Light-emitting Devices Research Articles

Photoluminescence lifetime of perovskites on modified substrates

Lead halide perovskites have gained attention for their potential in optoelectronic applications, including photovoltaics and light-emitting devices, due to their remarkable optical and electronic properties. However, performance of these materials is highly dependent on morphological properties of the underlying substrates. In this study, the effects of substrate modifications on the photoluminescence lifetimes of CsPbBr₃ perovskites deposited on TiO2 substrates that were annealed at various temperatures were investigated. TiO2 substrates were characterized using glancing-angle x-ray diffraction and spectroscopic ellipsometry to assess changes in crystallinity and surface roughness. Time-correlated single photon counting spectroscopy was employed to measure the photoluminescent lifetimes of the perovskites. Scanning electron microscopy and x-ray diffraction were used to determine morphology and crystallinity. Results show a clear relationship between substrate annealing temperature and the photoluminescent lifetime of perovskite microcrystals. Substrates annealed at temperatures below 300 °C exhibited increased surface roughness with increased annealing temperature (22.4 Ȧ at room temperature and 48.05 Ȧ at 300 °C) and correspondingly shorter photoluminescent lifetimes (3.5 ns at room temperature and 0.4 ns at 300 °C) suggesting more rapid charge carrier recombination. In contrast, substrates annealed at 350 °C exhibited the longest lifetimes at 4.19 ns indicating a decrease in trap-mediated nonradiative recombination. Substrates annealed at 400 °C showed a further increase in crystallinity but did not extend the lifetime beyond that seen at 350 °C, suggesting an optimal balance between surface roughness and crystallization. These findings provide insights into the role of morphological substrate modifications in optimizing the optoelectronic properties of perovskite materials.

Electroluminescence in n-type GaAs unipolar nanoLEDs

In this Letter, we report the observation of electroluminescence (EL) at ∼866 nm from n-i-n unipolar (electron-transporting) III-V GaAs nanoLEDs. The devices consist of nanopillars with a top diameter of 166 nm, arranged in a 10 × 10 pillar array. Hole generation through impact ionization and Zener tunneling is achieved by incorporating an AlAs/GaAs/AlAs double-barrier quantum well within the epilayer structure of the n-i-n diode. Time-resolved EL measurements reveal decay lifetimes >300 ps, allowing us to estimate an internal quantum efficiency (IQE) higher than 2% at sub-mA current injection. These results demonstrate the potential for a new, to the best of our knowledge, class of n-type nanoscale light-emitting devices.

Plexciton Photoluminescence in Strongly Coupled 2D Semiconductor-Plasmonic Nanocavity Hybrid.

Strong plasmon-exciton interaction between two-dimensional transition metal dichalcogenides and a plasmonic nanocavity under ambient conditions has been reported extensively. But the suspicion on whether it has reached a true "strong coupling" is always there because the commonly used dark-field scattering spectroscopy shows a larger spectral splitting and the splitting in the photoluminescence spectra is absent. Here, by using a nanobipyramid-over-mirror to enhance the in-plane vacuum field, we achieve spectral Rabi splitting in both scattering and differential reflection spectra and observe a clear photoluminescence emission of the lower plexciton branch. The established nanocavity offers two polarization-dependent gap plasmon resonances to provide excitation and quantum yield enhancement simultaneously, yielding a total photoluminescence enhancement of 2.1 × 104 times. This allows the acquisition of emission spectra from an individual coupled system regardless of the presence of an uncoupled emitting background in the collection area. The sharp tips of the nanobipyramid lead to a large single-exciton coupling strength up to a few meV. Correlated scattering, differential reflection, and photoluminescence spectra reveal the similarity between the scattering and normalized photoluminescence spectra. These correlative measurements on a single coupled system clear up the suspicions of strong plasmon-exciton interactions and will promote the development of light-emitting plexcitonic devices at room temperature.

Heavy Atom as a Molecular Sensor of Electronic Density: The Advanced Dimer-Type Light-Emitting System for NIR Emission.

