Dissociation of singlet excitons dominates photocurrent improvement in high-efficiency non-fullerene organic solar cells. - In: Nano research energy, ISSN 2790-8119, Bd. 3 (2024), 1, e9120099, S. 1-8
In organic solar cells, the singlet and triplet excitons dissociate into free charge carriers with different mechanisms due to their opposite spin state. Therefore, the ratio of the singlet and triplet excitons directly affects the photocurrent. Many methods were used to optimize the performance of the low-efficiency solar cell by improving the ratio of triplet excitons, which shows a long diffusion length. Here we observed that in high-efficiency systems, the proportion of singlet excitons under linearly polarized light excitation is higher than that of circularly polarized light. Since the singlet charge transfer state has lower binding energy than the triplet state, it makes a significant contribution to the charge carrier generation and enhancement of the photocurrent. Further, the positive magnetic field effect reflects that singlet excitons dissociation plays a major role in the photocurrent, which is opposite to the case of low-efficiency devices where triplet excitons dominate the photocurrent.
https://doi.org/10.26599/NRE.2023.9120099
Interfacial molecular screening of polyimide dielectric towards high-performance organic field-effect transistors. - In: Chinese chemical letters, ISSN 1878-5964, Bd. 35 (2024), 2, 108796
The compatibility of the gate dielectrics with semiconductors is vital for constructing efficient conducting channel for high charge transport. However, it is still a highly challenging mission to clearly clarify the relationship between the dielectric layers and the chemical structure of semiconductors, especially vacuum-deposited small molecules. Here, interfacial molecular screening of polyimide (Kapton) dielectric in organic field-effect transistors (OFETs) is comprehensively studied. It is found that the semiconducting small molecules with alkyl side chains prefer to form a high-quality charge transport layer on polyimide (PI) dielectrics compared with the molecules without alkyl side chains. On this basis, the fabricated transistors could reach the mobility of 1.2 cm2 V−1 s−1 the molecule with alkyl side chains on bare PI dielectric. What is more, the compatible semiconductor and dielectric would further produce a low activation energy (EA) of 3.01 meV towards efficient charge transport even at low temperature (e.g., 100K, 0.9 cm2 V−1 s−1). Our research provides a guiding scheme for the construction of high-performance thin-film field-effect transistors based on PI dielectric layer at room and low temperatures.
https://doi.org/10.1016/j.cclet.2023.108796
Electron spin finds a fresh excitation. - In: Nature physics, ISSN 1745-2481, Bd. 20 (2024), 1, S. 4-5
The Kondo effect - the screening of an impurity spin by conduction electrons - is a fundamental many-body effect. However, recent experiments combined with simulations have caused a long-standing model system for the single-atom Kondo effect to fail.
https://doi.org/10.1038/s41567-023-02265-3
Dual-functional electrode promoting dendrite-free and CO2 utilization enabled high-reversible symmetric Na-CO2 batteries. - In: Energy & Environmental Materials, ISSN 2575-0356, Bd. 7 (2024), 3, e12626, S. 1-10
Sodium-carbon dioxide (Na-CO2) batteries are regarded as promising energy storage technologies because of their impressive theoretical energy density and CO2 reutilization, but their practical applications are restricted by uncontrollable sodium dendrite growth and poor electrochemical kinetics of CO2 cathode. Constructing suitable multifunctional electrodes for dendrite-free anodes and kinetics-enhanced CO2 cathodes is considered one of the most important ways to advance the practical application of Na-CO2 batteries. Herein, RuO2 nanoparticles encapsulated in carbon paper (RuCP) are rationally designed and employed as both Na anode host and CO2 cathode in Na-CO2 batteries. The outstanding sodiophilicity and high catalytic activity of RuCP electrodes can simultaneously contribute to homogenous Na+ distribution and dendrite-free sodium structure at the anode, as well as strengthen discharge and charge kinetics at the cathode. The morphological evolution confirmed the uniform deposition of Na on RuCP anode with dense and flat interfaces, delivering enhanced Coulombic efficiency of 99.5% and cycling stability near 1500 cycles. Meanwhile, Na-CO2 batteries with RuCP cathode demonstrated excellent cycling stability (>350 cycles). Significantly, implementation of a dendrite-free RuCPNa anode and catalytic-site-rich RuCP cathode allowed for the construction of a symmetric Na-CO2 battery with long-duration cyclability, offering inspiration for extensive practical uses of Na-CO2 batteries.
https://doi.org/10.1002/eem2.12626
Master memory function for delay-based reservoir computers with single-variable dynamics. - In: IEEE transactions on neural networks and learning systems, ISSN 2162-2388, Bd. 35 (2024), 6, S. 7712-7725
We show that many delay-based reservoir computers considered in the literature can be characterized by a universal master memory function (MMF). Once computed for two independent parameters, this function provides linear memory capacity for any delay-based single-variable reservoir with small inputs. Moreover, we propose an analytical description of the MMF that enables its efficient and fast computation. Our approach can be applied not only to single-variable delay-based reservoirs governed by known dynamical rules, such as the Mackey-Glass or Stuart-Landau-like systems, but also to reservoirs whose dynamical model is not available.
