Charge Transfer Energy Research Articles

Activation Energy Rechargeable Prussian Yellow Nano Film Electrode using Hydrated Ions

Aim: Interfacial charge transfer is a fundamental issue in both the science and technology of the batteries. In this work, the activation energy for the interfacial charge transfer, Ea, though PY thin film was estimated by measurement measurements of electrochemical impedance spectroscopy (EIS) for both monovalent and multivalent hydration cations: Li+, Na+, K+, Ca+2 and Mg+2 in aqueous electrolytes. Background: Rechargeable batteries have become quintessential energy conversion devices that are widely used in portable electronic devices and hybrid electric vehicles. PB and its analogues have open channels that allow rapid insertion/extraction of different cations and that lead to a long cycle of its in such as batteries (Na+, Li+ and K+). Objective: preparation of Prussian yellow Nanofilm on ITO glass by a simple chemical facial method and study of its charge/discharge processes of intercalation compounds in rechargeable features. Methods: The electrochemical measurements of potentiostat/galvanostat cyclic voltammograms and EIS were carried out in three-electrode cells, with Ag/AgCl as a reference electrode. Pt. and ITO|PY as working and counter electrodes respectively. The electrolytes were solutions of 0.1 M+z cation in water where M+z was one of the following cations: Li+, Na+, K+, Ca+2 or Mg+2. Results: The effect of hydration on the activation energy for the PY thin film was studied by the EIS at different temperatures. The ions K+ have an activation energy interfacial, which is lower than that of Na+ and Li+. So the coulombic repulsion at the interface is largely suppressed by the screening effect of ions hydration, explaining the small values of Ea with aqueous electrolyte. Furthermore, the hydration helped the Ca+2 and Mg+2 intercalation in PBA but with large values of Ea that were due to coulombic repulsion at the interface. Conclusion: Prussian blue can be considered among the most promising cathode materials for energy storage batteries because of their rigid open framework with large interstitial sites that can pertain to mono and bivalent cation mobility and accommodate volume variation during ions insertion/ extraction.

Pair density wave and superconductivity in a kinetically frustrated doped Emery model on a square lattice

The quest to understand the nature of superconductivity in the cuprates has spotlighted the pair density wave (PDW)–a superconducting state characterized by a spatially modulated order parameter. Despite significant advances in understanding PDW properties, conclusively demonstrating its presence in systems pertinent to cuprate superconductors remains elusive. In this study, we present a systematic density-matrix renormalization group study to investigate the Emery model (or the three-band Hubbard model) on two-leg square cylinders with negative electron hopping term tpp between adjacent oxygen sites. Kinetic frustration - introduced by changing the sign of oxygen-oxygen hopping - leads to a much reduced Cu-Cu antiferromagnetic exchange along with an enlarged charge transfer energy that changes the local properties of the model. At light doping levels, our findings reveal a ground state remarkably consistent with a PDW, exhibiting mutually commensurate superconducting (SC), charge, and spin density wave correlations. Intriguingly, the dominant SC pairing is observed between neighboring oxygen sites, diverging from the expected Cu sites in the positive tpp case. When the system incorporates moderate near-neighbor interactions, particularly an attractive Vpp between adjacent oxygen sites, the SC correlations become quasi-long-ranged, accompanied by a pronounced divergence in the PDW susceptibility. When the attractive Vpp increases further, the system gives way to an unconventional d-wave superconductivity.

