Direct in situ photolithography of perovskite quantum dots based on photocatalysis of lead bromide complexes

Pixelation of perovskite quantum wire thin films with 0.18-μm features and 63,500-ppi pixel density

Halide perovskite materials excel in broad optoelectronic applications, and there is an urgent demand to develop perovskite-based integrated optoelectronic devices. However, the limitations posed by the incompatibility of perovskite thin film with wet lithography greatly hinder its potential in many important applications, including ultrahigh-density displays, high-resolution image sensors, high-density memristors, and integrated photonic circuitry. To tackle this bottleneck problem, we develop the self-aligned close-spaced sublimation growth of perovskite quantum wires and demonstrate 0.18-micrometer feature size perovskite patterns, meanwhile achieving a pixel density of 63,500 pixels per inch, the highest reported for perovskite. We showcase pixelation of perovskite quantum wires with color conversion films, addressing the need for full-color microdisplays. In addition, we demonstrate these films on curved substrates, holding promise for near-eye microdisplays. Processes shown here can also apply to other perovskite devices such as high-resolution displays, image sensing, and memristor arrays.

3D Patterning of Perovskite Quantum Dots via Direct In Situ Femtosecond Laser Writing

Perovskite quantum dots (PQDs) exhibit remarkable optical properties, making them highly promising for next-generation display technologies. However, achieving precise PQDs patterning is hindered by significant challenges, including the inability to achieve true three-dimensional (3D) structuring and the risk of damaging the delicate perovskite crystal lattice. Existing methods struggle to achieve true 3D structuring while preserving the optical integrity. This study introduces an in situ patterning technique using direct laser writing (DLW). By leveraging the nonlinear absorption properties of femtosecond lasers, thiol-Ene photopolymerization is triggered, transforming perovskite precursors into complex fluorescent structures. Unlike conventional methods, this precursor-based approach minimizes laser power requirements and prevents quantum dot degradation caused by high-energy exposure. It enables precise, scalable fabrication while maintaining the structural and optical stabilities of PQDs. This innovation provides a robust platform for developing advanced display technologies, optoelectronic devices, and miniaturized on-chip systems, paving the way for future high-performance applications.

Direct photo-patterning of halide perovskites toward machine-learning-assisted erasable photonic cryptography

The patterning of perovskites is significant for optical encryption, display, and optoelectronic integrated devices. However, stringent and complex fabrication processes restrict its development and applications. Here, we propose a conceptual methodology to realize erasable patterns based on binary mix-halide perovskite films via a direct photo-patterning technique. Controllable ion migration and photochemical degradation mechanism of iodine-rich regions ensure high-fidelity photoluminescence images with different patterns, sizes, and fast self-erasure time within 5 seconds, yielding erasable photonic cryptography chip, which guarantees the efficient transmission of confidential information and avoids the secondary leakage of information. The ultrafast information encryption, decryption, and erasable processes are attributed to the modulation of the crystallographic orientation of the perovskite film, which lowers the ion migration activation energy and accelerates the ion migration rate. Neural network-assisted multi-level pattern encoding technology with high accuracy and efficiency further enriches the content of the transmitted information and increases the security of the information. This pioneering work provides a strategy and opportunity for the integration of erasable photonic patterning devices based on perovskite materials.

Laser-Induced Fabrication of Multicolor Perovskite Quantum Dot Patterns with Multiple Information Encryption Modes

The development of patterned metal halide perovskite quantum dots (MHP QDs) has become an important strategy to explore new functionalities and applications in optoelectronics. Herein, a laser-induced technology is developed to fabricate multicolor MHP QD patterns to achieve multiple information encryption modes. To precisely control the synthesis reactions, PbBr2 and CsBr, the precursors of CsPbBr3 QDs, are separately coated on the donor glass and target substrates and stacked into a donor-PbBr2-CsBr-target structure. A femtosecond laser is focused at the interface of PbBr2 and CsBr to induce localized ionic transportation and reaction so that CsPbBr3 QDs are precisely synthesized at the laser spot. By applying the environmental lability and low formation energy of perovskites, the PL emission of the laser-synthesized CsPbBr3 QDs can be reversibly eliminated under a moisture environment and recovered in situ by laser scanning for many cycles. This reversible PL behavior is attributed to the phase transformation between CsPbBr3 and CsPb2Br5 induced by the repeated laser irradiation and moisture treatment and is promising for applications in information encryption, anticounterfeit, and optical data storage. Furthermore, MHP patterns with multiple color emissions are synthesized by adjusting the precursors, demonstrating the flexibility of the developed technology in color tuning of MHP QDs.

