Wettability-Guided Screen Printing of Perovskite Microlaser Arrays for Current-Driven Displays

Ultracompact and Uniform Nanoemitter Array Based on Periodic Scattering

As emerging gain materials, lead halide perovskites have drawn considerable attention in coherent light sources. With the development of patterning and integration techniques, a perovskite laser array has been realized by distributing perovskite microcrystals periodically. Nevertheless, the packing density is limited by the crystal size and the channel gap distance. More importantly, the lasing performance for individual laser units is quite random due to variation of size and crystal quality. Herein an ultracompact perovskite nanoemitter array with uniform emission has been demonstrated. Individual emitters are formed via scattering evanescent components from a shared Fabry-Perot laser, ensuring uniform lasing emission in a unit cell with a side length of 160 nm and lattice constant of 400 nm. And the periodic silicon scatterers do not deteriorate the lasing threshold dramatically. In addition, the surface emitting efficiency increased significantly. The direct integration of a densely packed nanoemitter array with a silicon platform promises high-throughput sensing and high-capacity optical interconnects.

Van der Waals integrated single-junction light-emitting diodes exceeding 10% quantum efficiency at room temperature

The construction of miniaturized light-emitting diodes (LEDs) with high external quantum efficiency (EQE) at room temperature remains a challenge for on-chip optoelectronics. Here, we demonstrate microsized LEDs fabricated by a dry-transfer van der Waals (vdW) integration method using typical layered Ruddlesden-Popper perovskites (RPPs). A single-crystalline layered RPP nanoflake is used as the active layer and sandwiched between two few-layer graphene contacts, forming van der Waals LEDs (vdWLEDs). Strong electroluminescence (EL) emission with a low turn-on current density of ~20 pA μm-2 and high EQE exceeding 10% is observed at room temperature, which sets the benchmark for the EQE of vdWLEDs ever recorded. Such efficient EL emission is attributed to the inherent multiple quantum well structure and high photoluminescence quantum yield (~35%) of RPPs and a low charge injection barrier of ~0.10 eV facilitated by the Fowler-Nordheim tunneling mechanism. These findings promise a scalable pathway for accessing high-performance miniaturized light sources for on-chip optical optoelectronics.

Multilevel Printed Wearable Radio-Frequency Intelligent Identification Platform for Object Recognition

As a noncontact target recognition technique, radio-frequency identification (RFID) technology demonstrates attractive potential in constructing human-machine interaction (HMI) systems. However, the current development of RFID technologies in HMI systems is hampered by critical challenges in manufacturing high-performance RFID readers with superior flexibility and wearing comfort. Hence, we propose a multilevel printing strategy to overcome the difficulties in manufacturing high-performance large-scale microwave systems. Compared to traditional processes, the RFID system fabricated by the hybrid additive manufacturing technique exhibits equivalent electromagnetic performance and has obvious advantages in terms of manufacturing cost and environmental friendliness. A printed reconfigurable antenna with intelligent radiation mode is seamlessly integrated with the reader circuit via a "one-step" printing technology. Additionally, through chemical doping and artificial intelligence (AI) prediction, we have developed a modified polydimethylsiloxane (PDMS) encapsulation to miniaturize the system volume and enhance reliability. Electromagnetic and mechanical measurements demonstrated that our flexible RFID platform offers superior reliability and stability during long-term daily use. The RFID platform possesses exceptional capabilities in target positioning and accurate identification, demonstrating unique potential in noncontact sensing and recognition, which are highly demanded by flexible and wearable HMI systems.

