Multi‐resonant thermally activated delayed fluorescent (MR‐TADF) materials are blooming for high‐resolution organic light‐emitting diodes (OLEDs). However, boron/nitrogen (B/N)‐integrated MR‐TADF ...emitters suffer severe efficiency roll‐off from their strong inter‐molecular π–π interactions. Herein, versatile narrowband pure blue emitters (mono‐mx‐CzDABNA and tri‐mx‐CzDABNA) are demonstrated featuring a ring‐fused extended π‐skeleton: a classic steric hindrance and rigidity accessed by integrating with meta‐xylene (mx) rotors. tri‐mx‐CzDABNA shows a narrowband (FWHM, 26 nm) pure blue emission (λmax, 462 nm) with substantial hypsochromic shift (12 nm) while maintaining MR‐TADF characteristics. The key solid‐state analyses conclude that they conceivably suppress the non‐radiative energy loss, thus improving the photoluminescence quantum yield (PLQY > 90%) and rate of reverse intersystem crossing (RISC) (kRISC ≈2.85 × 105 s−1). The integration of tri meta‐xylene significantly leads to an enhanced horizontal dipole ratio (HDR) from 65% to 85%. Hyperfluorescent‐OLEDs are fabricated using designed MR‐TADF as terminal emitter, achieving a narrowband (FWHM, 34 nm) pure blue electroluminescence (λmax, 472 nm) and maximum external quantum efficiency (EQEmax) of 26.97% with magnificently suppressed efficiency roll‐off (7.8%) at 1000 cd m−2. So, it is believed that regulation of internal efficiencies and high color purity can amplify the route to achieving a narrowband pure blue emission through new synthetic MR‐TADF approaches.
The architecture of the ring fuses and extends π‐skeleton based on high‐order B/N‐embedded steric rooted and structurally rigid hypsochromic‐shifted narrow‐band pure blue multi‐resonant thermally activated delayed fluorescent emitter for efficient and ultralow‐efficiency roll‐off hyperfluorescent‐organic light‐emitting diodes.
The energy efficiency of irrigation systems is an aspect of great importance in all design and management processes; For this reason, an investigation was carried out in the "Tio Pedro" farm located ...in the municipality of Venezuela, Ciego de Avila province during the years 2021 and 2022 with the objective of estimating the general energy yield in the furrow irrigation system. During this period, the pump unit offers the following average operating regime: pump flow rate of 61.1 L s.sup.-1; pumping time of 2,8 hours and pumping head of 18.2 m. This behavior reduces a hydraulic power of 10.9 kW and a pump efficiency of 85.2%. The energy supplied in pumping was 429.4 kWh and the energy absorbed in the evaluated period was 631.9 kWh. In relation to the energy parameters of the system, an energy balance of the supply of 7,4 m was obtained; a system energy load index of 15.2 m; an energy efficiency of the pumping of 68.2% (excellent) and a general energy efficiency of the system of 34.0% (normal).
A new strategy of constructing an additional heterojunction on the surface of epitaxially grown Ga2O3 film with a distorted lattice is proposed to solve the problem of low external quantum efficiency ...(EQE) in traditional Ga2O3 heterojunction photovoltaic devices. Experimentally, an organic–inorganic hybrid poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate/Ga2O3/p‐type Si solar‐blind ultraviolet (SBUV) photovoltaic detector is constructed to achieve an ultrahigh EQE of ≈15% at 0 V bias, which is 1–2 orders of magnitude higher than that of the Ga2O3 photovoltaic devices reported previously. Here, an enhanced mechanism of photogenerated carrier separation efficiency induced by dual built‐in fields is proposed to explain the high EQE of Ga2O3 SBUV photovoltaic devices. In addition, the organic–inorganic hybrid detector displays a high SBUV–visible rejection ratio (R255 nm/R405 nm of ≈450) and fast response speed (rise time of 60 ms and decay time of 88 ms). All these results indicate that the strategy proposed could provide reference for the fabrication of high‐performance Ga2O3 SBUV photovoltaic detectors.
Hybridizing PEDOT: PSS with the outer surface of an epitaxial Ga2O3 film is proposed to solve the problem of low external quantum efficiency (EQE) in traditional Ga2O3 heterojunction photovoltaic devices. At 0 V bias, the device exhibits an ultrahigh EQE (≈15%), which is attributed to the enhanced carrier separation by the construction of an additional organic‐inorganic hybrid heterojunction.