Tailorable Fluorescent Perovskite Quantum Dots for Multiform Manufacturing via Two-Step Thiol-Ene Click Chemistry

In practical applications, fluorescent perovskite quantum dots (PQDs) must exhibit high efficiency, stability, and processibility. So far, it remains a challenge to synthesize PQDs with stable dispersibility in tailorable monomers both before and after photocuring. In this work, a novel strategy of UV-induced two-step thiol-ene "click chemistry" is proposed to prepare PQDs with these attributes. The first step aims to epitaxially grow a shell around the PQD core to ensure stable dispersibility in a thiol-ene monomer solution. The second step is to achieve stable dispersibility in the photocured thiol-ene matrixes for multiform manufacturing processes. The tailorable PQDs (T-PQDs) not only have the highest photoluminescence quantum yield (PLQY) to ≈100% for green emission and over 96% for red emission, but also exhibit remarkable stability under severe conditions, including "double 85" aging, water exposure, and mechanical stress. Moreover, their exceptional processability allows for various processing techniques, including slot-die coating, inkjet printing, direct-laser writing, UV-light 3D printing, nanoimprinting, and spin coating. The high efficiency and stability of T-PQDs facilitate their multiform manufacturing for a wide range of applications.

Light-Emitting Diodes Based on Metal Halide Perovskite and Perovskite Related Nanocrystals

Light-emitting diodes (LEDs) based on halide perovskite nanocrystals have attracted extensive attention due to their considerable luminescence efficiency, wide color gamut, high color purity, and facile material synthesis. Since the first demonstration of LEDs based on MAPbBr3 nanocrystals was reported in 2014, the community has witnessed a rapid development in their performances. In this review, a historical perspective of the development of LEDs based on halide perovskite nanocrystals is provided and then a comprehensive survey of current strategies for high-efficiency lead-based perovskite nanocrystals LEDs, including synthesis optimization, ion doping/alloying, and shell coating is presented. Then the basic characteristics and emission mechanisms of lead-free perovskite and perovskite-related nanocrystals emitters in environmentally friendly LEDs, from the standpoint of different emission colors are reviewed. Finally, the progress in LED applications is covered and an outlook of the opportunities and challenges for future developments in this field is provided.

Inverse design of promising electrocatalysts for CO2 reduction via generative models and bird swarm algorithm

Directly generating material structures with optimal properties is a long-standing goal in material design. Traditional generative models often struggle to efficiently explore the global chemical space, limiting their utility to localized space. Here, we present a framework named Material Generation with Efficient Global Chemical Space Search (MAGECS) that addresses this challenge by integrating the bird swarm algorithm and supervised graph neural networks, enabling effective navigation of generative models in the immense chemical space towards materials with target properties. Applied to the design of alloy electrocatalysts for CO2 reduction (CO2RR), MAGECS generates over 250,000 structures, achieving a 2.5-fold increase in high-activity structures (35%) compared to random generation. Five predicted alloys- CuAl, AlPd, Sn2Pd5, Sn9Pd7, and CuAlSe2 are synthesized and characterized, with two showing around 90% Faraday efficiency for CO2RR. This work highlights the potential of MAGECS to revolutionize functional material development, paving the way for fully automated, artificial intelligence-driven material design.

Patterning technologies of quantum dots for color-conversion micro-LED display applications

Quantum dot (QD) materials and their patterning technologies play a pivotal role in the full colorization of next-generation Micro-LED display technology. This article reviews the latest development in QD materials, including II-VI group, III-V group, and perovskite QDs, along with the state of the art in optimizing QD performance through techniques such as ligand engineering, surface coating, and core-shell structure construction. Additionally, it comprehensively covers the progress in QD patterning methods, such as inkjet printing, photolithography, electrophoretic deposition, transfer printing, microfluidics, and micropore filling method, and emphasizes their crucial role in achieving high precision, density, and uniformity in QD deposition. This review delineates the impact of these technologies on the luminance of QD color-conversion layers and devices, providing a detailed understanding of their application in enhancing Micro-LED display technology. Finally, it explores future research directions, offering valuable insights and references for the continued innovation of full-color Micro-LED displays, thereby providing a comprehensive overview of the potential and scope of QD materials and patterning technologies in this field.

Ultraelastic Lead Halide Perovskite Films via Direct Laser Patterning

The precise patterning of elastic semiconductors holds encouraging prospects for unlocking functionalities and broadening the scope of optoelectronic applications. Here, perovskite films with notable elasticity capable of stretching over 250% are successfully fabricated by using a continuous-wave (CW) laser-patterning technique. Under CW laser irradiation, perovskite nanoparticles (NPs) undergo meticulous crystallization within the thermoplastic polyurethane (TPU) matrix, which yields the capability of an unparalleled stretch behavior. Furthermore, the strategic integration of β-phase poly(vinylidene fluoride) (β-PVDF) introduces a highly ordered dipolar framework, augmenting the crystallization dynamics of perovskite NPs during the laser-patterning process, thereby elevating the patterning efficiency and film quality. Furthermore, full-spectrum visible perovskite films that possess high transparency, high resolution, and adequate stability are achieved through the precise tuning of halide components, thereby emphasizing the impressive versatility of the high-elasticity printing technique. Our findings are meaningful for the direct patterning of high-precision, highly elastic semiconductors, finding a way for advancements in stretchable photonic and optoelectronic devices.

