Energy Level Matching Research Articles

Improved Efficiency and Stability in Pure-Red CdSe Nanoplatelet LEDs Enabled by Gradient Alloyed CdSeS/CdZnS Crown/Shell.

Anisotropic nanoplatelets (NPLs) possess strong in-plane transition dipole moments and out-of-plane emission, which enable a maximum photon out-coupling efficiency of 40% and a high gain coefficient, making them ideal candidates for light-emitting diodes (LEDs) and lasers. However, the unbalanced surface energy between the side and top facets of NPLs results in poor thermal stability and high susceptibility to ripening at elevated temperatures, which complicates the growth of the shell. To address this issue, a gradient crown (CdSeS) around the CdSe NPLs is designed to stabilize the high energy side facets. Consequently, the gradient alloyed shell (CdZnS) is successfully grown, and the CdSe/CdSeS/CdZnS core/crown/shell NPLs exhibited near-unity photoluminescence quantum yield. The CdSeS/CdZnS crown/shell structure suppressed non-radiative Auger recombinations, achieving a record-low amplification spontaneous emission threshold of 2.11 µJcm-2 under femtosecond laser excitation. In addition, by selecting the carrier transport layers with matched energy levels, the NPL-LEDs demonstrate a record-high external quantum efficiency of 30.1% in the pure-red range, driven by the 94% in-plane transition dipole moment distribution of NPL film. The NPL-LEDs also exhibited a long operational lifetime of T95 > 600 h at a luminance of 1000 cdm-2.

2D/3D heterojunction carrier dynamics and interface evolution for efficient inverted perovskite solar cells

The 2D/3D heterojunction perovskites have garnered increasing attention due to their exceptional moisture and thermal stability. However, few works have paid attention to the influence of the subsequent change process of 2D/3D heterojunction PSC on the stability of PSCs. Moreover, the evolution of the interface and carrier dynamic behavior of the 2D/3D perovskite films with long-term operation has not been systematically developed before. In this work, the effects of 2D/3D heterojunction evolution on the interface of perovskite films and different carrier dynamics during 2D/3D evolution are systematically analyzed for the first time. The decomposition of 2D/3D heterojunction in the perovskite film will have a certain impact on the surface and carrier dynamics behavior of perovskite. During the evolution of 2D/3D heterojunction, PbI2 crystals will appear, which will improve the interfacial energy level matching between the electron transport layer and perovskite film. With a long evolution time, some holes will appear on the surface of perovskite film. The open circuit voltage (VOC) of PSCs increased from 1.14 to 1.18 V and the PCE increased to 23.21% after 300 h storage in the nitrogen atmosphere, and maintained 89% initial performance for with 3000 h stability test in N2 box. This discovery has a significant role in promoting the development of inverted heterojunction PSCs and constructing the revolution mechanism of charge carrier dynamic.

The Design of WTe2/Graphene/Ag NPs Heterostructure for the Improvement of the Chemical Enhancement in SERS.

Combining the advantages of metal and two-dimensional (2D) nanomaterials, various 2D/metal composite structures are proposed as surface-enhanced Raman spectroscopy (SERS) substrates. However, the chemical enhancement in the composite structure is usually less responsible for the total enhancement. In this work, we proposed a heterostructure including WTe2/graphene/Ag nanoparticles (WTe2/Gr/Ag) as an effective platform for SERS. The matching of energy levels facilitates charge transfer (CT) within the composite structure, which in turn significantly improves the chemical enhancement of SERS. Compared with WTe2/Ag or Gr/Ag substrate, the SERS signals can be amplified up to 18-fold, and the detection limit could further reduce 3 orders of magnitude. Furthermore, the CT process in the SERS test can be further promoted after introducing the pyroelectric field based on the ferro-electricity of WTe2. The enhancement factor of the WTe2/Gr/Ag substrate finally reached 1.34 × 1012. This work proposes a new idea for the design of highly sensitive SERS sensors.

