High Photoluminescence Quantum Yield Research Articles

Cu‐Catalyzed Oxidative Tandem Coupling and Cyclization of 2‐Aminonaphthalenes to Synthesize Dibenzo[c, g]carbazoles

AbstractA Cu(II) complex with a bipyridyl ligand bearing a Brønsted acid was used to catalyze the tandem oxidative coupling and cyclization of 2‐aminonaphthalenes to give N‐substituted‐dibenzo[c,g]carbazoles. The incorporation of an appended acidic moiety to the ligand was found to be key to the selective formation of dibenzocarbazoles over 2,2’‐diamino‐1,1’‐binaphthalene (BINAM), which is known as an irreversible byproduct. This highly efficient method yields a wide array of dibenzo[c,g]carbazoles featuring diverse functional groups as well as electronic properties. The selected dibenzo[c,g]carbazoles exhibited high photoluminescence quantum yields of up to 100 % and are promising chromophores for advanced materials.

Thickness and Doping Density Influence of a High-Voltage Inorganic Perovskite Solar Cell: A SCAPS 1-D Simulation Study

Recently, all inorganic perovskite solar cells have triggered great attention thanks to the rising performance during their development in solid state photovoltaics showing enhanced characteristics, such as: good stability, high photoluminescence quantum yield, tunable size, and morphology. In this work, a high open-circuit voltage solar cell based on all-inorganic perovskite through SCAPS simulator program is presented by analysing electron transport layer (ETL), perovskite layer, hole transport layer (HTL) thickness and doping density from a FTO/TiO2/CsPbBr3/Spiro-OMeTAD/Au structure were modified to observe its influence on solar cell performance. Therefore, simulation results show that a thicker ETL hinders carrier transport towards the FTO layer due to larger distance which leads to higher recombination rate, reducing carrier’s lifetime. Albeit high doping density values in ETL enhances the overall solar cell performance. As for the absorber layer, while its thickness increases, carrier collection rate decreases due to recombination impacting Voc, which results from thickness increase. Based on the results, solar cell efficiency improvement is attributed to the built-in electric field as absorber layer doping density increases. While HTL thickness has minimum impact on the solar cell output, doping density enhances device parameters significantly. Summarising the results obtained from thickness and doping density simulations, the optimal solar cell operation was obtained at 10 nm, 600 nm, and 100 nm layer thickness as well as 1020 cm-3, 1016 cm-3, and 1020 cm-3 doping density (TiO2, CsPbBr3 and Spiro-OMeTAD). Results from three different sources, collected from literature, were used to compare, and fitting them along with simulation results.

Progress on perovskite quantum dots and light-emitting diodes

Abstract. Perovskite quantum dots have become a popular material for the development of new high-efficiency light-emitting diodes (LED) because of their high photoluminescence quantum yield, adjustable luminescence spectrum, narrow spectral width, high defect tolerance and unique quantum limit effect. We review the recent progress based on LED of different types of perovskite quantum dots. First, the properties, existing problems and applications of fully inorganic perovskite quantum dots are introduced. Subsequently, both organic and inorganic perovskites and their applications are discussed, and several methods to improve the LED efficiency of perovskite quantum dots are explored. Finally, this paper analyzes the current challenges of LED of perovskite quantum dots, such as instability and toxicity, and its application prospect in the field of high-efficiency display and lighting is discussed. That is, the EQE of LED based on perovskite quantum dots has increased to more than 20% in four years, and the service life has been extended to tens of hours. This review provides useful insights for the development of more efficient and safer perovskite quantum dot luminescence devices.

