Self-Healing Lithographic Patterning of Perovskite Nanocrystals for Large-Area Single-Mode Laser Array

Lead halide perovskites exhibit extraordinary optoelectronic performances and are being considered as a promising medium for high-quality photonic devices such as single-mode lasers. However, for perovskite-based single-mode lasers to become practical, fabrication and integration on a chip via the standard top-down lithography process are strongly desired. The chief bottleneck to achieving lithography of perovskites lies in their reactivity to chemicals used for lithography as illustrated by issues of instability, surface roughness, and internal defects with the fabricated structures. The realization of lithographic perovskite single-mode lasers in large areas remains a challenge. In this work, a self-healing lithographic patterning technique using perovskite CsPbBr₃ nanocrystals is demonstrated to realize high-quality and high-crystallinity single-mode laser arrays. The self-healing process is compatible with the standard lithography process and greatly improves the quality of lithographic laser cavities. A single-mode microdisk laser array is demonstrated with a low threshold of 3.8 µJ cm⁻². Moreover, the control of the lasing wavelength is made possible over a range of up to 6.4 nm by precise fabrication of the laser cavities. This work presents a general and promising strategy for standard top-down lithography fabrication of high-quality perovskite devices and enables research on large-area perovskite-based integrated optoelectronic circuits.     

Fluorinated Organic A-Cation Enabling High-Performance Hysteresis-Free 2D/3D Hybrid Tin Perovskite Transistors

2D tin-based perovskites have gained considerable attention for use in diverse optoelectronic applications, such as solar cells, lasers, and thin-film transistors (TFTs), owing to their good stability and optoelectronic properties. However, their intrinsic charge-transport properties are limited, and the insulating bulky organic ligands hinder the achievement of high-mobility electronics. Blending 3D counterparts into 2D perovskites to form 2D/3D hybrid structures is a synergistic approach that combine the high mobility and stability of 3D and 2D perovskites, respectively. In this study, reliable p-channel 2D/3D tin-based hybrid perovskite TFTs comprising 3D formamidinium tin iodide (FASnI₃) and 2D fluorinated 4-fluoro-phenethylammonium tin iodide ((4-FPEA)₂SnI₄) are reported. The optimized FPEA-incorporated TFTs show a high hole mobility of 12 cm² V⁻¹ s⁻¹, an on/off current ratio of over 10⁸, and a subthreshold swing of 0.09 V dec⁻¹ with negligible hysteresis. This excellent p-type characteristic is compatible with n-type metal-oxide TFT for constructing complementary electronics. Two procedures of antisolvent engineering and device patterning are further proposed to address the key concern of low-performance reproducibility of perovskite TFTs. This study provides an alternative A-cation engineering method for achieving high-performance and reliable tin-halide perovskite electronics.     

Electrohydrodynamically Printed High‐Resolution Full‐Color Hybrid Perovskites

Hybrid perovskites show enormous potential for display due to their tunable emission, high color purity, strong photoluminescence and electroluminescence. For display applications, full‐color and high‐resolution patterning is compulsory, however, current perovskite processing such as spin‐coating fails to meet these requirements. Here, electrohydrodynamic (EHD) printing, with the unique advantages of high‐resolution patterning and large scalability, is introduced to fabricate full‐color perovskite patterns. Perovskite inks via simple precursor mixing are prepared to in situ crystallize tunable‐ and bright‐photoluminescence perovskite arrays without adding antisolvent. Through optimizing the EHD printing process, a high‐resolution dot matrix of 5 µm is achieved. The as‐printed patterns and pictures show full color and high controllability in micrometer dimension, indicating that the EHD printing is a competitive technique for future halide perovskite‐based high‐quality display.     