Targeted Topological Routine Regulation of RuNiOx Precursors for Excellent Alkaline Overall Water Splitting

Designing efficient and stable electrocatalysts for the hydrogen and oxygen evolution reactions (HER and OER) is crucial for green hydrogen production via the water‐splitting system. The bifunctional electrocatalyst offers a promising strategy due to the simplified preparation process and reduced expenses. However, the single‐component bifunctional catalysts often struggle to match the redox potential of water and to achieve proper adsorption/desorption of Gibbs free energy for both H and O intermediates simultaneously. Herein, through precisely controlling the topological transformation path of the RuNiOx precursor, we successfully prepared high‐performance RuNi/Ni and Ru/NiO heterostructure electrocatalysts for the HER and OER, respectively. The energy level matching between the fabricated electrocatalyst and water oxidation/reduction potential confirms the feasibility of HER and OER. The synergistic effect between the active sites ensures rapid, intermediate adsorption/desorption kinetics. As a result, the assembled alkaline overall water splitting setup achieves a current density of 1 A cm‐2 at 2 V and maintains stable operation at 100 mA cm‐2 for 100 hours.

A Scorpion–Type Dopant‐Free Hole Transport Material for n‐i‐p Organic–Inorganic Hybrid Perovskite Solar Cells

AbstractIt is significant to develop dopant‐free hole transport materials (HTMs) to improve the long‐term stability of n‐i‐p organic–inorganic hybrid perovskite solar cells (PSCs). In this work, two HTMs (DTTP‐T and DTTP‐D) based on dithienothiopyrrole (DTTP) core were synthesized to explore the effects of different substituents on the nitrogen atom on the properties of HTMs. Compared with anisole‐substituted DTTP‐D, triarylamine‐substituted scorpion‐type DTTP‐T shows better matching energy level, stronger charge transfer and defect passivation ability. Therefore, the power conversion efficiency (PCE) of dopant‐free DTTP‐T‐based n‐i‐p PSCs reaches 18.67 %, which is comparable to that of doped Spiro‐OMeTAD (19.51 %). More encouragingly, the efficiency of DTTP‐T‐based devices remains above 80 % of its initial efficiency after 1728 h of storage in air, while the Spiro‐OMeTAD‐based devices could only maintain 600 h. This work provides a good reference for the development of dopant‐free small molecular HTMs for efficient and stable PSCs.

Dynamic Rare-Earth Metal-Organic Frameworks Based on Molecular Rotor Linkers with Efficient Emissions and Ultrasensitive Optical Sensing Performance.

4,4',4″-Triphenylamine tricarboxylate (TPA-COOH) with a distinct molecular rotor structure was reacted with rare-earth (RE) metal ions to obtain seven dynamic RE-based luminescent MOFs (RE-LMOFs) (i.e., emission colors in the blue, yellow-green, red, and near-infrared regions and emission peak wavelengths between 400 and 1600 nm) via the effective transfer of absorbed energy from TPA-COOH to the RE metal ions through the antenna effect. Due to the large energy level difference between RE ions, it was rare in the early days to use the same ligand to construct energy-level matching RE-LMOF homologues with multiple RE metal centers. The uncoordinated oxygen atoms on the molecular rotor linkers in RE-LMOFs provide active sites that can specifically capture highly toxic metal ions and strong oxidative pollutants. The limit of detection (LOD) of RE-LMOF for Al(III) ions is far below the maximum concentration of Al(III) ions in drinking water stipulated by the U.S. Environmental Protection Agency (USEPA) and that for H2O2 is much lower than the H2O2 content in cancer cells, showing excellent application potential for diagnosing early cell cancelation.

Computational Screening Two-Dimensional Conjugated Microporous Polymer Applied in Perovskite Solar Cells.

A two-dimensional (2D) conjugated microporous polymer with a structure of 2D nanosheets has been synthesized. Theoretical calculations and experimental results reveal that the Fermi level of this 2D polymer aligns well with perovskite absorber, and its conduction band is high enough to block electron transport into the anode. This 2D polymer is used to modify the hole transport layer, significantly improving its photoelectric properties, including enhanced hole mobility, matched energy level, and reduced recombination. Furthermore, the 2D polymer exhibits a mesoporous structure, allowing perovskite to fill into its loose framework, increasing the hole export area and providing a large hole transport flux. As a result, the efficiency of inverted perovskite solar cells enhances to 24.64 % from 21.17 % of control device without 2D conjugated microporous polymer. Given that this material can be synthesized on a large scale, this work has significant implications for the future development of 2D polymers in perovskite solar cells, potentially accelerating industrialization.