Simple synthesis of AgInS2/ZnS core/shell quantum dots with wide tunable emission wavelength for white light-emitting diodes

Phosphor with efficient and broad range emission is necessary for lighting applications. I-III-VI group quantum dots (QDs) have the advantages of non-toxic composition and large adjustable spectrum range, and have potential applications in the field of lighting. However, the efficient luminescence of these QDs at shorter wavelengths still needs further study, which is crucial for the development of high color rendering index white light LED devices (WLEDs). In this work, wide visible range emitting AgInS2/ZnS QDs with broad band and high luminous efficiency were obtained by altering the Ag/In ratios and Zn2+ inter-diffusion with cation of AgInS2. Photo-luminescent (PL) wavelength range of the obtained core-shell structured AgInS2/ZnS extended from 703 nm to 524 nm with high PL quantum yield (QY) and stability. The champion device based on the optimized AgInS2/ZnS QDs exhibits warm white light (correlated color temperature = 3652 K) characteristics with high color rendering index (CRI Ra) of 92.85 while maintaining excellent color stability under different driving currents. These properties are far superior to those of WLEDs with YAG phosphor.

Simple‐Structure and Anti‐Quenching Deep‐Blue Multi‐Resonance TADF Emitters Enable High‐Efficiency OLEDs with BT.2020 Blue Gamut

AbstractDeveloping highly efficient pure‐blue organic light‐emitting diodes (OLEDs) that meet the stringent BT.2020 standard by using multi‐resonance thermally activated delayed fluorescence (MR‐TADF) materials has long been a formidable challenge. In this study, a strategy is demonstrated for high‐performance blue MR‐TADF emitters by gradually decorating the MR framework with alkyl groups, and subsequently introducing a diarylamino group at the para‐position of boron atom. The proof‐of‐concept molecule, IPrBN‐mCP, exhibits a narrowband deep‐blue emission peaking at 452 nm, with a very narrow full‐width at half maximum (FWHM) of 19 nm in solution, and a remarkably high photoluminescence quantum yield (PLQY) approaching unity in doped films. As a result, OLEDs based on IPrBN‐mCP achieve not only a high maximum external quantum efficiency (EQEmax) of 33.4% but also ultrapure blue emission with a Commission Internationale de L'Eclairage (CIE) y value of 0.046, fully satisfying the BT.2020 blue standard. This represents the first OLED example fully meeting the rigorous color requirements of the BT.2020 blue standard while simultaneously achieving an EQE exceeding 30%.

Chiral Rare-Earth (Ce, Eu) Metal Halides with Bright Circularly Polarized Luminescence.

Chiral metal halide materials are emerging chiroptical materials that are easy to synthesize and have a wide tunability. Rare-earth (RE) metals are desirable components to be incorporated in the hybrid regime; however, they are typically difficult to handle for solution-based halide chemistry. Here, we report two new examples of chiral RE metal halides with Ce(III) and Eu(III) with chiral alkanolammonium cations (R/S-3-hydroxyquinuclidium). These compounds crystallize in the non-centrosymmetric space group R3, where their mirror-like symmetric circular dichroism (CD) and circularly polarized luminescence (CPL) further witness the chiral nature. The superior emission properties, including the high photoluminescence quantum yield of the Ce-based materials (84-90%) and Eu-based materials (27-29%), have led to distinct and sharp symmetrical CPL in the ultraviolet and visible regions, with dissymmetry factors (glum) of ∼2 × 10-3 and ∼4 × 10-3, respectively. This work has established and expanded the materials space for chiral RE metal halides and demonstrated their potential for chiroptical and spintronic applications.

Loading Dyes into Chiral Cd/Zn‐Metal–Organic Frameworks for Efficient Full‐Color Circularly Polarized Luminescence

