A Fluorination Strategy and Low-Acidity Anchoring Group in Self-Assembled Molecules for Efficient and Stable Inverted Perovskite Solar Cells.

Herein, we synthesized two donor-acceptor (D-A) type small organic molecules with self-assembly properties, namely MPA-BT-BA and MPA-2FBT-BA, both containing a low acidity anchoring group, benzoic acid. After systematically investigation, it is found that, with the fluorination, the MPA-2FBT-BA demonstrates a lower highest occupied molecular orbital (HOMO) energy level, higher hole mobility, higher hydrophobicity and stronger interaction with the perovskite layer than that of MPA-BT-BA. As a result, the device based-on MPA-2FBT-BA displays a better crystallization and morphology of perovskite layer with larger grain size and less non-radiative recombination. Consequently, the device using MPA-2FBT-BA as hole transport material achieved the power conversion efficiency (PCE) of 20.32 % and remarkable stability. After being kept in an N2 glove box for 116 days, the unsealed PSCs' device retained 93 % of its initial PCE. Even exposed to air with a relative humidity range of 30±5 % for 43 days, its PCE remained above 91 % of its initial condition. This study highlights the vital importance of the fluorination strategy combined with a low acidity anchoring group in SAMs, offering a pathway to achieve efficient and stable PSCs.

Perovskite light-emitting diodes based on spontaneously formed submicrometre-scale structures.

Light-emitting diodes (LEDs), which convert electricity to light, are widely used in modern society-for example, in lighting, flat-panel displays, medical devices and many other situations. Generally, the efficiency of LEDs is limited by nonradiative recombination (whereby charge carriers recombine without releasing photons) and light trapping1-3. In planar LEDs, such as organic LEDs, around 70 to 80 per cent of the light generated from the emitters is trapped in the device4,5, leaving considerable opportunity for improvements in efficiency. Many methods, including the use of diffraction gratings, low-index grids and buckling patterns, have been used to extract the light trapped in LEDs6-9. However, these methods usually involve complicated fabrication processes and can distort the light-output spectrum and directionality6,7. Here we demonstrate efficient and high-brightness electroluminescence from solution-processed perovskites that spontaneously form submicrometre-scale structures, which can efficiently extract light from the device and retain wavelength- and viewing-angle-independent electroluminescence. These perovskites are formed simply by introducing amino-acid additives into the perovskite precursor solutions. Moreover, the additives can effectively passivate perovskite surface defects and reduce nonradiative recombination. Perovskite LEDs with a peak external quantum efficiency of 20.7 per cent (at a current density of 18 milliamperes per square centimetre) and an energy-conversion efficiency of 12 per cent (at a high current density of 100 milliamperes per square centimetre) can be achieved-values that approach those of the best-performing organic LEDs.

Regio- and Stereoselective Reductive Coupling of Alkynes and Crotononitrile.

A new regio- and stereoselective reductive coupling of alkynes and crotononitrile has been developed via visible light organophotoredox cobalt dual catalysis. A variety of enantioenriched homoallylic nitriles bearing a stereodefined trisubstituted alkene have been easily synthesized with good to excellent regio- (up to >20:1 rr), stereo- (>20:1 E/Z), and enantioselectivity (up to 98% ee) control under mild conditions. The corresponding nitrile products were smoothly converted into various chiral building blocks. Remarkably, a simple organic base together with water have been utilized as hydrogen sources in this photoinduced reductive reaction.

High-Performance Inverted Planar Perovskite Solar Cells Enhanced by Thickness Tuning of New Dopant-Free Hole Transporting Layer.

A new hole transporting material (HTM) named DMZ is synthesized and employed as a dopant-free HTM in inverted planar perovskite solar cells (PSCs). Systematic studies demonstrate that the thickness of the hole transporting layer can effectively enhance the morphology and crystallinity of the perovskite layer, leading to low series resistance and less defects in the crystal. As a result, the champion power conversion efficiency (PCE) of 18.61% with JSC = 22.62 mA cm-2 , VOC = 1.02 V, and FF = 81.05% (an average one is 17.62%) is achieved with a thickness of ≈13 nm of DMZ (2 mg mL-1 ) under standard global AM 1.5 illumination, which is ≈1.5 times higher than that of devices based on poly(3,4-ethylenedioxythiophene)/poly(styrene sulfonic acid) (PEDOT:PSS). More importantly, the devices based on DMZ exhibit a much better stability (90% of maximum PCE retained after more than 556 h in air (relative humidity ≈ 45%-50%) without any encapsulation) than that of devices based on PEDOT:PSS (only 36% of initial PCE retained after 77 h in same conditions). Therefore, the cost-effective and facile material named DMZ offers an appealing alternative to PEDOT:PSS or polytriarylamine for highly efficient and stable inverted planar PSCs.