Bimolecular Passivation-Dipole Bridge for Highly Efficient Inverted Perovskite Solar Cells with Low Nonradiative Recombination Loss.

Constructing charge-selective heterointerface with minimized defect state and matched energy level alignment is essential to reduce nonradiative recombination for achieving high-performance perovskite solar cells (PSCs). Herein, a bimolecular passivation-dipole bridge comprised of sodium phenylmethanesulfonate (SPM) and 2-phenylethylammonium iodide (PEAI) is carefully developed to regulate perovskite heterointerface. SPM passivates defect states and upshifts Fermi level (EF) of perovskite surface, and subsequent PEAI further induces additional negative dipole and causes the surface EF of perovskite pinning to negative polaron transport state of electron transport layer PCBM, which significantly promotes electron extraction at the perovskite electron-selective contact. These advantages are confirmed by a remarkably improved efficiency from 21.74% for control to 25.12% for treated PSC with excellent stability. Moreover, corresponding nonradiative recombination loss impressively diminishes from 123 to 70 meV, and charge transport-induced fill factor loss is only 3.00%. This work provides a promising approach via passivation-energetic synergy for engineering perovskite heterointerface toward highly efficient and stable PSCs.

Implementing Lattice and Energy Level Matching to Optimize Buried Interfaces for High-Performance Perovskite Solar Cells.

In n-i-p type perovskite solar cells (PSCs), mismatches in energy level and lattice at the buried interface is highly detrimental to device performance. Here, thin PbS interconnect layer in situ coating on the SnO2 surface is grown. The function of PbS at the interface is different from the commonly used function of crystalline seeds in perovskite bulk. The theoretical calculation show that it helps construct an interconnect structure of SnO2/PbS/Perovskite with matched energy level and lattice. This not only increases conductivity of SnO2, but also upshifts Fermi energy levels (EF) of both SnO2 and buried perovskite due to charge transfer and perovskite's internal defect changes. Such a suitable energy level arrangement ensures a better energy level match at the interface, favoring efficient charge transfer and less open circuit voltage (Voc) loss. Additionally, in situ PL reveals that the template effect of PbS enable perovskite grain to grow bottom-up because of their highly matched lattice parameters. This growth mode optimizes buried interface contact and crystallinity of perovskite. Ultimately, after PbS modification, a remarkable power conversion efficiency (PCE) exceeding 24% and better device stability are obtained. This work demonstrates an effective interconnect layers strategy to realize ideal interface contact toward high-performance PSCs.

Validating the Novel Electron Transport Layer with the Use of Experimentally Studied D18:Y6 Bulk Heterojunction Solar Cell

AbstractOrganic solar cells (OSC) are showing steady efficiency improvement due to the development in the materials synthesis, sophisticated characterization techniques, in‐depth understanding of materials and devices. In the recent years, bulk heterojunction OSC with a non‐fullerene acceptor /polymer acceptor shows significant enhancement in efficiency (≈19%). Efficiency of the polymer acceptor OSCs is much higher than the fullerene derivative‐based acceptors. In this work, OSC simulations are done using D18 donor and Y6 acceptor bulk heterojunction as a photoactive layer. As a first step, validity of the experimental results for ITO/PEDOT:PSS/D18:Y6/PDIN/Ag structure is done. To investigate efficiency, 2,8,15‐trifluoro‐3,9,14‐tris(heptylsulfonyl)diquinoxalino[2,3‐a:2′,3′‐c]phenazine (HATNASO2C7‐Cs) electron transport layer is validated in place of PDIN in the following device structure, ITO/PEDOT:PSS/D18:Y6/HATNASO2C7‐Cs/Ag. Energy level matching of the HATNASO2C7‐Cs is well aligned compared with PDIN at the cathode interface. Device simulation optimization are carried out for various photoactive layer, ETL and HTL condition. Highest efficiency of 20.99% is obtained for ITO/PEDOT:PSS/D18:Y6/HATNASO2C7‐Cs/Ag when the HATNASO2C7‐Cs thickness, bandgap, electron affinity, carrier mobility, and defect density is matched for ≈30 nm, ≈2.8 eV, ≈4.16 eV, ≈2 × 10−3 cm2 V−1 s−1, and 1014 cm−3 respectively. Obtained results are discussed in details and results will be helpful for preliminary understanding of the system.