Direct Synthesis of Perovskite Quantum Dot Photoresist for Direct Photolithography

Perovskite quantum dots (PQDs) photoresists are promising building blocks for photolithographically patterned devices. However, their complex synthesis and combination processes limit their optical properties and potential patterning applications. Here, we present an exceptionally simple strategy for the synthesis of PQDs photoresist. Unlike traditional approaches that involve centrifugation, separation, and combination processes, our direct synthesis technique using polymerizable acrylic monomer as solvent to fabricate PQDs photoresists without complex post-synthesis process. We demonstrate that the change in solubility of the precursors is the main reason for the formation of PQDs in the polymerizable monomer. By direct photolithography, colorful PQD patterns with high photoluminescence quantum yields and high thickness are successfully demonstrated. This work opens a new avenue for the direct synthesis of PQDs photoresist, expanding their applications in various integrated applications, such as photonic, energy harvesting, and optoelectronic devices.

Direct Photolithography of WOx Nanoparticles for High-Resolution Non-Emissive Displays

High-resolution non-emissive displays based on electrochromic tungsten oxides (WOx) are crucial for future near-eye virtual/augmented reality interactions, given their impressive attributes such as high environmental stability, ideal outdoor readability, and low energy consumption. However, the limited intrinsic structure of inorganic materials has presented a significant challenge in achieving precise patterning/pixelation at the micron scale. Here, we successfully developed the direct photolithography for WOx nanoparticles based on in situ photo-induced ligand exchange. This strategy enabled us to achieve ultra-high resolution efficiently (line width < 4 µm, the best resolution for reported inorganic electrochromic materials). Additionally, the resulting device exhibited impressive electrochromic performance, such as fast response (< 1 s at 0 V), high coloration efficiency (119.5 cm2 C-1), good optical modulation (55.9%), and durability (> 3600 cycles), as well as promising applications in electronic logos, pixelated displays, flexible electronics, etc. The success and advancements presented here are expected to inspire and accelerate research and development (R&D) in high-resolution non-emissive displays and other ultra-fine micro-electronics.

In Situ Fabricated Perovskite Quantum Dots: From Materials to Applications

Due to the low formation enthalpy and high defect tolerance, in situ fabricated perovskite quantum dots offer advantages such as easy fabrication and superior optical properties. This paper reviews the methodologies, functional materials of in situ fabricated perovskite quantum dots, including polymer nanocomposites, quantum dots doped glasses, mesoporous nanocomposites, quantum dots-embedded single crystals, and electroluminescent films. This study further highlights the industrial breakthroughs of in situ fabricated perovskite quantum dots, especially the scale-up fabrication and stability enhancement. Finally, the fundamental challenges in developing perovskite quantum dots for industrial applications are discussed, with a focus on photoinduced degradation under high-intensity light irradiation, ion migration under electrical bias and thermal quenching at high temperature.

Monolithic Integration of Full-Color Microdisplay Screen with Sub-5 µm Quantum-Dot Pixels

Monolithic integration of color-conversion materials onto blue-backlight micro-light-emitting-diodes (micro-LEDs) has emerged as a promising strategy for achieving full-color microdisplay devices. However, this approach still encounters challenges such as the blue-backlight leakage and the poor fabrication yield rate due to unsatisfied quantum dot (QD) material and fabrication process. Here, the monolithic integration of 0.39-inch micro-display screens displaying colorful pictures and videos are demonstrated, which are enabled by creating interfacial chemical bonds for wafer-scale adhesion of sub-5 µm QD-pixels on blue-backlight micro-LED wafer. The ligand molecule with chlorosulfonyl and silane groups is selected as the synthesis ligand and surface treatment material, facilitating the preparation of high-efficiency QD photoresist and the formation of robust chemical bonds for pixel integration. This is a leading record in micro-display devices achieving the highest brightness larger than 400 thousand nits, the ultrahigh resolution of 3300 PPI, the wide color gamut of 130.4% NTSC, and the ultimate performance of service life exceeding 1000 h. These results extend the mature integrated circuit technique into the manufacture of micro-display device, which also lead the road of industrialization process of full-color micro-LEDs.

Continuous wave laser fabrication of small pitch/size perovskite pixels realizes high-resolution color conversion micro-LED displays

As a new generation of display technology, micro-light-emitting diodes (micro-LEDs) have been widely recognized owing to their excellent performance in brightness, contrast ratio, resolution, etc. This work proposes a continuous wave (CW) laser writing strategy to achieve perovskite quantum dots (PQDs) array with small pixel size and pitch, overcoming the processing difficulties and limitations of mass transfer. Since PQDs have highly dynamic surface ligand states and low ionic bond energy, suitable laser power can quench PQDs and form an array area. The use of low-power CW lasers in the laser direct writing process, on the one hand, greatly maintains the luminescence performance and edge flatness of each PQD array, and the pixel pitch (1.5 μm-9 μm)/size can be adjusted arbitrarily, which meets the high-resolution micro-display requirements. On the other hand, we found that after the low-power laser quenches the PQDs, its residual oxide can absorb photons, thus reducing the backlight leakage in color conversion micro-LEDs. Finally, red/green/blue three-color conversion micro-LED and laser projection displays were realized; these results provide a feasible strategy for next-generation micro-LED displays.

