Improving Buried Interface Contact by Bidentate Anchoring for Inverted Perovskite Solar Cells.

Nickel oxide (NiOx) is a promising hole transport layer (HTL) to fabricate efficient and large-scale inverted perovskite solar cells (PSCs) due to its low cost and superior chemical stability. However, inverted PSCs based on NiOx are still lagging behind that of other HTL because of the poor quality of buried interface contact. Herein, a bidentate ligand, 4,6-bis (diphenylphosphino) phenoxazine (2DPP), is used to regulate the NiOx surface and perovskite buried interface. The diphosphine Lewis base in the 2DPP molecule can coordinate both with NiOx and lead ions at NiOx/perovskite interface, leading to high-quality perovskite films with minimized defects. It is found that the inverted PSCs with 2DPP-modified buried interface exhibit double advantages of being both fast charge extraction and reduced nonradiative recombination, which is a combination of multiple factors including favorable energetic alignment, improved interface contact and strong binding between NiOx/2DPP and perovskite. The optimal PSC based on 2DPP modification yields a champion power conversion efficiency (PCE) of 21.9%. The unencapsulated PSC maintains above 75% of its initial PCE in the air with a relative humidity (RH) of 30-40% for 1000 h.

Current status of liver transplantation for human immunodeficiency virus-infected patients in mainland China.

According to the report from the Chinese Center for Disease Control and Prevention, the prevalence of human immunodeficiency virus (HIV) infection exceeded 1.2 million individuals by the year 2022, with an annual increase of about 80000 cases. The overall prevalence of hepatitis B surface antigen among individuals co-infected with HIV reached 13.7%, almost twice the rate of the general population in China. In addition to the well-documented susceptibility to opportunistic infections and new malignancies, HIV infected patients frequently experience liver-related organ damage, with the liver and kidneys being the most commonly affected. This often leads to the development of end-stage liver and kidney diseases. Therefore, organ transplantation has emerged as an important part of active treatment for HIV infected patients. However, the curative effect is not satisfactory. HIV infection has been considered a contraindication for organ transplantation. Until the emergence of highly active anti-retroviral therapy in 1996, the once intractable replication of retrovirus was effectively inhibited. With prolonged survival, the failure of important organs has become the main cause of death among HIV patients. Therefore, transplant centers worldwide have resumed exploration of organ transplantation for HIV-infected individuals and reached a positive conclusion. This study provides an overview of the current landscape of HIV-positive patients receiving liver transplantation (LT) in mainland China. To date, our transplant center has conducted LT for eight end-stage liver disease patients co-infected with HIV, and all but one, who died two months postoperatively due to sepsis and progressive multi-organ failure, have survived. Comparative analysis with hepatitis B virus-infected patients during the same period revealed no statistically significant differences in acute rejection reactions, cytomegalovirus infection, bacteremia, pulmonary infections, acute kidney injury, new-onset cancers, or vascular and biliary complications.

Realizing highly efficient deep-blue organic light-emitting diodes towards Rec.2020 chromaticity by restricting the vibration of the molecular framework.

Deep-blue organic light-emitting diodes (OLEDs) with narrow emission spectra and high efficiency, meeting the Rec.2020 standard, hold significant promise in the realm of 4K/8K ultrahigh-definition displays. However, the development of light-emitting materials exhibiting both narrowband emission and high efficiency, particularly in the realm of deep-blue thermally activated delayed fluorescence (TADF), confronts substantial challenges. Herein, a novel deep-blue TADF emitter, named BOC-PSi, was designed by integrating a rigid B-heterotriangulene acceptor (A) with a rigid phenazasiline donor (D). The replacement of a sp3 carbon atom with a sp3 silicon atom in the D moiety helps to restrict the low-frequency bending vibration throughout the entire D-A molecular backbone, while concurrently accelerating the multi-channel reverse intersystem crossing (RISC) processes. Notably, OLEDs using the BOC-PSi emitter exhibit exceptional performance, with a high maximum external quantum efficiency (EQEmax) approaching 20%, and a superior color purity closely aligning with the Rec.2020 blue standard.

Extended Conjugation Strategy Enabling Red-Shifted and Efficient Emission of Orange-Red Thermally Activated Delayed Fluorescence Materials.