AbstractHost‐guest chemistry of chiral metal‐organic frameworks (MOFs) has endowed them with circularly polarized luminescence (CPL), it is still limited for MOFs to systematically tune full‐color CPL emissions and sizes. This work directionally assembles the chiral ligands, metal sites and organic dyes to prepare a series of crystalline enantiomeric D/L‐Cd/Zn‐n MOFs (n=1~5, representing the adding amount of dyes), where D/L‐Cd/Zn with the formula of Cd2(D/L–Cam)2(TPyPE) and Zn2(D/L–Cam)2(TPyPE) (D/L‐Cam=D/L‐camphoric acid, TPyPE=4,4’,4’’,4’’’‐(1,2‐henediidenetetra‐4,1‐phenylene)tetrakis[pyridine]) were used as the chiral platforms. The framework‐dye‐enabled emission and through‐space chirality transfer facilitate D/L‐Cd/Zn‐n bright full‐color CPL activity. The ideal yellow CPL of D‐Cd‐5 and D‐Zn‐4, with |glum| as 4.9 × 10−3 and 1.3×10−3 and relatively high photoluminescence quantum yield of 40.79 % and 45.40 %, are further assembled into a white CPL light‐emitting diode. The crystal sizes of D/L‐Cd/Zn‐n were found to be strongly correlated to the types and additional amounts of organic dyes, that the positive organic dyes allow for the preparation of > 7 mm bulks and negative dyes account for sub‐20 μm particles. This work opens a new avenue to fabricate full‐color emissive CPL composites and provides a potentially universal method for controlling the size of optical platforms.

Stable Organic‐Inorganic Hybrid Sb(III) Halide Scintillator for Nonplanar Ultra‐Flexible X‐Ray Imaging

AbstractFlexible scintillator screens with excellent stability and low detection limits are crucial for X‐ray imaging applications. 0D organic metal halide materials have emerged as a strong contender in the scintillator fields, owing to their excellent optical characteristics and simple maneuverability. Herein, high‐quality and large quantities of C38H36P2Sb2Cl8 single crystals are synthesized through a simple solution approach. The prepared single crystals with dimer‐structure [Sb2Cl8]2− exhibit yellow emission with a near‐unity high photoluminescence quantum yield (PLQY) of 99.8%, and possess an exceptional light yield of 41300 photons MeV−1, and a detection limit as low as 45.6 nGyair s−1. On this basis, a large‐size and ultra‐flexible C38H36P2Sb2Cl8 scintillator utilized for X‐ray imaging is prepared by template assembled method, demonstrating a high spatial resolution of 8.15 lp mm−1. The prepared ultra‐flexible scintillator screen can achieve excellent X‐ray imaging even after multiple bending and stretching, which can also provide clear non‐planar X‐ray imaging for irregular objects. In addition, the scintillator shows excellent stability in light, heat, X‐ray irradiation, and water. These results not only expand the optoelectronic application field of organic‐inorganic hybrid antimony halides but also promote the rapid development of efficient ultra‐flexible scintillators.

Introducing electron-rich thiophene bridges in hot exciton emitter for efficient non-Doped near-infrared OLEDs with low turn-on voltages

The development of near-infrared (NIR) luminescent materials featuring high photoluminescence quantum yield (ΦPL) at aggregated state is of great significance for achieving highly efficient non-doped organic light-emitting diodes (OLEDs) but remains formidable challenging. Herein, a design strategy of introducing electron-rich thiophene groups between electron acceptor and donor is proposed for efficient NIR luminescent materials, and a tailored D-π-A-π-D type emitter, namely, 4,4′-(benzo[c][1,2,5]thiadiazole-4,7-diylbis(thiophene-5,2-diyl))bis(N,N-diphenylaniline) (TPATBT), is designed and prepared. The photophysical investigation and density functional theory analysis disclose that TPATBT is a hot exciton emitter feature with hybridized local and charge-transfer state. Additionally, TPATBT demonstrates aggregation-induced emission characteristic, prefers high thermal stability, and exhibits a strong emission at 692 nm with a decent ΦPL of 20 % in the neat film. The non-doped device based on TPATBT neat film presents a maximum external quantum efficiency (ηext,max) of 1.22 % with electroluminescence peak at 718n m. Moreover, we first try to use interlayer sensitization to sensitize non-doped devices, which achieves better ηext,max of 1.34 % with low turn-on voltage of 3.2 V. The proposed molecular design strategy in this work is promising for exploring robust NIR luminescent materials for high-performance OLEDs.

Reducing Non-Radiative Energy Losses in Non-fullerene Organic Solar Cells.