Metal-Halide Perovskite Lasers: Cavity Formation and Emission Characteristics

Hybrid metal-halide perovskites (MHPs) have shown remarkable optoelectronic properties as well as facile and cost-effective processability. With the success of MHP solar cells and light-emitting diodes, MHPs have also exhibited great potential as gain media for on-chip lasers. However, to date, stable operation of optically pumped MHP lasers and electrically driven MHP lasers-an essential requirement for MHP laser's insertion into chip-scale photonic integrated circuits-is not yet demonstrated. The main obstacles include the instability of MHPs in the atmosphere, rudimentary MHP laser cavity patterning methods, and insufficient understanding of emission mechanisms in MHP materials and cavities. This review aims to provide a detailed overview of different strategies to improve the intrinsic properties of MHPs in the atmosphere and to establish an optimal MHP cavity patterning method. In addition, this review discusses different emission mechanisms in MHP materials and cavities and how to distinguish them.

Recent Advances in Patterning Strategies for Full-Color Perovskite Light-Emitting Diodes

Metal halide perovskites have emerged as promising light-emitting materials for next-generation displays owing to their remarkable material characteristics including broad color tunability, pure color emission with remarkably narrow bandwidths, high quantum yield, and solution processability. Despite recent advances have pushed the luminance efficiency of monochromic perovskite light-emitting diodes (PeLEDs) to their theoretical limits, their current fabrication using the spin-coating process poses limitations for fabrication of full-color displays. To integrate PeLEDs into full-color display panels, it is crucial to pattern red-green-blue (RGB) perovskite pixels, while mitigating issues such as cross-contamination and reductions in luminous efficiency. Herein, we present state-of-the-art patterning technologies for the development of full-color PeLEDs. First, we highlight recent advances in the development of efficient PeLEDs. Second, we discuss various patterning techniques of MPHs (i.e., photolithography, inkjet printing, electron beam lithography and laser-assisted lithography, electrohydrodynamic jet printing, thermal evaporation, and transfer printing) for fabrication of RGB pixelated displays. These patterning techniques can be classified into two distinct approaches: in situ crystallization patterning using perovskite precursors and patterning of colloidal perovskite nanocrystals. This review highlights advancements and limitations in patterning techniques for PeLEDs, paving the way for integrating PeLEDs into full-color panels.

Exciton Chirality Transfer Empowers Self-Triggered Spin-Polarized Amplified Spontaneous Emission from 1D-Anchoring-3D Perovskites

Spin-polarized lasers, arising from stimulated emission of imbalanced spin populations, play a vital role in spin-optoelectronics. It is usually tackled by external spin injection, inevitably suffering from additional losses across the barriers from injection sources to gain materials. Herein, spin-polarized coherent light emission is self-triggered from the 1D-anchoring-3D perovskites, where the imbalanced populations in achiral 3D perovskites are endowed with the spin selectivity of exciton chirality (EC) underpinned by chiral 1D perovskites. Efficient transfer of EC is enabled by rapid energy transfer, thereby creating an imbalance of the spin population of excited states. Stimulated emission of such populations brings self-triggered spin-polarized amplified spontaneous emission in the composite perovskites, yielding a higher degree of polarization (DOP) than that based on optical spin injection into bare achiral 3D perovskites. Chemical diversity of composite perovskites not only enables to adjust band gap for broadband output of spin-polarized light signals but also promises to manipulate radiative decay and spin relaxation toward remarkably increased DOP. These results highlight the importance of EC transfer mechanism for spin-polarized lasing and represent a crucial step toward the development of chiral-spintronics.

Wafer-scale patterning of high-resolution quantum dot films with a thickness over 10 μm for improved color conversion

