Dual Electron Research Articles

Band order reversal and valley engineering driving to dual high electron and hole mobility in strained monolayer BS

Strain engineering is an effective method to tune the physical properties of materials. In this work, we found that applying 5% biaxial compression to monolayer boron sulfur can simultaneously induce a band order reversal of valence bands and valley engineering of conduction bands. This change significantly enhances the room temperature intrinsic mobility, boosting it from 2 to 260 cm2 V−1 s−1 for holes and 63 to 543 cm2 V−1 s−1 for electrons. The high hole mobility surpasses that of bulk GaN and silicon. We further demonstrate that the valence band order reversal not only lifts the px/y state above the pz states, giving to a more dispersive highest valence band, and thus smaller electron scattering channels and hole effective mass, but also shifts the stronger σz bonding to weaker π-bonding characteristics, resulting in smaller electron–phonon coupling strength. Those combined effects results in a substantial increase in hole mobility.

Dual Electron Donating Metal‐Boron Reaction Center Boosts Electrocatalytic Urea Synthesis from N2 and CO2

AbstractUrea (NH2CONH2) production by electrosynthesis at mild conditions has been hampered due to the lack of systematic evaluation of pathways in effectively activating inert N2 and CO2 molecules and facilitating the formation of C−N bonds. In this work, we evaluated 16 transition metal (M) atoms anchored on carbon nitride nanosheet with boron (B) doping (M−B@C2N) for boosting urea production by theoretical calculations. All possible urea synthesis pathways, (i) CO2 pathway, (ii) OCOH pathway, (iii) CO pathway, and (iv) NCON pathway, were comparatively studied on Cu, Fe, Co, Ni−B@C2N. This systematic calculation identified that the first reduction of *N2 is the key step for urea synthesis. We found that the bond index of *N2 shows a strong correlation with ΔG*N2→*NNH, so they are promising descriptors for screening. Through the screening, we found that Nb‐ and Mo−B@C2N show a low limiting potential of −0.56 and −0.53 V. Although previous studies found that spin could promote C−C bond formation on M−B@C2N, we found that for C−N coupling, such effects by spin were only active for Nb−B@C2N. Combining boron and early transition metal atoms allows for neighboring reaction sites that simultaneously donate electrons to activate inert N2 and CO2 for efficient urea synthesis.

Reversed I1Cu4 single-atom sites for superior neutral ammonia electrosynthesis with nitrate

Electrochemical ammonia (NH3) synthesis from nitrate reduction (NITRR) offers an appealing solution for addressing environmental concerns and the energy crisis. However, most of the developed electrocatalysts reduce NO3- to NH3 via a hydrogen (H*)-mediated reduction mechanism, which suffers from undesired H*-H* dimerization to H2, resulting in unsatisfactory NH3 yields. Herein, we demonstrate that reversed I1Cu4 single-atom sites, prepared by anchoring iodine single atoms on the Cu surface, realized superior NITRR with a superior ammonia yield rate of 4.36 mg h-1 cm-2 and a Faradaic efficiency of 98.5% under neutral conditions via a proton-coupled electron transfer (PCET) mechanism, far beyond those of traditional Cu sites (NH3 yield rate of 0.082 mg h-1 cm-2 and Faradaic efficiency of 36.5%) and most of H*-mediated NITRR electrocatalysts. Theoretical calculations revealed that I single atoms can regulate the local electronic structures of adjacent Cu sites in favor of stronger O-end-bidentate NO3- adsorption with dual electron transfer channels and suppress the H* formation from the H2O dissociation, thus switching the NITRR mechanism from H*-mediated reduction to PCET. By integrating the monolithic I1Cu4 single-atom electrode into a flow-through device for continuous NITRR and in situ ammonia recovery, an industrial-level current density of 1 A cm-2 was achieved along with a NH3 yield rate of 69.4 mg h-1 cm-2. This study offers reversed single-atom sites for electrochemical ammonia synthesis with nitrate wastewater and sheds light on the importance of switching catalytic mechanisms in improving the performance of electrochemical reactions.