With the rapid advancement of non-fullerene acceptors (NFAs), the power conversion efficiency (PCE) of organic solar cells (OSCs) has surpassed the 20% threshold, highlighting their considerable potential as next-generation energy conversion devices. In comparison to inorganic or perovskite solar cells, the open-circuit voltage (Voc) of OSCs is constrained by substantial non-radiative energy losses (ΔEnr), leading to values notably below those anticipated by the Shockley-Queisser limit. In OSCs, non-radiative energy losses are intimately associated with the electroluminescent quantum efficiency (EQEEL) of charge transfer states, which is in turn directly affected by the photoluminescence quantum yield (PLQY) of acceptor materials. Consequently, enhancing the PLQY of low-bandgap acceptor materials has emerged as a pivotal strategy to effectively mitigate ΔEnr. This review article delves into the intrinsic correlation between molecular structure and PLQY from the vantage point of acceptor material design. It further explores methodologies for designing acceptor materials exhibiting high PLQY, with the ultimate goal of realizing OSCs that combine high efficiency with minimal ΔEnr.

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.

Calcination-Controlled Synthesis of Carbon Dots@MgF2 Composites with Yellow, White, and Ultraviolet-Blue Thermally Activated Delayed Fluorescence for Multilevel Information Encryption.

It is attractive but challenging to develop carbon dot (CD) based materials with tunable thermally activated delayed fluorescence (TADF), especially in the long wavelength region. Here, by simply calcinating the mixture of m-phenylenediamine and MgF2 at 300-500 °C, a series of CDs@MgF2 composites exhibiting yellow, white, and ultraviolet-blue TADF with high photoluminescence quantum yields of up to 37.6% are prepared. Photophysical studies reveal that the yellow TADF with long lifetimes of 810-1106ms originates from the surface emission centers of CDs, while the ultraviolet-blue TADF with short lifetimes of 266-379ms is related to the carbon core emission centers. The combination of yellow and ultraviolet-blue TADF in a single material triggers dynamic afterglow with time-dependent colors from white to yellow. The MgF2 matrix offers multiple confinement of CDs through a rigid network, strong space constraint, and robust covalent/hydrogen bonding, thus preventing the triplet excitations from non-radiative transitions. The electron-withdrawing fluorine atoms induce substantial spin-orbit coupling and reduce the singlet-triplet energy gap, consequently facilitating the reverse intersystem crossing to enhance TADF efficiency. Importantly, the CDs@MgF2 composites possess outstanding optical stability against water, organic solvents, strong acids, bases, and oxidants. The fascinating TADF features enable the successful demonstration of multilevel information encryption using CDs@MgF2.

Clar's Aromatic π‐Sextet Rule for the Construction of Red Multiple Resonance Emitter

AbstractDespite the proliferation of multiple resonance (MR) materials in the blue to green spectral ranges, red MR emitters remain scarce in the literature, an area that certainly warrants attention for future applications. Here, through a clever application of classic Clar's aromatic π‐sextet rule, we triumphantly constructed the first red MR emitter by substituting the conventional benzene ring core with anthracene (fewer π‐sextets). Theoretical studies indicate that the quantity of π‐sextets ultimately determines the optical band gap of a molecule, rather than the number of fused benzene rings. Benefiting from the high photoluminescence quantum yield of ~94 % and horizontal dipole ratio of ~90 %, the corresponding narrowband red (luminescence wavelength: 608 nm) organic light‐emitting diode shows a high external quantum efficiency of 27.3 %, with only a slight decrease of 3.7 % at an elevated luminance level of 100,000 cd/m2.

Reversible Structural Phase Transitions in Zero‐Dimensional Cu(I)‐Based Metal Halides for Dynamically Tunable Emissions