Quantum dots (QDs) are promising color conversion materials for efficient full-color micro light-emitting diode (micro-LED) displays owing to their high color purity and wide color gamut. However, achieving high-resolution QD patterns with enough thickness for efficient color conversion is challenging. Here, we demonstrate a facile and compatible approach by combining replicate molding, plasma etching and transfer printing to produce QD patterns with a sufficient thickness over ten micrometers in a wide range of resolutions. Our technique can remarkably simplify the preparation of QD inks and minimize optical damage to QD materials. The pixel resolution and thickness of QD patterns can be controlled by well-defining the microstructures of the molding template and the etching process. The transfer printing process allows QD patterns to be assembled sequentially onto a receiving substrate, which will further improve the original pixel resolution and avoid repetitive optical damage to QDs during the patterning process. Consequently, various QD patterns can be fabricated in this work, including perovskite quantum dot (PQD) patterns with a pixel resolution of up to 669 pixels per inch (ppi) and a maximum thickness of up to 19.74 μm, a wafer-scale high-resolution PQD pattern with sufficient thickness on a flexible substrate, and a dual-color pattern comprising green PQDs and red CdSe QDs. Furthermore, these fabricated QD films with a thickness of over 10 μm show improved color conversion when integrated onto a blue micro-LED, revealing the potential of our technique for full-color micro-LED displays.

Strategies to Extend the Lifetime of Perovskite Downconversion Films for Display Applications

Metal halide perovskite nanocrystals (PeNCs) have outstanding luminescent properties that are suitable for displays that have high color purity and high absorption coefficient; so they are evaluated for application as light emitters for organic light-emitting diodes, light-converters for downconversion displays, and future near-eye augmented reality/virtual reality displays. However, PeNCs are chemically vulnerable to heat, light, and moisture, and these weaknesses must be overcome before devices that use PeNCs can be commercialized. This review examines strategies to overcome the low stability of PeNCs and thereby permit the fabrication of stable downconversion films, and summarizes downconversion-type display applications and future prospects. First, methods to increase the chemical stability of PeNCs are examined. Second, methods to encapsulate PeNC downconversion films to increase their lifetime are reviewed. Third, methods to increase the long-term compatibility of resin with PeNCs, and finally, how to secure stability using fillers added to the resin are summarized. Fourth, the method to manufacture downconversion films and the procedure to evaluate their reliability for commercialization is then described. Finally, the prospects of a downconversion system that exploits the properties of PeNCs and can be employed to fabricate fine pixels for high-resolution displays and for near-eye augmented reality/virtual reality devices are explored.

Screen-Printing Technology for Scale Manufacturing of Perovskite Solar Cells

As a key contender in the field of photovoltaics, third-generation thin-film perovskite solar cells (PSCs) have gained significant research and investment interest due to their superior power conversion efficiency (PCE) and great potential for large-scale production. For commercialization consideration, low-cost and scalable fabrication is of primary importance for PSCs, and the development of the applicable film-forming techniques that meet the above requirements plays a key role. Currently, large-area perovskite films are mainly produced by printing techniques, such as slot-die coating, inkjet printing, blade coating, and screen-printing. Among these techniques, screen printing offers a high degree of functional layer compatibility, pattern design flexibility, and large-scale ability, showing great promise. In this work, the advanced progress on applying screen-printing technology in fabricating PSCs from technique fundamentals to practical applications is presented. The fundamentals of screen-printing technique are introduced and the state-of-the-art studies on screen-printing different functional layers in PSCs and the control strategies to realize fully screen-printed PSCs are summarized. Moreover, the current challenges and opportunities faced by screen-printed perovskite devices are discussed. This work highlights the critical significance of high throughput screen-printing technology in accelerating the commercialization course of PSCs products.

High-Resolution, Highly Transparent, and Efficient Quantum Dot Light-Emitting Diodes

Aiming at next-generation displays, high-resolution quantum dot light-emitting diodes (QLEDs) with high efficiency and transparency are highly desired. However, there is limited study involving the improvements of QLED pixel resolution, efficiency, and transparency simultaneously, which undoubtedly restricts the practical applications of QLED for next-generation displays. Here, the strategy of electrostatic force-induced deposition (EF-ID) is proposed by introducing alternating polyethyleneimine (PEI) and fluorosilane patterns to synergistically improve the pixel accuracy and transmittance of QD patterns. More importantly, the leakage current induced by the void spaces between pixels that is usually reported for high-resolution QLEDs is greatly suppressed by substrate-assisted insulating fluorosilane patterns. Finally, high-performance QLEDs with high resolution ranging from 1104 to 3031 pixels per inch (PPI) and a high efficiency of 15.6% are achieved, among the best performances of high resolution QLEDs. Notably, the high resolution QD pixels greatly enhance the transmittance of the QD patterns, thus prompting an impressive transmittance of 90.7% for the transparent QLEDs (2116 PPI), which represents the highest transmittance of transparent QLED devices. Consequently, this work contributes an effective and general approach for high-resolution QLEDs with high efficiency and transparency.