Enhancing anaerobic ammonium oxidation via polymeric ferric sulfate (PFS)-Mediated dual-electron Acceptor: A solution to nitrite deficiency

In addressing the issue of the unstable supply of electron acceptors (nitrite) during Anammox, researchers have often overlooked that the electron transfer process in anammox bacteria (AnAOB) is not restricted to the intracellular, extracellular electron transfer can also serve as an alternative pathway. This study utilized Fe3+ as an adjunctive electron acceptor, coupling Anammox with ferric iron reduction (Feammox) by introducing polymeric ferric sulfate (PFS) in the Anammox system. This approach achieved effective nitrogen removal even when nitrite was deficient. At a NO2–-N to NH4+-N ratio of 0.5, the Feammox-Anammox combined system maintained stable nitrogen removal under the dual electron acceptor, with total nitrogen and NH4+-N removal efficiency of 85 % and 91 %, respectively. The contribution of Feammox and Anammox to NH4+-N removal was 45 % and 55 %, respectively. TEM-EDS confirmed the presence of iron elements across the periphery, periplasm, and cytoplasm of AnAOB, suggesting the involvement of PFS in the metabolic and electron transfer processes. Notably, the introduction of Fe3+ and the limitation of nitrite availability resulted in increased relative abundances of FeOB (Thermomonas) and FeRB (Ignavibacterium) to 30 % and 3.6 %, respectively, indicating that the electron transfer process with Fe3+ as the electron acceptor was continuously intensified, as well as a cycle of Fe3+ / Fe2+ was established. Due to unique nitrogen metabolism mode and high Fe3+ tolerance, the abundance of Candidatus_Brocadia was enriched up to 7.2 %, which alternately dominated the Anammox process with Candidatus_Kuenenia, providing favorable conditions for AnAOB to carry out the extracellular electron transfer process. These findings provide a novel strategy for improving the stability and efficiency of the Anammox process under deficient nitrite supply.

Enhanced Energy Storage Properties and DFT Investigation of a Zn-Co-Mo Heterojunction Rich in Oxygen Vacancies with Dual Electron Transport Pathways.

Petal-like heterojunction materials ZnCo2O4/CoMoO4 with abundant oxygen vacancies are prepared on nickel foam (NF) using modified ionic hybrid thermal calcination technology. Nanoscale ion intermixing between Zn and Mo ions induces oxygen vacancies in the annealing process, thus creating additional electrochemical active sites and enhancing the electrical conductivity. The ZnCo2O4/CoMoO4 conductive network skeleton forms the primary transport pathway for electrons, while the internal electric field of the heterojunction serves as the secondary pathway. ZnCo2O4/CoMoO4 exhibits excellent rate performance and high capacity attributable to its unique double electron transport mode and the effect of oxygen vacancies. The initial discharge capacity at a current of 0.1 A g-1 is approximately 1774 mAh g-1, and the reversible capacity remains at 1100 mAh g-1 after 200 cycles. After a high current of 1 A g-1, the reversible capacity is observed to remain at approximately 1240 mAh g-1. The electronic structure, crystal structure, and work function of the heterojunction interface model are then analyzed by density functional theory (DFT). The analysis results indicate that the charge at the ZnCo2O4/CoMoO4 interface is unevenly distributed, which leads to an enhanced degree of electrochemical reaction. The presence of an internal electric field improves the transport efficiency of the carriers. Experimental and theoretical calculations demonstrate that the ZnCo2O4/CoMoO4 anode material designed in this work provides a reference for fabricating transition metal oxide-based lithium-ion batteries.