The construction of monolithic two‐terminal tandem solar cells (2T TSCs) offers the possibility of pursuing high power conversion efficiency (PCE) by overcoming the single‐junction Shockley–Queisser ...limit in photovoltaics. However, little attention is paid to simultaneously improve the stability by utilizing the complementary properties of various photoactive layers. Here, beyond the stacked photoactive layers featuring complementary absorption, all‐inorganic perovskite (CsPbI1.8Br1.2) is chosen as the photoactive layer of the front wide‐bandgap subcell for its intrinsic high thermal stability and ultraviolet (UV)‐filtering function to address the burn‐in and UV degradation of organic rear subcells. To realize their monolithic integration, the charge recombination efficiency in the interconnecting layer (ICL) between the two types of subcells is tentatively improved by surface reconstruction of all‐inorganic perovskite using trimethylammonium chloride. The repaired CsPbI1.8Br1.2 surface enables effective suppression of nonradiative recombination and facilitates hole transport, providing efficient charge recombination in the ICL in the 2T TSC. As a result, the all‐inorganic perovskite/organic 2T TSC delivers a promising PCE of 21.04%, accompanied by an ultrahigh open‐circuit voltage (Voc) of 2.05 V, which is nearly equal to the superposition of the respective Voc values of the subcells. More importantly, the 2T TSC simultaneously shows outstanding operational and UV stabilities.
A surface reconstruction strategy is proposed to optimize the surface defect states and crystallization dynamics in an all‐inorganic perovskite/organic two‐terminal tandem solar cell, leading to efficient hole transport and charge recombination in the interconnecting layer. Finally, a power conversion efficiency of 21.04% and robust operational stability are obtained.
Abstract
Improving power efficiency (
PE
) and reducing roll-off are of significant importance for the commercialization of white organic light-emitting diodes (WOLEDs) in consideration of energy ...conservation. Herein, record-beating
PE
of 130.7 lm W
−1
and outstanding external quantum efficiency (
EQE
) of 31.1% are achieved in all-fluorescence two-color WOLEDs based on a simple sandwich configuration of emitting layer consisting of sky-blue and orange delayed fluorescence materials. By introducing a red fluorescence dopant, all-fluorescence three-color WOLEDs with high color rendering index are constructed based on an interlayer sensitization configuration, furnishing ultrahigh
PE
of 110.7 lm W
−1
and
EQE
of 30.8%. More importantly, both two-color and three-color WOLEDs maintain excellent
PE
s at operating luminance with smaller roll-offs than the reported state-of-the-art WOLEDs, and further device optimization realizes outstanding comprehensive performances of low driving voltages, large luminance, high
PE
s and long operational lifetimes. The underlying mechanisms of the impressive device performances are elucidated by host-tuning effect and electron-trapping effect, providing useful guidance for the development of energy-conserving all-fluorescence WOLEDs.
This paper aims at investigating the problem of energy efficiency (EE) maximization for uplink multi-cell networks via a joint design of sub-channel assignment, power control, and antenna selection. ...We study the problem under two practical scenarios. In the first scenario, known as conventional antenna selection (CAS), there is only one radio frequency (RF) chain available at the mobile user and all the sub-channels for each user can be assigned to one of the antennas. For the second scenario, known as generalized antenna selection (GAS), the number of RF chains is equal to the number of antennas and the messages of each user can transmit over its assigned sub-channels via different antennas. The resource allocation design is formulated as a multi-objective optimization problem (MOOP) and then converted into a single objective optimization problem (SOOP) via the weighted Tchebycheff method. The considered problem is a mixed integer nonlinear programming (MINLP) which is generally intractable. To address this problem, a penalty function is introduced to handle the binary variable constraints. In order to obtain a computationally efficient suboptimal solution, the majorization minimization (MM) approach is proposed where a surrogate function serves as the lower bound of the objective function. Furthermore, we propose another low-complexity practical algorithm to further reduce the computational cost. Simulation results demonstrate the superiority of the proposed method and unveil an interesting trade-off between EE and SE for two considered scenarios.
Productivity of tree plantations is a function of the supply, capture and efficiency of use of resources, as outlined in the Production Ecology Equation. Species interactions in mixed-species stands ...can influence each of these variables. The importance of resource-use efficiency in determining forest productivity has been clearly demonstrated in monocultures; however, substantial knowledge gaps remain for mixtures. This review examines how the physiology and morphology of a given species can vary depending on whether it grows in a mixture or monoculture. We outline how physiological and morphological shifts within species, resulting from interactions in mixtures, may influence the three variables of the Production Ecology Equation, with an emphasis on nutrient resources nitrogen (N) and phosphorus (P). These include (i) resource availability, including soil nutrient mineralization, N₂ fixation and litter decomposition; (ii) proportion of resources captured, resulting from shifts in spatial, temporal and chemical patterns of root dynamics; (iii) resource-use efficiency. We found that more than 50% of mixed-species studies report a shift to greater above-ground nutrient content of species grown in mixtures compared to monocultures, indicating an increase in the proportion of resources captured from a site. Secondly, a meta-analysis showed that foliar N concentrations significantly increased for a given species in a mixture containing N₂-fixing species, compared to a monoculture, suggesting higher rates of photosynthesis and greater resource-use efficiency. Significant shifts in N- and P-use efficiencies of a given species, when grown in a mixture compared to a monoculture, occurred in over 65% of studies where resource-use efficiency could be calculated. Such shifts can result from changes in canopy photosynthetic capacities, changes in carbon allocation or changes to foliar nutrient residence times of species in a mixture. We recommend that future research focus on individual species' changes, particularly with respect to resource-use efficiency (including nutrients, water and light), when trees are grown in mixtures compared to monocultures. A better understanding of processes responsible for changes to tree productivity in mixed-species tree plantations can improve species, and within-species, selection so that the long-term outcome of mixtures is more predictable.