Centimeter-Sized Molecular Perovskite Crystal for Efficient X-Ray Detection

Molecular perovskites have demonstrated great potential for ferroelectrics and nonlinear optics; however, their charge transport properties for optoelectronics have rarely been explored. Here, understanding of charge transport behavior of molecular perovskite under X-ray excitation based on centimeter-scale TMCM-CdCl₃ (TMCM⁺, trimethylchloromethyl ammonium) single crystal is demonstrated. The crystal is fabricated from an aqueous solution and exhibits a large bandgap of 5.51 eV, with the valence band maximum mainly dominated by the Cl-p/Cd-d states and the conduction band minimum primarily by Cd-s/Cl-p states. Charge mobility exceeding 40 cm² V⁻¹ s⁻¹ and mobility–lifetime (µτ) product on the order of 10⁻⁴ cm² V⁻¹ for the crystal are observed. These excellent optoelectronic properties translate to an efficient photoresponse under X-ray excitation, with the sensitivity reaching 128.9 ± 4.64 µC Gy_air⁻¹ cm⁻² [fivefold higher than that of the commercialized amorphous selenium (α-Se)] and a low detection limit of 1.06 μC Gy_air⁻¹ s⁻¹ (10 V bias). This work pioneers a superior metal-based molecular perovskite single-crystal based paradigm for optoelectronic investigation, which may lead to the discovery of a new generation of X-ray detection and imaging materials.     

High-Performance Photodetector and Angular-Dependent Random Lasing from Long-Chain Organic Diammonium Sandwiched 2D Hybrid Perovskite Non-Linear Optical Single Crystal

3D organic-inorganic metal halide perovskites are excellent materials for optoelectronic applications due to their exceptional properties, solution processability, and cost-effectiveness. However, the lack of environmental stability highly restricts them from practical applications. Herein, a stable centimeter-long 2D hybrid perovskite (N-MPDA)[PbBr₄] single crystal using divalent N1-methylpropane-1,3-diammonium (N-MPDA) cation as an organic spacer, is reported. The as-grown single crystal exhibits stable optoelectronic performance, low threshold random lasing, and multi-photon luminescence/multi-harmonic generation. A photoconductive device fabricated using (N-MPDA)[PbBr₄] single crystal exhibits an excellent photoresponsivity (≈124 AW⁻¹ at 405 nm) that is ≈4 orders of magnitudes higher than that of monovalent organic spacer-assisted 2D perovskites, such as (BA)₂PbBr₄ and (PEA)₂PbBr₄, and large specific detectivity (≈10¹² Jones). As an optical gain media, the (N-MPDA)[PbBr₄] single crystal exhibits a low threshold random lasing (≈6.5 µJ cm⁻²) with angular dependent narrow linewidth (≈0.1 nm) and high-quality factor (Q ≈ 2673). Based on these results, the outstanding optoelectronic merits of (N-MPDA)[PbBr₄] single crystal will offer a high-performance device and act as a dynamic material to construct stable future electronics and optoelectronic-based applications.     

High-Resolution,Flexible, and Full-Color Perovskite Image Photodetector via Electrohydrodynamic Printing of Ionic-Liquid-Based Ink

Direct full-color image photodetectors without dichroic prisms or sophisticated color filters have considerable advantages in target recognition and information acquisition for electronic eyes and wearable sensors. However, the ability to combine various multispectral semiconductors in a high-resolution and cost-effective manner is still challenging. Here, high-resolution electrohydrodynamic (EHD) printing, together with ionic liquid methylammonium acetate (MAAc) as the solvent, is first introduced to directly integrate various spectral-response perovskite films into a pixelized full-color photodetector. EHD printing enables micro/nanopatterning by using high electrical force to induce jetting, and MAAc improves film quality with scant pinholes and large-size grains by decreasing the perovskite growth rate. By optimizing the printing process and crystallization condition, 1 µm perovskite dot arrays are EHD printed; this is, to the best of knowledge, the smallest printed feature size of perovskite application. And the photodetector still achieves high R and D* values of 14.97 A W^-1 and 1.41 × 10¹² Jones, respectively. Finally, an integrated flexible full-color image photodetector is constructed, which successfully realizes light signal detection and color recognition, paving a versatile and competitive approach for future full-color image sensors and artificial vision systems.     

