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A triarylamine-based macrocyclic donor is adopted to design new blue thermally activated delayed fluorescence (TADF) emitter. The restricted conformation of macrocyclic donor twisting against the dimethyl substituted phenylene bridge leads to the reduced singlet–triplet energy difference (ΔE _ST) as well as the enhanced horizontal ratio of emission dipole. These beneficial effects contribute to a highly efficient blue TADF organic light-emitting diode.

Abstract

This work reports the incorporation of a triphenylamine-based macrocyclic donor to design new donor-π-acceptor-configured blue thermally activated delayed fluorescence (TADF) emitters. The X-ray structure analyses manifest the degree of twisted conformations that can be modulated by methyl substituents of the π-bridge and macrocyclic donor, leading to well-separated highest occupied natural transition orbital and lowest unoccupied natural transition orbital frontier orbitals, thus sufficiently small singlet–triplet energy difference (ΔE _ST) for TADF. The theoretical analyses elucidate the structure–property relationship and reveal the beneficial effect of macrocyclic donor on increasing reverse intersystem crossing (RISC) process that can contribute to improved triplet-upconversion efficiency. The blue device employing c-NN-TRZ as emitter gave a maximum external quantum efficiecny (EQE_max) of 26.3% as compared to that (19.1%) of the device using the model compound DPA-MeTRZ without the macrocyclic donor, suggesting the contribution of macrocyclic donor to enhance device performance. Benefiting from the combined advantages of macrocyclic donor and methyl substituents, the device incorporating c-NN-MeTRZ as emitter achieves an outstanding EQE_max of 32.2%, which is attributed to the more horizontally oriented emission dipoles as well as the significantly accelerated RISC rate constant (k _RISC) resulting from reduced ΔE _ST. This work represents a new strategy of designing twisted TADF emitter incorporating macrocyclic donor to achieve highly efficient blue device.

Nature Photonics, Published online: 12 January 2023; doi:10.1038/s41566-022-01138-0

A thin-film of crystalline organic semiconductors yields a bright, efficient deep-blue OLED.

Anhydrous polyphosphoric acid is proposed as an enabler for creating an intimate Li | garnet interface with electron-blocking characteristics, resulting in ultralow interfacial impedance, a fast charge–discharge rate, and remarkable long durability of all-solid-state Li metal symmetric and full cells.

Abstract

Garnet-based solid-state Li-metal batteries (GSSBs) have the merits of high energy density and high safety. However, the realization of a stable and well-matched Li|garnet interface for GSSBs remains challenging due to electron leakage and lithiophobic Li₂CO₃ impurity. To address these issues, herein, new surface chemistry is reported that converts the undesired Li₂CO₃ contaminant into an ultra-thin lithium polyphosphate (Li-PPA) layer through anhydrous polyphosphoric acid -induced in situ substitution reaction without damaging the water-sensitive garnet electrolyte. In particular, the Li-PPA interlayer not only facilitates the homogenous spreading of molten Li but also creates a robust electron-blocking shield to suppress Li dendrite formation. As a result, the assembled Li symmetric cell exhibits a low interfacial impedance (4 Ω cm²) and high critical current density (1.8 mA cm⁻²) at 25 °C, which enables the cell to continuously cycle over 2500 h at 0.2 mA cm⁻². Furthermore, the GSSBs paired with LiFePO₄ deliver a high capacity of 149.3 mAh g⁻¹ at 1 C and maintain 92.3% of the initial capacity after 500 cycles and can be used for solar energy storage, suggesting the feasibility of this interfacial engineering strategy for GSSBs.

This review summarizes the structural modification strategies of organic small-molecule semiconductors with high electron mobilities, a promising candidate for the construction of next-generation complementary organic logic-digital circuits, to achieve chemical stability and high electron transport properties. In addition, the applications of n-type small-molecule semiconductor materials based on high mobility in organic electronic devices, such as organic field-effect transistors, organic light-emitting transistors, organic photodetectors, and gas sensors, are introduced.

Abstract

Organic electronics has made great progress in the past decades, which is inseparable from the innovative development of organic electronic devices and the diversity of organic semiconductor materials. It is worth mentioning that both of these great advances are inextricably linked to the development of organic high-performance semiconductor materials, especially the representative n-type organic small-molecule semiconductor materials with high electron mobilities. The n-type organic small molecules have the advantages of simple synthesis process, strong intermolecular stacking, tunable molecular structure, and easy to functionalize structures. Furthermore, the n-type semiconductor is a remarkable and important component for constructing complementary logic circuits and p-n heterojunction structures. Therefore, n-type organic semiconductors play an extremely important role in the field of organic electronic materials and are the basis for the industrialization of organic electronic functional devices. This review focuses on the modification strategies of organic small molecules with high electron mobility at molecular level, and discusses in detail the applications of n-type small-molecule semiconductor materials with high mobility in organic field-effect transistors, organic light-emitting transistors, organic photodetectors, and gas sensors.