Enhancing interfacial bonding between the copper foil and poly-ether-ether-ketone film via dual modification using UV/ozone and silane coupling

In this study, copper foil and poly-ether-ether-ketone (PEEK) film were directly bonded using nanosecond lasers. To strengthen the interfacial bonding between the copper foil and PEEK, ultraviolet/ozone (UV/ozone) and silane coupling treatment (APTMS) methods were proposed to modify the surface of the copper foil. The UV/ozone treatment led to the oxidation of the surface of the copper foil to Cu2O. The bonding interface and fracture were characterized and analyzed via optical digital microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The Cu/PEEK joints demonstrated a 95 % improvement in peel strength following UV/ozone + silane coupling treatments. Additionally, the red shift of the typical functional group wavenumbers demonstrated a strong hydrogen bond interaction between the copper foil treated with UV/ozone + silane coupling and the PEEK film. The mechanism behind the superior peel strength of UV/ozone + ATPMS-Cu/PEEK joints was subsequently validated through the density functional theory (DFT) analysis. Moreover, DFT was utilized to calculate the differential charge transfer and binding energies of Cu/silanol and Cu2O/silanol. As per the results, the bonding of Cu2O to silanol was more stable than that of Cu to silanol.

Promising impact of push–pull configuration into designed octacyclic naphthalene-based organic scaffolds for nonlinear optical amplitudes: a quantum chemical approach

In opto-electronics, non-fullerene (NF) derivatives are regarded as efficient non-linear optical (NLO) materials. The present investigation was based on designing NF naphthalene-based derivatives (PCMD1–D9) with D-π-A configuration from PCMR. DFT analysis at M06/6-311G (d,p) level was accomplished to explore the photonic behavior of PCMD1–D9 compounds. Various kind of analysis like; UV–Vis, density of state (DOS), natural bond orbitals (NBOs), transition density matrix (TDM) and frontier molecular orbitals (FMOs) analyses were accomplished to understand the NLO properties of said chromophores. The configuration change led to considerable charge distribution over highest occupied and lowest unoccupied molecular orbitals with minimum band difference. The energy gap trend for all the entitled compounds was observed as; PCMD8 < PCMD5 = PCMD9 < PCMD6 < PCMD7 < PCMD4 < PCMD3 < PCMD2 < PCMD1 with the least band gap of 2.048 eV in PCMD8 among all the compounds. The UV–Visible spectrum of the entitled chromophores manifested high values of λmax in derivatives contrary to PCMR. Additionally, NBO findings explored effective intramolecular charge transfer and maximum energy of stabilization (34.31 kcal/mol) for PCMD8 chromophore. The highest linear polarizability (<α>) and dipole moment (µtot) values were exhibited by PCMD5 at 2.712 × 10–22. and 1.995 × 10–17 esu, respectively. PCMD8 push–pull configured molecular entity exhibited highest first hyper-polarizability (βtot) at 4.747 × 10–27 esu and second hyper-polarizability at 6.867 × 10–32 esu. Overall, all the formulated chromophores exhibited significant NLO results contrary to PCMR. Hence, through this structural tailoring via various acceptors, effective NLO materials were obtained for optoelectronic applications.

Electronic comprehension of exchange bias effect in Sr2CoRuO6−δ thin-film

Sr2CoRuO6 in its bulk form shows spin glass behavior with a transition temperature of 95 K, and in its epitaxial thin film, it shows similar behavior with a transition temperature of 135 K. We have studied the structural, electronic, and magnetic properties of a polycrystalline thin film of oxygen-deficient Sr2CoRuO6−δ (SCRO), which shows ferrimagnetic or glassy behavior up to room temperature. The presence of oxygen deficiency causes multivalent cations Co3+ and Co2+ and Ru4+ and Ru5+, which introduces various kinds of magnetic interactions between Co3+–O–Co2+, Co3+–O–Ru4+, Co2+–O–Ru4+, Co3+–O–Ru5+, and Co2+–O–Ru5+ exchange paths, producing unusual exchange bias effects in the single layer thin film of SCRO. The interionic charge transfer between Co and Ru ions as a result of the negative charge transfer energy of the system helps in visualizing the unconventional exchange bias effect in the system.

