High PLQY Research Articles

Dual-phase Cs4PbBr6/CsPbBr3 perovskite quantum dot borosilicate glass for WLED applications

Owing to inherent structural instability of perovskite quantum dots, they are instability in humid environments and high temperatures conditions. To address this issue, a simple, environmentally friendly glass encapsulated technology is used to protect the perovskite quantum dots. Meanwhile, the dual-phase perovskite structure realized by phase transition engineering can further increase the stability of perovskite quantum dots. In this study, 3D CsPbBr3/0D Cs4PbBr6 dual-phase coexisting perovskite quantum dot glass powders were synthesized through melt quenching and subsequent crystallization induction of thermal treatment and water molecule, respectively. Results showed that compared with thermal treatment induction, perovskite QDs glass powders by water molecules induction exhibited a high PLQY of 24.7 % with a central wavelength of 519 nm and displayed excellent environmental stability. By combining green fluorescence from 3D CsPbBr3/0D Cs4PbBr6 QDs glass powders and red fluorescence powders (CaAlSiN3:Eu), a WLED device with an impressive EQE of 20.6 % was created, indicating a promising application potential.

Mg2+‐Doped Cesium Copper Halide for Bright Electroluminescent White Light‐Emitting Diodes

AbstractLead‐based perovskite nanocrystals (NCs) as one of the most promising materials in the fields of display and lighting, have outstanding optical performance and simple solution preparation process. However, the toxicity of lead and poor stability limit their commercialization. Meanwhile, as a key component of display and lighting, white light‐emitting diodes (WLEDs) still faces challenges such as low luminance and complex preparation process. A method is proposed for preparing nontoxic and stable Cs3Cu2I5 NCs by doping Mg2+ ions, achieved broadband blue light emission with a high PLQY of 96.2% and excellent thermal cycling stability and air stability. Then, the Mg2+ ions doped Cs3Cu2I5 NCs are used as emissive layer, while the 1,3,5‐Tri (m‐pyridine‐3‐ylphenyl) benzene (TmPyPb) is selected as electron transport layer to interact with Cs3Cu2I5 thin films for the formation of Cu‐I complex with broadband yellow light emission. This approach obviated the need for multi‐layer sedimentary emission layers, resulting in WLEDs featuring a high color rendering index (CRI) of 91, a peak external quantum efficiency (EQE) of 0.71% and maximum luminance of 2116 cd m−2 that is the highest values of lead‐free perovskite WLEDs at present. Therefore, Cs3Cu2I5 NCs have good application prospects in WLEDs.

Experimental and theoretical investigations on the photophysical and electronic properties of new synthesized organic small molecule for optoelectronic applications

In the present work, we report the chemical synthesis of a newly π-conjugated system using a Wittig reaction. The chemical structure of the synthesized molecule named 1,4-Bis((E)-2-(1-methyl-pyrrol-2-yl)vinyl)benzene (BisPyrBz) was supported by Fourier transform infrared spectroscopy. The optical properties were investigated first using optical absorption (O.A) and steady-state photoluminescence (PLs) tools. Otherwise, transient photoluminescence (TRPL) and quantum yield measurements (PLQY) are present in a diluted solution and condensed state. Theoretical investigations on the synthesized molecule were performed using density functional density (DFT). Experimental and theoretical data show the formation of a planar π-conjugated system. The obtained molecule presents a blue emission with high PLQY, at around 35 % in the solution state. The emission is red-shifted to the green color, with a drastic decrease of the PLQY to around 1 % indicating a possible aggregation-caused quenching behavior in the condensed state. The use of the synthesized BisPyrBz as a π linker in a newly designed A-π-D small molecule permits to obtain a newly near-infrared absorbing material with a weak energy gap Eg = ELUMO − EHOMO, which is at around 1.93 eV, and a weak optical band gap which is estimated to be 1.67 eV.

Single-Molecule White Circularly Polarized Photoluminescence and Electroluminescence from Dual-Emission Enantiomers.

