Decreasing exciton dissociation rates for reduced voltage losses in organic solar cells.

Enhancing the device electroluminescence quantum efficiency (EQEEL) is a critical factor in mitigating non-radiative voltage losses (VNR) and further improving the performance of organic solar cells (OSCs). While the common understanding attributes EQEEL in OSCs to the dynamics of charge transfer (CT) states, persistent efforts to manipulate these decay dynamics have yielded limited results, with the EQEEL of high-efficiency OSCs typically remaining below 10-2%. This value is considerably lower than that observed in high efficiency inorganic photovoltaic devices. Here, we report that EQEEL is also influenced by the dissociation rate constant of singlet states (kDS). Importantly, in contrast to the traditional belief that advocates maximizing kDS for superior photovoltaic quantum efficiency (EQEPV), a controlled reduction in kDS is shown to enhance EQEEL without compromising EQEPV. Consequently, a promising experimental approach to address the VNR challenge is proposed, resulting in a significant improvement in the performance of OSCs.

Potential application of anti-osteoporotic therapy to relieve sarcopenia in the elderly.

Sarcopenia is a progressive and systemic skeletal muscle disorder associated with aging that usually occurs with age in the elderly. Sarcopenia currently lacks effective pharmacological treatment modalities. Multiple pharmacological intervention modalities are available for osteoporosis, a comprehensive disease characterized by decreased systemic bone mass, degradation of bone microarchitecture, and increased bone fragility. Several recent studies have shown an extremely strong correlation between sarcopenia and osteoporosis, leading to the concept of "osteosarcopenia". Therefore, it is possible to alleviate sarcopenia simultaneously by improving osteoporosis.

Enhanced Operational Stability by Cavity Control of Single-Layer Organic Light-Emitting Diodes Based on Thermally Activated Delayed Fluorescence.

Highly efficient organic light-emitting diodes (OLEDs) based on thermally activated delayed fluorescence (TADF) emitters are realized in recent years, but the device lifetime needs further improvement for practical display or lighting applications. In this work, a device design principle is presented by tuning the optical cavity of single-layer undoped devices, to realize efficient and long-lived TADF OLEDs. Extending the cavity length to the second-order interference maximum by increasing the emissive layer thickness broadens the recombination zone, while the optical outcoupling efficiency remains close to that of the thinner first-order devices. Such a device design leads to efficient and stable single-layer undoped OLEDs with a maximum external quantum efficiency of 16%, an LT90 of 452 h, and an LT50 of 3693 h at an initial luminance of 1000 cd m-2 , which is doubled compared to the first-order counterparts. It is further demonstrated that the widely-used empirical relation between OLED lifetime and light intensity originates from triplet-polaron annihilation, resulting in an extrapolated LT50 at 100 cd m-2 of close to 90 000 h, approaching the demands for practical backlight applications.

Single-Layer Blue Organic Light-Emitting Diodes With Near-Unity Internal Quantum Efficiency.

Efficient organic light-emitting diodes (OLEDs) commonly comprise a multilayer stack including charge-transport and charge- and exciton-blocking layers, to confine charge recombination to the emissive layer. Here, a highly simplified single-layer blue-emitting OLED is demonstrated based on thermally activated delayed fluorescence with the emitting layer simply sandwiched between ohmic contacts consisting of a polymeric conducting anode and a metal cathode. The single-layer OLED exhibits an external quantum efficiency of 27.7% with minor roll-off at high brightness. The internal quantum efficiency approaches unity, demonstrating that highly simplified single-layer OLEDs without confinement layers can achieve state-of-the-art performance, while greatly reducing the complexity of the design, fabrication, and device analysis.

Reduced bimolecular charge recombination in efficient organic solar cells comprising non-fullerene acceptors.

Bimolecular charge recombination is one of the most important loss processes in organic solar cells. However, the bimolecular recombination rate in solar cells based on novel non-fullerene acceptors is mostly unclear. Moreover, the origin of the reduced-Langevin recombination rate in bulk heterojunction solar cells in general is still poorly understood. Here, we investigate the bimolecular recombination rate and charge transport in a series of high-performance organic solar cells based on non-fullerene acceptors. From steady-state dark injection measurements and drift-diffusion simulations of the current-voltage characteristics under illumination, Langevin reduction factors of up to over two orders of magnitude are observed. The reduced recombination is essential for the high fill factors of these solar cells. The Langevin reduction factors are observed to correlate with the quadrupole moment of the acceptors, which is responsible for band bending at the donor-acceptor interface, forming a barrier for charge recombination. Overall these results therefore show that suppressed bimolecular recombination is essential for the performance of organic solar cells and provide design rules for novel materials.