Study on electrochemical supercapacitor performance of modified lavender biochar

In this study, we proposed a simple and low-cost method for the synthesis of heteroatom-doped porous carbons. Lavender waste residue as biomass precurso, using hydrothermal method synthesized N and S doped nano-layered porous carbon (NLPC-N/S) with high conductivity triumphantly. In the three-electrode system, NLPC-S showed an excellent capacitance (0.5A·g−1, 637.5 F·g−1) in 6 M KOH aqueous solution, which exceeded the specific capacitance of many reported biomass-derived porous carbons, and elucidated charge transfer mechanism and energy storage mechanism were both typical double-layer capacitance characteristics and pseudo-capacitance characteristics. The results of this study provide a cost-effective strategy for the recycling of biological waste, and that biomass carbon materials have high electrochemical performance potential in the field of energy storage.

Insight of charge injection barrier at the copper/epoxy resin interface with cross-linking molecules: First-principles calculation and experimental verification

Understanding charge injection at a metal/cross-linking epoxy resin (EP) interface facilitates the design and application of high-power electric and electronic devices. This paper focuses on the charge injection barrier at the metal/EP interfaces using first-principles calculation. Two fragmentary structures, obtained from cross-linking EP with amine and anhydride curing agent, were selected to construct interface models on a Cu(111) slab. The injection barrier, dipole moment, charge transfer, and vacuum energy level shift (Δ) at the interfaces were examined. The model with the anhydride groups produced higher electron and hole injection barriers than the interface model with the amine groups. The model with the amine groups had a higher Δ, which was derived from molecule dipole and charge transfer. An increase in the work function and Δ caused by an electric field caused an increase in the electron injection barrier and a decrease in the hole injection barrier. Experimental results of the methyl tetrahydrophthalic anhydride cross-linking EP showed a higher charge injection than that of m-phenylenediamine cross-linking EP, providing experimental verification of the theoretical calculation.

Facile synthesis of synergetic MoO2/MoS2@GO nanohybrid as energy-efficient electrode material for high-performance asymmetric supercapacitor applications

Rechargeable batteries and supercapacitors have been unitized extensively for energy storage applications, but each possesses its downsides, such as gradual charge transfer and low energy density, respectively. Hybrid supercapacitors are gaining extreme consideration due to their versatility in merging both power density and energy storage performance to an optimum level. Still, increasing energy and power density requires significant attention for their utilization in industrial applications. For this purpose, a prospective MoO2/MoS2@GO ternary nanohybrid is synthesized by employing a wet-chemical-aided approach and used as a synergistic electrode for high-performance asymmetric supercapacitor applications. FESEM images revealed that the enriched active sites, provided by highly porous shape, MoS2-covered MoO2 nanoparticles interconnected with large area GO sheets facilitate quicker ions transport along with an exceptional surface area. From half-cell measurements, the integrated electrode displayed a high specific capacitance of 1530 F/g at a current density of 2 A/g. For practical applications, an asymmetric device (ASC) device MoO2/MoS2@GO||AC||KOH was assembled which displayed the specific energy and specific power of 76 Wh/kg and 825 W/kg, respectively, in conjunction with excellent capacitance retention of 91.3 % after 10,000 continuous cycles. The theoretical Dunn model was used to validate experimental findings by quantitatively analyzing the maximum diffusive and capacitive contribution of 78 % (10 mV/s) and 72 % (100 mV/s) to overall ASC device capacity, respectively. These fascinating results show that graphene-hybridized metal oxide/sulfide composites could potentially be a great choice for high-performance energy and power applications in industrial, biomedical, and sensing technologies.

Charge transfer energy and band filling effects on two-hole Auger resonances in strongly correlated systems

Charge transfer energy and band filling effects on two-hole Auger resonances in strongly correlated systems

Improving the accuracy of the FMO binding affinity prediction of ligand-receptor complexes containing metals.