The approaches to design and control intermolecular interactions for a selective enhancement of specific process(es) are of high interest in technologies using molecular materials. Here, we describe how π-π stacking enables control over the heavy-atom effect and spin-orbit coupling (SOC) through dimerization of an organic emitter in solid media. π-π interactions in a red thermally activated delayed fluorescence (TADF) emitter Ac-CNBPz afford specific types of dimers. In its brominated derivative Ac-CNBPzBr, the vicinity of the Br atom and the electronic density of the dimer involved in a spin-flip transition afford up to 200-fold increase of the SOC, in the most favorable case, attributed to the external heavy-atom effect (EHAE) of the halogen atom. The presence of such dimers in the films of Ac-CNBPzBr provides enhancement of reverse intersystem crossing, and thus, TADF occurs mostly within a few microseconds, up to 20 times faster than in Ac-CNBPz. For this reason, organic light-emitting diodes using Ac-CNBPzBr as an emitter and an assistant dopant show a decreased efficiency roll-off by a factor of 4 and 1.5, respectively. The crucial aspects of the intermolecular electronic interactions between a chromophore system and an HA together with the particularly favorable dimer geometry not only help to understand the nature of the EHAE but also provide guidelines for the molecular design of emitters for all-organic light-emitting devices with enhanced stability.

Circularly Polarized Organic Light-Emitting Diode Based on Device Functional Layer Materials.

Circularly polarized light-emitting devices have found extensive application prospects in 3D displays and optoelectronic information. Among them, circularly polarized organic light-emitting diodes (CP-OLED), as a rising star of circularly polarized light-emitting devices, achieved good research results. However, the preparation of CP-OLED with a high electroluminescence asymmetry factor and high external quantum efficiency is a hot and difficult research topic. At present, the approaches for achieving circularly polarized electroluminescence via CP-OLED are: 1) Using chiral materials as luminescent materials, 2) Utilizing chiral functional materials. This review summarizes recent methodologies used for manufacturing CP-OLED. It focuses on the construction strategies and applications of chiral functional materials (chiral host materials, chiral hole transport materials, and chiral electron transport materials) in CP-OLED. While challenges such as complex chiral design and material interactions persist, advancements in material design and device architecture propel CP-OLED forward. These developments promise to elevate CP-OLED as a focal point in optoelectronic research, facilitating high-performance, circularly polarized luminescence (CPL)-capable devices for practical applications.

Equivalent-circuit modeling of electron-hole recombination in semiconductors and mixed ionic-electronic conductors

The analysis and optimization of solar energy conversion and light-emitting devices can greatly benefit from equivalent circuit models describing their response. However, a general model of electron-hole recombination in semiconductors is currently missing. This study presents equivalent circuit models of radiative and nonradiative electron-hole recombination processes in the small-signal regime based on their linearized analytical treatment. While resistors accurately describe radiative recombination, bipolar transistors represent the general model of nonradiative recombination, and they can be replaced by resistive elements only in special cases. The proposed recombination model is integrated into a transmission-line circuit representation of complete devices that is equivalent to the linearized drift-diffusion equations in one dimension. For mixed conducting devices, such as halide perovskite solar cells, appropriate simplifications of the complete model provide analytical solutions describing the bulk and interfacial polarization effects that influence the small-signal electrostatics, recombination currents, and overall impedance. The resulting analysis facilitates data interpretation and is relevant to a wide range of materials and devices used for solar energy conversion as well as other optoelectronic and photoelectrochemical applications. Published by the American Physical Society 2025

Making Mo(0) a Competitive Alternative to Ir(III) in Phosphors and Photocatalysts.

