptography and optical communication call for covert bit sequences with high coding capacity and efficient authentication. Stimuli-responsive lasing emissions with easily distinguishable readout are promising in the coding field as a novel cryptographic primitive, while the application is frequently restricted by the limited number of emission states. Here, we report a strategy of achieving multiple competitive lasing signals in responsive organic microspheres where a donor–acceptor pair was introduced. The competitive lasing from the donor and acceptor was reversibly switched by modulating the competition between the radiative rate of the donor and the rate of energy transfer, and the generated multiple lasing signals enabled a quaternary coding for recognizable cryptographic implementation. Data encryption and extraction were demonstrated using a 4 × 4 microlaser array, showing vast prospects in avoiding the disclosure of security information. The results offer a comprehensive understanding of excited-state dynamics in organic composite materials, which may play a major role in high-security optical recording and information encryption.

Microscale laser switches have been playing irreplaceable roles in the development of photonic devices with high integration levels. However, it remains a challenge to switch the lasing wavelengths across a wide range due to relatively fixed energy bands in traditional semiconductors. Here, we report a strategy to switch the lasing wavelengths among multiple states based on a proton-controlled intramolecular charge-transfer (ICT) process in organic dye-doped flexible microsphere resonant cavities. The protonic acids can effectively bind onto the ICT molecules, which thus enhance the ICT strength of the dyes and lead to a red-shifted gain behavior. On this basis, the gain region was effectively modulated by using acids with different proton-donating ability, and as a result, laser switching among multiple wavelengths was achieved. The results will provide guidance for the rational design of miniaturized lasers with performances based on the characteristic of organic optoelectronic materials.

Two-dimensional (2D) layered materials, with large second-order nonlinear susceptibility, have received much scientific interest due to their potential applications in nonlinear optical devices. However, the atomic thickness of 2D layered materials leads to poor field confinement and weak light–matter interaction at the nanoscale, resulting in low nonlinear conversion efficiency. Here, 2D pyramid-like multilayer (P-multilayer) layered structures are fabricated for efficient edge second-harmonic generation (SHG) based on the enhanced light–matter interaction in whispering-gallery mode (WGM) cavities. The P-multilayer 2D layered materials, where the basal planes shrink gradually from the bottom to the top layers, exhibit efficient edge SH radiation due to the partial destructive interference of nonlinear polarizations between the neighboring atomic layers. Moreover, the well-defined 2D plate-like triangle morphology of P-multilayer WS2 forms a WGM resonance cavity, which results in enhanced light–matter int...

Low-dimensional organic materials have given rise to tremendous interest in optoelectronic applications, owing to their controllable photonic properties. However, the controlled-synthesis approaches for organic nano-/micro-architectures are very difficult to attain, because the weak interaction (van der Waals force) between the organic molecules cannot dominate the kinetic process of crystal growth. We report a simple method, which involves selective adhesion to the organic crystal plane by hydrogen-bonding interaction for modulating the crystal growth process, which leads either to the self-assembly of one organic molecule into two-dimensional (2D) microsheets with an obvious asymmetric light propagation or one-dimensional (1D) microrods with low propagation loss. The method of tailoring the structures and photonic properties for fabricating different micro-structures would provide enlightenment for the development of tailor-made mini-sized devices for photonic integrated circuits.

Directing the architecture of complex organic nanostructures is desirable and still remains a challenge in areas of materials science due to their structure-dependent collective optoelectronic properties. Herein, we demonstrate a simple and versatile solution strategy that allows surface tension to drive low-dimensional nanostructures to aggregate into complex structures via a lab in a droplet technique. By selecting a suitable combination of a solvent and an anti-solvent with controllable surface tension difference, the droplets can be automatically cracked into micro-droplets, which provides an aggregation force directed toward the centre of the droplet to drive the low-dimensional building blocks to form the special aggregations during the self-assembly process. This synthetic strategy has been shown to be universal for organic materials, which is beneficial for further optimizing the optoelectronic properties. These results contribute to gaining an insightful understanding on the detailed growth mechanism of complex organic nanostructures and greatly promoting the development of organic nanophotonics.