Polarization and charge transfer strongly characterize the ligand-receptor interaction when metal atoms are present, as for the Au(I)-biscarbene/DNA G-quadruplex complexes. In a previous work (J Comput Aided Mol Des2022, 36, 851-866) we used the ab initio FMO2 method at the RI-MP2/6-31G* level of theory with the PCM [1] solvation approach to calculate the binding energy (ΔEFMO) of two Au(I)-biscarbene derivatives, [Au(9-methylcaffein-8-ylidene)2]+ and [Au(1,3-dimethylbenzimidazole-2-ylidene)2]+, able to interact with DNA G-quadruplex motif. We found that ΔEFMO and ligand-receptor pair interaction energies (EINT) show very large negative values making the direct comparison with experimental data difficult and related this issue to the overestimation of the embedded charge transfer energy between fragments containing metal atoms. In this work, to improve the accuracy of the FMO method for predicting the binding affinity of metal-based ligands interacting with DNA G-quadruplex (Gq), we assess the effect of the following computational features: (i) the electron correlation, considering the Hartree-Fock (HF) and a post-HF method, namely RI-MP2; (ii) the two (FMO2) and three-body (FMO3) approaches; (iii) the basis set size (polarization functions and double-ζ vs. triple-ζ) and (iv) the embedding electrostatic potential (ESP). Moreover, the partial screening method was systematically adopted to simulate the solvent screening effect for each calculation. We found that the use of the ESP computed using the screened point charges for all atoms (ESP-SPTC) has a critical impact on the accuracy of both ΔEFMO and EINT, eliminating the overestimation of charge transfer energy and leading to energy values with magnitude comparable with typical experimental binding energies. With this computational approach, EINT values describe the binding efficiency of metal-based binders to DNA Gq more accurately than ΔEFMO. Therefore, to study the binding process of metal containing systems with the FMO method, the adoption of partial screening solvent method combined with ESP-SPCT should be considered. This computational protocol is suggested for FMO calculations on biological systems containing metals, especially when the adoption of the default ESP treatment leads to questionable results.

Electronic correlations in epitaxial CrN thin film

Chromium nitride (CrN) spurred enormous interest due to its coupled magnetostructural and unique metal-insulator transition. The underneath electronic structure of CrN remains elusive. Herein, the electronic structure of epitaxial CrN thin film has been explored by employing resonant photoemission spectroscopy (RPES) and X-ray absorption near edge spectroscopy study in combination with the first-principles calculations. The RPES study indicates the presence of a charge-transfer screened 3d ^n{underline{L}} (L: hole in the N-2p) and 3d ^{n-1} final-states in the valence band regime. The combined experimental electronic structure along with the orbital resolved electronic density of states from the first-principles calculations reveals the presence of Cr(3d)-N(2p) hybridized (3d ^n{underline{L}}) states between lower Hubbard (3d ^{n-1}) and upper Hubbard (3d ^{n+1}) bands with onsite Coulomb repulsion energy (U) and charge-transfer energy (Delta) estimated as approx 4.5 and 3.6 eV, respectively. It verifies the participation of ligand (N-2p) states in low energy charge fluctuations and provides concrete evidence for the charge-transfer (Delta<U) insulating nature of CrN thin film.

Identifying A Universal Activity Descriptor and a Unifying Mechanism Concept on Perovskite Oxides for Green Hydrogen Production.

Producing indispensable hydrogen and oxygen for social development via water electrolysis shows more prospects than other technologies. Although electrocatalysts have been explored for centuries, a universal activity descriptor for both hydrogen-evolving (HER) and oxygen-evolving reactions (OER) has not been developed. Moreover, a unifying concept has not been established to simultaneously understand HER/OER mechanisms. Here, we rationally bridge the relationships between HER/OER activities in three common electrolytes and over 10 representative material properties on 12 3d-metal-based model oxides through statistical methodologies. Orbital charge-transfer energy (Δ) can serve as an ideal universal descriptor, where a neither too large nor too small Δ (∼1eV) with optimal electron-cloud density around Fermi level affords the best activities, fulfilling Sabatier's principle. Systematic experiments and computations unravel that pristine oxide with Δ ≈ 1eV possesses metal-like high-valence configurations and active lattice-oxygen sites to help adsorb key protons in HER and induce lattice-oxygen participation in OER, respectively. After reactions, partially generated metals in HER and high-valence hydroxides in OER dominate proton adsorption and couple with pristine lattice-oxygen activation, respectively. These can be successfully rationalized by the unifying orbital charge-transfer theory. This work provides the foundation of rational material design and mechanism understanding for many potential applications. This article is protected by copyright. All rights reserved.