Iridium is used in commercial light-emitting devices and in photocatalysis but is among the rarest stable chemical elements. Therefore, replacing iridium(III) in photoactive molecular complexes with abundant metals is of great interest. First-row transition metals generally tend to yield poorer luminescence behavior, and it remains difficult to obtain excited states with redox properties that exceed those of noble-metal-based photocatalysts. Here, we overcome these challenges with a nonprecious second-row transition metal. Tailored coordination spheres for molybdenum(0) lead to photoluminescence quantum yields that rival those of iridium(III) complexes and photochemical reduction reactions not normally achievable with iridium(III) become possible. These developments open new perspectives for replacing noble metals in lighting applications with Earth-abundant metals and for advancing metal-based photocatalysis beyond current limits.

Core–Shell Composite GaP Nanoparticles with Efficient Electroluminescent Properties

Gallium-based light-emitting diodes (LEDs), including AlGaInP and GaN, have become the most widely used light-emitting devices in modern scientific research and practical applications. However, structures like carrier injection layers, active layers, and quantum well layers ensure the high luminescence efficiency of LEDs but also limit their applications at the micro- and nanoscale. Although the next generation of micrometer-scale light-emitting diodes (Micro-LEDs) has alleviated these issues to some extent, challenges such as edge effects and etching damage caused by size reduction lead to lower luminous efficiency and shorter lifetimes. Inspired by LED structure, this study designed and synthesized core–shell composite GaP:Zn/GaP/GaInP and GaP:Te/GaP nanoparticles using a thermal injection method. After high-temperature annealing, these composite materials demonstrated efficient electroluminescent performance under electric field excitation through band-edge transitions and the ZnGa-OP recombination mechanism. Experimental results show that the GaP:Zn/GaP/GaInP-GaP:Te/GaP composite samples with doping concentrations of 15%Zn-8%Te, a core–shell precursor ratio of 1:1:1, and reaction times of 1 h:20 min:20 min exhibit the best electron–hole injection efficiency and bound-recombination efficiency. Under excitation by an external electric field, they demonstrated optimal electroluminescence performance, with a relative luminous intensity of 11,109.21 at 600 nm, approximately 15 times higher than that of the initial condition samples. In addition, this study systematically investigated the structure, morphology, and elemental composition of the composite materials using various characterization techniques, including X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). These GaP-doped nanoparticles with a core–shell composite structure, inspired by LED design, exhibited outstanding electroluminescent performance, providing new insights into the development of novel micro- and nanoscale electroluminescent materials.

Bipolar Solid-Solution Hosts for Efficient Crystalline Organic Light-Emitting Diodes.

Crystalline organic semiconductors, recognized for their highly ordered structures and high carrier mobility, have emerged as a focal point in the field of high-performance optoelectronic devices. Nevertheless, the intrinsic unipolar properties, characterized by imbalanced hole and electron transport capabilities, have continuously represented a significant challenge in the advancement of high-performance crystalline thin-film organic light-emitting diodes (C-OLEDs). Here, a bipolar solid-solution thin film with a maintained crystal structure has been fabricated using 2-(4-(9H-carbazol-9-yl)phenyl)-1(3,5-difluorophenyl)-1H-phenanthro [9,10-d]imidazole (2FPPICz) and 4-(1-(3,5-difluorophenyl)-1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl)-N,N-diphenylaniline (2Fn) via a weak epitaxial growth (WEG) process, exhibiting nearly equivalent hole and electron mobilities (10-2-10-1 cm2 V-1 s-1). We have demonstrated a blue C-OLED that achieves high efficiency while maintaining low-efficiency roll-off, employing the bipolar solid-solution thin film as the crystalline host matrix and 4,4'-bis[2-(4-(N,N-diphenylamino)phenyl)vinyl]biphenyl (DPAVBi) as the doped emitter. This device achieves a maximum external quantum efficiency (EQE) of 4.6% with Commission Internationale de L'Eclairage (CIE) coordinates lying around (0.15, 0.22). Among crystalline light-emitting devices utilizing carrier-balanced transport, this EQE stands as one of the highest recorded values. Notable advancements include enhanced photon emission capabilities, optimized driving voltage (4.0 V @ 1000 cd m-2), and a lower series resistance Joule heat loss ratio (11.8% @ 1000 cd m-2). This research marks a significant stride in modulating the inherent electrical properties of crystalline host materials, offering a novel and efficacious strategy for the advancement of high-performance crystalline OLEDs.