Fluorination Triggered New Small Molecule Donor Materials for Efficient As-Cast Organic Solar Cells.

Solution-processable small molecules (SMs) have attracted intense attention due to their definite molecular structures, less batch-to-batch variation, and easier structure control. Herein, two new SM donors based on substituted isatin unit (DI3T, DI3T-2F) are synthesized and applied as electron donors with the mixture of PC71 BM to construct organic photovoltaics. As a result, 5,6-difluoro isatin derivative (DI3T-2F) obtains a power conversion efficiency of 7.80% by a simple solution spin-coating fabrication process without any additives, solvent, or thermal annealing process. More intuitively, due to stronger intermolecular interaction and higher hole mobility after the incorporation of fluorine atoms in end units, the devices present good tolerance to active layer thickness. The results indicate that DI3T-2F shows promising potential for large-scale printing processes and flexible application of efficient small molecule organic solar cells.

N-annulated perylene-substituted and fused porphyrin dimers with intense near-infrared one-photon and two-photon absorption.

Fusion of two N-annulated perylene (NP) units with a fused porphyrin dimer along the S0-S1 electronic transition moment axis has resulted in new near-infrared (NIR) dyes 1 a/1 b with very intense absorption (ε>1.3×10(5) M(-1) cm(-1)) beyond 1250 nm. Both compounds displayed moderate NIR fluorescence with fluorescence quantum yields of 4.4×10(-6) and 6.0×10(-6) for 1 a and 1 b, respectively. The NP-substituted porphyrin dimers 2 a/2 b have also been obtained by controlled oxidative coupling and cyclodehydrogenation, and they showed superimposed absorptions of the fused porphyrin dimer and the NP chromophore. The excited-state dynamics of all of these compounds have been studied by femtosecond transient absorption measurements, which revealed porphyrin dimer-like behaviour. These new chromophores also exhibited good nonlinear optical susceptibility with large two-photon absorption cross-sections in the NIR region due to extended π-conjugation. Time-dependent density functional theory calculations have been performed to aid our understanding of their electronic structures and absorption spectra.

Abnormal thermally-stimulated dynamic organic phosphorescence.

Dynamic luminescence behavior by external stimuli, such as light, thermal field, electricity, mechanical force, etc., endows the materials with great promise in optoelectronic applications. Upon thermal stimulus, the emission is inevitably quenched due to intensive non-radiative transition, especially for phosphorescence at high temperature. Herein, we report an abnormal thermally-stimulated phosphorescence behavior in a series of organic phosphors. As temperature changes from 198 to 343 K, the phosphorescence at around 479 nm gradually enhances for the model phosphor, of which the phosphorescent colors are tuned from yellow to cyan-blue. Furthermore, we demonstrate the potential applications of such dynamic emission for smart dyes and colorful afterglow displays. Our results would initiate the exploration of dynamic high-temperature phosphorescence for applications in smart optoelectronics. This finding not only contributes to an in-depth understanding of the thermally-stimulated phosphorescence, but also paves the way toward the development of smart materials for applications in optoelectronics.

Organocatalytic aryl-aryl bond formation: an atroposelective [3,3]-rearrangement approach to BINAM derivatives.

Herein we disclose an organocatalytic aryl-aryl bond-forming process for the regio- and atroposelective synthesis of 2,2'-diamino-1,1'-binaphthalenes (BINAMs). In the presence of catalytic amounts of axially chiral phosphoric acids, achiral N,N'-binaphthyl hydrazines undergo a facile [3,3]-sigmatropic rearrangement to afford enantiomerically enriched BINAM derivatives in good to excellent yield. This transformation represents the first example of a metal-free, catalytic C(sp(2))-C(sp(2)) bond formation between two aromatic rings with concomitant de novo atroposelective installation of an axis of chirality. Density functional calculations reveal that, in the transition state for C-C bond formation, the phosphoric acid proton of the catalyst is fully transferred to one of the N-atoms of the substrate, and the resulting phosphate acts as a chiral counterion.