A Stable Perovskite Sensitized Photonic Crystal P-N Junction with Enhanced Photoelectrochemical Hydrogen Production

The slow photon effect in inverse opal photonic crystals represents a promising approach to manipulate the interactions between light and matter through the design of material structures. This study introduces a novel ordered inverse opal photonic crystal (IOPC) sensitized with perovskite quantum dots (PQDs), demonstrating its efficacy for efficient visible-light-driven H2 generation via water splitting. The rational structural design contributes to enhanced light harvesting. The sensitization of the IOPC with PQDs improves optical response performance and enhances photocatalytic H2 generation under visible light irradiation compared to the IOPC alone. The designed photoanode exhibits a photocurrent density of 3.42 mA cm-2 at 1.23 V vs RHE. This work advances the rational design of visible light-responsive photocatalytic heterostructure materials based on wide band gap metal oxides for photoelectrochemical applications.

Crosslinkable Ligands for High-Density Photo-Patterning of Perovskite Nanocrystals

Perovskite nanocrystals (PNCs) are promising luminescent materials for electronic color displays due to their high luminescence efficiency, widely-tunable emission wavelengths, and narrow emission linewidth. Their application in emerging display technologies necessitates precise micron-scale patterning while maintaining good optical performance. Although photolithography is a well-established micro-patterning technique in the industry, conventional processes are incompatible with PNCs as the use of polar solvents can damage the ionic PNCs, causing severe luminescence quenching. Here, we report the rational design and synthesis of a new bidentate photo-crosslinkable ligand for the direct photo-patterning of PNCs. Each ligand contains two photosensitive acrylate groups and two carboxylate groups, and is introduced to the PNCs via an entropy-driven ligand exchange process. In a close-packed thin film, the acrylate ligands photo-polymerize and crosslink under ultraviolet light, rendering the PNCs insoluble in developing solvents. A high-density crosslinked PNC film with an optical density of 1.1 is attained at 1.4 µm thickness, surpassing industry requirements on the absorption coefficient. Micron-scale patterning is further demonstrated using direct laser writing, producing well-defined 20 µm features. This study thus offers an effective and versatile approach for micro-patterning PNCs, and may also be broadly applicable to other nanomaterial systems.

Freeze Metal Halide Perovskite for Dramatic Laser Tuning: Direct Observation via In Situ Cryo-Electron Microscope

A frozen-temperature (below -28 °C) laser tuning way is developed to optimize metal halide perovskite (MHP)'s stability and opto-electronic properties, for emitter, photovoltaic and detector applications. Here freezing can adjust the competitive laser irradiation effects between damaging and annealing/repairing. And the ligand shells on MHP surface, which are widely present for many MHP materials, can be frozen and act as transparent solid templates for MHP's re-crystallization/re-growth during the laser tuning. With model samples of different types of CsPbBr3 nanocube arrays,an attempt is made to turn the dominant exposure facet from low-energy [100] facet to high-energy [111], [-211], [113] and [210] ones respectively; selectively removing the surface impurities and defects of CsPbBr3 nanocubes to enhance the irradiation durability by 101 times; and quickly (tens of seconds) modifying a Ruddlesden-Popper (RP) boundary into another type of boundary like twinning, and so on. The laser tuning mechanism is revealed by an innovative in situ cryo-transmission electron microscope (cryo-TEM) exploration at atomic resolution.

Ultrahigh-resolution, high-fidelity quantum dot pixels patterned by dielectric electrophoretic deposition

The high pixel resolution is emerging as one of the key parameters for the next-generation displays. Despite the development of various quantum dot (QD) patterning techniques, achieving ultrahigh-resolution (>10,000 pixels per inch (PPI)) and high-fidelity QD patterns is still a tough challenge that needs to be addressed urgently. Here, we propose a novel and effective approach of orthogonal electric field-induced template-assisted dielectric electrophoretic deposition to successfully achieve one of the highest pixel resolutions of 23090 (PPI) with a high fidelity of up to 99%. Meanwhile, the proposed strategy is compatible with the preparation of QD pixels based on perovskite CsPbBr3 and conventional CdSe QDs, exhibiting a wide applicability for QD pixel fabrication. Notably, we further demonstrate the great value of our approach to achieve efficiently electroluminescent QD pixels with a peak external quantum efficiency of 16.5%. Consequently, this work provides a general approach for realizing ultrahigh-resolution and high-fidelity patterns based on various QDs and a novel method for fabricating QD-patterned devices with high performance.