Solid-state fluorescent materials have attracted a surge of interest in recent years due to their wide applications in the fields of photoelectric devices, memory storage and fluorescent probes. Compared to the synthesis of new molecules, exploring new properties in known molecules is a facile approach to obtain functionalized fluorescent materials. In this report, we systematically explored the solid-state photoluminescence properties and applications of 7-(diethylamino)coumarin-3-aldehyde (DCA) and 7-(diethylamino)coumarin-3-carboxylic acid (DCCA). Both fluorophores exhibited a special concentration-dependent emission effect. They displayed polymorphism dependent solid-state emission and single crystal analysis revealed that enhanced overlap between neighbouring molecules resulted in a red-shifted emission. Crystal-to-crystal transformation has also been achieved for both DCA and DCCA by employing an external thermal treatment. In addition, the solid powder of DCA and DCCA displayed fluorescence response to HCl and NH3 gas with high sensitivity. Furthermore, 1D micromaterials were assembled for both fluorophores and DCA exhibited outstanding optical waveguide behavior.

Although many efforts have been attempted by scientists worldwide, electrically pumped organic lasing emission still remains as one of the greatest challenges in the field of optoelectronics. Recently, Shuai and coworkers proposed a computational strategy based on time-dependent density functional theory(TDDFT), offering a new avenue to the molecule design and materials selection towards electrically pumped organic lasers. Molecular material property prediction package(MOMAP) previously developed by this group was utilized to obtain photophysical parameters of various organic lasing molecules, and to estimate whether they can fulfill the criteria for electrical pumping. Under systematic calculation and evaluation, three compounds, BP3T, CzPVSBF, and BSBCz were screened out as promising candidates, revealing the reliability and universality of the proposed computational strategy. This work has been published online in the Nature Communications in September 8, 2020.

The excitation of surface plasmons by optical emitters based on exciton-plasmon coupling is important for plasmonic devices with active optical properties. It has been theoretically demonstrated that the orientation of exciton dipole can significantly influence the coupling strength, yet systematic study of the coupling process in nanostructures is still hindered by the lack of proper material systems. In this work, we have experimentally investigated the orientation-dependent exciton-plasmon coupling in a rationally designed organic/metal nanowire heterostructure system. The heterostructures were prepared by inserting silver nanowires into crystalline organic waveguides during the self-assembly of dye molecules. Structures with different exciton orientations exhibited varying coupling efficiencies. The near-field exciton-plasmon coupling facilitates the design of nanophotonic devices based on the directional surface plasmon polariton propagations.

Rare earth doping has been widely applied in many functional nanomaterials with desirable properties and functions, which would have a significant effect on the growth process of the materials. However, the controlling strategy is limited into high concentration of lanthanide doping, which produces concentration quenching of the lanthanide ion luminescence with an increase in the Ln3+ concentration, resulting in lowering the fluorescence quantum yield of lanthanide ion. Herein, for the first time, we demonstrate simultaneous control of the structures and luminescence properties of BaCO3 nanocrystals via a small amount of Tb3+ doping strategy. In fact, Tb3+ would partially occupy Ba2+ sites, resulting in the changes to the structures of the BaCO3 nanocrystals, which is primarily determined by charge modulation, including the contributions from the surfaces of crystal nuclei and building blocks. These structurally modified nanocrystals exhibit tunable luminescence properties, thus emerging as potential candidates for photonic devices such as light-emitting diodes and color displays.

All-color subwavelength output of lasers was demonstrated in a rationally designed organic microdisk/silver nanowire heterostructures. The dye-doped flexible microdisks served as the wavelength tunable whispering-gallery-mode lasers with low lasing thresholds, whereas the silver nanowires supported the output of the lasing mode as subwavelength coherent light sources. The wavelength of the outcoupled laser was tuned over the full visible spectrum scope owing to the flexibility of the microdisks and their compatibility with various organic laser dyes. Furthermore, a multicolor subwavelength laser was achieved in a single heterostructure and the laser output was successfully modulated by varying the surface plasmon polariton propagation length.