The strategy of integrating conformational isomerization donors and chiral acceptors in a single molecule was proposed to construct white circularly polarized luminescence (WCPL) materials in this work. Consequently, a pair of dual-emission enantiomers, namely (R/S)-DO-PTZ, were designed and synthesized, which displayed white emission with blue and yellow dual-emission bands in solution and solid films with Commission Internationale de l'Eclairage (CIE) coordinates of (0.30, 0.33) and (0.33, 0.35), respectively. Meanwhile, (R/S)-DO-PTZ exhibited a high PLQY of up to 67 % in doped films and clear mirror-image WCPL signals with a |glum| value of 3.0×10-3. Moreover, white circularly polarized electroluminescence (WCPEL) based on organic light-emitting diodes (OLEDs) with (R/S)-DO-PTZ as emitters were also achieved with CIE coordinates of (0.32, 0.37) and EQEmax of 4.7 %, representing the state-of-the-art level of white OLEDs based on single-molecule purely organic emitters. By optimizing the device structure, warm WCPEL devices were further obtained with a |gEL| value of 2.8×10-3, CIE coordinates of (0.37, 0.48) and EQEmax of up to 15.6 %. To our knowledge, this is the first report of CP-WOLEDs based on single-molecule purely organic emitters.

Chiral Co-Assembly with Narrowband Multi-Resonance Characteristics for High-Performance Circularly Polarized Organic Light-Emitting Diodes.

A promising kind of ternary chiral co-assemblies with high PLQY, large dissymmetry factor (glum), and narrowband multi-resonance characteristics are achieved by codoped-thermal annealing treatments of achiral luminescent polymer F8BT, chiral inducers R/S-5011, and achiral FRET acceptor DBN-ICZ. The optimized co-assemblies (F8BT)0.9-(R/S-5011)0.1-(DBN-ICZ)0.005 display narrowband yellow emission with full-width half maximum (FWHM) of 37 nm, PLQY of 79%, and intense CPL signals with |glum| of up to 0.26. Meaningfully, solution-processed CP-OLEDs by using those ternary chiral co-assemblies as emitting layer are successfully fabricated, which display yellow circularly polarized electroluminescence (CPEL) with EQEmax of 4.6% and gEL of up to 0.16. The corresponding Q-factor could reach up to 7.36 × 10-3, which is the highest of all the reported CP-OLEDs. Moreover, the devices also exhibit excellent comprehensive device performance with low Von of 7.0 V, high Lmax of about 25000 cd m-2, extremely low efficiency roll-off with EQE of 4.3% at 10000 cd m-2, as well as narrowband EL with FWHM of only 39 nm. The proposed ternary co-assembly strategy in fabricating CP-OLED provides the possibility to achieve high comprehensive device performance such as balancing high EQE and large gEL value, as well as narrowband emission, high brightness and low efficiency roll-off simultaneously.

53‐3: Distinguished Paper: Developing Pure Green Polycyclo‐Heteraborin MR‐TADF Scaffolds for Efficient, Stable Narrowband OLEDs

We developed two symmetrical green MR‐TADF emitters, BpIC‐DPA and BpIC‐Cz, based on the rigidification and regulation of molecular orbitals (MO) engineering strategies. Both emitters exhibited pure green emission with narrow FWHM below 25 nm and high PLQY over 84%. Among the fabricated OLEDs, BpIC‐Cz‐device showed maximum external quantum efficiency (EQEmax) of 25.7% with alleviated efficiency roll‐off characteristics (EQE1000nits = 24.3%) and longer device‐lifetime (LT90) of 291 h at the initial luminance of 1000 nits.

Near‐unity broadband emissive hybrid manganese bromides as highly‐efficient radiation scintillators