Perovskite Probe-Based Machine Learning Imaging Model for Rapid Pathologic Diagnosis of Cancers

Accurately distinguishing tumor cells from normal cells is a key issue in tumor diagnosis, evaluation, and treatment. Fluorescence-based immunohistochemistry as the standard method faces the inherent challenges of the heterogeneity of tumor cells and the lack of big data analysis of probing images. Here, we have demonstrated a machine learning-driven imaging method for rapid pathological diagnosis of five types of cancers (breast, colon, liver, lung, and stomach) using a perovskite nanocrystal probe. After conducting the bioanalysis of survivin expression in five different cancers, high-efficiency perovskite nanocrystal probes modified with the survivin antibody can recognize the cancer tissue section at the single cell level. The tumor to normal (T/N) ratio is 10.3-fold higher than that of a conventional fluorescent probe, which can successfully differentiate between tumors and adjacent normal tissues within 10 min. The features of the fluorescence intensity and pathological texture morphology have been extracted and analyzed from 1000 fluorescence images by machine learning. The final integrated decision model makes the area under the receiver operating characteristic curve (area under the curve) value of machine learning classification of breast, colon, liver, lung, and stomach above 90% while predicting the tumor organ of 92% of positive patients. This method demonstrates a high T/N ratio probe in the precise diagnosis of multiple cancers, which will be good for improving the accuracy of surgical resection and reducing cancer mortality.

Dual-Ligand Red Perovskite Ink for Electrohydrodynamic Printing Color Conversion Arrays over 2540 dpi in Near-Eye Micro-LED Display

The lack of stability of red perovskite nanocrystals (PeNCs) remains the main problem that restricts their patterning application. In this work, the dual-ligand passivation strategy was introduced to stabilize PeNCs and inhibit their halogen ion migration during high-voltage electrohydrodynamic (EHD) inkjet printing. The as-printed red arrays exhibit the highest emisson intensity and least blue shift compared with samples with other passivation strategies under a high electric field during EHD inkjet printing. Combining with blue and green PeNC inks, single-color and tricolor color conversion layer arrays were successfully printed, with minimum pixel size of 5 μm and the highest spatial resolution of 2540 dpi. The color coordinate of CsPbBrI2 NCs arrays are located close to the red point, with a color gumat of 97.28% of Rec. 2020 standard. All of these show great potential in the application of color conversion layers in a near-eye micro-LED display.

Nondestructive Direct Optical Patterning of Perovskite Nanocrystals with Carbene-Based Ligand Cross-Linkers

Microscale patterning of colloidal perovskite nanocrystals (NCs) is essential for their integration in advanced device platforms, such as high-definition displays. However, perovskite NCs usually show degraded optical and/or electrical properties after patterning with existing approaches, posing a critical challenge for their optoelectronic applications. Here we achieve nondestructive, direct optical patterning of perovskite NCs with rationally designed carbene-based cross-linkers and demonstrate their applications in high-performance light-emitting diodes. We reveal that both the photochemical properties and the electronic structures of cross-linkers need to be carefully tailored to the material properties of perovskite NCs. This method produces high-resolution (∼4000 ppi) NC patterns with preserved photoluminescent quantum efficiencies and charge transport properties. Prototype light-emitting diodes with patterned/cross-linked NC layers show a maximum luminance of over 60000 cd m-2 and a peak external quantum efficiency of 16%, among the highest for patterned perovskite electroluminescent devices. Such a material-adapted patterning method enabled by designs from a photochemistry perspective could foster the applications of perovskite NCs in system-level electronic and optoelectronic devices.

Ligand-Nondestructive Direct Photolithography Assisted by Semiconductor Polymer Cross-Linking for High-Resolution Quantum Dot Light-Emitting Diodes

The photolithographic patterning of fine quantum dot (QD) films is of great significance for the construction of QD optoelectronic device arrays. However, the photolithography methods reported so far either introduce insulating photoresist or manipulate the surface ligands of QDs, each of which has negative effects on device performance. Here, we report a direct photolithography strategy without photoresist and without engineering the QD surface ligands. Through cross-linking of the surrounding semiconductor polymer, QDs are spatially confined to the network frame of the polymer to form high-quality patterns. More importantly, the wrapped polymer incidentally regulates the energy levels of the emitting layer, which is conducive to improving the hole injection capacity while weakening the electron injection level, to achieve balanced injection of carriers. The patterned QD light-emitting diodes (with a pixel size of 1.5 μm) achieve a high external quantum efficiency of 16.25% and a brightness of >1.4 × 105 cd/m2. This work paves the way for efficient high-resolution QD light-emitting devices.

Light Management of Metal Halide Scintillators for High-Resolution X-Ray Imaging

The ever-growing need to inspect matter with hyperfine structures requires a revolution in current scintillation detectors, and the innovation of scintillators is revived with luminescent metal halides entering the scene. Notably, for any scintillator, two fundamental issues arise: Which kind of material is suitable and in what form should the material exist? The answer to the former question involves the sequence of certain atoms into specific crystal structures that facilitate the conversion of X-ray into light, whereas the answer to the latter involves assembling these crystallites into particular material forms that can guide light propagation toward its corresponding pixel detector. Despite their equal importance, efforts are overwhelmingly devoted to improving the X-ray-to-light conversion, while the material-form-associated light propagation, which determines the optical signal collected for X-ray imaging, is largely overlooked. This perspective critically correlates the reported spatial resolution with the light-propagation behavior in each form of metal halides, combing the designing rules for their future development.