Lanthanide metal–organic frameworks (Ln-MOFs) have received much attention owing to their structural tunability and widely photofunctional applications. However, successful examples of Ln-MOFs with well-defined photonic performances at micro-/nanometer size are still quite limited. Herein, self-assemblies of 1,3,5-benzenetricarboxylic acid (BTC) and lanthanide ions afford isostructural crystalline Ln-MOFs. Tb-BTC, Eu@Tb-BTC, and Eu-BTC have 1D microrod morphologies, high photoluminescence (PL) quantum yields, and different emission colors (green, orange, and red). Spatially PL resolved spectra confirm that Ln-MOF microrods exhibit an optical waveguide effect with low waveguide loss coefficient (0.012≈0.033 dB μm−1) during propagation. Furthermore, these microrods feature both linear and chiral polarized photoemission with high anisotropy.

The rational design of multifunctional materials with both emissive and semiconducting properties remains a challenge. A multifunctional cruciform donor–acceptor (D–A) molecule, 2,2′-(((4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl)bis(thiophene-5,2-diyl))bis(methanylylidene))dimalononitrile (BDTTM), which contains a benzodithiophene as the central core, has been synthesized and, based on the output and transfer characteristics of the corresponding FETs, thin films of BDTTM exhibited ambipolar semiconducting behavior. Notably, FETs with thin films of BDTTM showed a photoresponse in both p- and n-channels, and drain-source-current enhancement under white-light irradiation could be detected, even at a low light intensity of 0.1 mW cm−2. Furthermore, BDTTM exhibited red-light emission both in solution and as a crystalline solid. A microplate of BDTTM with red-light emission displayed typical optical waveguiding behavior.

In this work, we chose tris(2,2′-bipyridyl)ruthenium(II)hexafluorophosphate (Ru(bpy)3(PF6)2), a metal-organic complex material, to prepare nanowires, which were subsequently applied for the construction of electrochemiluminescence (ECL) biosensor by immobilizing them onto a glassy carbon electrode (GCE) with graphene-Nafion composite films. The graphene therein, being a two-dimensional carbon nanomaterial with outstanding electronic properties, can obviously improve the conductivity of the Nafion film, as well as enhance the electrochemical signal and ECL intensity of the Ru(bpy)3(PF6)2 nanowires (RuNWs) at low graphene concentration. The developed biosensor exhibited excellent ECL stability with tripropylamine (TPrA) as co-reactant. The ECL biosensor exhibited high sensitive ECL response in a wide linear range and low detection limit for the detection of proline. It is considered that the oxidation products of proline would be responsible for the ECL enhancement. The large electro-active area of the nanowires and the enhancement effect of the graphene played critical roles in the high detection performance of the ECL biosensor. The results demonstrated herein may provide a useful enlightenment for the design of more sensitive ECL biosensors.

Organic microlasers are miniaturized coherent light sources with great promise for advancing the field of optoelectronics. Recently, host–guest composite organic microlasers, where the host materials provide spatial confinement for the organic gain materials, have captured much research interest because the host–guest composite material systems endow the organic microlasers with improved lasing performances, such as low threshold, high stability, and excellent tunability. In this Review, we explore the latest advancements in the development of host–guest composite organic microlasers, and offer our perspective on future improvements and trends. Special emphasis is put on the construction strategies and the unique laser properties of the organic microlasers based on host–guest confinement systems. The comprehensive understanding of the relationship between laser performances and the synergistic interactions of the host and guest materials would provide a useful guidance for the design and fabrication of novel organic microlasers.