https://doi.org/10.1109/TNNLS.2022.3220532
Modulating functions analysis for wireless data transmission because of advanced sensors in energy-saving process of washing. - In: Renewable energy & power quality journal, ISSN 2172-038X, Bd. 21 (2023), 6, S. 695-700
The vibration measurement of flows in transient or steady-state is a very complicated task. Moreover, to correlate it with a temperature process is quite important according to get information regarding molecular kinetic energy of thermal sources (such as flow measurement used in cleaning tasks) according to achieve heating transfer information of a thermal process. However, there is a trouble concerning the transduction stage in the measurement while it is not a transducer designed algorithm as a consequence of a mathematical model, which correlates the calibration data with the theoretical model of the heating/vibration transfer. For this reason, in this research is proposed intelligent sensors/transducers, which are based on Anodic Aluminium Oxide (AAO) and a mathematical procedure of the measurement instrumentation according to adaptive coefficients in the Modulating Functions strategies analysis and getting optimal measurements. In this research is explained and analysed the temperature measurement process and the transduction process as the strict correlation of the calibration of the temperature/vibration sensor. For this reason, there were evaluated different transducers and the temperature/vibration reference for the calibration. The based on nanostructures temperature sensors are designed by specific and complex procedures according to achieve quite operation range, robustness and precision. Moreover, the transduction can be obtained through different electrical answer variables such as voltage, electrical current or capacitance and possible to send by wireless mechanisms and protocols to the main control system. Therefore, the evaluation of the designed advanced sensor performance was achieved by the vibration and temperature measurement of the water surface of a ultrasound washing machine, for which the designed sensor enhances energy-saving of the washing process.
https://doi.org/10.24084/repqj21.453
Submicrometer optical frequency combs based on SPPs metallic multi-ring resonators. - In: Photonics research, ISSN 2327-9125, Bd. 11 (2023), 12, S. 2105-2112
Optical frequency combs (OFCs) have great potential in communications, especially in dense wavelength-division multiplexing. However, the size of traditional OFCs based on conventional optical microcavities or dispersion fibers is at least tens of micrometers, far larger than that of nanoscale electronic chips. Therefore, reducing the size of OFCs to match electronic chips is of necessity. Here, for the first time to our knowledge, we introduce surface plasmon polaritons (SPPs) to the construction of OFCs to realize a miniature device. The thickness of our device is reduced below 1 μm. Though the presence of SPPs may induce ohmic and scattering loss, the threshold of the device is obtained as 9 μW, comparable to the conventional device. Interestingly, the response time is 13.2 ps, much faster than the optical counterparts. This work provides a feasible strategy for the miniaturization of OFCs.
https://doi.org/10.1364/PRJ.488160
Structural fingerprints in the reflectance anisotropy of AlInP(001). - In: Physical review, ISSN 2469-9969, Bd. 108 (2023), 4, 045410, S. 045410-1-045410-6
The surface optical anisotropy of AlInP(001) surfaces is studied from both experiment and theory. The comparison of the data measured on epitaxially grown Al0.52In0.48P(001) epilayers lattice matched to GaAs with spectra calculated for energetically favored AlInP(001) surface structures suggests that the surface is covered with a monolayer of buckled phosphorus dimers, where half of the phosphorus atoms are hydrogen saturated. While the optical anisotropies for photon energies below about 3 eV provide clear fingerprints for the structure of the outermost surface atomic layer, the spectral features at higher energies provide insight into the near surface bulk ordering of AlInP. In particular optical anisotropies at the AlInP critical point energies are found to be related to the CuPt ordering in the material.
https://doi.org/10.1103/PhysRevB.108.045410
Photonic reservoir computing for energy efficient and versatile machine learning application. - In: Proceedings of the Royal Society of Victoria, Bd. 135 (2023), 2, S. 38-40
Time-multiplexed reservoir computing is a machine learning concept which can be realised in photonic hardware systems using only one physical node. The concept can be used for various problems, ranging from classification problems to time-series prediction tasks, while being fast and energy efficient. Here, a theoretical analysis of a reservoir computer realised via delay-coupled semiconductor lasers is presented and the role of the internal system time-scales and the bifurcation structure is discussed. It is further shown that optimal performance can be reached by tailoring the coupling delays to the specific memory requirements of the given task.
https://doi.org/10.1071/rs23006
Delay-based reservoir computing with spin-VCSELs: interplay between internal dynamics and performance. - In: 2023 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC), (2023), insges. 1 S.
Machine learning setups that are able to process data in the optical domain are ideal for on -chip hardware implementations [1]. Due to the fact that the training of hardware based solutions is complicated, a delay-based reservoir computing (RC) realization, where only the output weights need to be trained via linear regression, is very promising [2]. In this paper we investigate vertical cavity surface emitting laser with two mode emission (spin-VCSEL) as the nonlinear node for a delay-based RC setup. These lasers have the ability to exibit reprodicible and high speed dynamics [3] and are thus ideal candidates to increase the data injection rates which are limited by the clocktime [4], [5]. The focus of our numerical investigations is on the interplay between the internal charge carrier dynamics of the spin-VCSEL and its performance when operated in a delay-based RC setup with optically-injected phase-modulated data injection.
https://doi.org/10.1109/CLEO/Europe-EQEC57999.2023.10232555