All-inorganic lead halide perovskite nanocrystals applied in advanced display devices

Advanced display devices are in greater demand due to their large color gamut, high color purity, ultrahigh visual resolution, and small size pixels. All-inorganic lead halide perovskite (AILHP) nanocrystals (NCs) possess inherent advantages such as narrow emission width, saturated color, and flexible integration, and have been developed as functional films, light sources, backlight components, and display panels. However, some drawbacks still restrict the practical application of advanced display devices based on AILHP NCs, including working stability, large-scale synthesis, and cost. In this review, we focus on AILHP NCs, review the recent progress in materials synthesis, stability improvement, patterning techniques, and device application. We also highlight the important role of materials systems in creating advanced display devices, followed by the challenges and opportunities in industrial processes. This review provides beneficial inspiration for the future development of AILHP NCs in colorful and white backlight, as well as high resolution full-color displays.

Controlled on-chip fabrication of large-scale perovskite single crystal arrays for high-performance laser and photodetector integration

Metal halide perovskites possess intriguing optoelectronic properties, however, the lack of precise control of on-chip fabrication of the large-scale perovskite single crystal arrays restricts its application in integrated devices. Here, we report a space confinement and antisolvent-assisted crystallization method for the homogeneous perovskite single crystal arrays spanning 100 square centimeter areas. This method enables precise control over the crystal arrays, including different array shapes and resolutions with less than 10%-pixel position variation, tunable pixel dimensions from 2 to 8 μm as well as the in-plane rotation of each pixel. The crystal pixel could serve as a high-quality whispering gallery mode (WGM) microcavity with a quality factor of 2915 and a threshold of 4.14 μJ cm^-2. Through directly on-chip fabrication on the patterned electrodes, a vertical structured photodetector array is demonstrated with stable photoswitching behavior and the capability to image the input patterns, indicating the potential application in the integrated systems of this method.

Light-Emitting Organic Semiconductor-Incorporated Perovskites: Fundamental Properties and Device Applications

Recently, organic semiconductor-incorporated perovskites (OSiPs) have emerged as a new subclass of next-generation organic-inorganic hybrid materials. OSiPs combine the advantages of organic semiconductors, such as large design windows and tunable optoelectronic functionalities, with the excellent charge-transport properties of the inorganic metal-halide counterparts. OSiPs provide a new materials platform for the exploitation of charge and lattice dynamics at the organic-inorganic interfaces for various applications. This Perspective reviews recent achievements in OSiPs highlighting the benefits from organic semiconductor incorporation and elucidates the fundamental light-emitting mechanism, energy transfer, as well as band alignment structures at the organic-inorganic interface. Insights on the emission tunability lead toward a discussion of the potential of OSiPs in light-emitting applications, such as perovskite light-emitting diodes or lasing systems.