Near‐Infrared and Short‐Wavelength Infrared Photodiodes Based on Dye–Perovskite Composites

Organohalide perovskites have emerged as promising light‐sensing materials because of their superior optoelectronic properties and low‐cost processing methods. Recently, perovskite‐based photodetectors have successfully been demonstrated as both broadband and narrowband varieties. However, the photodetection bandwidth in perovskite‐based photodetectors has so far been limited to the near‐infrared regime owing to the relatively wide band gap of hybrid organohalide perovskites. In particular, short‐wavelength infrared photodiodes operating beyond 1 µm have not yet been realized with organohalide perovskites. In this study, narrow band gap organic dyes are combined with hybrid perovskites to form composite films as active photoresponsive layers. Tuning the dye loading allows for optimization of the spectral response characteristics and excellent charge‐carrier mobilities near 11 cm² V^?1 s^?1, suggesting that these composites combine the light‐absorbing properties or IR dyes with the outstanding charge‐extraction characteristics of the perovskite. This study demonstrates the first perovskite photodiodes with deep near‐infrared and short‐wavelength infrared response that extends as far as 1.6 µm. All devices are solution‐processed and exhibit relatively high responsivity, low dark current, and fast response at room temperature, making this approach highly attractive for next‐generation light‐detection techniques.     

Inkjet Printing Flexible Thermoelectric Devices Using Metal Chalcogenide Nanowires

Development of flexible thermoelectric devices offers exciting opportunities for wearable applications in consumer electronics, healthcare, human–machine interface, etc. Despite the increased interests and efforts in nanotechnology-enabled flexible thermoelectrics, translating the superior properties of thermoelectric materials from nanoscale to macroscale and reducing the manufacturing costs at the device level remain a major challenge. Here, an economic and scalable inkjet printing method is reported to fabricate high-performance flexible thermoelectric devices. A general templated-directed chemical transformation process is employed to synthesize several types of 1D metal chalcogenide nanowires (e.g., Ag₂Te, Cu₇Te₄, and Bi₂Te_2.7Se_0.3). These nanowires are made into inks suitable for inkjet printing by dispersing them in ethanol without any additives. As a showcase for thermoelectric applications, fully inkjet-printed Ag₂Te-based flexible films and devices are prepared. The printed films exhibit a power factor of 493.8 µW m⁻¹ K⁻² at 400 K and the printed devices demonstrate a maximum power density of 0.9 µW cm⁻² K⁻², both of which are significantly higher than those reported in state-of-the-art inkjet-printed thermoelectrics. The protocols of metal chalcogenide ink formulations, as well as printing are general and extendable to a wider range of material systems, suggesting the great potential of this printing platform for scalable manufacturing of next-generation, high-performance flexible thermoelectric devices.     

Centimeter-Sized Single Crystals of Two-Dimensional Hybrid Iodide Double Perovskite (4,4-Difluoropiperidinium)4AgBiI8 for High-Temperature Ferroelectricity and Efficient X-Ray Detection

Ferroelectricity and X-ray detection property have been recently implemented for the first time in hybrid bromide double perovskites. It sheds a light on achieving photosensitive and ferroelectric multifunctional materials based on 2D lead-free hybrid halide double perovskites. However, the low T_c, small P_s, and relatively low X-ray sensitivity in the reported bromide double perovskites hinder practical applications. Herein, the authors demonstrate a novel 2D lead-free iodide double perovskite (4,4-difluoropiperidinium)₄AgBiI₈ (1) for high-performance X-ray sensitive ferroelectric devices. Centimeter-sized single crystal of 1 is obtained and exhibits an excellent ferroelectricity including a high T_c up to 422 K and a large P_s of 10.5 μC cm⁻². Moreover, due to a large X-ray attenuation and efficient charge carrier mobility (μ)–charge carrier lifetime (τ) product, the crystal 1 also exhibits promising X-ray response with a high sensitivity up to 188 μC·Gy_air⁻¹ cm⁻² and a detection limit below 3.13 μGy_air·s⁻¹. Therefore, this finding is a step further toward practical applications of lead-free halide perovskite in high-performance photoelectronic devices. It will afford a promising platform for exploring novel photosensitive ferroelectric multifunctional materials based on lead-free double perovskites.     