Intrinsic Photoconductivity Spectral Dependence as a Tool for Prediction of Open-Circuit Voltage in Organic Solar Cells

Organic materials are known for their variety of molecules. Methods to predict the parameters of organic photovoltaic (OPV) cells are required to avoid the time- and resource-consuming processes of manufacturing and testing OPVs. Usually, the open-circuit voltage (Uoc) is estimated as the difference between the ionization energy level of the electron donor molecule (Id) and the electron affinity level of the electron acceptor molecule (EAa). Various measurement methods are used to determine the energy level values of pure materials, which, when combined with energy level shifts due to the donor:acceptor interactions, make these estimations less precise. In this work, photoconductivity measurements were applied to the donor:acceptor films. Near threshold energy, the electron can be directly transferred from the donor to the acceptor molecule. The obtained charge transfer energy (ECT) shows the difference between Id and EAa in the film. This difference was compared to the Uoc value of an OPV made of the same donor:acceptor combination. We show that this approach provides less scattered results and a higher correlation coefficient compared to the Uoc estimation using energy level values.

Linear Scaling Calculations of Excitation Energies with Active-Space Particle-Particle Random-Phase Approximation.

We developed an efficient active-space particle-particle random-phase approximation (ppRPA) approach to calculate accurate charge-neutral excitation energies of molecular systems. The active-space ppRPA approach constrains both indexes in particle and hole pairs in the ppRPA matrix, which only selects frontier orbitals with dominant contributions to low-lying excitation energies. It employs the truncation in both orbital indexes in the particle-particle and the hole-hole spaces. The resulting matrix, whose eigenvalues are excitation energies, has a dimension that is independent of the size of the systems. The computational effort for the excitation energy calculation, therefore, scales linearly with system size and is negligible compared with the ground-state calculation of the (N - 2)-electron system, where N is the electron number of the molecule. With the active space consisting of 30 occupied and 30 virtual orbitals, the active-space ppRPA approach predicts the excitation energies of valence, charge-transfer, Rydberg, double, and diradical excitations with the mean absolute errors (MAEs) smaller than 0.03 eV compared with the full-space ppRPA results. As a side product, we also applied the active-space ppRPA approach in the renormalized singles (RS) T-matrix approach. Combining the non-interacting pair approximation that approximates the contribution to the self-energy outside the active space, the active-space GRSTRS@PBE approach predicts accurate absolute and relative core-level binding energies with the MAEs around 1.58 and 0.3 eV, respectively. The developed linear scaling calculation of excitation energies is promising for applications to large and complex systems.

Atomic layer deposition of SnO2 on In2O3 enables ultrasensitive NO2 detection at room temperature and DFT mechanism research

The unique electronic and chemical properties of metal oxide heterostructures are critical to the development of room temperature (RT) sensors. In this work, we report the design of In2O3/SnO2 heterostructures based on atomic layer deposition (ALD), which regulates the energy band structure of the material and promotes the electron transfer, thus enhancing the adsorption of target gases. The sensor based on In2O3/SnO2 demonstrates outstanding sensing performance at RT with an extreme response of 2900 to 10 ppm NO2, which to our knowledge outperforms the reported metal oxide sensors, as well as a detection limit of 61 ppb. Density functional theory (DFT) calculations show that the charge transfer (0.494 e) and interaction energy (2.19 eV) between In2O3/SnO2 and NO2 are significantly enhanced. This work highlights the critical function of heterostructured materials in enhancing the sensing capabilities of semiconductors, providing some hints for the design of ultrasensitive NO2 sensors.