Constructing 3D flower-like LaFe bimetal oxides with abundant mesoporous and controllable active sites for high-efficient phosphorus removal: Synthesis, mechanism, and application.

The design of high-performance porous adsorbents for phosphorus removal is a persistently hot topic to maintain a sustainable aquatic ecosystem. In the present study, a self-templating strategy using LaFe cyanometallates (CMs) as precursors was adopted to prepare porous LaFe bimetal oxides with optimizable structure and composition for phosphate adsorption. The results showed that a high supplied LaIII/FeII ratio enabled an adequate coordination polymerization in the preparation of LaFe CM precursor and led to a striking three-dimensional (3D) structure of "twin lotus flower" with high coordinated water content, which resulted in a 3D flower-like LaFe oxide with high surface area and high porosity (mainly in mesopore). The LaFe oxide of LaFe15T possessing the optimal La/Fe ratio (1.5: 1) exhibited the most superior performance of phosphate adsorption, where La was confirmed to be the main active site for phosphate capture via ligand exchange mechanism. The batch and column tests of phosphate adsorption showed that the 3D flower-like LaFe oxides are effective adsorbents for phosphate removal. Therefore, the structure optimization in the template preparation stage is an effective strategy to design porous LaFe bimetal oxides as high-performance phosphorus removal materials.

Substantial transition to clean household energy mix in rural China.

The household energy mix has significant impacts on human health and climate, as it contributes greatly to many health- and climate-relevant air pollutants. Compared to the well-established urban energy statistical system, the rural household energy statistical system is incomplete and is often associated with high biases. Via a nationwide investigation, this study revealed high contributions to energy supply from coal and biomass fuels in the rural household energy sector, while electricity comprised ∼20%. Stacking (the use of multiple sources of energy) is significant, and the average number of energy types was 2.8 per household. Compared to 2012, the consumption of biomass and coals in 2017 decreased by 45% and 12%, respectively, while the gas consumption amount increased by 204%. Increased gas and decreased coal consumptions were mainly in cooking, while decreased biomass was in both cooking (41%) and heating (59%). The time-sharing fraction of electricity and gases (E&G) for daily cooking grew, reaching 69% in 2017, but for space heating, traditional solid fuels were still dominant, with the national average shared fraction of E&G being only 20%. The non-uniform spatial distribution and the non-linear increase in the fraction of E&G indicated challenges to achieving universal access to modern cooking energy by 2030, particularly in less-developed rural and mountainous areas. In some non-typical heating zones, the increased share of E&G for heating was significant and largely driven by income growth, but in typical heating zones, the time-sharing fraction was <5% and was not significantly increased, except in areas with policy intervention. The intervention policy not only led to dramatic increases in the clean energy fraction for heating but also accelerated the clean cooking transition. Higher income, higher education, younger age, less energy/stove stacking and smaller family size positively impacted the clean energy transition.

Well-defined bimetal oxides derived from Prussian blue analogues with regulable active sites for phosphate removal.

Two well-defined CoFe bimetal oxides are prepared from Prussian blue analogues (PBAs) as precursors with designable structures, which are further explored for phosphate removal. A speed-controlled coordination strategy is used to fabricate two CoFe PBA microcrystals with different morphologies, then two regular CoFe oxides are obtained via an intermediate-temperature calcination. CoFeS, a slow-speed coordination product with truncated microcube structure, contains less coordinated water and Fe3+ in its framework, but can create more mesopores and Fe3+ in its oxidative product of CoFeST300. CoFeST300 has been demonstrated to have higher adsorption capacity and affinity for phosphate adsorption compared to that of the fast-speed coordination product, due to its more Fe3+ as effective adsorption sites via ligand exchange. Besides, the inner-sphere complexation mechanism makes CoFeST300 high selectivity for phosphate removal compared to other co-existing anions. The application performance of CoFeST300 is examined by multiple continuous treatment of actual sewage, and the result of all effluent concentrations below 0.5 mg P/L verifies a promising potential of the fabricated adsorbent for phosphorus removal. Thus, design or regulation of the precursors is an efficiency method to fabricate an ideal metal oxide for phosphate adsorption.

Efficiency of Polymer Light-Emitting Diodes: A Perspective.