Transparent and Reusable Nanostencil Lithography for Organic–Inorganic Hybrid Perovskite Nanodevices

Organic—inorganic hybrid perovskites have attracted considerable attention for developing novel optoelectronic devices owing to their excellent photoresponses. However, conventional nanolithography of hybrid perovskites remains a challenge because they undergo severe damage in standard lithographic solvents, which prohibits device miniaturization and integration. In this study, a novel transparent stencil nanolithography (t-SL) technique is developed based on focused ion beam (FIB)-assisted polyethylene terephthalate (PET) direct patterning. The proposed t-SL enables ultrahigh lithography resolution down to 100 nm and accurate stencil mask alignment. Moreover, the stencil mask can be reused more than ten times, which is cost-effective for device fabrication. By applying this lithographic technique to hybrid perovskites, a high-performance 2D hybrid perovskite heterostructure photodetector is fabricated. The responsivity and detectivity of the proposed heterostructure photodetector can reach up to 28.3 A W⁻¹ and 1.5 × 10¹³ Jones, respectively. This t-SL nanolithography technique based on FIB-assisted PET direct patterning can effectively support the miniaturization and integration of hybrid-perovskite-based electronic devices.     

Air-Stable Self-Powered Photodetectors Based on Lead-Free CsBi3I10/SnO2 Heterojunction for Weak Light Detection

Lead halide perovskites (LHPs) have been widely investigated in photodetection applications owing to their intriguing optoelectronic properties. However, the application of LHPs-based photodetectors (PDs) is hindered because of the toxicity of lead and instability in ambient air. Here, an air-stable self-powered photodetector is designed based on all-inorganic lead-free CsBi₃I₁₀/SnO₂ heterojunction. The device exhibits broad spectral response in both UV and visible light, fast response on µs scale, and decent long-term stability. The device holds a faster response speed (t_r/t_d = 7.8/8.8 µs), among the best reported self-powered lead-free perovskites photodetectors. More importantly, the device can display obvious photoresponses even under ultra-weak light intensity as low as 10 pW cm^–2, showing better weak-light sensitivity than previously reported lead-free perovskites photodetectors, to the best of our knowledge. Moreover, the device holds good air stability in the 73 days test without encapsulation. These results suggest that CsBi₃I₁₀/SnO₂-based self-powered PDs with high photodetection capability possess enormous potential in stable and broadband PDs for weak light detection in the future.     

Record‐Low‐Threshold Lasers Based on Atomically Smooth Triangular Nanoplatelet Perovskite

Single‐crystalline perovskites are ideal candidates for lasing and other optoelectronic applications. Although significant efforts have been made to grow both bulk single‐crystalline perovskites in liquid solution, their dimensions are still too large to make nanoscale whispering‐gallery‐mode (WGM) resonator based lasers that possess high quality (Q) factor and small volume. Besides, most reported perovskite resonators do not possess atomically smooth surfaces and facets, which limits the Q and thereby increases the lasing threshold. Here, atomically smooth triangular PbI₂ templates are fabricated on a mica substrate by the vapor phase deposition method and are converted to atomically smooth perovskites which have regular and unwrinkled facets with average surface roughness less than 2 nm. By using a CH₃NH₃PbI₃ nanoplatelet with a side length of 27 µm and thickness of 80 nm, room temperature WGM lasing with a Q up to 2600 is demonstrated, the highest reported for hybrid organic–inorganic perovskite nanoplatelets. In addition, the volume of the WGM mode is reduced significantly in comparison with the prior reports. The realized high‐quality triangular CH₃NH₃PbI₃ perovskite nanoplatelets with high Q factor and small volume are expected to perform as ideal cavities for long pulse durations lasers and would find potential applications in integrated optoelectronic devices.     

High Q-Factor and Low Threshold Continuous-Wave Near-Infrared Lasing with Quasi-2D Perovskites

Quasi-2D perovskites have shown great potential in achieving solution-processed electrically pumped laser diodes due to their multiple-quantum-well structure, which induces a carrier cascade process that can significantly enhance population inversion. However, continuous-wave (CW) optically pumped lasing has yet to be achieved with near-infrared (NIR) quasi-2D perovskites due to the challenges in obtaining high-quality quasi-2D films with suitable phase distribution and morphology. This study regulates the crystallization of a NIR quasi-2D perovskite ((NMA)₂FA_n−1Pb_nI_3n+1) using an 18-crown-6 additive, resulting in a compact and smooth film with a largely improved carrier cascade efficiency. The amplified spontaneous emission threshold of the film is reduced from 47.2 to 35.9 µJ cm⁻². Furthermore, by combining the film with a high-quality distributed feedback grating, this study successfully realizes a CW NIR laser of 809 nm at 110 K, with a high Q-factor of 4794 and a low threshold of 911.6 W cm⁻². These findings provide an important foundation for achieving electrically pumped laser diodes based on the unique quasi-2D perovskites.     