Nature Photonics, Published online: 09 January 2023; doi:10.1038/s41566-022-01106-8

An organoboron-emitter, DBTN-2, yields a green organic light-emitting diode with ultrapure colour and high efficiency.

By molecular engineering of 1,4-dihydropyridine derivatives, a photoactivatable probe (TPA-DHPy-Py) with high photoactivatable and photodynamic efficiency is developed. Upon photoactivation, TPA-DHPy-Py can monitor lipid droplets and endoplasmic reticulum alteration under light irradiation, and achieve fluorescent visualization of tumor in vivo. Furthermore, TPA-DHPy-Py can effectively kill cancer cells and significantly inhibit tumor growth.

Abstract

Photoactivatable agent is a powerful tool in biomedicine studies due to high-precision spatiotemporal control of light. However, those previously reported agents generally suffer from short wavelength, fluorescence self-quenching effect, and the lack of photosensitizing property, which severely restrict their practical applications. To address these issues, molecular engineering of 1,4-dihydropyridine derivatives is conducted to obtain an optimized agent, namely TPA-DHPy-Py, which exhibits low oxidation potential, high photoactivation efficiency, and excellent type I/II combined photodynamic activity. Concurrently, its photoactivated counterpart is featured by aggregation-induced near-infrared emission and remarkable reactive oxygen species (ROS) production efficiency. Upon photoactivation, TPA-DHPy-Py is capable of precisely identifying cancer cells from co-culturing cancer cells and normal cells without the assistance of any extra targeting units, and in situ monitoring lipid droplets and endoplasmic reticulum alteration under ROS stress, as well as achieving fluorescent visualization of tumor in vivo with supremely high imaging contrast. Furthermore, the unprecedented performance on photodynamic cancer therapy is demonstrated by the significant inhibition of tumor growth. Therefore, the photoactivatable TPA-DHPy-Py with dual-organelle-targeted and excellent photodynamic activity associated with self-monitoring ability is highly promising for cancer theranostics in clinical trials.

Nature Communications, Published online: 03 January 2023; doi:10.1038/s41467-022-35745-w

Nanoscale circularly polarized light sources are an important building block for future integrated photonics. Here the authors demonstrate circularly polarized light emission from a thin organic single crystal light-emitting diode.

A triarylamine-based macrocyclic donor is adopted to design new blue thermally activated delayed fluorescence (TADF) emitter. The restricted conformation of macrocyclic donor twisting against the dimethyl substituted phenylene bridge leads to the reduced singlet–triplet energy difference (ΔE _ST) as well as the enhanced horizontal ratio of emission dipole. These beneficial effects contribute to a highly efficient blue TADF organic light-emitting diode.

Abstract

This work reports the incorporation of a triphenylamine-based macrocyclic donor to design new donor-π-acceptor-configured blue thermally activated delayed fluorescence (TADF) emitters. The X-ray structure analyses manifest the degree of twisted conformations that can be modulated by methyl substituents of the π-bridge and macrocyclic donor, leading to well-separated highest occupied natural transition orbital and lowest unoccupied natural transition orbital frontier orbitals, thus sufficiently small singlet–triplet energy difference (ΔE _ST) for TADF. The theoretical analyses elucidate the structure–property relationship and reveal the beneficial effect of macrocyclic donor on increasing reverse intersystem crossing (RISC) process that can contribute to improved triplet-upconversion efficiency. The blue device employing c-NN-TRZ as emitter gave a maximum external quantum efficiecny (EQE_max) of 26.3% as compared to that (19.1%) of the device using the model compound DPA-MeTRZ without the macrocyclic donor, suggesting the contribution of macrocyclic donor to enhance device performance. Benefiting from the combined advantages of macrocyclic donor and methyl substituents, the device incorporating c-NN-MeTRZ as emitter achieves an outstanding EQE_max of 32.2%, which is attributed to the more horizontally oriented emission dipoles as well as the significantly accelerated RISC rate constant (k _RISC) resulting from reduced ΔE _ST. This work represents a new strategy of designing twisted TADF emitter incorporating macrocyclic donor to achieve highly efficient blue device.

The hygroscopicity of lithium-rich antiperovskites (LiRAPs) is successfully suppressed by weakening the intermolecular hydrogen bond between LiRAPs and H₂O with fluorine doping. Based on the high moisture resistivity and the low melting point of LiRAPs, two prototypes of all ceramic lithium batteries (ACLBs) are assembled in ambient air by means of co-coating sintering and melt-infiltration, respectively.