The various contributions to the external quantum efficiency (EQE) of polymer light-emitting diodes (PLEDs) are discussed. The EQE of an organic light-emitting diode is governed by a number of parameters, such as the electrical efficiency, the photoluminescence quantum yield (PLQY), the optical outcoupling efficiency and the spin statistics for singlet exciton generation. In the last decade, the electrical efficiency has been determined from a numerical PLED device model. More recently, an optical model to simulate the fraction of photons outcoupled to air for PLEDs with a broad recombination zone has been developed. Together with the directly measured PLQY, the EQE of a PLED can then be estimated. However, it has been observed that the measured EQEs of fluorescent PLEDs, including the model system super-yellow poly(p-phenylene vinylene) (SY-PPV) often exceed the expected values. To solve this discrepancy, it is demonstrate that the electrical PLED model has to be expanded by the inclusion of triplet-triplet annihilation (TTA), which is shown to be responsible for a substantial EQE enhancement. Experimentally, it is obtained that TTA contributes to a singlet-exciton generation efficiency of ≈40% in SY-PPV PLEDs, giving rise to an EQE of ≈4% instead of the expected value of 2.5%.

Quantify individual variation of real-time PM2.5 exposure in urban Chinese homes based on a novel method.

Fine particulate matter (PM2.5 ) concentrations show high variations in different microenvironments indoors, which has considerable impact on risk management. However, the real-time variations of PM2.5 exposure associated with per activity/microenvironment and intra-variation among family members remain undefined. In this study, real-time monitors were used to collect real-time PM2.5 data in different microenvironments in 32 households in urban community of China. Peak concentrations of PM2.5 were found in kitchen. The parallel levels of PM2.5 household indoor and outdoor indicated the benefit of clean energies use. To validly assess the health risk of individuals, we proposed a novel method to estimate the real-time exposure of all residents and firstly investigate the intra-variation of PM2.5 exposure among family members. The member who is responsible for cooking in the family had the maximum PM2.5 exposure. The ratios among intraindividual variations demonstrated children usually had lower exposure compared to the adults as they stayed more time in lower polluted microenvironments such as living room and bedroom. The exposure intensity in living room was above 1.0 for most residents, indicating it is warranted to alleviate the air pollution in living room. This study firstly focused on the intra differences of PM2.5 exposure among family members and provided a new insight for indoor air pollution management. The results suggested when adopting measures to reduce exposure, the microenvironments pattern of each member should be taken into consideration. Future work is welcomed to move another big step on this issue to protect the human health.

New Rehabilitation Assessment Method of the End-Effector Finger Rehabilitation Robot Based on Multi-Sensor Source.

In the process of rehabilitation, the objectivity and the accuracy of rehabilitation assessment have an obvious impact on the follow-up training. To improve this problem, using a multi-sensor source, this paper attempts to establish a comprehensive assessment method of the finger rehabilitation effect, including three indicators of finger muscle strength, muscle fatigue degree, and range of motion. Firstly, on the basis of the fingertip pressure sensor of the End-Effector Finger Rehabilitation Robot, a mathematical model of finger muscle strength estimation was established, and the estimated muscle strength was scored using the entropy weight method. Secondly, using an sEMG signal sensor, a fatigue monitoring system was designed in the training process, and the fatigue degree was determined on the basis of the change trend of the eigenvalues of MAV and RMS. Lastly, a human-machine motion coupling model was established, and the joint range of motion acquisition and scoring model were obtained on the basis of the motor encoder. According to the above three indicators, using the AHP assessment method to establish a comprehensive rehabilitation assessment method, the effectiveness of the method was verified by experiments. This paper provides a potential new idea and method for objective, accurate, and convenient assessment of finger function rehabilitation, which is of positive significance for alleviating the burden on rehabilitation doctors and improving rehabilitation efficiency.

Reduced Intrinsic Non-Radiative Losses Allow Room-Temperature Triplet Emission from Purely Organic Emitters.

Persistent luminescence from triplet excitons in organic molecules is rare, as fast non-radiative deactivation typically dominates over radiative transitions. This work demonstrates that the substitution of a hydrogen atom in a derivative of phenanthroimidazole with an N-phenyl ring can substantially stabilize the excited state. This stabilization converts an organic material without phosphorescence emission into a molecular system exhibiting efficient and ultralong afterglow phosphorescence at room temperature. Results from systematic photophysical investigations, kinetic modeling, excited-state dynamic modeling, and single-crystal structure analysis identify that the long-lived triplets originate from a reduction of intrinsic non-radiative molecular relaxations. Further modification of the N-phenyl ring with halogen atoms affects the afterglow lifetime and quantum yield. As a proof-of-concept, an anticounterfeiting device is demonstrated with a time-dependent Morse code feature for data encryption based on these emitters. A fundamental design principle is outlined to achieve long-lived and emissive triplet states by suppressing intrinsic non-radiative relaxations in the form of molecular vibrations or rotations.

Removal of phosphorus and ammonium from municipal wastewater treatment plant effluent by manganese ore in a simulated constructed wetland.