Stereo-Active Lone Pairs Induced Giant Polarization in a 2D Ge-Based Halide Perovskite Antiferroelectric

Antiferroelectrics, characterized by electrically controlled antipolar-polar phase transformation, have attracted tremendous attention as a class of promising electroactive materials for assembling electronic devices. The emerging two-dimensional (2D) halide perovskites with superior compositional diversity offer an ideal platform for exploring electroactive materials, whereas lead-free antiferroelectric counterparts are still scarcely reported. Herein, for the first time, a new lead-free 2D germanium iodide perovskite antiferroelectric (i-BA)₂CsGe₂I₇ ( 1 , i-BA is iso-butylammonium) has been presented, which exhibits a high Curie temperature (T_c) up to 403 K. Remarkably, benefiting from the lone pair stereochemical activity in Ge²⁺ induced large structural distortion and Cs⁺ ion off-center displacement, 1 shows well-defined double P–E hysteresis loops in a wide temperature range with a giant maximum polarization up to 18.8 µC cm⁻², which achieves a new high record among molecular antiferroelectrics. Moreover, under a low external electric field of 22.5 kV cm⁻¹, the antipolar-polar phase transformation in 1 affords a recoverable energy storage density W_rec of 0.27 J cm⁻³ and high storage efficiency up to 79.76%. Such lead-free halide perovskite antiferroelectric with intriguing antiferroelectric behaviors, including high T_c, large polarization and remarkable energy storage properties, is exciting, which provides an alternative candidate for high-performance antiferroelectrics for environmentally friendly electronic devices.     

Giant Optical Anisotropy of Perovskite Nanowire Array Films

Polarizers play a key role in generating polarized light for display, imaging, and data communication, but adoption often suffers from high optical loss. Recently, due to superior optoelectronic properties, halide perovskites have been widely developed for lighting applications; however, highly polarized emission (polarization degree >0.8) has not yet been realized with perovskites. Herein, by incorporating inkjet printing and an anodic aluminum oxide (AAO) confinement strategy, highly ordered perovskite nanowire (NW) arrays are demonstrated for anisotropic optical applications. The optical device based on perovskite NW arrays reveals a high photoluminescence external quantum efficiency of 21.6% and emits highly polarized light with polarization degree up to 0.84. The highly polarized emission from perovskite NW arrays has potential to considerably reduce the optical loss of polarizers, which may attract great interest in developing polarized light sources for next‐generation optoelectronic applications.     

High-Sensitivity Flexible X-Ray Detectors based on Printed Perovskite Inks

The demand for high-energy radiation detection systems combining high sensitivity, low-cost and large-area fabrication has pushed the research on hybrid perovskites as promising materials for X- and γ-photon detection, thanks to their high Z atoms, solution-processability, and high optoelectronic performance. Here, flexible direct X-ray detectors are demonstrated with outstanding real-time detection properties. They are based on printed micrometers-thick films of methylammonium lead triiodide nanocrystals inks, formulated in low boiling point and benign solvents. Record optoelectronic performances, such as high X-ray sensitivity (up to 2270 µC Gy⁻¹ cm⁻²), radiation tolerance over 2.2 Gy of total dose, and fast response time (48 ms) have been achieved by using a simple device architecture and materials processing The functionality under strong bending stress (strain > 10%) and under high X-ray energy (up to 150 keV) has been assessed, opening the way for flexible real-time direct radiation detectors and imagers, operating at low-voltages (bias < 4V) and apt to be fabricated by means of large-area scalable processes.     