A self-sustaining effect induced by iron sulfide generation and reuse in pyrite-woodchip mixotrophic bioretention systems: An experimental and modeling study

Dual electron donor bioretention systems have emerged as a popular strategy to enhance dissolved nitrogen removal from stormwater runoff. Pyrite-woodchip mixotrophic bioretention systems showed a promoted and stabilized removal of dissolved nutrients under complex rainfall conditions, but the sulfate reduction process that can induce iron sulfide generation and reuse was overlooked. In this study, experiments and models were applied to investigate the effects of filler configuration and dissolved organic carbon (DOC) dissolution rate on treatment performance and iron sulfide generation in pyrite-woodchip bioretention systems. Key parameters govern that DOC dissolution and microbe-mediated processes were obtained by experiments. The water quality models that integrate one-dimensional constant flow, sorption and microbial transformation kinetics were used to predict the performance of bioretention systems. Results showed that the mixotrophic bioretention system with woodchip mixed in the vadose zone and pyrite in the saturated zone achieves a better performance in both nitrogen removal efficiency and by-product control. Comparably, woodchip and pyrite mixed in the saturated zone could encounter a high secondary pollution risk. The sensitivity coefficients of oxic/anoxic DOC dissolution rates to total nitrogen removal are 0.36 and -2.43 respectively. Iron sulfide generation was affected by DOC distribution and the competition between heterotrophic denitrifiers, autotrophic denitrifiers, and sulfate-reducing bacteria (SRB). DOC accumulation has an antagonistic effect on iron production and sulfate reduction. Extra DOC accumulation favors sulfate reduction while high DOC concentration inhibits pyrite-based denitrification and reduces Fe(III) production. The recycling of iron sulfide can improve the robustness and sustainability of bioretention systems.

Catalytic mechanisms for As(III) oxidation by H2O2 over TiO2 surfaces, and effects of support, vacancy and photoirradiation

As(III) is much more toxic than As(V) while shows apparently lower affinity at minerals surfaces. Oxidation of As(III) to As(V) by H2O2 over anatase surface provides an attractive avenue for pollution control, and the chemocatalytic and photocatalytic mechanisms are unraveled by means of the DFT + D3 approach. Impacts of anatase as support, O2c/O3c vacancy, photoirradiation are addressed as well. As(III) oxidation under various reaction conditions leads to As(V) through dual electron transfers, while energy barriers differ substantially and decline as 1.80 (direct oxidation) > 1.35 (anatase as support) > 1.24 (O3c vacancy) > 0.50 (chemocatalysis) > 0.28 (photocatalysis) ≥ 0.26 (O2c vacancy) eV. Anatase as support promotes the reaction through bonding with H2O2/As(OH)3 and electron transfers, and its close participation during chemocatalysis produces the TiOOH active site that causes As(III) oxidation to proceed facilely under ambient circumstances. TiOOH exists in two forms (monodentate and bidentate mononuclear) and is critical for chemocatalysis, while its destruction for O3c vacancy exhibits strongly adverse effects to As(III) oxidation. Photoirradiation readily generates the OH• radicals, and corresponding mechanism is plausible while less preferred than the newly posed mechanism based on the Ti(H2O2) active site. Synergism among a number of surface atoms conduces to the superior activity for O2c vacancy and photocatalysis. Results provide a comprehensive understanding for As(III) oxidation to As(V) by H2O2, and facilitate catalysts design for As(III) oxidation that alleviates environmental pollution.

Coupling Electro-Fenton and Electrocoagulation of Aluminum-Air Batteries for Enhanced Tetracycline Degradation: Improving Hydrogen Peroxide and Power Generation.

Electro-Fenton (EF) technology has shown great potential in environmental remediation. However, developing efficient heterogeneous EF catalysts and understanding the relevant reaction mechanisms for pollutant degradation remain challenging. We propose a new system that combines aluminum-air battery electrocoagulation (EC) with EF. The system utilizes dual electron reduction of O2 to generate H2O2 in situ on the air cathodes of aluminum-air batteries and the formation of primary cells to produce electricity. Tetracycline (TC) is degraded by ·OH produced by the Fenton reaction. Under optimal conditions, the system exhibits excellent TC degradation efficiency and higher H2O2 production. The TC removal rate by the reaction system using a graphite cathode reached nearly 100% within 4 h, whereas the H2O2 yield reached 127.07 mg/L within 24 h. The experimental results show that the novel EF and EC composite system of aluminum-air batteries, through the electroflocculation mechanism and ·OH and EF reactions, with EC as the main factor, generates multiple •OH radicals that interact to efficiently remove TC. This work provides novel and important insights into EF technology, as well as new strategies for TC removal.