Advances in lithographic techniques for precision nanostructure fabrication in biomedical applications

Nano-fabrication techniques have demonstrated their vital importance in technological innovation. However, low-throughput, high-cost and intrinsic resolution limits pose significant restrictions, it is, therefore, paramount to continue improving existing methods as well as developing new techniques to overcome these challenges. This is particularly applicable within the area of biomedical research, which focuses on sensing, increasingly at the point-of-care, as a way to improve patient outcomes. Within this context, this review focuses on the latest advances in the main emerging patterning methods including the two-photon, stereo, electrohydrodynamic, near-field electrospinning-assisted, magneto, magnetorheological drawing, nanoimprint, capillary force, nanosphere, edge, nano transfer printing and block copolymer lithographic technologies for micro- and nanofabrication. Emerging methods enabling structural and chemical nano fabrication are categorised along with prospective chemical and physical patterning techniques. Established lithographic techniques are briefly outlined and the novel lithographic technologies are compared to these, summarising the specific advantages and shortfalls alongside the current lateral resolution limits and the amenability to mass production, evaluated in terms of process scalability and cost. Particular attention is drawn to the potential breakthrough application areas, predominantly within biomedical studies, laying the platform for the tangible paths towards the adoption of alternative developing lithographic technologies or their combination with the established patterning techniques, which depends on the needs of the end-user including, for instance, tolerance of inherent limits, fidelity and reproducibility.

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.

Dispersion of the third-order optical nonlinearities in 2D (PEA)2PbI4 perovskite film

We report the wavelength-dependent third-order optical nonlinearity of two-dimensional halide organic-inorganic perovskite (PEA)2PbI4 film experimentally. The high-quality two-dimensional (PEA)2PbI4 film prepared via confinement-assisted drop-casting process exhibits ultrafast optical response and large third-order optical nonlinearities, and the measured nonlinear refractive index is closer to the quantum perturbation model accounting for the excitonic effect. In addition, the wavelength-dependent optical response transition from self-focusing to self-defocusing, saturable absorption to reverse saturable absorption has been observed and investigated. The experimental results confirm the large third-order optical nonlinearities in (PEA)2PbI4 film and may make inroads toward developing cost-effective high-performance optoelectronic devices.

Mask-Free Patterned Perovskite Microcavity Arrays via Inkjet Printing Targeting Laser Emission

Perovskite materials are promising candidates for the implementation of electrically pumped lasers considering the enhanced performance of perovskite-based light-emitting diodes. Nonetheless, current methods of fabricating perovskite optical microcavities require complex patterning technologies to build suitable resonant cavities for perovskite laser emission, burdening the device structure design. To address this issue, we applied inkjet printing, a maskless patterning technique, to directly create spontaneous formations of polycrystalline perovskite microcavity arrays to explore their laser-emitting action. The substrate surface tension was tuned to modulate the perovskite crystallization process in combination with optimization of printing ink recipes. As a result, polycrystalline perovskite microcavity arrays were achieved, contributing to the laser emission at 528 nm with a lasing threshold of 1.37 mJ/cm2, while simultaneously achieving high-definition patterning of flexible display. These results clearly illustrate the efficiency of inkjet printing technology in the preparation of polycrystalline perovskite optical microcavities and promote the development of flexible laser arrayed displays, providing a facile process toward the realization of perovskite-cavity laser devices.

Room-Temperature, Multigram-Scale Synthesis and Conversion Mechanism of Highly Luminescent Lead Sulfide Quantum Dots

PbS quantum dots (QDs) are attractive near-infrared (NIR) materials, but traditional synthetic methods require inert atmosphere and/or high temperature. Herein we develop a facile, room-temperature synthetic route for in situ halide passivated PbS QDs through controllable reactions between lead halide, N,N'-diphenyl thiourea, and oleyamine (OLA) in toluene. Contrast experiments and theoretical calculations reveal that the OLA plays a bifunctional role as a mild base to initiate the formation of PbS monomers and as a dynamic ligand to control the crystallization of PbS QDs and further ligand exchange. The oleic acid-capped PbS QDs exhibit high photoluminescence quantum yields up to 45%. The scaled-up synthesis on multigram scales shows great batch-to-batch consistency. We further demonstrate high-power NIR light-emitting diodes using the PbS QDs as color converters, delivering NIR optical power of 9.2 mW at 160 mA. This work provides a simple and versatile synthetic route for high-quality PbS QDs and boosts the applications of NIR materials.

Direct photocatalytic patterning of colloidal emissive nanomaterials

We present a universal direct photocatalytic patterning method that can completely preserve the optical properties of perovskite nanocrystals (PeNCs) and other emissive nanomaterials. Solubility change of PeNCs is achieved mainly by a photoinduced thiol-ene click reaction between specially tailored surface ligands and a dual-role photocatalytic reagent, pentaerythritol tetrakis(3-mercaptopropionate) (PTMP), where the thiol-ene reaction is enabled at a low light intensity dose (~ 30 millijoules per square centimeter) by the strong photocatalytic activity of PeNCs. The photochemical reaction mechanism was investigated using various analyses at each patterning step. The PTMP also acts as a defect passivation agent for the PeNCs and even enhances their photoluminescence quantum yield (by ~5%) and photostability. Multicolor patterns of cesium lead halide (CsPbX3)PeNCs were fabricated with high resolution (<1 micrometer). Our method is widely applicable to other classes of nanomaterials including colloidal cadmium selenide-based and indium phosphide-based quantum dots and light-emitting polymers; this generality provides a nondestructive and simple way to pattern various functional materials and devices.