An electronic origin of charge order in infinite-layer nickelates

A charge order (CO) with a wavevector {{{{{{{bf{q}}}}}}}}simeq left(frac{1}{3},, 0,, 0right) is observed in infinite-layer nickelates. Here we use first-principles calculations to demonstrate a charge-transfer-driven CO mechanism in infinite-layer nickelates, which leads to a characteristic Ni1+-Ni2+-Ni1+ stripe state. For every three Ni atoms, due to the presence of near-Fermi-level conduction bands, Hubbard interaction on Ni-d orbitals transfers electrons on one Ni atom to conduction bands and leaves electrons on the other two Ni atoms to become more localized. We further derive a low-energy effective model to elucidate that the CO state arises from a delicate competition between Hubbard interaction on Ni-d orbitals and charge transfer energy between Ni-d orbitals and conduction bands. With physically reasonable parameters, {{{{{{{bf{q}}}}}}}}=left(frac{1}{3},, 0,, 0right) CO state is more stable than uniform paramagnetic state and usual checkerboard antiferromagnetic state. Our work highlights the multi-band nature of infinite-layer nickelates, which leads to some distinctive correlated properties that are not found in cuprates.

Ternary-Metal Sn-Pb-Zn Perovskite to Reconstruct Top Surface for Efficient and Stable Less-Pb Perovskite Solar Cells.

Though Sn-Pb alloyed perovskite solar cells (PSCs) achieved great progress, there is a dilemma to further increase Sn for less-Pb requirement. High Sn ratio (>70%) perovskite exhibits nonstoichiometric Sn:Pb:I at film surface to aggravate Sn2+ oxidation and interface energy mismatch. Here, ternary metal alloyed (FASnI3 )0.7 (MAPb1- x Znx I3 )0.3 (x = 0-3%) is constructed for Pb% < 30% perovskite. Zn with smaller ionic size and stronger ionic interaction than Sn/Pb assists forming high-quality perovskite film with ZnI6 4- enriched at surface to balance Sn:Pb:I ratio. Differing from uniform bulk doping, surface-rich Zn with lower lying orbits pushes down the energy band of perovskite and adjusts the interface energy for efficient charge transfer. The alloyed PSC realizes efficiency of 19.4% at AM1.5 (one of the highest values reported for Pb% < 30% PSCs). Moreover, stronger bonding of Zn─I and Sn─I contributes to better durability of ternary perovskite than binary perovskite. This work highlights a novel alloy method for efficient and stable less-Pb PSCs.

Probing the effect of Y3+/Gd3+ on the optical properties of Gd2-xYxTiO5:Eu3+: Insight into local site-luminescence correlation

Phosphor converted light emitting diodes (pcLEDs) are considered as the most efficient materials to resolve the issue of energy scarcity. In this regard, the design of an efficient red phosphor could be a game changer due to the lack of the same in the current existing phosphor library. Here in this work, we have investigated high color purity, moderate photoluminescence quantum yield (PLQY) and long excited state lifetime red emitting Gd2-xYxTiO5:1.0 %Eu3+ phosphor with varying Y3+/Gd3+ ratio. It was found that higher Y3+ containingGd0.5Y1.50TiO5:1% Eu3+ emerged victorious in terms of luminescence intensity, asymmetry ratio and PLQY ∼ 10 %. Higher PLQY of this particular composition has been attributed to lowest non-radiative channels in them. The same has been further supported by PALS as it suggested lowest defect density in Gd0.5Y1.50TiO5:1% Eu3+ as most of the vacancies have moved out of the lattice to the surface and is responsible for improved optical properties as defect triggered non-radiative pathways reduced significantly. The O2–→ Eu3+ charge transfer energy on the other hand eases in higher gadolinium counterparts owing to more structural distortion of distorted pentagonal bipyramid (DPB) and distorted hexagonal bipyramid (DHB) in them. Based on the number of Stark components of 5D0→7F0 there are two types of Eu3+ with distinct chemical environments. It was inferred that longer lived trivalent europium ions are the one located at a less distorted DPB whereas short lived Eu3+is ascribed to the one occupying a highly distorted DHB. The trend in Judd-Ofelt parameter Ω4 < Ω2 revealed that Eu3+ ions are localized in high asymmetric locations in all the samples under the doping level used in this work. The high branching ratio of 5D0→7F2 transitions for all the samples reflected in very high color purity of more than 99 %. These results suggest that Eu3+doped A2TiO5 luminescent crystals with moderate PLQY, high red color purity and long excited state lifetime could serve as efficient red phosphor and with further improvement can be potential candidate for various applications.