Perovskite solar cells based on screen-printed thin films

One potential advantage of perovskite solar cells (PSCs) is the ability to solution process the precursors and deposit films from solution^1,2. At present, spin coating, blade coating, spray coating, inkjet printing and slot-die printing have been investigated to deposit hybrid perovskite thin films^3-6. Here we expand the range of deposition methods to include screen-printing, enabled by a stable and viscosity-adjustable (40-44,000 cP) perovskite ink made from a methylammonium acetate ionic liquid solvent. We demonstrate control over perovskite thin-film thickness (from about 120 nm to about 1,200 nm), area (from 0.5 × 0.5 cm² to 5 × 5 cm²) and patterning on different substrates. Printing rates in excess of 20 cm s^-1 and close to 100% ink use were achieved. Using this deposition method in ambient air and regardless of humidity, we obtained the best efficiencies of 20.52% (0.05 cm²) and 18.12% (1 cm²) compared with 20.13% and 12.52%, respectively, for the spin-coated thin films in normal devices with thermally evaporated metal electrodes. Most notably, fully screen-printing devices with a single machine in ambient air have been successfully explored. The corresponding photovoltaic cells exhibit high efficiencies of 14.98%, 13.53% and 11.80% on 0.05-cm², 1.00-cm² and 16.37-cm² (small-module) areas, respectively, along with 96.75% of the initial efficiency retained over 300 h of operation at maximum power point.

Ultrahigh-resolution full-color perovskite nanocrystal patterning for ultrathin skin-attachable displays

High-definition red/green/blue (RGB) pixels and deformable form factors are essential for the next-generation advanced displays. Here, we present ultrahigh-resolution full-color perovskite nanocrystal (PeNC) patterning for ultrathin wearable displays. Double-layer transfer printing of the PeNC and organic charge transport layers is developed, which prevents internal cracking of the PeNC film during the transfer printing process. This results in RGB pixelated PeNC patterns of 2550 pixels per inch (PPI) and monochromic patterns of 33,000 line pairs per inch with 100% transfer yield. The perovskite light-emitting diodes (PeLEDs) with transfer-printed active layers exhibit outstanding electroluminescence characteristics with remarkable external quantum efficiencies (15.3, 14.8, and 2.5% for red, green, and blue, respectively), which are high compared to the printed PeLEDs reported to date. Furthermore, double-layer transfer printing enables the fabrication of ultrathin multicolor PeLEDs that can operate on curvilinear surfaces, including human skin, under various mechanical deformations. These results highlight that PeLEDs are promising for high-definition full-color wearable displays.

High-Luminance Microsized CH3NH3PbBr3 Single-Crystal-Based Light-Emitting Diodes via a Facile Liquid-Insulator Bridging Route

Micro-/nanosized organic-inorganic hybrid perovskite single crystals (SCs) with appropriate thickness and high crystallinity are promising candidates for high-performance electroluminescent (EL) devices. However, their small lateral size poses a great challenge for efficient device construction and performance optimization, causing perovskite SC-based light-emitting diodes (PSC-LEDs) to demonstrate poor EL performance. Here, we develop a facile liquid-insulator bridging (LIB) strategy to fabricate high-luminance PSC-LEDs based on single-crystalline CH₃NH₃PbBr₃ microflakes. By introducing a blade-coated poly(methyl methacrylate) (PMMA) insulating layer to effectively overcome the problems of leakage current and possible short circuits between electrodes, we achieve the reliable fabrication of PSC-LEDs. The LIB method also allows us to systematically boost the device performance through crystal growth regulation and device architecture optimization. Consequently, we realize the best CH₃NH₃PbBr₃ microflake-based PSC-LED with an ultrahigh luminance of 136100 cd m^-2 and a half-lifetime of 88.2 min at an initial luminance of ∼1100 cd m^-2, which is among the highest for organic-inorganic hybrid perovskite LEDs reported to date. Moreover, we observe the strong polarized edge emission of the microflake-based PSC-LEDs with a high degree of polarization up to 0.69. Our work offers a viable approach for the development of high-performance perovskite SC-based EL devices.