Recent progress in construction methods and applications of perovskite photodetector arrays

Metal halide perovskites are considered promising materials for next-generation optoelectronic devices due to their excellent optoelectronic performances and simple solution preparation process. Precise micro/nano-scale patterning techniques enable perovskite materials to be used for array integration of photodetectors. In this review, the device types of perovskite-based photodetectors are introduced and the structural characteristics and corresponding device performances are analyzed. Then, the typical construction methods suitable for the fabrication of perovskite photodetector arrays are highlighted, including surface treatment technology, template-assisted construction, inkjet printing technology, and modified photolithography. Furthermore, the current development trends and their applications in image sensing of perovskite photodetector arrays are summarized. Finally, major challenges are presented to guide the development of perovskite photodetector arrays.

Direct Optical Patterning of Quantum Dots: One Strategy, Different Chemical Processes

Patterning, stability, and dispersion of the semiconductor quantum dots (scQDs) are three issues strictly interconnected for successful device manufacturing. Recently, several authors adopted direct optical patterning (DOP) as a step forward in photolithography to position the scQDs in a selected area. However, the chemistry behind the stability, dispersion, and patterning has to be carefully integrated to obtain a functional commercial device. This review describes different chemical strategies suitable to stabilize the scQDs both at a single level and as an ensemble. Special attention is paid to those strategies compatible with direct optical patterning (DOP). With the same purpose, the scQDs' dispersion in a matrix was described in terms of the scQD surface ligands' interactions with the matrix itself. The chemical processes behind the DOP are illustrated and discussed for five different approaches, all together considering stability, dispersion, and the patterning itself of the scQDs.

Light Amplification in Fe-Doped CsPbBr3 Crystal Microwire Excited by Continuous-Wave Laser

Electrically pumped halide perovskite laser diodes remain unexplored, and it is widely acknowledged that continuous-wave (CW) lasing will be a crucial step. Here, we demonstrate room-temperature amplified spontaneous emission of Fe-doped CsPbBr₃ crystal microwire excited by a CW laser. Temperature-dependent photoluminescence spectra indicate that the Fe dopant forms a shallow level trap states near the band edge of the lightly doped CsPbBr₃ microcrystal. Pump intensity-dependent time-resolved PL spectra show that the introduced Fe dopant level makes the electron more stable in excited states, suitable for the population inversion. The emission peak intensity of the lightly Fe-doped microwire increases nonlinearly above a threshold of 12.3 kW/cm² under CW laser excitation, indicating a significant light amplification. Under high excitation, the uniform crystal structure and surface outcoupling in Fe-doped perovskite crystal microwires enhanced the spontaneous emission. These results reveal the considerable promise of Fe-doped perovskite crystal microwires toward low-cost, high-performance, room-temperature electrical pumping perovskite lasers.

High-Resolution Patterning of Perovskite Quantum Dots via Femtosecond Laser-Induced Forward Transfer

High-resolution patterning of perovskite quantum dots (PQDs) is of significant importance for satisfying various practical applications, including high-resolution displays and image sensing. However, due to the limitation of the instability of PQDs, the existing patterning strategy always involves chemical reagent treatment or mask contact that is not suitable for PQDs. Therefore, it is still a challenge to fabricate high-resolution full-color PQD arrays. Here, we present a femtosecond laser-induced forward transfer (FsLIFT) technology, which enables the programmable fabrication of high-resolution full-color PQD arrays and arbitrary micropatterns. The FsLIFT process integrates transfer, deposition, patterning, and alignment in one step without involving a mask and chemical reagent treatment, guaranteeing the preservation of the photophysical properties of PQDs. A full-color PQD array with a high resolution of 2 μm has been successfully achieved. We anticipate that our facile and flexible FsLIFT technology can facilitate the development of diverse practical applications based on patterned PQDs.

Patterning Perovskite Quantum Dots Using Photopolymerization

All-inorganic cesium lead halide perovskite quantum dots (QDs) have several potential applications, owing to their unique optical and electronic properties. However, patterning perovskite QDs using conventional methods is difficult because of the ionic nature of QDs. Here, we demonstrate a unique approach, in which perovskite QDs are patterned in polymer films through the photocuring of monomers under patterned light illumination. The pattern illumination creates the transient polymer concentration difference, which drives the QDs to form patterns; hence controlling polymerization kinetics is essential for the generation of the QD pattern. For the patterning mechanism, a light projection system equipped with a digital micromirror device (DMD) is developed; thus, light intensity, an important factor to determine polymerization kinetics, is precisely controlled per position on the photocurable solution, resulting in the understanding of the mechanism and the formation of distinct QD patterns. The demonstrated approach assisted by the DMD-equipped projection system can form desired perovskite QD patterns solely by patterned light illumination, paving the way for the development of patterning methods for perovskite QDs and other nanocrystals.