Natural manganese ore (NM) is selected as a distinguished constructed wetland (CW) substrate for nutrient pollutants removal, however, the study on municipal wastewater treatment plant (WWTP) effluent treatment remains scarce. The current study was to investigate the sorption characteristics of NM and the removal efficiency of ammonium and phosphorus from one WWTP effluent in a simulated vertical flow NM constructed wetland (NM-VFCW). Results indicated that NM could effectively sorb ammonium and phosphorus within 24 h, and the desorption ratio was less than 7%. The sorption of ammonium and phosphorus enhanced when increasing the particle size of NM, but was not sensitive with temperature. The removal efficiencies for ammonium and phosphorus were 65% and 76% in NM-VFCW, which were 61% and 31% in gravel VFCW. The much higher removal efficiency for phosphorus was mainly attributed to the precipitation of phosphorus which was identified by the SEM and EDS spectrum. Therefore, the manganese ore sand is highlighted as a powerful substrate for simultaneous advanced removal of phosphorus and ammonium in constructed wetland systems.

Adsorption of Strontium onto Adaxial and Abaxial Cuticle of Photinia serrulata Leaf.

Leaf cuticle sorption is one important process for the uptake of environment pollutants in plants, and mixed powder including adaxial and abaxial cuticle is generally used to demonstrate the sorption behavior. However, the difference of adaxial and abaxial cuticle on plant cuticle sorption is not well understood. Abaxial cuticle (PAC) and adaxial cuticle (PBC) were isolated from hypostomatic Photinia serrulata to investigate their adsorption of a model radionuclide (strontium). The elemental composition and FTIR spectra for two cuticles were quite similar and both show high affinity (H/C, 1.59 and 1.65) and polarity ((O + N)/C, 0.470 and 0.499). Both adsorption isotherms fit well with Langmuir model (R2, 0.97 and 0.97), and the maximum adsorption capacity of PAC was 12.1 mg/g, little higher than that of PBC (10.3 mg/g). Adsorption of strontium increased with the increase of pH, and the maximum was attained when pH ≥4. Electrostatic attraction was demonstrated to be the main mechanism of -strontium adsorption onto PAC and PBC, and the similar adsorption of adaxial and abaxial cuticle was consistent with their similar isoelectric point.

TiO2 quantum dots loaded sulfonated graphene aerogel for effective adsorption-photocatalysis of PFOA.

With the pollution of perfluoroalkyl substances (PFASs) became increasingly serious, the researches focused on removal of PFASs by adsorption-photocatalysis method has attracted considerable attention. To make the catalyst TiO2 disperse uniformly as quantum dots onto hydrophobic surface which was liable to attract perfluorooctanoic acid (PFOA), the surfactant sodium dodecyl sulfate (SDS) were used in this work, which not only connected the hydrophilic TiCl3 to the hydrophobic sulfonated graphene (SG) nanosheets, but also behaved as the molecular template for controlled nucleation and growth of the nanostructured TiO2. After 3D SG-TiO2 QD nanosheets were fabricated, a series of 3D SG-TiO2 QD aerogels were self-assembled by ice-template. TiO2 uniformly distributed on the surface of SG aerogel at QD size level (2-3 nm) and the size of TiO2 could be effectively regulated by concentration of SDS. Compared with aggregated TiO2 material, 3D SG-TiO2 QD aerogels owned higher adsorption and photocatalytic performance. Benefiting from the hydrophobic surface of 3D SG as well as dispersed TiO2 QDs, 3D SG-TiO2 QD could enrich PFOA instantaneously (0.0381/s) and photocatalytic decomposed them effectively (1.898 E-4/s). PFOA degradation by hole and hydroxyl radicals proceeded via a stepwise mechanism. The column made of 3D SG-TiO2 QD could remove PFOA persistently in cycles of permeation. 3D SG-TiO2 QD possessed powerful adsorption-photocatalytic decomposition capability of PFOA and steady reusability performance. The present work highlights the individual roles and synergistic effect of TiO2 QD and 3D SG for effectively removing PFOA.

The inappropriate application of the regression Langmuir Qm for adsorption capacity comparison.