Abstract

Lithium-rich antiperovskites (LiRAPs) solid electrolytes have attracted extensive interest due to their advantages of structural tunability, mechanical flexibility, and low cost. However, LiRAPs are instinctively hygroscopic and suffer from decomposition in air, which not only diversifies their electrochemical performances in present reports but also hinders their application in all-solid-state lithium batteries (ASSLBs). Herein, the origin of the hygroscopicity, and also the effect of the hygroscopicity on the electrochemical performances of Li_3−x (OH _x )Cl are systematically investigated. Li_3−x (OH _x )Cl is demonstrated to be unstable in the air and prone to decompose into LiOH and LiCl. Nevertheless, with fluorine doping on chlorine sites, the hygroscopicity of LiRAPs is suppressed by weakening the intermolecular hydrogen bond between LiRAPs and H₂O, forming a moisture-resistive Li_3−x (OH _x )Cl_0.9F_0.1. Taking advantage of its low melting point (274 °C), two prototypes of ASSLBs are assembled in the ambient air by means of co-coating sintering and melt-infiltration. With LiRAPs as the solder, low-temperature sintering of the ASSLBs with low interfacial resistance is demonstrated as feasible. The understanding of the hygroscopic behavior of LiRAPs and the integration of the moisture-resistive LiRAPs with ASSLBs provide an effective way toward the fabrication of the ASSLBs.

By synthesizing a high weight-average molecular weight polymer donor PBDB-TF and combining a ternary blending strategy, favorable phase separation morphology featuring more compact π–π stacking distance can be attained. A maximum power conversion efficiency of 18.2% (certified value of 17.7%) with excellent mechanical properties in all-polymer organic photovoltaic cells is demonstrated.

Abstract

All-polymer organic photovoltaic (OPV) cells possessing high photovoltaic performance and mechanical robustness are promising candidates for flexible wearable devices. However, developing photoactive materials with good mechanical properties and photovoltaic performance so far remains challenging. In this work, a polymer donor PBDB-TF with a high weight-average molecular weight (M _w) is introduced to enable highly efficient all-polymer OPV cells featuring excellent mechanical reliability. By incorporating the high-M _w PBDB-TF as a third component into the PBQx-TF:PY-IT blend, the bulk heterojunction morphology is finely tuned with a more compact π–π stacking distance, affording efficient pathways for charge transport as well as mechanical stress dissipation. Hence, all-polymer OPV cells based on the ternary blend film demonstrate a maximum power conversion efficiency (PCE) of 18.2% with an outstanding fill factor of 0.796. The flexible OPV cell delivers a decent PCE of 16.5% with high mechanical stability. These results present a promising strategy to address the mechanical properties and boost the photovoltaic performance of all-polymer OPV cells.

A high-mobility fullerene liquid crystal is introduced into the active layer of organic solar cells (OSCs) to provide a fast channel for charge-carrier transport, reduce energetic disorder and trap density via enhancing crystallization, and then realize micrometer-scale charge-carrier diffusion, leading to the impressive power conversion efficiencies of 15.23% for OSCs with the thickness approaching 500 nm.

Abstract

The short charge-carrier diffusion length (L _D) (100–300 nm) in organic bulk heterojunction (BHJ) impedes the further improvement in power conversion efficiency (PCE) of organic solar cells (OSCs), especially for thick-film (>400 nm) devices matching with industrial solution processing. Here a facile method is developed to efficiently increase L _D and then improve PCEs of OSCs via introducing a fullerene liquid crystal, F1, into the active layer. F1 combines the inherent high electron mobility of fullerene and strong self-assembly capacity of liquid crystal, providing a fast channel for charge-carrier transport and reducing energetic disorder and trap density in BHJ film via enhancing crystallization. Typically, in PM6:Y6:F1 BHJ, the enhanced charge-carrier mobility (>10⁻² cm⁻² V⁻¹ s⁻¹) and prolonged charge-carrier lifetime (55.3 µs) are acquired to realize the record L _D of 1.6 or 2.4 µm for electron or hole, respectively, which are much higher than those of the PM6:Y6 binary sample and comparable to or even better than those values reported for some inorganic/hybrid materials, such as CuIn _x Ga_{(1− x )}Se₂ (CIGS) and perovskite thin films. Benefitting from the micrometer-scale L _D, the PM6:Y6:F1 ternary OSCs sustain a remarkable PCE of 15.23% with the active layer thickness approaching 500 nm.