Phenyl-Terminated Coupling Interface Enabled Highly Efficient and Stable Multiwavelength Perovskite Single Crystal/Silicon Integrated Photodetector

The use of amino-terminated siloxanes as coupling interface for perovskite single crystals (PSCs)/silicon integrated devices has been demonstrated to be an effective method toward CMOS compatible optoelectronics; however, it suffers from the coupling stability against the hydrophilicity of the exposed terminal amino groups. In this work, a phenyl-terminated interfacial molecule, anilino-methyl-triethoxysilane (AMTES), is proposed to achieve the effectively galvanic coupling between PSCs and silicon, which can not only improve the device environmental reliability but also lower the surface energy of the silicon substrate so as to facilitate the epitaxial growth of PSCs. Benefiting from the interfacial coupling of AMTES, the obtained MAPbI₃ SC/silicon integrated device possesses highly efficient multiwavelength photodetection properties across the X-ray and NIR range, which exhibits a specific detectivity D* of 3.84 × 10¹³ cm Hz^1/2 W^-1 in the visible-NIR region and an X-ray sensitivity of 1.18 × 10⁴ μC Gy_air^-1 cm^-2 with the lowest detection limit of 49.6 nGy_air s^-1. The ultra wide -3 dB bandwidth of 67,300 Hz and the linear dynamic range (LDR) of 112 dB also prove its impressive dynamic response capabilities. Moreover, the AMTES modified integrated device almost maintains 96% of the initial photodetection performance even after keeping in the atmosphere environment for 28 days. This work opens a new avenue for interfacial engineering toward the development of on-chip PSC integrated silicon optoelectronic devices.

Research advances in ZnO nanomaterials-based UV photode tectors: a review

Ultraviolet photodetectors (UV PDs) have always been the research focus of semiconductor optoelectronic devices due to their wide application fields and diverse compositions. As one of the best-known n-type metal oxides in third-generation semiconductor electronic devices, ZnO nanostructures and their assembly with other materials have received extensive research. In this paper, the research progress of different types of ZnO UV PDs is reviewed, and the effects of different nanostructures on ZnO UV PDs are summarized in detail. In addition, physical effects such as piezoelectric photoelectric effect, pyroelectric effect, and three ways of heterojunction, noble metal local surface plasmon resonance enhancement and formation of ternary metal oxides on the performance of ZnO UV PDs were also investigated. The applications of these PDs in UV sensing, wearable devices, and optical communication are displayed. Finally, the possible opportunities and challenges for the future development of ZnO UV PDs are prospected.

A Review on Low-Dimensional Nanomaterials: Nanofabrication, Characterization and Applications

The development of modern cutting-edge technology relies heavily on the huge success and advancement of nanotechnology, in which nanomaterials and nanostructures provide the indispensable material cornerstone. Owing to their nanoscale dimensions with possible quantum limit, nanomaterials and nanostructures possess a high surface-to-volume ratio, rich surface/interface effects, and distinct physical and chemical properties compared with their bulk counterparts, leading to the remarkably expanded horizons of their applications. Depending on their degree of spatial quantization, low-dimensional nanomaterials are generally categorized into nanoparticles (0D); nanorods, nanowires, and nanobelts (1D); and atomically thin layered materials (2D). This review article provides a comprehensive guide to low-dimensional nanomaterials and nanostructures. It begins with the classification of nanomaterials, followed by an inclusive account of nanofabrication and characterization. Both top-down and bottom-up fabrication approaches are discussed in detail. Next, various significant applications of low-dimensional nanomaterials are discussed, such as photonics, sensors, catalysis, energy storage, diverse coatings, and various bioapplications. This article would serve as a quick and facile guide for scientists and engineers working in the field of nanotechnology and nanomaterials.

Perovskite Random Lasers, Process and Prospects

Random lasers (RLs) are a kind of coherent light source with optical feedback based on disorder-induced multiple scattering effects instead of a specific cavity. The unique feedback mechanism makes RLs different from conventional lasers. They have the advantages of small volume, flexible shape, omnidirectional emission, etc., and have broad application prospects in the fields of laser illumination, speckle-free imaging, display, and sensing. Colloidal metal-halide perovskite nanomaterials are a hot research field in light sources. They have been considered as desired gain media owing to their superior properties, such as high photoluminescence, tunable emission wavelengths, and easy fabrication processes. In this review, we summarize the research progress of RLs based on perovskite nanomaterials. We first present the evolution of the RLs based on the perovskite quantum dots (QDs) and perovskite films. The fabrication process of perovskite nano-/microstructures and lasers is discussed in detail. After that, the frontier applications of perovskite RLs are discussed. Finally, the challenges are discussed, and the prospects for further development are proposed.