In account of the energy gap law, the development of efficient narrow-band gap thermally activated delayed fluorescence (TADF) materials remains a major challenge for the application of organic light-emitting diodes (OLEDs). The orange-red TADF materials are commonly designed with either large π-conjugated systems or strong intramolecular donor-acceptor (D-A) interactions for red-shift emission and small singlet-triplet energy gap (ΔEST). There are rare reports on the simultaneous incorporation of these two strategies on the same material systems. Herein, two orange-red emitters named 1P2D-BP and 2P2D-DQ have been designed by extending the conjugation degree of the center acceptor DQ and increasing the number distribution of the peripheral donor PXZ units, respectively. The emission peak of 1P2D-BP is red-shifted to 615 nm compared to 580 nm for 2P2D-DQ, revealing the pronounced effect of the conjugation extension on the emission band gap. In addition, the distorted molecular structure yields a small ΔEST of 0.02 eV, favoring the acquisition of a high exciton utilization through an efficient reverse intersystem crossing process. As a result, orange-red OLEDs with both 1P2D-BP and 2P2D-DQ have achieved an external quantum efficiency (EQE) of more than 17%. In addition, the efficient white OLED based on 1P2D-BP is realized through precise exciton assignment and energy transport modulation, showing an EQE of 23.6% and a color rendering index of 82. The present work provides an important reference for the design of high-efficiency narrow-band gap materials in the field of solid-state lighting.

Synchronous Regulation Strategy of Pyrrolidinium Thiocyanate Enables Efficient Perovskite Solar Cells and Self-Powered Photodetectors.

Developing inventive approaches to control crystallization and suppress trap defects in perovskite films is crucial for achieving efficient perovskite photovoltaics. Here, a synchronous regulation strategy is developed that involves the infusion of a zwitterionic ionic liquid additive, pyrrolidinium thiocyanate (PySCN), into the perovskite precursor to optimize the subsequent crystallization and defects. PySCN modification not only orchestrates the crystallization process but also deftly addresses trap defects in perovskite films. Within this, SCN- compensates for positively charged defects, while Py+ plays the role of passivating negatively charged defects. Based on the vacuum flash evaporation without anti-solvent, the air-processed perovskite solar cells (PSCs) with PySCN modification can achieve an extraordinary champion efficiency of 22.46% (0.1 cm2 ) and 21.15% (1.0 cm2 ) with exceptional stability surpassing 1200 h. Further, the self-powered photodetector goes above and beyond, showcasing an ultra-low dark current of 2.13 × 10-10 A·cm-2 , a specific detection rate of 6.12 × 1013  Jones, and an expansive linear dynamic range reaching an astonishing 122.49 dB. PySCN modification not only signifies high efficiency but also ushers in a new era for crystallization regulation, promising a transformative impact on the optoelectronic performance of perovskite-based devices.

Regulating Perovskite Crystallization through Interfacial Engineering Using a Zwitterionic Additive Potassium Sulfamate for Efficient Pure-Blue Light-Emitting Diodes.

Quasi-two-dimensional (quasi-2D) perovskites are emerging as efficient emitters in blue perovskite light-emitting diodes (PeLEDs), while the imbalanced crystallization of the halide-mixed system limits further improvements in device performance. The rapid crystallization caused by Cl doping produces massive defects at the interface, leading to aggravated non-radiative recombination. Meanwhile, unmanageable perovskite crystallization is prone to facilitate the formation of nonuniform low-dimensional phases, which results in energy loss during the exciton transfer process. Here, we propose a multifunctional interface engineering for nucleation and phase regulation by incorporating the zwitterionic additive potassium sulfamate into the hole transport layer. By using potassium ions (K+ ) as heterogeneous nucleation seeds, finely controlled growth of interfacial K+ -guided grains is achieved. The sulfamate ions can simultaneously regulate the phase distribution and passivate defects through coordination interactions with undercoordinated lead atoms. Consequently, such synergistic effect constructs quasi-2D blue perovskite films with smooth energy landscape and reduced trap states, leading to pure-blue PeLEDs with a maximum external quantum efficiency (EQE) of 17.32 %, spectrally stable emission at 478 nm and the prolonged operational lifetime. This work provides a unique guide to comprehensively regulate the halide-mixed blue perovskite crystallization by manipulating the characteristics of grain-growth substrate.

Top-Down Exfoliation Process Constructing 2D/3D Heterojunction toward Ultrapure Blue Perovskite Light-Emitting Diodes.