Dimesitylborane as Electron Accepting Unit in High Performance Yellow Single-Layer Phosphorescent Organic Light Emitting Diode.

A new host material for Single-Layer Phosphorescent Organic Light-Emitting Diodes (SL-PhOLED) is reported, namely SPA-2-FDMB, using the dimesitylborane (DMB) fragment as an acceptor unit. The molecular design is constructed on the general donor-spiro-acceptor architecture, which consists of connecting, via a spiro bridge, a donor and an acceptor units in order to avoid strong interaction between them. The DMB fragment is known for many electronic applications (notably Aggregation-Induced Emission) but has not been used yet for SL-PhOLED applications. This appears particularly interesting, as the development of this simplified technology has shown that only a few electron-accepting fragments such as diphenylphosphine oxide can provide high-performance devices. Herein, the yellow-emitting SL-PhOLED using SPA-2-FDMB as host presents an External Quantum Efficiency of 8.1% (Current Efficiency of 24.9cd.A-1) with a low threshold voltage of 2.6V. As SPA-2-FDMB presents a sharp HOMO/LUMO difference, the good matching of HOMO and LUMO energy levels with the Fermi level of the electrodes is responsible for these performances. The low LUMO level of -2.61eV also appears particularly important. These performances are, to date, the highest reported for a yellow/orange-emitting SL-PhOLED and show the potential of DMB unit in the single-layer technology.

Single-component white afterglow from dual emission based on carbazole-pyrimidine-benzene derivatives

Achieving single-component organic white afterglow material remains a great challenge owing to the difficulties in simultaneously supporting long-lived emissions from varied excited states and getting complementary emission color. Here, a dual emission model that the radiative decays from singlet and triplet excited states was proposed to afford white afterglow. Based on the constructed carbazole-pyrimidine-benzene (CPB) building block, white afterglow was successfully achieved by CPB-H, CPB-MeO, and CPB-F at room temperature. Especially, CPB-H exhibits white afterglow with a lifetime about 0.3 s. The white afterglow was realized by dual emissions including blue TADF and yellow phosphorescence emission. The dual emissions are mainly dependent on the electronic structures of designed molecules, where the appropriate energy level matching between singlet and triplet states are necessary for ISC process in monomer or stacked dimer and for RISC process in other monomer or dimer.

Two-dimensional Ruddlesden-Popper perovskite solar cells with an efficiency exceeding 19 % by inserting a self-assembled monolayer

Two-dimensional Ruddlesden-Popper (2DRP) phase perovskites have excellent long-term environmental and structure stability. However, the efficiency of 2DRP perovskite solar cells (PSCs) still lags seriously behind 3D counterparts due to the large exciton binding energy between the large-volume organic spacer and the inorganic plate compared to their 3D analogs. Here, a thin layer of self-assembled monolayer material (2-(3,6-dibromo-9H-carbazol-9-yl)ethyl)phosphonic acid (2PACz-Br) is employed between poly (3,4-ethylene dioxythiophene): poly(styrene sulfonate) (PEDOT: PSS) and β-guanidinopropanoic acid (β-GUA)-based perovskite film (β-GUA)2(FA)4Pb5I16 for efficient and stable 2DRP-based PSCs. The 2PACz-Br-based 2DRP perovskite films show superior crystallinity and quality compared with the control perovskite films. The defect density in 2PACz-Br-based perovskite films is reduced, and the non-radiative recombination is further suppressed. The experimental results show that introducing 2PACz-Br can effectively promote the matched energy levels between the perovskite thin film and the charge-carrier transport layer. Benefiting from the conducive collection and transmission of charge carriers, (β-GUA)2(FA)4Pb5I16 (n = 5)-based PSCs can realize an outstanding power conversion efficiency of 19.13 %, much higher than that of devices without 2PACz-Br modification (17.70 %). Moreover, 2PACz-Br-based 2DRP PSCs show better stability than the control devices. Our work paves the way to efficient and stable 2DRP-based PSCs by inserting a multifunctional self-assembled monolayer.

Dual-Mechanism Quenching Electrochemiluminescence System by Coupling Energy Transfer with Electron Transfer for Sensitive Competitive Aptamer-Based Detection of Furanyl Fentanyl in Food.