The doped-free structure is used to realize organic light-emitting devices with low blue harm, low color temperature and high color rendering index

The doped-free structure is used to realize organic light-emitting devices with low blue harm, low color temperature and high color rendering index

High contrast ratio light-emitting liquid crystal device based on AIEE dyes

In this paper, we have fabricated a light-emitting liquid crystal device (LELCD) with high contrast ratio (CR) using aggregation-induced emission enhancement (AIEE) dye, a photoluminescent (PL) material connected with liquid crystals (LCs) on weak surface anchoring boundaries. This LELCD can continually vary the PL intensity by controlling the direction of AIEE-dye molecules following the orientation of the LCs responding to the strength of the electric field. In order to check the effect of surface anchoring on the CR of this device, we used both horizontal and vertical alignment layers. For the horizontal alignment layer, we investigated the effect of CR at three different types of alignment layers with different anchoring energy and at different rubbing conditions for each alignment layer. For the vertical alignment layer, changes in the CR according to the rubbing strength were observed. Additionally, our study was conducted on the impact of LELCD cell thickness variations on the CR. Consequently, we achieved CR of about 30:1 at LELCD with cell thickness of 10 µm using polymethyl methacrylate as a horizontal alignment layer with weak surface anchoring boundary. This is the best result to date for CR of display devices using AIEE. We anticipate that the results of this study can be applied to optical devices and various other applications.

Determining Parameters of Metal-Halide Perovskites Using Photoluminescence with Bayesian Inference

In this work, we demonstrate that time-resolved photoluminescence data of metal halide perovskites can be effectively evaluated by combining Bayesian inference with a Markov-chain Monte-Carlo algorithm and a physical model. This approach enables us to infer a high number of parameters that govern the performance of metal halide perovskite-based devices, alongside the probability distributions of those parameters, as well as correlations among all parameters. Via studying a set of halfstacks, comprising electron- and hole-transport materials contacting perovskite thin films, we determine surface recombination velocities at these interfaces with high precision. From the probability distributions of all inferred parameters, we can simulate intensity-dependent photoluminescence quantum efficiency and compare it to experimental data. Finally, we estimate mobility values for vertical charge-carrier transport, which is perpendicular to the plane of the substrate, for all samples using our approach. Since this mobility estimation is derived from charge-carrier diffusion over the length scale of the film thickness and in the vertical direction, it is highly relevant for transport in photovoltaic and light-emitting devices. Our approach of coupling spectroscopic measurements with advanced computational analysis will help speed up scientific research in the field of optoelectronic materials and devices and exemplifies how carefully constructed computational algorithms can derive valuable plurality of information from simple datasets. We expect that our approach can be expanded to a variety of other analysis techniques and that our method will be applicable to other semiconductors. Published by the American Physical Society 2025

Superfluorescence and nonlinear optical response of CH3NH3PbBr3-based mesostructures: applications to amplified spontaneous emission and ultrafast lasers.

Metal halide perovskites have unique luminescent properties that make them an attractive alternative for high quality light-emitting devices. However, the poor stability of perovskites with many defects and the long cycle time for the preparation of perovskite nanocomposites have hindered their production and application. Here, we prepared the perovskite mesostructures by embedding MAPbBr3 nanocrystals in the mesopores on the surface of silica nanospheres and mixing the nanospheres with silver nanowires and poly(methyl methacrylate) (PMMA), and further explored their optical properties. The perovskite mesostructures exhibited superfluorescence (SF) under 785 nm laser excitation and the decay time was as short as 0.59 ps using a double exponential decay fit. The optical nonlinearity of these perovskite mesostructures under two-photon excitation was investigated by the Z-scanning technique. The samples exhibited both two-photon absorption (TPA) and saturation absorption (SA) with nonlinear absorption coefficients β ranging approximately 0.15 to 0.89 cm/GW corresponding to the TPA, and a saturation intensity of about 0.026 GW/cm2 was determined. In addition, the quality of the perovskite mesostructures was shown to be significantly improved, including an increase in radiative efficiency and an extension of the optical gain lifetime. The samples were excited by a two-photon femtosecond laser pump at room temperature and atmospheric pressure, and the laser peak appeared at 540.1 nm with a low amplified spontaneous emission (ASE) threshold of 0.52 mJ/cm2. Moreover, the perovskite mesostructures have been added to the fiber laser system as a saturable absorber, and the Q-switched pulse is generated at the wavelength of 1.5 µm. Our work effectively demonstrates that perovskite mesostructured materials can be functionalized for photonic devices, paving the way for further exploration of complex, functional and practical perovskite.