3D perovskites with low energy disorder and high ambipolar charge mobility represent a promising solution for efficient and bright light-emitting diodes. However, the challenges of regulating the nanocrystal size to trigger the quantum confinement effect and control the surface trap states to reduce charge loss hinder the applications of 3D perovskites in blue perovskite light-emitting diodes (PeLEDs). In this study, we present a top-down exfoliation method to obtain blue 3D perovskite films with clipped nanocrystals and tunable bandgaps by employing methyl cyanide (MeCN) for post-treatment. In this method, the MeCN solvent exfoliates the surface components of the 3D perovskite grains through a partial dissolution process. Moreover, the dissolved precursor can be further utilized to construct an ingenious 2D/3D heterostructure by incorporating an organic spacer into the MeCN solvent, contributing to efficient defect passivation and improved energy transfer. Consequently, efficient PeLEDs featuring ultrapure blue emission at 478 nm achieve a record external quantum efficiency of 12.3% among their 3D counterparts. This work emphasizes the significance of inducing the quantum confinement effect in 3D perovskites for efficient blue PeLEDs and provides a viable scheme for the in situ regulation of perovskite crystals.

Comprehensive Crystal Regulation Reduces Interfacial Energy Loss for Efficient Blue Perovskite Light-Emitting Diodes.

As an essential component of future full-color displays, blue perovskite light-emitting diodes (PeLEDs) still lag far behind the red and green counterparts in the device performances. In the mainstream quasi-2D blue perovskite system, trap-mediated nonradiative loss, low energy transfer efficiency, and interface fluorescence quenching remain significant challenges. Herein, guanidinium thiocyanate (GASCN) and potassium cinnamate (PCA) are respectively introduced into the hole transport layer (HTL) and the perovskite precursor to achieve a dense and uniform perovskite thin film with greatly improved optoelectronic properties. Therefore, adequate GA+ acts as pre-nucleation sites on the HTL surface, regulating crystallization through strong hydrogen bonding with perovskite intermediates. The realized polydisperse domain distribution is conducive to cascade energy transfer, and the improved hole transport ability alleviates interface fluorescence quenching. In addition, the SCN- and CA- groups can form coordination bonds with the defects at the buried perovskite interface and grain boundaries, respectively, which effectively suppresses the detrimental nonradiative recombination. Benefitting from the comprehensive crystal regulation, blue PeLEDs featuring stable emission at 484 and 468 nm exhibit improved external quantum efficiencies of 11.5% and 4.3%, respectively.

Rational Multidimensional Shielded Multiple Resonance Emitter Suppresses Concentration Quenching and Spectral Broadening for Solution-Processed Organic Light-Emitting Diodes.

Thermally activated delayed fluorescence (TADF) emitters based on multiple resonance (MR) effects are promising for high-definition organic light-emitting diodes (OLEDs) with narrowband emission and high efficiency. However, they still face the challenges of aggregation-caused quenching (ACQ) and spectral broadening. Solution-processable MR-TADF emitters with an external quantum efficiency (EQE) of >20% and a full width at half-maximum (fwhm) of <30 nm have rarely been reported. To construct ACQ-resistant emitters without sacrificing color purity, the aggregation-induced MR-TADF material 6TBN with a rigid B,N-containing polycyclic aromatic hydrocarbon core and four carbazole substituents as well as 12 tert-butyl groups on the periphery is designed. The multidimensional shielded effect largely limits the ACQ, intermolecular interactions, and spectral broadening. Consequently, solution-processed OLEDs based on 6TBN exhibit a maximum EQE of 23.0% and high color purity with a fwhm of 25 nm. Furthermore, the nondoped device achieves a high efficiency (12.3%) and merely a slight widening of the fwhm to 27 nm. This work provides a feasible strategy to achieve MR-TADF materials with resistance to concentration quenching and high color purity.

Hyperbolic polaritonic crystals with configurable low-symmetry Bloch modes.

Photonic crystals (PhCs) are a kind of artificial structures that can mold the flow of light at will. Polaritonic crystals (PoCs) made from polaritonic media offer a promising route to controlling nano-light at the subwavelength scale. Conventional bulk PhCs and recent van der Waals PoCs mainly show highly symmetric excitation of Bloch modes that closely rely on lattice orders. Here, we experimentally demonstrate a type of hyperbolic PoCs with configurable and low-symmetry deep-subwavelength Bloch modes that are robust against lattice rearrangement in certain directions. This is achieved by periodically perforating a natural crystal α-MoO3 that hosts in-plane hyperbolic phonon polaritons. The mode excitation and symmetry are controlled by the momentum matching between reciprocal lattice vectors and hyperbolic dispersions. We show that the Bloch modes and Bragg resonances of hyperbolic PoCs can be tuned through lattice scales and orientations while exhibiting robust properties immune to lattice rearrangement in the hyperbolic forbidden directions. Our findings provide insights into the physics of hyperbolic PoCs and expand the categories of PhCs, with potential applications in waveguiding, energy transfer, biosensing and quantum nano-optics.