Resonance energy transfer (RET) quenching is significantly important for developing electrochemiluminescence (ECL) sensors, but RET platforms face challenges like interference from other fluorescent substances and reliance on energy transfer efficiency. This study used Zn-PTC, formed by zinc ions coordinated with perylene-3,4,9,10-tetracarboxylate, as a dual-mechanism quencher to reduce the ECL intensity of carbon nitride nanosheets (Tg-CNNSs). Co3O4/NiCo2O4 acts as a coreaction promoter, enhancing and stabilizing the luminescence of Tg-CNNSs. Zn-PTC absorbs energy from Tg-CNNSs, altering the fluorescence lifetime to confirm energy transfer, while energy-level matching demonstrates electron transfer. By leveraging both RET and electron transfer mechanisms, the designed ECL aptasensor significantly reduces signal fluctuations that may arise from a single mechanism, resulting in more stable and reliable detection outcomes. The ECL aptasensor designed for furanyl fentanyl (FUF) detection shows excellent performance with a detection limit of 5.7 × 10-15 g/L, offering new pathways for detecting FUF and other small molecules.

A novel signal-on photoelectrochemical immunosensor based on anthocyanin-sensitized poly(indole-5-carboxylic acid) for ultrasensitive detection of CEA

A signal-on photoelectrochemical (PEC) immunosensor for carcinoembryonic antigen (CEA) detection was constructed using anthocyanin (ACN)-sensitized poly(indole-5-carboxylic acid) (P5ICA) nanofibers as the photoactive material. P5ICA is a p-π conjugated cathode photosensitive material with excellent optical and film-forming properties. P5ICA sensitized with ACN prevents hydrolysis of P5ICA, ensures the stability and further improves the base signal of the PEC immunosensor. The sensitive detection of CEA was achieved by introducing the signaling probe TiO2/In2S3 through biotin-avidin protein specific recognition. ACN-sensitized P5ICA and TiO2/In2S3 exhibit the effective matching of energy levels, which facilitates the separation and transfer of photogenerated e-/h+ pairs and achieves the amplification of PEC signals and the improvement of sensor sensitivity. Under optimal conditions, the range of detection for CEA was 0.01–500 ng mL−1 with lower detection limit of 3.3 pg mL−1. The PEC immunosensor has good stability and high detection sensitivity to CEA. This work provides a novel PEC assay platform for monitoring CEA in real serum samples, which has a promising application in the sensitive detection of tumor markers.

A multifunctional interlayer between mesoporous TiO2 and perovskite for perovskite solar cells with high efficiency and stability

The industrialization of the perovskite solar cells (PSCs) requires further lifting their power conversion efficiency (PCE). There are some important factors to hinder the PCE improvement, such as interface defects and energy level mismatching betwee electron transport layer (ETL) and perovskite layer, and solar energy loss due to no absorption of near infrared (NIR) for the perovsktie. Thus in this study, a multifunctional material of W-Er-Yb doped TiO2 (W-UC-TiO2) was prepared and applied to PSCs as an interlayer between mesoporous TiO2 and perovskite. The experimental results demonstrate that the interlayer of W-UC-TiO2 has the functions of improving NIR absorption for PSCs, passivating inerface defects and improving energy level matching between TiO2 and perovskite. A high efficiency of 21.32% was acquired for the PSCs with W-UC-TiO2 interlayer from 19.26% for the control device. Moreover, stability of the PSCs was improved by the insertion of W-UC-TiO2 interlayer.

Robust Imidazole-Linked Covalent Organic Framework Enabling Crystallization Regulation and Bulk Defect Passivation for Highly Efficient and Stable Perovskite Solar Cells.

The low crystallinity of the perovskite layers and many defects at grain boundaries within the bulk phase and at interfaces are considered huge barriers to the attainment of high performance and stability in perovskite solar cells (PSCs). Herein, a robust photoelectric imidazole-linked porphyrin-based covalent organic framework (PyPor-COF) is introduced to precisely control the perovskite crystallization process and effectively passivate defects at grain boundaries through a sequential deposition method. The 1D porous channels, abundant active sites, and high crystallization orientation of PyPor-COF offer advantages for regulating the crystallization of PbI2 and eliminating defects. Moreover, the intrinsic electronic characteristics of PyPor-COF endow a more closely matched energy level arrangement within the perovskite layer, which promotes charge transport and thereby suppresses the recombination of photogenerated carriers. The champion PSCs containing PyPor-COF achieved power conversion efficiencies of 24.10% (0.09 cm2) and 20.81% (1.0 cm2), respectively. The unpackaged optimized device is able to maintain its initial efficiency of 80.39% even after being exposed to air for 2000 h. The device also exhibits excellent heating stability and light stability. This work gives a new impetus to the development of highly efficient and stable PSCs via employing COFs.