AbstractExploring structural phase transitions and luminescence mechanisms in zero‐dimensional (0D) metal halides poses significant challenges, that are crucial for unlocking the full potential of tunable optical properties and diversifying their functional capabilities. Herein, we have designed two inter‐transformable 0D Cu(I)‐based metal halides, namely (C19H18P)2CuI3 and (C19H18P)2Cu4I6, through distinct synthesis conditions utilizing identical reactants. Their optical properties and luminescence mechanisms were systematically elucidated by experiments combined with density functional theory calculations. The bright cyan‐fluorescent (C19H18P)2CuI3 with high photoluminescence quantum yield (PLQY) of 77 % is attributed to the self‐trapped exciton emission. Differently, the broad yellow‐orange fluorescence of (C19H18P)2Cu4I6 displays a remarkable PLQY of 83 %. Its luminescence mechanism is mainly attributed to the combined effects of metal/halide‐to‐ligand charge transfer and cluster‐centered charge transfer, which effects stem from the strong Cu−Cu bonding interactions in the (Cu4I6)2− clusters. Moreover, (C19H18P)2CuI3 and (C19H18P)2Cu4I6 exhibit reversible structural phase transitions. The elucidation of the phase transitions mechanism has paved the way for an unforgeable anti‐counterfeiting system. This system dynamically shifts between cyan and yellow‐orange fluorescence, triggered by the phase transitions, bolstering security and authenticity. This work enriches the luminescence theory of 0D metal halides, offering novel strategies for optical property modulation and fostering optical applications.

Anion regulation for surface passivation enables ultrahigh-stability perovskite nanocrystals.

All-inorganic perovskite CsPbBr3 nanocrystals (NCs) display high photoluminescence quantum yield and narrow emission, which show great potential application in optoelectronic devices. However, the poor environment stability of NCs will hinder their practical application. Herein, a series of ionic liquids with different anions (BF4-, Br-, and NO3-) were used as a sole capping ligand to synthesize NCs. Among the three samples, 1-hexadecyl-3-methylimidazolium tetrafluoroborate ([C16MIM]BF4) capped NCs have the highest stability in light, thermal, and water, possibly attributing to the in situ passivation of bromine vacancy via pseudohalogen BF4- and tight binding of ionic liquid ligands and lead atoms. In addition, green-emission [C16MIM]BF4 NCs were used to assemble a white light-emitting diode device, and it possessed a wide National Television System Committee color gamut of 124.5% and a stable emission peak at high driving currents of 380 mA. This work paves the way for resurfacing perovskite NCs with ultrahigh stability, thereby driving the perovskite NC display industry closer to real-world application.

Recent Advances in Thermally Activated Delayed Fluorescence-Based Organic Afterglow Materials.

Thermally activated delayed fluorescence (TADF)-based materials are attracting widespread attention for different applications owing to their ability of harvesting both singlet and triplet excitons without noble metals in their structures. As compared to the conventional fluorescence and room-temperature phosphorescence pathways, TADF originates from the reverse intersystem crossing process from the excited triplet state (T1) to the singlet state (S1). Therefore, TADF emitters enabling activated and long lifetime T1 excitons are potential candidates for generating long-lived afterglow emission, an effect that can still be observed for a while by the naked eye after the removal of the excitation light source. Recently, TADF-based organic afterglow materials featuring high photoluminescence quantum yields and long lifetimes above 100 ms under ambient conditions, have emerged for advanced information security, high-contrast biological imaging, optoelectronic devices, and intelligent sensors, whereas the related systematic review is still lacking. Herein, the recent progress in TADF-based organic afterglow materials is summarized and an overview of the photophysical mechanism, design strategies, and the performances for relevant applications is given. In addition, the challenge and perspective of this area are given at the end of the review.

Enhanced Stability of Melt-Processable Organic-Inorganic Hybrid Manganese Halides for X-Ray Imaging.

Mn-based metal halides scintillators with high photoluminescence quantum yield (PLQY) have recently emerged as promising large-size candidates for X-ray imaging but still remains as difficult challenge in stability and high processing temperatures. Here, three manganese halides are designed by introducing branched chains into organic cations and extending the carbon chains, namely (i-PrTPP)2MnBr4, (i-BuTPP)2MnBr4 and (i-AmTPP)2MnBr4, successfully lowered the melting point of manganese halides to 120.2 °C. Three materials show striking light yields of 59000, 40000, and 52000 photons MeV-1, respectively. The lowest detection limits are 42.30, 50.92, and 45.71 nGy s-1, respectively. Meanwhile, compared to their counterparts with linear carbon chains, the introduction of branched chains has significantly enhanced the stability of the scintillators in the glass state. A transparent glass has been prepared using a melt-quenching method, which exhibited 80% transmittance at 400-700nm. The glass is utilized for X-ray imaging, achieving a high spatial resolution up to 46.6 lp mm-1. This result provides a new approach to enhancing the performance of such scintillator materials.