Outcomes of ABO-incompatible liver transplantation in end-stage liver disease patients co-infected with hepatitis B and human immunodeficiency virus.

BACKGROUND: Human immunodeficiency virus (HIV)-positive patients coinfected with hepatitis B virus (HBV) are eligible for liver transplantation (LT) in Africa and Southeast Asia, particularly China. However, the outcome of HIV-HBV coinfected patients referred for ABO-incompatible LT (ABOi-LT) is unknown. AIM: To clarify the outcome of ABOi-LT for HIV-HBV coinfected patients with end-stage liver disease (ESLD). METHODS: We report on two Chinese HIV-HBV coinfected patients with ESLD who underwent A to O brain-dead donor LT and reviewed the literature on HIV-HBV coinfected patients treated with ABO-compatible LT. The pretransplantation HIV viral load was undetectable, with no active opportunistic infections. Induction therapy consisted of two sessions of plasmapheresis and a single dose of rituximab in two split doses, followed by an intraoperative regimen of intravenous immunoglobulin, methylprednisolone, and basiliximab. Post-transplant maintenance immunosuppressive agents consisted of tacrolimus and mycophenolate mofetil, and prednisone. RESULTS: At the intermediate-term follow-up, patients showed undetectable HIV viral load, CD4(+) T cell counts greater than 150 cells/µL, no HBV recurrence, and stable liver function. A liver allograft biopsy showed no evidence of acute cellular rejection. Both patients survived at 36-42 mo of follow-up. CONCLUSION: This is the first report of ABOi-LT in HIV-HBV recipients with good intermediate-term outcomes, suggesting that ABOi-LT may be feasible and safe for HIV-HBV coinfected patients with ESLD.

Suppressed Voltage Deficit and Degradation of Perovskite Solar Cells by Regulating the Mineralization of Lead Iodide.

Both the uncoordinated Pb2+ and excess PbI2 in perovskite film will create defects and perturb carrier collection, thus leading to the open-circuit voltage (VOC ) loss and inducing rapid performance degradation of perovskite solar cells (PSCs). Herein, an additive of 3-aminothiophene-2-carboxamide (3-AzTca) that contains amide and amino and features a large molecular size is introduced to improve the quality of perovskite film. The interplay of size effect and adequate bonding strength between 3-AzTca and uncoordinated Pb2+ regulates the mineralization of PbI2 and generates low-dimensional PbI2 phase, thereby boosting the crystallization of perovskite. The decreased defect states result in suppressed nonradiative recombination and reduced VOC loss. The power conversion efficiency (PCE) of modified PSC is improved to 22.79% with a high VOC of 1.22 V. Moreover, the decomposition of PbI2 and perovskite films is also retarded, yielding enhanced device stability. This study provides an effective method to minimize the concentration of uncoordinated Pb2+ and improve the PCE and stability of PSCs.

Unveiling the degraded electron durability in reduced-dimensional perovskites.

The operational stability of reduced-dimensional metal halide perovskites (RD-MHPs) lags far behind the practical requirements for future high-definition displays. Thereinto, the electron durability of RD-MHPs plays a critical role in stable LEDs during continuous operation, however, it still lacks adequate research and a deep understanding. Herein, the electron durability and deterioration mechanism of phenethylammonium (PEA+)-modified RD-MHPs are systematically conducted through an in situ photoelectron spectroscopy technique by implementing tunable electron-beam radiation to simulate device operation. The formation of detrimental metallic lead (Pb0) caused by the reduction of lead ions (Pb2+) is observed along with the decomposition of PEA+ under electron-beam radiation, thereby changing the photophysical properties of PEA+-doped RD-MHPs. These results provide deep insight into the process of how injected electrons affect the performance of PEA+-doped perovskite LEDs, which may also provide potential guidance for designing robust and effective organic spacers for RD-MHPs.

Regulating Charge Carrier Recombination in the Interconnecting Layer to Boost the Efficiency and Stability of Monolithic Perovskite/Organic Tandem Solar Cells.