AbstractZero‐dimensional (0D) hybrid manganese halides have gained wide attention for the various crystal structures, excellent optical performance and scintillation properties compared with 3D lead halide perovskite nanocrystals. In this work, a new family of 0D hybrid manganese halides of A2MnBr4 (A = BzTPP, Br‐BzTPP, and F‐BzTPP) based on discrete [MnBr4]2− tetrahedral units is reported as highly efficient lead‐free scintillators. Excited by UV or blue light, these hybrids emit bright green light originating from the d–d transition of Mn2+ with near‐unity PLQY (99.5%). Significantly, high PLQY and low self‐absorption render extraordinary radioluminescence properties with the highest light yield of 80,100 photons MeV−1, which reached the climax of present hybrid manganese halides and surpassed most commercial scintillators. The radioluminescence intensity features a linear response to X‐ray doses with a detection limit of 30 nGyair s−1, far lower than the requirement of medical diagnostic (5.5 µGyair s−1). X‐ray imaging demonstrates ultrahigh spatial resolution of 14.06 lp mm−1 and short afterglow of 0.3 ms showcasing promising application prospects in radiography. Overall, we demonstrated new hybrid manganese halides as promising scintillators for advanced applications in X‐ray imaging with multiple superiorities of nontoxicity, facile‐assembly process, high irradiation light yield, excellent resolution, and stability.

Developing sensitized green fluorescence for efficient, stable narrowband organic light emitting diodes

AbstractThe thermally activated delayed fluorescence (TADF) or phosphorescence‐sensitized organic light‐emitting diodes (OLEDs) based on multi‐resonance TADF (MR‐TADF) emitters are greatly studied to develop an effective narrowband emitting system for wide color gamut display applications. However, developing pure green OLEDs to meet BT2020 and NTSC requirements is challenging. In this study, we investigated the TADF and phosphorescence‐sensitized OLEDs based on two green MR‐TADF final emitters, namely, BpIC‐DPA and BpIC‐Cz. The unique molecular structure of these emitters resulted in a pure green emission with narrow full width at half‐maximum (FWHM) and high PLQY in both solution and solid state. Notably, under optimal conditions, the BpIC‐Cz‐based OLEDs demonstrated a maximum external quantum efficiency (EQEmax) of 25.7% with alleviated efficiency roll‐off characteristics even at high luminescence (EQE5000 nits = 22.6%). The corresponding CIE coordinates are almost at the level of BT2020 and NTSC green‐color industrial standards. Additionally, the BpIC‐Cz‐based device displayed remarkable stability as seen by a noticeably longer device lifetime (LT90) of 25.3 h at a high initial luminance of 5000 nits.

High-brightness green InP-based QLEDs enabled by in-situ passivating core surface with zinc myristate

The performance of red InP and blue ZnTeSe-based quantum dots (QDs) and corresponding QD light emitting diodes (QLEDs) has already been improved significantly, whose external quantum efficiencies (EQEs) and luminances have exceeded 20% and 80 000 cd m−2, respectively. However, the inferior performance of the green InP-based device hinders the commercialization of full-color Cd-free QLED technology. The ease of oxidation of the highly reactive InP cores leads to high non-radiative recombination and poor photoluminescence quantum yield (PL QY) of the InP-based core/shell QDs, limiting the performance of the relevant QLEDs. Here, we proposed a fluoride-free synthesis strategy to in-situ passivate the InP cores, in which zinc myristate reacted with phosphine dangling bonds to form Zn–P protective layer and protect InP cores from the water and oxygen in the environment. The resultant InP/ZnSe/ZnS core/shell QDs demonstrated a high PL QY of 91%. The corresponding green-emitting electroluminescence devices exhibited a maximum EQE of 12.74%, along with a luminance of over 175 000 cd m−2 and a long T50@100 cd m−2 lifetime of over 20 000 h.

Ca2+ induced highly fluorescent CsPb(Br/Cl)3 perovskite quantum dots via fast Anion-Exchange & Cation-Doping Inter-Promotion strategy for efficient deep-blue light-emitting diodes

Despite the impressive development of perovskite light-emitting diodes (PeLEDs), it is still challenging to achieve high-efficiency deep-blue PeLEDs using colloid perovskite quantum dots (PQDs). The efficiency of PQDs with a wavelength below 460 nm, which meets the requirements for deep-blue emission in the Telecommunication Union UHD television standard (ITU REC. 2020), lags far behind those of their sky-blue counterparts. To address this issue, a novel strategy of fast anion-exchange & cation-doping inter-promotion (FAECDIP) is proposed to achieve highly efficient deep-blue PQDs by introducing CaBr2 into the CsPbCl3 PQDs. Owing to the presence of Ca2+, the speed of ion exchange is increased, driven by the smaller cation, Ca2+, improving the preparation efficiency. Additionally, Ca2+ was doped on the surface of PQDs. Based on studies of fast anion-exchange and theoretical calculations, Ca2+ improves the optical performance by decreasing the number of traps and increasing the crystallinity of target PQDs, facilitating the stability of treated films and PeLEDs by enhancing the formation energy of halogen vacancies. Here, a high PLQY of 80.3 % CaBr2-induced CsPb(Cl/Br)3 deep-blue PQDs (∼446 nm) was achieved. The correspondent PeLEDs (∼447 nm) achieved a superior EQE of 5.88 %, which is the state-of-the-art among the reported deep-blue PeLEDs. Our strategy provides a potential route to achieve deep-blue PeLEDs, which differs from the previous tedious-complex methods.