Fluorescence Properties of Novel Multiresonant Indolocarbazole Derivatives for Deep-Blue OLEDs from Multiscale Computer Modelling.

Multiresonant fluorophores are a novel class of organic luminophores with a narrow emission spectrum. They can yield organic light-emitting devices, e.g., OLEDs, with high colour purity. In this study, we applied DFT and multiscale modelling to predict the electronic and optical properties of several novel derivatives of indolocarbazole pSFIAc, which had recently shown a high potential in deep-blue OLEDs. We found that the addition of phenyls to a certain position of the pSFIAc core can considerably increase the fluorescent rate, leaving other properties (HOMO, LUMO, lowest excited singlet and lowest triplet states' energies) virtually unaffected. This can improve the efficiency and stability of deep-blue organic light-emitting devices; the suggested phenyl-substituted indolocarbazoles have been shown to be compatible with two popular anthracene-based hosts. On the contrary, the addition of phenyls to another positions of the core is detrimental for optoelectronic properties. QM/MM and QM/EFP calculations yielded negligible inhomogeneous broadening of the emission spectrum of the studied luminophores when embedded as dopants in anthracene-based hosts, predicting high colour purity of the corresponding devices. On the basis of the obtained results, we selected one novel multiresonant indolocarbazole derivative that is most promising for organic light-emitting devices. We anticipate the revealed structure-property relationships will facilitate the rational design of efficient materials for organic (opto)electronics.

High-Temperature Optoelectronic Transport Behavior of n-TiO2 Nanoball-Stick/p-Lightly Boron-Doped Diamond Heterojunction.

The n-TiO2 nanoballs-sticks (TiO2 NBSs) were successfully deposited on p-lightly boron-doped diamond (LBDD) substrates by the hydrothermal method. The temperature-dependent optoelectronic properties and carrier transport behavior of the n-TiO2 NBS/p-LBDD heterojunction were investigated. The photoluminescence (PL) of the heterojunction detected four distinct emission peaks at 402 nm, 410 nm, 429 nm, and 456 nm that have the potential to be applied in white-green light-emitting devices. The results of the I-V characteristic of the heterojunction exhibited excellent rectification characteristics and good thermal stability at all temperatures (RT-200 °C). The forward bias current increases gradually with the increase in external temperature. The temperature of 150 °C is ideal for the heterojunction to exhibit the best electrical performance with minimum turn-on voltage (0.4 V), the highest forward bias current (0.295 A ± 0.103 mA), and the largest rectification ratio (16.39 ± 0.005). It is transformed into a backward diode at 200 °C, which is attributed to a large number of carriers tunneling from the valence band (VB) of TiO2 to the conduction band (CB) of LBDD, forming an obvious reverse rectification effect. The carrier tunneling mechanism at different temperatures and voltages is analyzed in detail based on the schematic energy band structure and semiconductor theoretical model.

Blue Electroluminescent Carbon Dots Derived from Victorian Lignite.