Molten Salt Synthesis of Ti3C2/Cu Cocatalyst for Enhanced TiO2 Photocatalytic CO2 Reduction

AbstractPhotocatalytic reduction of CO2 is considered as a crucial pathway towards achieving sustainable energy and environmental goals. Nonetheless, attaining efficient CO2 conversion poses significant challenges, primarily due to the slow dynamics of charge carriers and the high activation energy required to break C=O bonds. In this study, a novel strategy involving Lewis acid molten salt etching is investigated to engineer a titanium oxide (TiO2)‐based photocatalysts with dual electron transfer channels (i. e., Ti3C2/Cu), which targets the photoreduction of CO2 to CO and CH4. Thanks to the dual electron transfer channels presented in the cocatalysts (Ti3C2/Cu), in conjunction with the numerous heterogeneous interfaces between TiO2 and the Ti3C2/Cu cocatalysts, this hybrid catalyst not only reduces charge transfer resistance but also accelerates the dynamics of photogenerated charge carriers. Consequently, the TiO2/Ti3C2/Cu hybrid catalyst demonstrates an exceptional photocatalytic CO2 reduction rate of 13.67 μmol g−1 h−1, with a total utilized photoelectron number (UPN) of 102.34 μmol g−1 h−1. which is 3.99‐fold higher than that of unmodified TiO2. This research provides a new approach for the preparation of dual cocatalysts through a one‐step molten salt synthesis process.

Stable and efficient all-inorganic quantum dot light-emitting diodes based on a double-layer electron transport layer

Abstract The most advanced quantum light-emitting diodes (QLEDs) have achieved almost unity external quantum efficiency (EQE) due to organic materials for high transport efficiency, but organic materials are less stable and can lead to irreversible degradation of the devices. The use of stable inorganic hole-transporting layers (HTLs), such as NiOx, becomes a promising alternative. ZnO is a common electron-transporting material in QLEDs, which possesses high mobility and tunable conductivity properties, but ZnO-based QLEDs devices undergo loss of efficiency due to exciton bursting, poor shelf stability, and pronounced positive aging effects. SnO2, as a common electron-transporting material, has better stability than ZnO. In this work, the SnO2/ZnO dual electron transport layer strategy is adopted, which can reduce the non-radiative burst and aging behavior, and at the same time, the electron transport is regulated by adjusting the film thickness. Inorganic QLEDs with high external quantum efficiency (9.5%) as well as high operational stability have been fully realized. This strategy provides effective ideas for future high-performance display devices.

Catalytic performance and mechanism of PtxVW catalyst for selective catalytic oxidation of high-concentration NH3

It is foreseeable that a high-concentration NH3 may exist in exhaust gas of NH3-fuel engines, which may result in some negative damages to ecological environment. Herein, a series of PtxVW catalysts with extremely low Pt doping amounts were synthesized with the aim to remove high-concentration NH3 efficiently via selective catalytic oxidation (SCO) method. The results showed that, Pt0.04VW catalyst (0.04 wt% Pt) achieved a complete NH3 conversion at 250 ºC. Both catalytic activity and N2 selectivity of Pt0.04VW catalyst were much superior over Pt/Al2O3 catalyst (1 wt% Pt) in a wide temperature range of 250–450 ºC. XPS, Raman and H2-TPR results indicated that Pt existed in the lattice of VOx and formed Pt-V bimetallic oxides. The interaction between Pt and V played a key role in the NH3-SCO reactions. DFT calculation demonstrated that dual electron transfer pathways between Pt and V atoms in PtxVW catalysts were beneficial for NH3 coordination on Lewis acid sites, then enhancing NH3-SCO reactions. In-situ DRIFTS and NH3-TPD product analysis suggested that NH3-SCO reactions on Pt0.04VW catalyst surface abide by internal selective catalytic reduction (i-SCR) and hydrazine mechanisms. Moreover, coordinated NH3 species on Lewis acid sites, bidentate nitrate species were the main intermediates in NH3-SCO reactions over Pt0.04VW catalyst.