Perovskite microcells fabricated using swelling-induced crack propagation for colored solar windows

Perovskite microcells have a great potential to be applied to diverse types of optoelectronic devices including light-emitting diodes, photodetectors, and solar cells. Although several perovskite fabrication methods have been researched, perovskite microcells without a significant efficiency drop during the patterning and fabrication process could not be developed yet. We herein report the fabrication of high-efficiency perovskite microcells using swelling-induced crack propagation and the application of the microcells to colored solar windows. The key procedure is a swelling-induced lift-off process that leads to patterned perovskite films with high-quality interfaces. Thus, a power conversion efficiency (PCE) of 20.1 % could be achieved with the perovskite microcell, which is nearly same as the PCE of our unpatterned perovskite photovoltaic device (PV). The semi-transparent PV based on microcells exhibited a light utilization efficiency of 4.67 and a color rendering index of 97.5 %. The metal–insulator–metal structure deposited on the semi-transparent PV enabled to fabricate solar windows with vivid colors and high color purity.

Perovskite microcells can be applied to various types of optoelectronic devices. Here, authors report high efficiency perovskite microcells fabricated using swelling-induced crack propagation and demonstrate solar windows using the microcells.

Screen-Overprinted Perovskite RGB Microdisk Arrays Based on Wet-Solute-Chemical Dynamics for Full-Color Laser Displays

Owing to outstanding optoelectronic properties, halide perovskites are great candidates for novel laser display applications. However, the realization of their practical flat-panel display applications is challenging because of the incapacity to controllably assemble different halide perovskite microlaser arrays onto an identical substrate as pixelated full-color panels due to intrinsic fragile crystal lattices. Here, perovskite red-green-blue (RGB) microdisk arrays are reported, acting as flat-panels for full-color laser displays. A universal screen-overprinting technology is developed to integrate full-color perovskite microdisk arrays on a prepatterned template, which is on the basis of wet-solute-chemical dynamics involving a combination of surface tailoring and solvent selection. Via such an overprinting method, perovskite RGB microlaser matrices with precise localizations and well-defined dimensions were fabricated on an identical substrate, and each set of RGB microlaser served as a pixel for full-color display panels. On this basis, static and dynamic laser displays have been demonstrated with as-prepared full-color panels. These results will provide novel design concepts and device structures for future full-color laser display applications.

Chiral Hybrid Perovskite Single-Crystal Nanowire Arrays for High-Performance Circularly Polarized Light Detection

Circularly polarized light (CPL) detection has emerged as a key technology for various optoelectronics. Chiral hybrid perovskites (CHPs) that combine CPL-sensitive absorption induced by chiral organic ligands and superior photoelectric properties of perovskites are promising candidates for direct CPL detection. To date, most of the CHP detectors are made up of polycrystalline thin-film, which results in a rather limited discrimination of CPL due to the existence of redundant impurities and intrinsic defect states originating from rapid crystallization process. Here, it is developed a direct CPL detector with high photocurrent and polarization selectivity based on low-defect CHP single-crystal nanowire arrays. Large-scale CHP nanowires are obtained through a micropillar template-assisted capillary-bridge rise approach. Thanks to the high crystallinity and ordered crystallographic alignment of these arrays, a CPL photodetector with high light on/off ratio of 1.8 × 104 , excellent responsivity of 1.4 A W-1 , and an outstanding anisotropy factor of 0.24 for photocurrent has been achieved. These results would provide useful enlightenment for direct CPL detection in high-performance chiral optoelectronics.

Mixed Halide Perovskite Films by Vapor Anion Exchange for Spectrally Stable Blue Stimulated Emission

Solution-processed all-inorganic CsPbX₃ perovskites exhibit outstanding optoelectronic properties and are being considered as a promising optical gain medium, with impressive performance in the green and red region. However, the development of CsPbX₃ for blue emission is still lagging far behind, owing to difficulties in thin films synthesis and spectral instability subject to light irradiation. Here, a facile vapor anion exchange (VAE) method that enables preparation of blue-emitting perovskite films with both excellent surface morphology and good photo-stability is reported. The mixed-Br/Cl quasi-2D perovskite films show spectrally stable pure blue emission (471 nm) under continuous-wave laser irradiation with power density as high as 81 W cm^-2 . Furthermore, optically pumped blue amplified spontaneous emission (ASE) is realized based on the mixed-Br/Cl perovskite films. By changing the duration of VAE treatment, the ASE peak can be tuned from 537 nm down to 475 nm. This work not only presents a facile method to prepare high quality mixed halide Cs-based perovskite films, but also pave the way for further exploration of stable blue perovskite lasing.