Carbon dots (CDs) derived from natural products have attracted considerable interest as eco-friendly materials with a wide range of applications, such as bioimaging, sensors, catalysis, and solar energy harvesting. Among these applications, electroluminescence (EL) is particularly desirable for light-emitting devices in display and lighting technologies. Typically, EL devices incorporating CDs feature a layered structure, where CDs function as the central emissive layer, flanked by charge transport layers and electrodes. Under an applied external bias, electrons and holes are introduced into the active CD layer, resulting in EL through radiative recombination. However, achieving EL with natural product-derived CDs has remained elusive due to challenges such as production difficulties and quenching in the solid state. In this study, we present, for the first time, the successful realization of EL from natural product-derived CDs, synthesized using Victorian lignite through a straightforward single-step pyrolysis method. The CDs demonstrated excellent dispersibility in solvents, allowing them to serve as an emissive layer in light-emitting diodes (LEDs). This was achieved by spin-coating a concentrated CD solution between the organic hole and electron transport layers on a glass substrate coated with indium tin oxide. Remarkably, the CDs retained their dispersibility and emissive efficiency both in solution (toluene) and after film formation. Moreover, the resulting LED demonstrated blue EL, characterized by a peak emission at 460 nm and a maximum luminance of 100.4 cd/m2. This luminance is comparable to that achieved with CDs synthesized from conventional chemical carbon sources. These results highlight the promise of natural product-derived CDs as sustainable and eco-friendly materials for use in LED applications.

Enhancing Optical Properties of Lead-Free Cs2NaBiCl6 Nanocrystals via Indium Alloying.

This study presents the synthesis and characterization of Cs2NaBiCl6 nanocrystals (NCs) doped with varying concentrations of In3+ to improve their luminescent properties. Utilizing a colloidal solution method, we systematically varied the In3+ concentration to identify the optimal alloying level for enhancing the photoluminescence (PL) properties of the Cs2NaBiCl6 NCs. Structural analysis confirmed that the In-alloyed NCs maintained high crystallinity and a uniform cubic shape. The optical properties were significantly improved with the In3+ alloying, reaching a peak photoluminescence quantum yield (PLQY) at an In/(Bi + In) ratio of 0.7. This optimal alloying concentration led to a nearly 2-fold increase in the average exciton lifetime to 6.98 ns, indicating an enhanced self-trapped exciton generation and improved radiative recombination efficiency. Temperature-dependent PL spectra revealed that the Cs2NaBi0.30In0.70Cl6 NCs exhibited a higher exciton binding energy and longitudinal optical phonon energy compared to the undoped NCs, suggesting superior thermal stability and reduced nonradiative recombination pathways. Density functional theory (DFT) calculations were employed to elucidate the charge density distribution, highlighting significant charge localization at the In-Cl and Bi-Cl bonds, which is attributed to the enhanced charge mobility in the alloyed NCs. The findings of this research not only address the limitations of current lead-free perovskites but also establish In-alloyed Cs2NaBiCl6 NCs as a promising candidate for blue light-emitting devices. This work advances the development of environmentally friendly optoelectronic technologies.

Electrically pumped random lasing from light-emitting devices based on ZnO films: Suppression of randomness

We report on the significant suppression of randomness of the electrically pumped random lasing (RL) from ZnO-based metal-insulator-semiconductor (MIS) structured light-emitting devices (LEDs), by means of adopting the appropriately patterned hydrothermal ZnO films featuring large crystal grains as the light-emitting layer. The hydrothermal ZnO films on silicon substrates, with the crystal grains sized over 500 nm, were firstly patterned into a number of square blocks separated by streets by using laser direct writing photolithography. Based on such patterned ZnO films, the MIS (Au/SiO<sub>2</sub>/ZnO) structured LEDs on silicon were prepared. Under the same injection current, the LED with the patterned ZnO film exhibited much fewer RL modes than the counterpart with the non-patterned ZnO film and, moreover, the former exhibited ever-fewer RL modes with the decreasing block size. Besides, the wavelength of the strongest RL modes from the LED with the patterned ZnO film fluctuated in a much narrower range with respect to that from the LED with the non-patterned ZnO film. It is worth mentioning that the LED with the patterned hydrothermal ZnO film can even be pumped into the single-mode RL under the desirable conditions such as low injection current and small patterned blocks. Moreover, the comparative investigation indicated that the LED with the large-grain hydrothermal ZnO film exhibited the smaller RL threshold current than the counterpart with the small-grain sputtered ZnO film, and, the former had fewer RL modes and a higher output lasing power than the latter under the same injection current. As for the physical mechanism underlying the aforementioned results, it is analyzed as follows. Regarding the LED with the patterned ZnO film, on one hand, due to limited numbers of crystal grains and grain boundaries within a single block, the multiple optical scattering is remarkably suppressed. Then, the paths through which the net optical gain and therefore the lasing action can be achieved via the multiple optical scattering are much fewer than those in the case of the non-patterned ZnO film. On the other hand, due to optical gain competition among different RL modes occurring within the limited space of a single block, the RL modes with significant spatial overlap could not lase simultaneously. For the two-fold reasons as mentioned above, the LED exhibits ever-fewer RL modes with decreasing size of blocks. Moreover, the inter-block optical coupling enables the optical gain competition among different RL modes to be more violent within a single block, leading to further reduction of RL modes.