Covalent Organic Framework with Donor1‐Acceptor‐Donor2 Motifs Regulating Local Charge of Intercalated Single Cobalt Sites for Photocatalytic CO2 Reduction to Syngas

AbstractCovalent organic framework (COF) has attracted increasing interest in photocatalytic CO2 reduction, but it remains a challenge to achieve high conversion efficiency owing to the insufficient active site and fast charge recombination. Rationally optimizing the electronic structures of COF to regulate the local charge of active sites precisely is the key point to improving catalytic performance. Herein, intercalated single Co sites coordinated by imine‐N motifs have been designed by using trinuclear copper‐based imine‐COFs with distinct electronic moieties via a molecular engineering strategy. It is confirmed that the charge delivery property and local charge distribution of these heterometallic frameworks can be profoundly influenced by electronic structures. Among these featured structures with mixed‐state copper clusters, Co/Cu3‐TPA‐COF stands out for an exceptional photocatalytic CO2 reduction activity and tunable syngas (CO/H2) ratio by changing various bipyridines. Experimental and theoretical results indicate that interlayer Co‐imine N motifs on the donor1‐acceptor‐donor2 structures facilitate the formation of a highly separated electron‐hole state, which effectively induces the oriented electron transfer from dual electron donors to Co centers, achieving an enhanced CO2 activation and reduction. This work opens up an avenue for the design of high‐performance COF‐based catalysts for photocatalytic CO2 reduction.

Covalent Organic Framework with Donor1-Acceptor-Donor2 Motifs Regulating Local Charge of Intercalated Single Cobalt Sites for Photocatalytic CO2 Reduction to Syngas.

Covalent organic framework (COF) has attracted increasing interest in photocatalytic CO2 reduction, but it remains a challenge to achieve high conversion efficiency owing to the insufficient active site and fast charge recombination. Rationally optimizing the electronic structures of COF to regulate the local charge of active sites precisely is the key point to improving catalytic performance. Herein, intercalated single Co sites coordinated by imine-N motifs have been designed by using trinuclear copper-based imine-COFs with distinct electronic moieties via a molecular engineering strategy. It is confirmed that the charge delivery property and local charge distribution of these heterometallic frameworks can be profoundly influenced by electronic structures. Among these featured structures with mixed-state copper clusters, Co/Cu3-TPA-COF stands out for an exceptional photocatalytic CO2 reduction activity and tunable syngas (CO/H2) ratio by changing various bipyridines. Experimental and theoretical results indicate that interlayer Co-imine N motifs on the donor1-acceptor-donor2 structures facilitate the formation of a highly separated electron-hole state, which effectively induces the oriented electron transfer from dual electron donors to Co centers, achieving an enhanced CO2 activation and reduction. This work opens up an avenue for the design of high-performance COF-based catalysts for photocatalytic CO2 reduction.

Dual electron donor sites assist rapid migration of carriers for organic elimination under sunlight: From batch experiment to pilot-plant operation

The novel perovskite-type photocatalyst Y2Ba4O7 (YBaO) was designed based on the high temperature superconductor YBCO, utilizing first-principles calculations. The catalytic degradation and mineralization ability of YBaO material towards ciprofloxacin (CIP) were analyzed under visible light for the first time. The successfully prepared YBaO consists of Y2O3: BaO = 32.519: 59.901% by performing EDS and XRF analysis. The band gap of YBaO is estimated to be 2.47 eV by UV–vis, indicating the visible-light absorption ability. Based on DFT calculations, the formation energy of YBaO is −3.3 eV, indicating this crystal structure is relatively stable. Ba and Y act as electron donors at the same time, while O acts as electron acceptor, which means the dual electron donor sites exist. In addition, calculated by state density, the valence band maximum (VBM) is mostly attributed to the O-p orbital. For conductive band minimum (CBM) on spin-up part, the total DOS is the attribution of Ba, Y and O, as well as the contribution degree is Ba > Y > O in turn. Fukui index indicates the N34 and N37 (f0 = 0.0347 and 0.0494) on the piperazine ring, F atoms on benzene ring (f0 = 0.0431), C1 (f0 = 0.0345) and C2 (f0 = 0.0388) in quinolone structures are the active sites attacked by free superoxide radical due to saturated bonds and steric hindrance effects. In addition, a solar photocatalytic reaction device was developed, which effectively amplified the light flux by 80 times. The reaction rate constants under concentrated day conditions are 9.39 times and 18.86 times of those under unconcentrated day conditions, respectively, suggesting its potential to address a pressing environmental issue by offering a cost-effective, sustainable, and efficient solution for organic contaminants removal in water matrices.