Optically Tunable Many-Body Exciton-Phonon Quantum Interference.

This study introduces a novel paradigm for achieving widely tunable many-body Fano quantum interference in low-dimensional semiconducting nanostructures, beyond the conventional requirement of closely matched energy levels between discrete and continuum states observed in atomic Fano systems. Leveraging Floquet engineering, the remarkable tunability of Fano lineshapes is demonstrated, even when the original discrete and continuum states are separated by over 1eV. Specifically, by controlling the quantum pathways of discrete phonon Raman scattering using femtosecond laser pulses, the Raman intermediate states across the excitonic Floquet band are tuned. This manipulation yields continuous transitions of Fano lineshapes from antiresonance to dispersive and to symmetric Lorentzian profiles, accompanied by significant variations in Fano parameter q and Raman intensity spanning 2 orders of magnitude. A subtle shift in the excitonic Floquet resonance is further shown, achieved by controlling the intensity of the femtosecond laser, which profoundly modifies quantum interference strength from destructive to constructive interference. The study reveals the crucial roles of Floquet engineering in coherent light-matter interactions and opens up new avenues for coherent control of Fano quantum interference over a broad energy spectrum in low-dimensional semiconducting nanostructures.

Accelerating Toluene Oxidation over Boron-Titanium-Oxygen Interface: Steric Hindrance of the Methyl Group Induced by the Plane-Adsorption Configuration.

Elimination of dilute gaseous toluene is one of the critical concerns within the field of indoor air remediation. The typical degradation route on titanium-based catalysts, "toluene-benzaldehyde-carbon dioxide", necessitates the oxidation of the methyl group as a prerequisite for photocatalytic toluene oxidation. However, the inherent planar adsorption configuration of toluene molecules, dominated by the benzene rings, leads to significant steric hindrance for the methyl group. This steric hindrance prevents the methyl group from contacting the active species on the catalyst surface, thereby limiting the removal of toluene under indoor conditions. To date, no effective strategy to control the steric hindrance of the methyl group has been identified. Herein, we showed a B-Ti-O interface that exhibits significantly enhanced toluene removal efficiency under indoor conditions. In-depth investigations revealed that, compared to typical Ti-based photocatalysts, the steric hindrance between the methyl group and the catalyst surface decreased from 3.42 to 3.03 Å on the designed interface. This reduction originates from the matching of orbital energy levels between Ti 3dz2 and C 2pz of the benzene ring. The decreased steric hindrance improved the efficiency of toluene being attacked by surface active species, allowing for rapid conversion into benzaldehyde and benzoic acid species for subsequent reactions. Our work provides novel insights into the steric hindrance effect in the elimination of aromatic volatile organic compounds.

Target therapy on buried interface engineering enables stable inverted perovskite solar cells with 25 % power conversion efficiency

buried interfaces are crucial for achieving efficient and stable perovskite solar cells (PSCs). However, studying and optimizing buried interfaces remains a challenging issue due to its non-exposed characteristics. Here, a simple and effective targeting strategy is proposed to regulate the NiOx/perovskite buried interface by passivating buried defects in perovskite and adjusting the growth of perovskite crystals through modifying multifunctional molecules (DTD) on the surface of NiOx. DTD has multifunctional targeting groups that enable it to interact strongly with both perovskite and NiOx simultaneously, thereby building a molecular bridge at the NiOx/perovskite buried interface, enabling high-quality upper perovskite films, excellent interface contact and more matched energy levels between perovskite and NiOx. As a result, the modification of DTD significantly improves the efficiency of perovskite devices from 22.19 % to 25.00 % (certified value of 24.12 %), along with excellent long-term and operational stability. This strategy provides a simple and effective targeted therapy for the buried interface in PSC, achieving high efficiency and stability.