We demonstrate the fabrication of organic high Q active whispering-gallery-mode (WGM) resonators from π-conjugated polymer by a controlled emulsion-solvent-evaporation method, which can simultaneously provide optical gain and act as an effective resonant cavity. By measuring the shift of their lasing modes on exposure to organic vapor, we successfully monitored the slight concentration variation in the chemical gas. These microlaser sensors demonstrated high detection sensitivity and good signal repeatability under continuous chemical gas treatments. The results offer an effective strategy to design miniaturized optical sensors.

Wavelength switchable micro/nanoscale laser is essential to construct various ultracompact photonic devices. However, traditional semiconductors as the gain media generally provide only monochromatic laser output due to their continuous energy band structures. For luminescent conjugated molecules, the broad emission band usually contains a series of vibronic peaks, which is very helpful for extending the lasing spectrum to several different wavelengths. Here we propose a novel strategy to realize wavelength switchable lasers based on the controlled competition of dual-wavelength vibronic lasing in single-component organic microcrystals. The vibrationally structured fluorescence property of the single-crystal organic microdisks brings dual-wavelength lasing at different vibronic bands. Their relative optical gain intensity was modulated by controlling the population on the certain vibronic level of the ground state with varied temperature, which consequently enabled the reversible switching of the dual-wav...

Photonic materials use photons as information carriers and offer the potential for unprecedented applications in optical and optoelectronic devices. In this study, we introduce a new strategy for photonic materials using metal-organic frameworks (MOFs) as the host for the rational construction of donor-acceptor (D-A) heterostructure crystals. We have engineered a rich library of heterostructure crystals using the MOF NKU-111 as a host. NKU-111 is based upon an electron-deficient tridentate ligand (acceptor) that can bind to various electron-rich guests (donors). The resulting heterocrystals exhibit spatially segregated multi-color emission resulting from the guest-dependent charge-transfer (CT) emission. Spatially effective mono-directional energy transfer results from tuning the energy gradient between adjacent domains through the selection of donor guest molecules, which suggests potential applications in integrated optical circuit devices, for example, photonic diodes, on-chip signal processing, optical logic gates.

Polymorphism and anisotropy are fundamental phenomena of crystalline materials. However, the structure-dependent photoluminescent (PL) anisotropy in polymorphic organic crystals has remained unexplored. Herein, two polymorphic nanocrystals, green-emitting nanorods (PtD-g) and yellow-emitting nanoplates (PtD-y), were obtained from a platinum(II)−β-diketonate complex. The PtD-y crystals display remarkable PL anisotropy with an anisotropy ratio of up to 0.87 whereas the emission of the PtD-g crystals is nearly unpolarized. The polarization properties are rationalized on the different molecular packing of these crystals. By light-harvesting energy transfer, the PtD-y crystals are successfully used to amplify the emission polarization of a red-emitting platinum acceptor (PtA) doped into the donor crystalline matrix, which is otherwise weakly polarized as pure crystals.

We propose a general approach for obtaining dual-wavelength organic microlasers in amphiphilic Janus resonators, where hydrophilic and hydrophobic dyes can be spatially separated via polarity-driven encapsulation. Low-threshold dual-wavelength lasing was achieved in a single Janus particle with well-modulated output. This universal approach enables flexibly designing the lasing wavelength of the Janus microlasers in the full visible spectrum by systematically altering the encapsulated laser dyes. Our findings demonstrate a promising route to the photonic integration at the micro-/nanoscale that may lead to the innovation of concepts and device architectures for multifunctional optoelectronic applications.

We demonstrate efficient and stable dual-wavelength microlasers fabricated by encapsulating different organic dyes into metal–organic framework (MOF) microcrystals. The intermolecular interactions between the organic dyes are suppressed effectively by the spatial confinement effect of the MOF pores, enabling a simultaneously efficient optical gain, and therefore lasing at different wavelengths. The results represent an important step towards a function-oriented laser material design.