3D Laser Displays Based on Circularly Polarized Lasing from Cholesteric Liquid Crystal Arrays

3D laser displays play an important role in next-generation display technologies owing to the ultimate visual experience they provide. Circularly polarized (CP) laser emissions, featuring optical rotatory power and invariability under rotations, are attractive for 3D displays due to potential in enhancing contrast ratio and comfortability. However, the lack of pixelated self-emissive CP microlaser arrays as display panels hinders the implementation of 3D laser displays. Here, full-color 3D laser displays are demonstrated based on CP lasing with inkjet-printed cholesteric liquid crystal (CLC) arrays as display panels. Individual CP lasers are realized by embedding fluorescent dyes into CLCs with their left-/right-handed helical superstructures serving as distributed feedback microcavities, bringing in ultrahigh circular polarization degree values (g_em  = 1.6). These CP microlaser pixels exhibit excellent far-field color-rendering features and a relatively large color gamut for high-fidelity displays. With these printed CLC red-green-blue (RGB) microlaser arrays serving as display panels, proof-of-concept full-color 3D laser displays are demonstrated via delivering images with orthogonal CP laser emissions into one's left and right eyes. These results provide valuable enlightenment for the development of 3D laser displays.

Geometry-Programmable Perovskite Microlaser Patterns for Two-Dimensional Optical Encryption

Lasing signals with easily distinguishable readout and cavity-geometry-dependent output are emerging as novel cryptographic primitives for two-dimensional (2D) optical encryption, while their practical application is restricted by the challenge of integrating different lasing elements onto an identical 2D pattern. Herein, a lithographic template-confined crystallization approach was proposed to prepare large-scale perovskite microstructures with any desired geometries and locations, which enabled them to serve as 2D lasing patterns for reliable encryption and authentication. These prepatterned perovskite microstructures realized whispering-gallery-mode lasing and also demonstrated outstanding reproducibility of lasing actions. Benefiting from the feature of their cavity-geometry-dependent lasing thresholds, we achieved controllable laser output from different shaped elements, which was further utilized for the proof-of-concept demonstration of a cryptographic implementation. The remarkable lasing performance and feasible preparation of 2D microlaser patterns with customized geometries and locations provide us deep insights into the concepts and fabrication technologies for 2D optical encryption.

Optically Pumped Lasing in Microscale Light-Emitting Electrochemical Cell Arrays for Multicolor Displays

Laser displays, which offer wide achievable color gamut and excellent color rendering, have emerged as a promising next-generation display technology. Constructing display panels composed of pixelated microlaser arrays is of great significance for the actualization of laser displays in the flat-panel sector. Here, we report microscale light-emitting electrochemical cell (LEC) arrays that operate as both optically pumped lasers and electroluminescence devices, which can be applied as self-emissive panels for high quality displays. Optically pumped red, green, and blue laser emissions were achieved in individual circular microcells consisting of corresponding conjugated polymers and electrolytes, suggesting that the microstructures can act as resonators for coherent outputs. As-prepared microstructures possess a narrowed recombination region, which dramatically increases the current density by 3 orders of magnitude under pulsed operation, compared with the corresponding thin-film devices, representing a promising solution-processed device platform for electrical pumping. Under programmable electrical excitation, both static and dynamic displays were demonstrated with such microscale LEC arrays as display panels. The prominent performance of the demonstrated structures (microlaser arrays embedded in LEC devices) provide us deep insight into the concepts and device constructions of electrically driven laser displays.