Carbon coated heterojunction CoSe2/Sb2Se3 nanospheres for high-efficiency sodium storage.

Multicomponent metal selenides with heterostructures are believed to effectively activate the surface pseudocapacitive contribution and improve the electrochemical dynamics, thus achieving high-performance anodes for sodium ion batteries (SIBs). Herein, a carbon coated CoSe2/Sb2Se3 heterojunction (CoSe2/Sb2Se3@C) is designed and constructed via an ion-exchange reaction between Co and Sb, and the subsequent selenization step. It is found that the hetero-structure and carbon shell effectively boost the charge transfer in the CoSe2/Sb2Se3@C composite electrode. The highly pseudocapacitive Na+ storage contribution is acquired due to the structural benefits of the heterojunction. Therefore, the CoSe2/Sb2Se3@C anode affords good cycling stability (264.5 mA h g-1 after 1000 cycles at 2 A g-1) and excellent rate capability (266.0 mA h g-1 at 5 A g-1). This study supplies a reference for developing an advanced anode with multicomponent and heterojunction structures for energy storage.

Pediatric paragonimiasis: a retrospective analysis of cases from a county in south-west China.

Introduction: The clinical manifestations of paragonimiasis are diverse and non-specific, and can easily lead to misdiagnosis. We aimed to analyze the clinical manifestations, laboratory features, treatment, and clinical outcome of children with paragonimiasis in order to improve recognition of this disease and avoid misdiagnosis. Methods: Children diagnosed with paragonimiasis from August 2016 to July 2022 were included in the study. Information on population informatics, medical history, and laboratory features was extracted from case data. The clinical features of paragonimiasis were retrospectively analyzed. Results: A total of 45 children were included in this study. All children had, at least, one risk factor. The clinical features mainly included fever, cough, pleural effusion, peritoneal effusion, and subcutaneous nodules. The main imaging findings were alveolar exudation, peritoneal effusion, pleural thickening, and local nodules. The "tunnel sign" finding on computed tomography (CT)/magnetic resonance imaging (MRI) was helpful in establishing the diagnosis of paragonimiasis. After praziquantel treatment, most of the children improved, and one child with cerebral paragonimiasis experienced sequelae. Conclusion: Most children with paragonimiasis have a good prognosis, but few children can experience sequelae. Avoidance of untreated water and raw food is a simple, feasible, and effective preventive measure.

Strong synergy between gold nanoparticles and cobalt porphyrin induces highly efficient photocatalytic hydrogen evolution.

The reaction efficiency of reactants near plasmonic nanostructures can be enhanced significantly because of plasmonic effects. Herein, we propose that the catalytic activity of molecular catalysts near plasmonic nanostructures may also be enhanced dramatically. Based on this proposal, we develop a highly efficient and stable photocatalytic system for the hydrogen evolution reaction (HER) by compositing a molecular catalyst of cobalt porphyrin together with plasmonic gold nanoparticles, around which plasmonic effects of localized electromagnetic field, local heating, and enhanced hot carrier excitation exist. After optimization, the HER rate and turn-over frequency (TOF) reach 3.21 mol g-1 h-1 and 4650 h-1, respectively. In addition, the catalytic system remains stable after 45-hour catalytic cycles, and the system is catalytically stable after being illuminated for two weeks. The enhanced reaction efficiency is attributed to the excitation of localized surface plasmon resonance, particularly plasmon-generated hot carriers. These findings may pave a new and convenient way for developing plasmon-based photocatalysts with high efficiency and stability.

Boosting the Plasmon-Mediated Electrochemical Oxidation of p-Aminothiophenol with p-Hydroxythiophenol as Molecular Cocatalyst.