Preparation and identification of a fluorescent probe with CsPbBr3perovskite quantum dots and CD44v6 specific peptide for gastric cancer imaging.

Since the sensitivity and accuracy of traditional detection for early gastric cancer diagnosis are still insufficient, it is significant to continuously optimize the optical molecular imaging detection technology based on an endoscopic platform. The signal intensity and stability of traditional chemical fluorescent dyes are low, which hinders the clinical application of molecular imaging detection technology. This work developed a probe based on perovskite quantum dots (PQDs) and peptide ligands. By utilizing CsPbBr3perovskite PQDs modified by azithromycin (AZI), combined with the specific polypeptide ligand of CD44v6, a gastric cancer biomarker, the perovskite-based probe (AZI-PQDs probe) which can specifically identify gastric cancer tumor was prepared. Owing to the high photoluminescence quantum yield of CsPbBr3PQDs, the naked eye can observe the imaging under the excitation of the hand-held ultraviolet light source. AZI-PQDs probe can accurately identify gastric cancer cells, tissues, and xenograft models with experiments ofex vivoandin vivofluorescence imaging detection. It also exhibited low toxicity and immunogenicity, indicating the safety of the probe. This work provides a probe combined with cancer specificity and a reliable fluorescent signal that has the potential for application in gastric cancer optical molecular imaging.

Double-Shell Encapsulation of Lead-Free Tin Halide Perovskite for Self-Powered Smart Windows.

Luminescent solar concentrators (LSC) have the potential application in building integrated photovoltaic (BIPV). 0D tin-based perovskites are a promising embedding phosphor in LSC due to the large Stokes shift and high photoluminescence quantum yield. But the instability and uncontrollable crystal growth are severe limiting their successful utilization in device fabrication. To tackle these issues, double-shell encapsulated configurations are presented, soft ligands of hypophosphorous acid and hard-shell of hollow mesoporous silica are simultaneously suppressing the oxidation of Sn2+ and restricting crystal growth within nano-matrix. The stable phosphor is subsequently embedded into LSC for harvesting solar energy and the resulting output power efficiently drives the combined electrochromic glass under natural light. These fabricated devices also offer the self-adaptable switch on/off functionality to regulate light absorption with variable solar irradiation intensity in real time. This approach is anticipated to open new avenues for utilizing lead-free perovskite nanomaterials in self-powered smart windows for BIPV.

Advancements in Eco‐Friendly Colloidal Quantum Dots and their Application in Light Emitting Diodes: Achieving Bright and Color‐Pure Emission for Displays

AbstractSolution‐processable colloidal quantum dots (QDs) are regarded as promising light emitters for next‐generation displays owing to their high photoluminescence quantum yield (PLQY) and broad color tunability. Even though cadmium (Cd)‐based QDs and relevant electroluminescent light‐emitting diodes (LEDs) progressed rapidly, their commercial deployment remains prohibited due to potential environmental concerns. In this review, recent advances in synthesizing eco‐friendly, bright, and color‐pure emitting QDs including InP, ZnSeTe, and AgInGaS2 (AIGS) QDs toward high‐performing LEDs are presented. In particular, the synthetic strategies such as regulating the composition, core/shell structure, and surface ligands of QDs for enhancing the PLQY and reducing the spectral bandwidth are comprehensively discussed. Moreover, various techniques to obtain high‐performance QDs‐based LEDs (QLEDs) involving device architecture and interface engineering as well as modification in electron and hole transport layers are overviewed. Finally, the existing challenges and outlook regarding the optimization of QD's synthesis and optical properties for boosted QLEDs device performance are put forward to enable prospective advanced displays.