The charge carriers of single-junction solar cells can be fluently extracted and then collected by electrodes, leading to weak charge carrier accumulation and low energy loss (Eloss ). However, in tandem solar cells (TSCs), it is a considerable challenge to obtain a balance between the densities of the holes and electrons extracted from the two respective subcells to facilitate an efficient recombination in the interconnecting layer (ICL). Herein, a charge-carrier-dynamic management strategy for inorganic perovskite/organic TSCs is proposed, centered on the simultaneous regulation of the defect states of CsPbI1.9 Br1.1 perovskite in the front subcell and hole transport ability from the perovskite to ICL. The target hole density on the perovskite surface and the hole loss before reaching the ICL are significantly improved. As a result, the hole/electron density offset in the ICL can be effectively narrowed, leading to a balanced charge carrier recombination, which reduces the Eloss in TSCs. The resulting inorganic perovskite/organic 0.062-cm2 TSC exhibits a remarkable power conversion efficiency (PCE) of 23.17% with an ultrahigh open-circuit voltage (Voc ) of 2.15 V, and the PCE of the 1.004-cm2 device (21.69%) exhibited a weak size-dependence. This charge-carrier-dynamic management strategy can also effectively enhance the operational and ultraviolet-light stabilities of the TSCs.

Unraveling the Hole-Transport-Layer-Manipulated Carrier Transfer Dynamics in Perovskite Light-Emitting Diodes.

Charge transfer dynamics is decisive for the performance of perovskite light emitting diodes (PeLEDs), and deep insight into the charge transfer process inside the working device is indispensable. Here, the influence of the hole transport layer on charge transport and recombination processes in PeLEDs is investigated via impedance spectroscopy. The results demonstrate that the rational interfacial energy level alignment can improve the radiative recombination by reducing the leakage current and carrier transport resistance. Shockley-Read-Hall recombination and Auger recombination enlarge the lifetime of carrier transfer in the working devices as determined from the electroluminescence spectrum. Our work provides a distinctive and reliable method to explore the charge transfer property and highlights the importance of interfaces to boost the performance of PeLEDs.

Reconstructing the portal vein through a posterior pancreatic tunnel: New choice for portal vein thrombosis during liver transplantation.

BACKGROUND: Thrombectomy and anatomical anastomosis (TAA) has long been considered the optimal approach to portal vein thrombosis (PVT) in liver transplantation (LT). However, TAA and the current approach for non-physiological portal reconstructions are associated with a higher rate of complications and mortality in some cases. AIM: To describe a new choice for reconstructing the portal vein through a posterior pancreatic tunnel (RPVPPT) to address cases of unresectable PVT. METHODS: Between August 2019 and August 2021, 245 adult LTs were performed. Forty-five (18.4%) patients were confirmed to have PVT before surgery, among which seven underwent PV reconstruction via the RPVPPT approach. We retrospectively analyzed the surgical procedure and postoperative complications of these seven recipients that underwent PV reconstruction due to PVT. RESULTS: During the procedure, PVT was found in all the seven cases with significant adhesion to the vascular wall and could not be dissected. The portal vein proximal to the superior mesenteric vein was damaged in one case when attempting thrombolectomy, resulting in massive bleeding. LT was successfully performed in all patients with a mean duration of 585 min (range 491-756 min) and mean intraoperative blood loss of 800 mL (range 500-3000 mL). Postoperative complications consisted of chylous leakage (n = 3), insufficient portal venous flow to the graft (n = 1), intra-abdominal hemorrhage (n = 1), pulmonary infection (n = 1), and perioperative death (n = 1). The remaining six patients survived at 12-17 mo follow-up. CONCLUSION: The RPVPPT technique might be a safe and effective surgical procedure during LT for complex PVT. However, follow-up studies with large samples are still warranted due to the relatively small number of cases.

Topological approach of liver segmentation based on 3D visualization technology in surgical planning for split liver transplantation.