Heteroions Radii Matching Produced Intensely Luminescent Bismuth-Ag2S Nanocrystals for through-Skull NIR-II Imaging of Orthotopic Glioma.

Heteroions doped Ag2S nanocrystals (NCs) exhibiting enhanced near-infrared-II emission (NIR-II) hold great promise for glioma diagnosis. Nevertheless, current doped Ag2S NCs paradoxically improved properties via toxic dopants, and the blood-brain barrier (BBB) constitutes another challenge for orthotopic glioma imaging. Thus, it is urgent to develop biofriendly high-bright Ag2S NCs with active BBB-penetration for glioma-targeted imaging. Herein, bismuth (Bi) was screened to obtain Bi-Ag2S NCs with high absolute PLQY (∼13.3%) for its matched ionic-radius (1.03 Å) with Ag+. The Bi-Ag2S NCs exhibited a higher luminance and deeper penetration (5-6 mm) than clinical indocyanine green. Upon conjugation with lactoferrin, the NCs acquired BBB-crossing and glioma-targeting abilities. Time-dependent NIR-II-imaging demonstrated their effective accumulation in glioma with skull/scalp intact after intravenous injection. Moreover, the toxic-metal-free NCs exhibited negligible toxicity and great biocompatibility. The success of leveraging the ion-radii comparison may unlock the full potential of doped-Ag2S NCs in bioimaging and inspire the development of various doped NIR-II NCs.

Efficient Near‐Infrared Emitting Halide Scintillators with Mitigating External Light Crosstalk for Portable X‐Ray Imaging

AbstractPortable X‐ray imaging technology plays a crucial role in enabling prompt diagnosis and treatment outdoors. Nevertheless, the persistent challenge of external optical signal crosstalk poses a significant bottleneck to its advancement. Herein, a solution utilizing near‐infrared (NIR) light to effectively mitigate optical crosstalk is proposed, thereby demonstrating the feasibility of portable X‐ray imaging even under ambient light. A series of rare earth ions doped Cs2AgxNa1‐xInyBi1‐yCl6 halide scintillators is reported, which possess bright broadband visible and NIR emissions. Taking Cs2Ag0.6Na0.4In0.95Bi0.05Cl6: 5%Tm as an example, it shows decent thermal quenching resistance, high PLQY up to 76.3%, and compelling light yield up to 33500 photons MeV−1. The highly efficient NIR emission is attributed to the energy transfer from the optimized host to lanthanide ions. A flexible scintillation film is prepared by mixing poly(dimethyl‐siloxane) with Cs2Ag0.6Na0.4In0.95Bi0.05Cl6: 5%Tm powder, realizing a low X‐ray detection limit of 55.2 nGyair/s and a high spatial resolution of 11.2 lp mm−1. Due to the efficient NIR emission, the scintillation film enables clear X‐ray imaging under bright LED illumination with the simple addition of filters, avoiding the necessity of a complex imaging apparatus. This work sheds light on NIR emissive scintillator for rapid outdoor response and portable X‐ray imaging.