Facilitating Atom Probe Tomography of 2D MXene Films by In Situ Sputtering.

2D materials are emerging as promising nanomaterials for applications in energy storage and catalysis. In the wet chemical synthesis of MXenes, these 2D transition metal carbides and nitrides are terminated with a variety of functional groups, and cations such as Li+ are often used to intercalate into the structure to obtain exfoliated nanosheets. Given the various elements involved in their synthesis, it is crucial to determine the detailed chemical composition of the final product, in order to better assess and understand the relationships between composition and properties of these materials. To facilitate atom probe tomography analysis of these materials, a revised specimen preparation method is presented in this study. A colloidal Ti3C2Tz MXene solution was processed into an additive-free free-standing film and specimens were prepared using a dual beam scanning electron microscope/focused ion beam. To mechanically stabilize the fragile specimens, they were coated using an in situ sputtering technique. As various 2D material inks can be processed into such free-standing films, the presented approach is pivotal for enabling atom probe analysis of other 2D materials.

Dual electron microregion with oxygen vacancy of Fe0.8La/MCM-48 in bridging peracetic acid and ozonation: Taking the pathway of free radical or nonradical generation?

Efficient tetracycline hydrochloride (TCH) degradation and interface reaction mechanism were investigated by constructing nonradical pathways in heterogeneous peracetic acid coupling with ozonation (O3/PAA) process. Ball-milling assisted Fe–La anchoring MCM-48 catalysts with dual electron microregion was designed to trigger 1O2-dominated non-radical for strong immunity to environment interference. Results exhibited that 83.4% degradation efficiency of TCH was achieved by Fe0.8La/MCM-48/O3/PAA system in only 2 min and 94% TCH was degraded in a 12-hour continuous flow experiment. La with oxygen vacancy regulated the local atomic environment and electron structure of Fe sites, which could initiate peracetic acid activation to promote 1O2 production by surface adsorbed atomic oxygen (*Oad) reaction and this process overcame a lower reaction energy barrier than the binding of surface *Oad to O3. This work offers a reasonable interpretation for Fe–La synergy for inducing non-free radical route, which furnishes theoretical support and practical application for heterogeneous O3/PAA.

Surface state modulation of carbon dots for efficient generation of hydrogen peroxide

Electrocatalytic dual electron oxygen reduction to hydrogen peroxide (2e ORR) is considered a special and sustainable method for on-site continuous production of hydrogen peroxide. Oxygen doped carbon based materials have demonstrated their superiority in the generation of H2O2. However, there is still a lack of direct experimental evidence to determine the true active site on complex carbon surfaces. In this work, we introduce only carboxyl functional groups on the surface of carbon dots by a mild and simple synthesis method to study the specific COOH functional groups on the generation of H2O2. The H2O2 selectivity was correlated with the contents of COOH functional groups. In alkaline environments, the citric acid modified CDs (CA-OCDs) own excellent catalytic ability for 2e ORR, showing a maximum starting potential of 0.829 V (vs. RHE) and a high selectivity of 89.7 % over a wide potential range of 0.2–0.7 V (vs. RHE). In actual H2O2 production, the Faraday efficiency (FE) of CA-OCDs can be up to 97 %, and the yield achieves 838 mmol gcatalyst−1 h−1. This work provides an effective and simple strategy for designing efficient carbon-based catalysts for sustainable H2O2 electrosynthesis.