Plasmon-mediated electrochemistry is an emerging area of interest in which the electrochemical reactions are enhanced by employing metal nanostructures possessing localized surface plasmon resonance (LSPR). However, the reaction efficacy is still far below its theoretical limit due to the ultrafast relaxation of LSPR-generated hot carriers. Herein, we introduce p-hydroxythiophenol (PHTP) as a molecular cocatalyst to significantly improve the reaction efficacy in plasmon-mediated electrochemical oxidation of p-aminothiophenol (PATP) on gold nanoparticles. Using electrochemical techniques, in situ Raman spectroscopy, and theoretical calculations, we elucidate that the presence of PHTP improves the hot hole-mediated electrochemical oxidation of PATP by 2-fold through the trapping of plasmon-mediated hot electrons. In addition, the selectivity of PATP oxidation could also be modulated by the introduction of PHTP cocatalyst. This tactic of employing molecular cocatalyst can be drawn out to endorse various plasmonic electrochemical reactions because of its simple protocol, high efficiency, and high selectivity.

Elusive metal-free primary amination of arylboronic acids: synthetic studies and mechanism by density functional theory.

Herein, we disclose the first metal-free synthesis of primary aromatic amines from arylboronic acids, a reaction that has eluded synthetic chemists for decades. This remarkable transformation affords structurally diverse primary arylamines in good chemical yields, including a variety of halogenated primary anilines that often cannot be prepared via transition-metal-catalyzed amination. The reaction is operationally simple, requires only a slight excess of aminating agent, proceeds under neutral or basic conditions, and, importantly, can be scaled up to provide multigram quantities of primary anilines. Density functional calculations reveal that the most likely mechanism involves a facile 1,2-aryl migration and that the presence of an ortho nitro group in the aminating agent plays a critical role in lowering the free energy barrier of the 1,2-aryl migration step.

Simple, Skin-Attachable, and Multifunctional Colorimetric Sweat Sensor.

In situ analysis of sweat provides a simple, convenient, cost-effective, and noninvasive approach for the early diagnosis of physical illness in humans and is particularly useful in family care. In this study, a flexible and skin-attachable colorimetric sweat sensor for multiplexed analysis is developed using a simple, cost-effective, and convenient method. The obtained sweat sensor can be used to simultaneously detect glucose, lactate, urea, and pH value in sweat, as well as sweat loss and skin temperature. Only 2.5 µL of sweat is enough for the whole test, and the sweat loss and chemical-sensing results can be read out conveniently by naked eyes or a smartphone. In addition, body temperature can also be detected with an additional electrical circuit. Our sweat sensor provides a new, cost-effective, and convenient approach for in vitro diagnosis of multiple components in sweat, and the easy fabrication and cost-effectiveness make our sensor commercializable in the near future.

Dopant-Free Hole Transporting Material Based on Nonconjugated Adamantane for High-Performance Perovskite Solar Cells.

A new dopant-free hole transporting material (HTM) 4',4‴,4‴'',4‴''''-(adamantane-1,3,5,7-tetrayl)tetrakis(N,N-bis(4-methoxyphenyl)-[1,1'-biphenyl]-4-amine) (Ad-Ph-OMeTAD) (named FDY for short), which consists of a nonconjugated 3D bulky caged adamantane (Ad) as the core, triphenyl amines as side arms, and phenyl units as a linking bridge, is synthesized and applied in an inverted planar perovskite solar cell (PSC). As a result, the champion device with FDY as HTM yields an impressive power of conversion efficiency (PCE) of 18.69%, with JSC = 22.42 mA cm-2, VOC = 1.05 V, and FF = 79.31% under standard AM 1.5G illumination, which is ca. 20% higher than that of the device based on PEDOT:PSS (only 15.41%). Notably, the stability of PSC based on FDY is much better than that of devices based on PEDOT:PSS, and the corresponding devices retain over 90% of their initial PCEs after storing for 60 days in a nitrogen glove box without any encapsulation. Even when stored in an open air condition with 50-60% relative humidity for 188 h, the retained PCE is still over 81% of its initial one. All these results demonstrate that the new design strategy by combing the bulky and nonconjugated (aliphatic) adamantane unit as the core and triphenyl amines as side arms can efficiently develop highly efficient HTMs for PSCs, which is different from the traditional way based on conjugated backbones, and it may open a new way for scientists to design small-molecule HTMs for PSCs.

Unveiling the additive-assisted oriented growth of perovskite crystallite for high performance light-emitting diodes.