Preparing the In-doped lead-free Cs3Cu2I5 perovskite scintillator by a co-firing technique for its application in high-resolution X-ray imaging

The perovskite scintillators have been extensively studied recently for their merits of tunable emission spectra and simple preparation processes. However, the practical applications of perovskite scintillator-based X-ray image sensor are still impeded by inadequate radioluminescence, poor environmental stability, and low imaging resolution. Herein, we demonstrate a scalable co-firing method to fabricate high-quality lead-free Cs3Cu2I5 perovskite scintillator and an Indium (In)-doping strategy is introduced to enhance its radioluminescence performance at the same time. The In-doped Cs3Cu2I5 obtains a high PLQY of 77.9% and a relative light output of 53372 ph/MeV, which are 0.34 and 1.08 times higher than those of the undoped counterpart, respectively. The X-ray detection limit of the In:Cs3Cu2I5 can reach 150.55 nGyair/s, 36.53 times lower than the requirement for X-ray medical diagnosis. The synthesized scintillator also shows superior stability under continuous high dose X-ray irradiation of 6800 μGyair/s for 120 minutes, maintaining 95% of its initial radioluminescence intensity. Furthermore, a large-area (300 cm2) flexible perovskite scintillator film is prepared, which owns a much competitive resolution of 10 lp/mm and less distortion in X-ray imaging. This work provides a practical path for the wide application of perovskite scintillator in the field of X-ray detection and imaging in near future.

Alkylammonium Halides for Phase Regulation and Luminescence Modulation of Cesium Copper Iodide Nanocrystals for Light-Emitting Diodes.

All-inorganic cesium copper halide nanocrystals have attracted extensive attention due to their cost-effectiveness, low toxicity, and rich luminescence properties. However, controlling the synthesis of these nanocrystals to achieve a precise composition and high luminous efficiency remains a challenge that limits their future application. Herein, we report the effect of oleylammonium iodide on the synthesis of copper halide nanocrystals to control the composition and phase and modulate their photoluminescence (PL) quantum yields (QYs). For CsCu2I3, the PL peak is centered at 560 nm with a PLQY of 47.3%, while the PL peak of Cs3Cu2I5 is located at 440 nm with an unprecedently high PLQY of 95.3%. Furthermore, the intermediate-state CsCu2I3/Cs3Cu2I5 heterostructure shows white light emission with a PLQY of 66.4%, chromaticity coordinates of (0.3176, 0.3306), a high color rendering index (CRI) of 90, and a correlated color temperature (CCT) of 6234 K, indicating that it is promising for single-component white-light-emitting applications. The nanocrystals reported in this study have excellent luminescence properties, low toxicity, and superior stability, so they are more suitable for future light-emitting applications.

Cover Image

The cover image shows the ligand mediated anion exchange (LMAE) process from CsPbBr3 QDs to CsPbI3 QDs. The incorporation of N‐Acetyl‐L‐cysteine creates more halogen vacancies in CsPbBr3 QDs, which provides sufficient adsorption sites for I‐ ions, leading to the acceleration of anion exchange. Benefiting from the synergistic‐LMAE process, high PLQY of 97% and remarkable stability of CsPbI3 QDs are obtained. image

One Stone, Two Birds: High-Brightness Aggregation-Induced Emission Photosensitizers for Super-Resolution Imaging and Photodynamic Therapy.

Most aggregation-induced emission (AIE) luminogens exhibit high brightness, excellent photostability, and good biocompatibility, but these AIE-active agents, which kill two birds with one stone to result in applications in both stimulated emission depletion (STED) super-resolution imaging and photodynamic therapy (PDT), have not been reported yet but are urgently needed. To meet the requirements of STED nanoscopy and PDT, D-A-π-A-D type DTPABT-HP is designed by tuning conjugated π spacers. It exhibits red-shifted emission, high PLQY of 32.04%, and impressive 1O2 generation (9.24 fold compared to RB) in nanoparticles (NPs). Then, DTPABT-HP NPs are applied in cell imaging via STED nanoscopy, especially visualizing the dynamic changes of lysosomes in the PDT process at ultrahigh resolution. After that, in vivo PDT was also conducted by DTPABT-HP NPs, resulting in significantly inhibited tumor growth, with an inhibition rate of 86%. The work here is beneficial to the design of multifunctional agents and the deep understanding of their phototheranostic mechanism in biological research.