Numerical simulation and performance optimization of all-inorganic CsGeI3 perovskite solar cells with stacked ETLs/C60 by SCAPS device simulation

Perovskite solar cells, particularly those featuring CsGeI3 as the absorption layer, are distinguished by their non-toxicity and inherent stability. In this work, to optimize the interface contact of the cells, enhance their built-in electric field, and consequently augment the power conversion efficiency, a C60 layer was incorporated into the electronic transport layer. This incorporation led to the formation of a novel dual-electron transport layer structure. Employing SCAPS-1D simulation software, a range of electron and hole transport layer combinations was explored. The optimal configuration was determined to be FTO/SnO2/C60/IDL1/CsGeI3/IDL2/Cu2O/Au. The absorption layer's thickness, doping concentration, defect density, and bandgap were optimized. Furthermore, an investigation was conducted on the performance implications arising from alterations in the dual electron conduction layer SnO2/C60's thickness, bandgap, and doping concentration. Concurrently, adjustments were made to refine the defect density in the interface defect layer, and an investigation was carried out to determine the optimal operational temperature. These endeavors culminated in the achievement of an impressive 30.34% optimal power conversion efficiency, representing a significant 54.25% enhancement over the pre-optimization efficiency of 19.67%. This work stands as a valuable reference for subsequent investigations into the dual electron transport layer structure in Ge-based perovskite solar cells.

Dual External Electron Injection Barrier Layers Enable High‐Performance Near‐Infrared Organic Photodetectors Realizing Real‐Time Heart Rate Monitoring

AbstractNear‐infrared organic photodetectors (NIR‐OPDs) play important roles in medical monitoring, bio‐imaging and night vision, etc. Among them, bulk heterojunction (BHJ)‐based photodiode type NIR‐OPDs exhibit extraordinary characteristics in photoresponse and photosensitivity. However, their dark current density (Jd) often increases severely as the bias voltage increases, which seriously reduces detection sensitivity for NIR light. Here, a novel structure of dual external electron injection barrier layers (DEBLs) composed of “m‐MTDATA/DPEPO:HAT‐CN” is proposed to overcome this challenge. For DEBLs, a barrier is established with high injection barrier and long effective injection barrier width to prevent external electrons injection under bias voltage for suppressing Jd (4.22 × 10−8 A cm−2 better than 1.47 × 10−5 A cm−2 of the traditional device at −2 V). More importantly, photo‐generated carriers have almost no loss through DEBLs. Therefore, high and stable detectivity (D*) over 1013 Jones are realized under 850 nm from 0 V to nearly −1 V and even far over 1012 Jones at −2 V. More strikingly, the structure of DEBLs is proven to be effective and universal in NIR‐OPDs and the device based on it successfully realize the real‐time heart rate monitoring of various human states, which exhibits great potential in human health monitoring.

Perovskite Solar Cells with Extremely High 24.63% Efficiency through Design of Double Electron Transport Layers and Double Luminescent Converter Layers

AbstractIntroduction of fluorescent down‐conversion layer inside perovskite solar cells (PSCs) can highly improve the ultraviolet response of the devices and the light stability. However, such a device is usually confronted with the problem of inter‐diffusion with the perovskite absorber layer, which severely limits its further development. To address this problem, herein, this work employs an interfacial dual electron transport layers (ETLs) strategy, sandwiching Cd‐CsPbCl3:Mn2+ luminescent quantum dots within gap of the ETLs, which not only reduces the interface energy level offset, but also improves the nucleation and crystallization kinetics of perovskite films and prevents their diffusion to the perovskite absorber layer. As a result, the efficient synergy effect effectively elevates both the open‐circuit voltage and fill factor of the PSCs, reaching maximum values of 1.181 V and 81.14%, respectively, finally delivering progressively increased device power conversion efficiency (PCE) of 24.32% with significantly improved light stability. To further improve the ultraviolet response, this work further adopts the strategy of dual fluorescent conversion layers inside and outside the PSCs, and finally obtains PCE of 24.63%, which is the best for various luminescent conversion cells. This work opens a new door for the development of efficient and stable photoluminescence conversion PSCs.