Solution-processed metal halide perovskites have been recognized as one of the most promising semiconductors, with applications in light-emitting diodes (LEDs), solar cells and lasers. Various additives have been widely used in perovskite precursor solutions, aiming to improve the formed perovskite film quality through passivating defects and controlling the crystallinity. The additive's role of defect passivation has been intensively investigated, while a deep understanding of how additives influence the crystallization process of perovskites is lacking. Here, we reveal a general additive-assisted crystal formation pathway for FAPbI3 perovskite with vertical orientation, by tracking the chemical interaction in the precursor solution and crystallographic evolution during the film formation process. The resulting understanding motivates us to use a new additive with multi-functional groups, 2-(2-(2-Aminoethoxy)ethoxy)acetic acid, which can facilitate the orientated growth of perovskite and passivate defects, leading to perovskite layer with high crystallinity and low defect density and thereby record-high performance NIR perovskite LEDs (~800 nm emission peak, a peak external quantum efficiency of 22.2% with enhanced stability).

Effects of Oxygen Atoms Introduced at Different Positions of Non-Fullerene Acceptors in the Performance of Organic Solar Cells with Poly(3-hexylthiophene).

With the development of large-area fabrication technologies for organic solar cells (OSCs), poly(3-hexylthiophene) (P3HT) is the best choice as a photovoltaic donor polymer because it can be easily synthesized in the scale of kilograms at low cost. However, non-fullerene acceptors (NFAs) matching with P3HT for high performance OSCs are very rare. Herein, by introducing oxygen atoms into the side chains or the fused-ring core of indaceno[1,2-b:5,6-b']dithiophene, we synthesized two new A2-A1-D-A1-A2 type NFAs, where benzotriazole (BTA) and 2-(1,1-dicyanomethylene)rhodanine were used as the bridged A1 and terminal A2, respectively. The final NFAs, named BTA43 and BTA53, show wider absorption spectra and enhanced intermolecular/intramolecular interaction in comparison with their analogue BTA3 without oxygen atoms. The photovoltaic devices based on P3HT:BTA43 and P3HT:BTA53 can achieve a high power conversion efficiency of 6.56 and 6.31%, respectively, which are obviously higher than that of BTA3 (5.64%). Our results provide a simple and effective strategy to design promising NFAs to pair with the classic photovoltaic polymer P3HT.

Asymmetric Friedel-Crafts reaction of 4,7-dihydroindoles with nitroolefins by chiral Brønsted acids under low catalyst loading.

Slowly does it! By adding the substrate by a syringe pump, a highly efficient Friedel-Crafts reaction of 4,7-dihydroindoles with nitroolefins was realized with 0.5 mol % of a chiral phosphoric acid. The Friedel-Crafts alkylation, together with a subsequent oxidation of the product, led to 2-substituted indoles in excellent enantiomeric excesses, which can be easily transformed to enantioenriched tetrahydro-gamma-carbolines.

A2-A1-D-A1-A2 Type Non-Fullerene Acceptors with 2-(1,1-Dicyanomethylene)rhodanine as the Terminal Groups for Poly(3-hexylthiophene)-Based Organic Solar Cells.

2-(1,1-Dicyanomethylene)rhodanine (RCN) is an important electron-deficient terminal unit to build non-fullerene acceptors (NFAs) having been realized high power conversion efficiency (PCE) beyond 12% with complicated p-type polymer as electron donor. However, the photovoltaic properties of RCN-based NFAs are unsatisfied when paired with the classic p-type polymer poly(3-hexylthiophene) (P3HT). In order to make a contribution in this regard, we designed two RCN-based small molecular acceptors with A2-A1-D-A1-A2 structure, BT3 and BTA3, where benzothiadiazole (BT) and benzotriazole (BTA) are bridged A1 segments, respectively, to modulate the optoelectronic properties. As a result, P3HT:BTA3 solar cell exhibits a promising PCE of 5.64%, with a VOC of 0.90 V and a fill factor (FF) of 0.65, which is obviously much better than that of P3HT:BT3 (PCE = 2.55%, VOC = 0.72 V, FF = 0.61). The higher electron mobility of P3HT:BTA3 film indicates BTA3 tends to form a continuous pathway for electron transport even at a lower weight ratio of 1:0.3 than 1:0.5 for P3HT:BT3 film. Our results indicate that introducing a weak electron-withdrawing building block BTA is an effective strategy compared with the BT counterpart to improve the performance of RCN-based NFA devices.