High‐Performance Ternary Organic Solar Cells with Enhanced Luminescence Efficiency and Miscibility Enabled by Two Compatible Acceptors

AbstractThe ternary strategy has proven to be an effective method for improving the efficiency of organic solar cells (OSCs). However, designing and selecting the third component still pose challenges. In this study, this issue is addressed by focusing on the PBDB‐T:Y18‐F binary system and introducing a new, strong luminescent, asymmetric small‐molecule acceptor (SMA) called L8‐CBIC‐Cl, which shares a similar skeleton with Y18‐F. The similarity in molecular framework facilitates good compatibility between the two acceptors, resulting in the formation of an alloy‐like acceptor phase. Furthermore, the norbornenyl‐modified end group in L8‐CBIC‐Cl contributes to its strong luminescent properties, which in turn leads to a low non‐radiative energy loss and a high open‐circuit voltage. Consequently, the PBDB‐T:L8‐CBIC‐Cl:Y18‐F based ternary devices realize a high power conversion efficiency (PCE) up to 17.01%, which is higher than PBDB‐T:Y18‐F device (14.49%). Importantly, L8‐CBIC‐Cl exhibits a good universality as a guest acceptor in other three binary systems (D18:Y6, D18:BTP‐eC9‐4F, and D18:L8‐BO). The D18:L8‐BO:L8‐CBIC‐Cl device shows an impressive efficiency of 19%. The work demonstrates that employing SMA with a high PLQY and better miscibility with host acceptor as the third component has a great potential for developing high‐efficiency ternary OSCs.

Engineering of Multidimensional Core-Shell Perovskite Precursors to Obtain Superior Luminescence and Incorporating in Luminescent Solar Concentrators

The luminescence feature of perovskite NPs with high PLQY directs them to lighting and display applications. 2D A2MAn−1PbnBr3n+1 (n=1−6) perovskites with A as octylammonium and benzylammonium cations are synthesized by the LARP method, in which the highest PL emission is attained to the n=6 sample with benzylamine cation. XRD results reveal the appearance of diffraction peaks related to 3D perovskites with increasing n value. Mixing 3D perovskites with 2D ones leads to the formation of core-shell MAPbBr3−A2MAn−1PbnBr3n+1 (n=1−6) nanostructures, confirmed by TEM images and optical properties. Incorporation of Zn to core-shell perovskites improves the PL intensity and induces higher crystallinity. A blue shift in absorption and emission spectra of Zn-doped perovskites is observed. The highest PLQY (94%) is attributed to the Zn-doped core-shell perovskite with n=6 among the all-synthesized samples. Luminescent solar concentrators with thicknesses of 2 mm and 5 mm are fabricated with benzylamine-based perovskites, because of their greater PLQY versus octylamine-based perovskites. The performance of LSC devices is boosted for the LSC with 5 mm thickness. The relative PCE obtained for the core-shell perovskite-based LSC with thickness of 5 mm reaches to almost 60%.

Rashba Spin Splitting Limiting the Application of 2D Halide Perovskites for UV-Emitting Devices.

Layered lead halide perovskites have attracted much attention as promising materials for a new generation of optoelectronic devices. To make progress in applications, a full understanding of the basic properties is essential. Here, we study 2D-layered (BA)2PbX4 by using different halide anions (X = I, Br, and Cl) along with quantum confinement. The obtained cell parameter evolution, supported by experimental measurements and theoretical calculations, indicates strong lattice distortions of the metal halide octahedra, breaking the local inversion symmetry in (BA)2PbCl4, which strongly correlates with a pronounced Rashba spin-splitting effect. Optical measurements reveal strong photoluminescence quenching and a drastic reduction in the PL quantum yield in this larger band gap compound. We suggest that these optical results are closely related to the appearance of the Rashba effect due to the existence of a local electric dipole. The results obtained in ab initio calculations showed that the (BA)2PbCl4 possesses electrical polarization of 0.13 μC/cm2 and spin-splitting energy of about 40 meV. Our work establishes that local octahedra distortions induce Rashba spin splitting, which explains why obtaining UV-emitting materials with high PLQY is a big challenge.

A highly Mn2+-doped narrowband green phosphor toward wide color-gamut display applications

The highly doped phosphor La0.827Al11.9O19.09:Mn2+ exhibits intense green emission with a narrow FWHM, high PL QY and excellent thermal stability, which confer great potential for wide-color gamut LCD backlight applications.