Surface modification unleashes light emitting applications of APbX3 perovskite nanocrystals.

Engineering the surface of metal halide perovskite nanocrystals (MHPNCs) is crucial for optimizing their optical properties, repairing surface defects, enhancing quantum yield, and ensuring long-term stability. These enhancements make surface-engineered MHPNCs ideal for applications in light-emitting devices (LEDs), displays, lasers, and photodetectors, contributing to energy efficiency. This article delves into an introduction to MHPNCs, their structure and types, particularly the ABX3 type (where A represents monovalent organic/inorganic cations, B represents divalent metal ions mainly Pb metal, and X represents halide ions), synthesis methods, unique optical properties, surface modification techniques using various agents (particularly inorganic molecules/materials, organic molecules, polymers, and biomolecules) to tune optical properties and applications in the aforementioned light-emitting technologies, challenges and opportunities, including advantages and disadvantages of surface-modified APbX3 MHPNCs, and a summary and future outlook. This article explores surface modification strategies to improve the optical performance of MHPNCs and aims to inspire advancements in light emitting applications. Importantly, the challenges and opportunities section of this article will illuminate the path to overcoming obstacles, providing invaluable insights for researchers in this field. This in-depth review explores the surface engineering of MHPNCs for light-emitting applications, highlighting their notable advantages and addressing ongoing challenges. By delving deep into various surface modification strategies, this article aims to revolutionize MHPNC-based light-emitting applications, setting a new benchmark in the field. This paves the way for revolutionary advancements, maximizing the capabilities of surface-engineered MHPNCs and heralding a transformative era in precise light-emitting research.

Modulating hot carrier relaxation and trapping dynamics in lead halide perovskite nanoplatelets by surface passivation.

Two-dimensional (2D) lead halide perovskite (LHP) nanoplatelets (NPLs) have recently emerged as promising materials for solar cells and light-emitting devices. The reduction of LHP dimensions introduces an abundance of surface defects, which can strongly influence the photophysical properties of these materials. However, an insightful understanding of the effect of surface defects on hot carrier (HC) relaxation, one of the important properties of LHP NPLs, is still inadequate. Herein, the HC relaxation and trapping dynamics in pristine and surface passivated two-layer (2L) CsPbBr3 NPLs have been investigated by using time-resolved spectroscopy. The results reveal that surface defects can trap HCs directly before they relax to the band edge, which accounts for the absence of the hot-phonon bottleneck (HPB) effect in LHP NPLs. After healing surface defects with a passivation agent, the relaxation time of HCs is extended from ∼73 to ∼130 fs in 2L CsPbBr3 NPLs, indicating that the channel of HCs trapped by the surface defects can be effectively blocked. Accordingly, the HPB effect is activated in surface-passivated CsPbBr3 NPLs. The finding of surface defect-related HC relaxation dynamics is important for guiding the development of high-performance LHP NPL devices related to HCs through surface defect engineering.