Synergistic Effect between Fe&lt;sup&gt;4+&lt;/sup&gt; and Co&lt;sup&gt;4+&lt;/sup&gt; on Oxygen Evolution Reaction Catalysis for CaFe&lt;sub&gt;1−&lt;/sub&gt;&lt;i&gt;&lt;sub&gt;x&lt;/sub&gt;&lt;/i&gt;Co&lt;i&gt;&lt;sub&gt;x&lt;/sub&gt;&lt;/i&gt;O&lt;sub&gt;3&lt;/sub&gt;

Chemical substitution is an effective way to improve electrocatalytic properties in transition metal oxides. We investigate the synergistic effect between Fe4+ and Co4+ ions on the catalytic activity for oxygen evolution reaction (OER) in the Fe-Co-mixed perovskite oxide CaFe1–xCoxO3. The OER activity of CaFe1–xCoxO3 is substantially increased by small amounts of Co (Fe) doping into CaFeO3 (CaCoO3), leading to the superiority compared to the pure Fe and Co perovskite oxides. The x dependences of the OER overpotential and specific activity for CaFe1–xCoxO3 (0.05 ≦ x ≦ 0.95) are expressed by constant offset from the weighted average between CaFeO3 and CaCoO3, which can be interpreted to be the synergistic effect between Fe4+ and Co4+ ions on OER activity. The absence of the optimum x for the highest activity for CaFe1–xCoxO3 contrasts with the volcano-like plots reported in various mixed-metal oxides. First-principle calculations using the special quasirandom structure models on CaFe1–xCoxO3 (x = 0.03–0.5) demonstrate that about half the amount of Fe4+ is electronically activated to possess smaller charge-transfer energies, corroborating the enhancement of catalytic activity in CaFe1–xCoxO3. These findings provide new insight into the synergistic effects in complex transition metal oxide catalysts.

Nonfused Ring Electron Acceptors for Ternary Polymer Solar Cells with Low Energy Loss and Efficiency Over 18.

Ternary polymer solar cells(PSCs) have been identified as an effective approach to improving power conversion efficiency (PCE) of binary PSCs. However, most of the third component, especially Y-series non-fullerene acceptors, is a fused ring acceptor which often requires a rather tedious synthesis and the use of hazardous organostannane reagents. In this work, two nonfused ring acceptors IOEH-4F and IOEH-N2F are synthesized by a green synthetic route and incorporated into PM6:Y6 blend. Encouragingly, the IOEH-4F and IOEH-N2F-based ternary PSCs exhibited more efficient charge transfer, exciton separation, and lower energy loss than PM6:Y6-based PSCs. And the IOEH-4F and IOEH-N2F-based ternary PSCs achieved an impressive PCE of 17.80% and 18.13%, respectively, which are higher than that of PM6:Y6 based PSCs (16.18%). Notably, these PCE values are also the highest PCEs for ternary PSCs including non-fused ring acceptors. Importantly, even when the IOEH-N2F:Y6 ratios increased from 0.05:1.2 to 0.50:1.2, the PCE of IOEH-N2F-based ternary PSCs (16.70%) are still higher than that of PM6:Y6 based PSCs, indicating the great potential for cost saving. It is believed that the findings will help the design of better nonfused ring acceptors and the optimization of corresponding ternary PSCs with cost-saving advantage.