•A meta-analysis was used to integrate yield and NUE from alternative fertilization practices under four rice types in China.•The eff ;ectiveness of organic fertilizer, straw return and ...secondary/micronutrient on rice yield was affected by rice type.•The highest nitrogen use efficiency among the alternative fertilization options was achieved by slow-release N fertilizer.•Decreases in chemical fertilizer input can be realized by applying slow-release fertilizer and organic substitution.
Applying alternative fertilization practices instead of conventional fertilizers might improve rice yield and nutrient use efficiency in rice cropping systems. However, the results range widely among individual studies, making generalizations difficult. Here, we investigated five alternative fertilization options (slow-release nitrogen fertilizer, SRF; organic fertilizer, OF; straw return, SR; green manure, GM; secondary/micronutrient fertilizer, SMF) and performed a meta-analysis to quantify their effects on rice yield and nitrogen (N) use efficiency across different rice types in China. Yield responses were significantly positive under all alternative fertilization options relative to those obtained with conventional fertilization, and the magnitude of yield increase exhibited the following the order: OF (7.8%) > SRF (7.4%) > GM (6.7%) > SR (5.4%) > SMF (4.6%). Furthermore, the recovery efficiency (REN), agronomic efficiency (AEN), and the partial factor productivity of nitrogen (PFPN) were increased by 6.0–34.8%, 10.2–29.5%, and 4.7–6.9%, respectively under the alternative fertilization options relative to conventional fertilization. The application of SRF and SMF generated higher yield responses in single rice than in other rice types, whereas OF and SR application resulted in better performance in early and middle rice. The rice yield response was maximized when approximately 70% slow-release N was combined with approximately 30% conventional N according to the quadratic relationship between the percentage of slow-release N substituting conventional N and the yield response. It was estimated that the total N rate could be reduced by up to 32% without yield loss with the application of slow-release N fertilizer instead of conventional N fertilizer. When organic N fully or partially substituted inorganic N, yield response declined with increasing substitution level, and the substitution proportion needed to be controlled below 20% to maintain rice yield. The meta-analysis results clearly demonstrate that appropriate alternative fertilization options can increase both rice yield and nitrogen use efficiency, and that conventional chemical fertilizers can be partially replaced with alternative ones without negatively affecting rice productivity.
The Internet today transmits hundreds of terabits per second, consumes 9% of all electricity worldwide and grows by 20–30% per year1,2. To support capacity demand, massively parallel communication ...links are installed, not scaling favourably concerning energy consumption. A single frequency comb source may substitute many parallel lasers and improve system energy-efficiency3,4. We present a frequency comb realized by a non-resonant aluminium-gallium-arsenide-on-insulator (AlGaAsOI) nanowaveguide with 66% pump-to-comb conversion efficiency, which is significantly higher than state-of-the-art resonant comb sources. This enables unprecedented high data-rate transmission for chip-based sources, demonstrated using a single-mode 30-core fibre. We show that our frequency comb can carry 661 Tbit s–1 of data, equivalent to more than the total Internet traffic today. The comb is obtained by seeding the AlGaAsOI chip with 10-GHz picosecond pulses at a low pump power (85 mW), and this scheme is robust to temperature changes, is energy efficient and facilitates future integration with on-chip lasers or amplifiers5,6.
Stability, structural morphology, and rheological and filtration properties of bentonite (BT)–water suspensions as influenced by the addition of lignocellulosic nanomaterials, including bleached ...nanofibrillated cellulose (NFC) and lignin-containing NFC (LNFC), and water-soluble polymers (WSPs) were investigated in this work. The performance of the formed fluids varied with the distinct fiber morphology and/or chemical composition of the NFC and LNFC. The NFC helped bridge BT particles for enhanced rheological performance but adversely affected filtration properties by forming thicker filter cakes. Reground NFC led to improved rheological properties owing to more individualized fibers with an enlarged surface area, but its effect on fluid loss was insignificant. LNFC enhanced viscosity, yield stress, and gelation properties of the fluid with effectiveness varying with the actual lignin content in the system. Enhanced filtration performance was seen with the presence of lignin in LNFC ascribed by its hydrophobic nature as well as the formation of more compact filter cakes. The applied biopolymers depicted better compatibility with smaller cellulosic fibril dimensions and lower lignin content. Thus, LNFC with moderate amounts of lignin in combination with biopolymer additives can help achieve much-improved rheological and filtration performance of BT-based fluids with lower cost and more environmental friendliness.
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