The Langmuir equation, the best known adsorption model in the past century, was extensively applied to describe adsorption isotherms. The saturated adsorption amount (Qm) obtained from the Langmuir model is an essential index to evaluate the maximum adsorption capacity of the adsorbent, which was assumed to be irrelevant to the aqueous concentration of the adsorbate. Adsorption isotherms of cadmium onto soil and biochar were performed in the current study, and the regression Langmuir Qm was demonstrated to be highly dependent on the aqueous concentration. The regression Qm increased from 0.066 to 2.17 mg·g-1 (by ~3-fold) for the selected soil, and from 2.12 to 48.4 mg·g-1 (by ~23-fold) for the chosen biochar when the highest initial aqueous concentration increased from 2.34 to 887 mg·L-1. One inappropriate application for comparison of the regression Langmuir Qm as the adsorption capacity is found, i.e., it is difficult to directly compare the regression Qm without neither a saturated isotherm nor considering the experimental conditions. It is also very hard to accurately predict adsorption behavior by the regressed Langmuir model obtained from a partial adsorption isotherm. It is suggested to pay more attention to the difference between the saturated adsorption capacity and the regression Qm value derived from one unsaturated isotherm.

Organic Light-Emitting Diodes Based on Conjugation-Induced Thermally Activated Delayed Fluorescence Polymers: Interplay Between Intra- and Intermolecular Charge Transfer States.

In this work, interactions between different host materials and a blue TADF polymer named P1 are systematically investigated. In photoluminescence, the host can have substantial impact on the photoluminescence quantum yield (PLQY) and the intensity of delayed fluorescence (Φ DF), where more than three orders of magnitude difference of Φ DF in various hosts is observed, resulting from a polarity effect of the host material and energy transfer. Additionally, an intermolecular charge-transfer (CT) emission with pronounced TADF characteristics is observed between P1 and 2,4,6-tris[3-(diphenylphosphinyl)phenyl]-1,3,5-triazine (PO-T2T), with a singlet-triplet splitting of 7 meV. It is noted that the contribution of harvested triplets in monochrome organic light-emitting diodes (OLEDs) correlates with Φ DF. For devices based on intermolecular CT-emission, the harvested triplets contribute ~90% to the internal quantum efficiency. The results demonstrate the vital importance of host materials on improving the PLQY and sensitizing Φ DF of TADF polymers for efficient devices. Solution-processed polychrome OLEDs with a color close to a white emission are presented, with the emission of intramolecular (P1) and intermolecular TADF (PO-T2T:P1).

Characteristics of Internal Ammonium Loading from Long-Term Polluted Sediments by Rural Domestic Wastewater.

Given long-term decentralized and centralized rural domestic wastewater (RDW) discharge, nitrogen is continuously depositing in sediments. RDW discharge is assumed to be an important source of ammonium in surface water; however, the effect of long-term RDW discharge on nitrogen pollution in sediments remains unknown. Batch incubations were conducted to investigate the characteristics of internal ammonium loading from long-term polluted sediments by RDW discharge. Four sediments were demonstrated to be heavily polluted by long-term RDW discharge, with total nitrogen (TN) values of 5350, 8080, 2730, and 2000 mg·kg-1, respectively. The internal ammonium release from sediment was a slow and long process, and the risk of ammonium release from sediment during the dry season was significantly greater than that during the wet season. Though all selected sediments were heavily polluted by long-term RDW discharge, the relative contribution of internal ammonium loading from sediments was generally lower than that of external pollution. Hence, dredging is not suggested for RDW-polluted sediments except in response to an emergency. The excessive ammonium in the selected catchment was mainly from untreated and centralized black water in RDW. Centralized black waters in rural communities are highlighted to be separately treated or reused to maintain ammonium content at a safe level.

Detection of Participation and Training Task Difficulty Applied to the Multi-Sensor Systems of Rehabilitation Robots.

In the process of rehabilitation training for stroke patients, the rehabilitation effect is positively affected by how much physical activity the patients take part in. Most of the signals used to measure the patients' participation are EMG signals or oxygen consumption, which increase the cost and the complexity of the robotic device. In this work, we design a multi-sensor system robot with torque and six-dimensional force sensors to gauge the patients' participation in training. By establishing the static equation of the mechanical leg, the man-machine interaction force of the patient can be accurately extracted. Using the impedance model, the auxiliary force training mode is established, and the difficulty of the target task is changed by adjusting the K value of auxiliary force. Participation models with three intensities were developed offline using support vector machines, for which the C and σ parameters are optimized by the hybrid quantum particle swarm optimization and support vector machines (Hybrid QPSO-SVM) algorithm. An experimental statistical analysis was conducted on ten volunteers' motion representation in different training tasks, which are divided into three stages: over-challenge, challenge, less challenge, by choosing characteristic quantities with significant differences among the various difficulty task stages, as a training set for the support vector machines (SVM). Experimental results from 12 volunteers, with tasks conducted on the lower limb rehabilitation robot LLR-II show that the rehabilitation robot can accurately predict patient participation and training task difficulty. The prediction accuracy reflects the superiority of the Hybrid QPSO-SVM algorithm.