Solid Ink Laser Patterning for High-Resolution Information Labels with Supervised Learning Readout

Tagging, tracking, or validation of products are often facilitated by inkjet-printed optical information labels. However, this requires thorough substrate pretreatment, ink optimization, and often lacks in printing precision/resolution. Herein, a printing method based on laser-driven deposition of solid polymer ink that allows for printing on various substrates without pretreatment is demonstrated. Since the deposition process has a precision of <1 µm, it can introduce the concept of sub-positions with overlapping spots. This enables high-resolution fluorescent labels with comparable spot-to-spot distance of down to 15 µm (444,444 spots cm⁻²) and rapid machine learning-supported readout based on low-resolution fluorescence imaging. Furthermore, the defined thickness of the printed polymer ink spots can be used to fabricate multi-channel information labels. Additional information can be stored in different fluorescence channels or in a hidden topography channel of the label that is independent of the fluorescence.     

Metal Halide Perovskite Arrays: From Construction to Optoelectronic Applications

Inorganic semiconductor arrays revolutionize many areas of electronics, optoelectronics with the properties of multifunctionality and large-scale integration. Metal halide perovskites are emerging as candidates for next-generation optoelectronic devices due to their excellent optoelectronic properties, ease of processing, and compatibility with flexible substrates. To date, a series of patterning technologies have been applied to perovskites to realize array configurations and nano/microstructured surfaces to further improve device performances. Herein, various construction methods for perovskite crystal or thin film arrays are summarized. The optoelectronic applications of the perovskite arrays are also discussed, in particular, for photodetectors, light-emitting diodes, lasers, and nanogratings.     

High-Resolution and Stable Ruddlesden–Popper Quasi-2D Perovskite Flexible Photodetectors Arrays for Potential Applications as Optical Image Sensor

The development of an efficient fabrication route to achieve high-resolution perovskite pixel array is key for large-scale flexible image sensor devices. Herein, a high-resolution and stable 10 × 10 flexible PDs array based on formamidinium(FA⁺) and phenylmethylammonium (PMA⁺) quasi-2D (PMA)₂FAPb₂I₇ (n = 2) perovskite is demonstrated by developing SiO₂-assisted hydrophobic and hydrophilic treatment process on polyethylene terephthalate substrate. By introducing Au nanoparticles (Au NPs),  the perovskite film quality is improved and grain boundaries are reduced. The mechanism by which Au NPs upgrade the photoelectric quality of perovskite is mainly revealed by glow discharge-optical emission spectroscopy (GD-OES) and grazing-incidence wide-angle X-ray scattering (GIWAXS). To further improve the photoelectric performance of the devices, a post-treatment strategy with formamidinium chloride (FACl) is used . The optimized flexible PDs arrays show excellent optoelectronic properties with a high responsivity of 4.7 A W⁻¹, a detectivity of 6.3 × 10¹² Jones, and a broad spectral sensitivity. The device also exhibits excellent electrical stability even under severe bending and excellent flexural strength, as well as excellent environmental stability. Finally, the integrated flexible PDs arrays are used as sensor pixels in an imaging system to obtain high-resolution imaging patterns, demonstrating the imaging capability of the PDs arrays.     

Vapor Phase Growth of Centimeter-Sized Band Gap Engineered Cesium Lead Halide Perovskite Single-Crystal Thin Films with Color-tunable Stimulated Emission

Single crystal metal halide perovskites thin films are considered to be a promising optical, optoelectronic materials with extraordinary performance due to their low defect densities. However, it is still difficult to achieve large-scale perovskite single-crystal thin films (SCTFs) with tunable bandgap by vapor-phase deposition method. Herein, the synthesis of CsPbCl_3(1–x)Br_3x SCTFs with centimeter size (1 cm × 1 cm) via vapor-phase deposition is reported. The Br composition of CsPbCl_3(1–x)Br_3x SCTFs can be gradually tuned from x = 0 to x = 1, leading the corresponding bandgap to change from 2.29 to 2.91 eV. Additionally, an low-threshold (≈23.9 µJ cm⁻²) amplified spontaneous emission is achieved based on CsPbCl_3(1–x)Br_3x SCTFs at room temperature, and the wavelength is tuned from 432 to 547 nm by varying the Cl/Br ratio. Importantly, the high-quality CsPbCl_3(1–x)Br_3x SCTFs are ideal optical gain medium with high gain up to 1369.8 ± 101.2 cm⁻¹. This study not only provides a versatile method to fabricate high quality CsPbCl_3(1–x)Br_3x SCTFs with different Cl/Br ratio, but also paves the way for further research of color-tunable perovskite lasing.