BACKGROUND: Split liver transplantation (SLT) is a complex procedure. The left-lateral and right tri-segment splits are the most common surgical approaches and are based on the Couinaud liver segmentation theory. Notably, the liver surface following right tri-segment splits may exhibit different degrees of ischemic changes related to the destruction of the local portal vein blood flow topology. There is currently no consensus on preoperative evaluation and predictive strategy for hepatic segmental necrosis after SLT. AIM: To investigate the application of the topological approach in liver segmentation based on 3D visualization technology in the surgical planning of SLT. METHODS: Clinical data of 10 recipients and 5 donors who underwent SLT at Shenzhen Third People's Hospital from January 2020 to January 2021 were retrospectively analyzed. Before surgery, all the donors were subjected to 3D modeling and evaluation. Based on the 3D-reconstructed models, the liver splitting procedure was simulated using the liver segmentation system described by Couinaud and a blood flow topology liver segmentation (BFTLS) method. In addition, the volume of the liver was also quantified. Statistical indexes mainly included the hepatic vasculature and expected volume of split grafts evaluated by 3D models, the actual liver volume, and the ischemia state of the hepatic segments during the actual surgery. RESULTS: Among the 5 cases of split liver surgery, the liver was split into a left-lateral segment and right tri-segment in 4 cases, while 1 case was split using the left and right half liver splitting. All operations were successfully implemented according to the preoperative plan. According to Couinaud liver segmentation system and BFTLS methods, the volume of the left lateral segment was 359.00 ± 101.57 mL and 367.75 ± 99.73 mL, respectively, while that measured during the actual surgery was 397.50 ± 37.97 mL. The volume of segment IV (the portion of ischemic liver lobes) allocated to the right tri-segment was 136.31 ± 86.10 mL, as determined using the topological approach to liver segmentation. However, during the actual surgical intervention, ischemia of the right tri-segment section was observed in 4 cases, including 1 case of necrosis and bile leakage, with an ischemic liver volume of 238.7 mL. CONCLUSION: 3D visualization technology can guide the preoperative planning of SLT and improve accuracy during the intervention. The simulated operation based on 3D visualization of blood flow topology may be useful to predict the degree of ischemia in the liver segment and provide a reference for determining whether the ischemic liver tissue should be removed during the surgery.

Bio-Inspired Pangolin Design for Self-Healable Flexible Perovskite Light-Emitting Diodes.

Despite tremendous developments in the luminescene performance of perovskite light-emitting diodes (PeLEDs), the brittle nature of perovskite crystals and their poor crystallinity on flexible substrates inevitably lead to inferior performance. Inspired by pangolins' combination of rigid scales and soft flesh, we propose a bionic structure design for self-healing flexible PeLEDs by employing a polymer-assisted crystal regulation method with a soft elastomer of diphenylmethane diisocyanate polyurethane (MDI-PU). The crystallinity and flexural strain resistance of such perovskite films on plastics with silver-nanowire-based flexible transparent electrodes are highly enhanced. The detrimental cracks induced during repeated deformation can be effectively self-healed under heat treatment via intramolecular/intermolecular hydrogen bonds with MDI-PU. Upon collective optimization of the perovskite films and device architecture, the blue-emitting flexible PeLEDs can achieve a record external quantum efficiency of 13.5% and high resistance to flexural strain, which retain 87.8 and 80.7% of their initial efficiency after repeated bending and twisting operations of 2000 cycles, respectively.

A Dislocated Twin-Locking Acceptor-Donor-Acceptor Configuration for Efficient Delayed Fluorescence with Multiple Through-Space Charge Transfer.

Organic materials featuring intramolecular through-space charge transfer (TSCT) excited states are advantageous for efficient thermally activated delayed fluorescence (TADF), although the realization of multiple TSCT systems remains challenging. Herein, a rigid molecule with a three-dimensional dislocated sandwich acceptor-donor-acceptor configuration has been developed by a linking biphenazine (2PXZ) donor and 2,4,6-triphenyl-1,3,5-triazine (TRZ) acceptor through the twin-locking of two spiro-fluorene bridges. The twin-locking construction with multiple TSCT effects suppresses the intramolecular rotations of various segments in 2PXZ-2TRZ, leading to a small singlet-triplet energy difference, a fast reverse intersystem crossing process, and high photoluminescence quantum yield. This material simultaneously possesses the capabilities of TADF and aggregation-induced emission. The device employing 2PXZ-2TRZ as a dopant displays an optimal external quantum efficiency of 27.1 % and a low efficiency roll-off.

Strategies to Improve the Stability of Perovskite Light-Emitting Diodes: Progress and Perspective.

Perovskite light-emitting diodes (PeLEDs) featuring excellent electroluminescent (EL) characteristics and facile production have been emerging as promising candidates for next-generation high-definition displays. In recent years, tremendous advances have been achieved in the EL efficiency of PeLEDs. However, their poor operational stability impedes practical applications. Particularly, the severe spectral instability of pure-blue and pure-red PeLEDs lags far behind the requirements of commercial displays. In this Perspective, the critical factors related to device degradation are first summarized, including perovskite crystal defects, unbalanced charge injection, Auger recombination, and Joule heating. Then, the recent progress in improving the operational and spectral stabilities is reviewed in categories. Considering the present achievements, we provide potential research directions for further development of stable PeLEDs.