We demonstrate highly efficient InGaN-based mini-size green light-emitting diodes (mLEDs) with AlGaN insertion layer in InGaN/GaN multiple quantum wells (MQWs) using metal organic chemical vapor deposition (MOCVD). High resolution transmission electron microscopy (HRTEM) results reveal that 'V' defects within active region can be effectively reduced by AlGaN insertion layer. Photoluminescence (PL) and time resolved photoluminescence (TRPL) results indicate an increase of radiative recombination efficiency. Very high performance 523 nm InGaN green flip-chip mLEDs (0.025 mm2) with distributed Bragg reflector (DBR) show a high external quantum efficiency (EQE) of 38.0%, a high wall-plug efficiency (WPE) of 32.1% and a low forward voltage of 2.8 V at a working current density of 20 A cm-2, which are very promising for display application.

Wavelength-tunable lasers were experimentally achieved through exciton funneling in light-harvesting organic microcrystals., Organic solid-state lasers are essential for various photonic applications, yet current-driven lasing remains a great challenge. Charge transfer (CT) complexes formed with p-/n-type organic semiconductors show great potential in electrically pumped lasers, but it is still difficult to achieve population inversion owing to substantial nonradiative loss from delocalized CT states. Here, we demonstrate the lasing action of CT complexes based on exciton funneling in p-type organic microcrystals with n-type doping. The CT complexes with narrow bandgap were locally formed and surrounded by the hosts with high-lying energy levels, which behave as artificial light-harvesting systems. Excitation light energy captured by the hosts was delivered to the CT complexes, functioning as exciton funnels to benefit lasing actions. The lasing wavelength of such composite microcrystals was further modulated by varying the degree of CT. The results offer a comprehensive understanding of exciton funneling in light-harvesting systems for the development of high-performance organic lasing devices.

Micro/nanoscale lasers that can deliver intense coherent light signals at (sub)wavelength scale have recently captured broad research interest because of their potential applications ranging from on-chip information processing to high-throughput sensing. Organic molecular materials are a promising kind of ideal platform to construct high-performance microlasers, mainly because of their superiority in abundant excited-state processes with large active cross sections for high gain emissions and flexibly assembled structures for high-quality microcavities. In recent years, ever-increasing efforts have been dedicated to developing such organic microlasers toward low threshold, multicolor output, broadband tunability, and easy integration. Therefore, it is increasingly important to summarize this research field and give deep insight into the structure-property relationships of organic microlasers to accelerate the future development. In this Account, we will review the recent advances in organic miniaturized lasers, with an emphasis on tunable laser performances based on the tailorable microcavity structures and controlled excited-state gain processes of organic materials toward integrated photonic applications. Organic π-conjugated molecules with weak intermolecular interactions readily assemble into regular nanostructures that can serve as high-quality optical microcavities for the strong confinement of photons. On the basis of rational material design, a series of optical microcavities with different structures have been controllably synthesized. These microcavity nanostructures can be endowed with effective four-level dynamic gain processes, such as excited-state intramolecular charge transfer, excited-state intramolecular proton transfer, and excimer processes, that exhibit large dipole optical transitions for strongly active gain behaviors. By tailoring these excited-state processes with molecular/crystal engineering and external stimuli, people have effectively modulated the performances of organic micro/nanolasers. Furthermore, by means of controlled assembly and tunable laser performances, efficient outcoupling of microlasers has been successfully achieved in various organic hybrid microstructures, showing considerable potential for the integrated photonic applications. This Account starts by presenting an overview of the research evolution of organic microlasers in terms of microcavity resonators and energy-level gain. Then a series of strategies to tailor the microcavity structures and excited-state dynamics of organic nanomaterials for the modulation of lasing performances are highlighted. In the following part, we introduce the construction and advanced photonic functionalities of organic-microlaser-based hybrid structures and their applications in integrated nanophotonics. Finally, we provide our outlook on the current challenges as well as the future development of organic microlasers. It is anticipated that this Account will provide inspiration for the development of miniaturized lasers with desired performances by tailoring of excited-state processes and microcavity structures toward integrated photonic applications.