arXiv subjects

Dongmei Li

Publications and source records attributed to Dongmei Li.

At least 19 recordsLinked to original sources

arXiv2026

Route-Constrained Robust Fusion Estimation for MEMS/GNSS Integrated Navigation of Unmanned Ground Vehicles in GNSS Degraded Environments

To address cumulative localization drift of unmanned ground vehicles in structured road environments under severe Global Navigation Satellite System signal occlusion, this paper proposes a robust route-constrained state estimation method. During periods without satellite signals, the proposed method establishes the correspondence between the historical dead reckoning trajectory and local segments of the mission route extracted from a high-definition map, and estimates a route-referenced position via a two-dimensional rigid transformation. The estimated position is then formulated as a pseudo-position observation and incorporated into an Extended Kalman Filter update. In this way, route constraints at the road level can be continuously injected into a unified state estimation framework, thereby suppressing position deviation relative to the mission route while indirectly improving azimuth estimation. To enhance practical applicability, engineering strategies, such as trigger control, matching quality validation, route offset compensation, and single update correction limiting, are further introduced. Experiments in three representative scenarios, including a long tunnel, a multi-segment tunnel, and a curved tunnel, show that the proposed method effectively suppresses error accumulation during satellite outages, reduces the risk of large maximum deviation, and improves localization continuity and road-level usability.

cs.RO↗

arXiv2026

IDOL: Inverse-Dynamics-Guided Future Prediction for End-to-End Autonomous Driving

End-to-end autonomous driving has emerged as a compelling paradigm for learning planning directly from sensor observations, while recent world-model-based approaches further enrich this paradigm by enabling explicit reasoning about how the scene may evolve in the future. Yet future prediction alone does not guarantee better planning unless the predicted evolution can be converted into planning-relevant trajectory updates. Many current methods still forecast future scene states without explicitly decoding the motion implications hidden in state transitions. As a result, future reasoning often remains descriptively useful but only weakly coupled to executable motion generation. To address this limitation, we propose \mathbf{IDOL}, an inverse-dynamics-guided future prediction framework for world-model-based end-to-end planning in latent BEV space, where inverse dynamics serves as the key bridge between future prediction and trajectory optimization. IDOL first predicts multiple future latent scene states with a BEV world model, then applies an inverse dynamics model to adjacent latent futures to decode transition-aware trajectory features and recover planning-relevant motion deltas that explain how the latent world evolves over time. These inverse-dynamics-derived signals are used to optimize the planned trajectory, turning future forecasting from passive scene anticipation into actionable planning guidance. A lightweight closed-loop refinement module further improves long-horizon consistency by reusing the optimized trajectory for another round of future-aware reasoning. By introducing inverse dynamics into latent future reasoning, IDOL tightens the coupling between world modeling and planning. Extensive experiments on the NAVSIM v1 and NAVSIM v2 benchmarks show that IDOL achieves state-of-the-art performance among comparable methods.

cs.RO↗

arXiv2026

Smith Form Equivalence for Several Classes of Multivariate Polynomial Matrices

This paper investigates the equivalence reduction for several classes of multivariate polynomial matrices and their Smith forms, establishing some criteria for such reduction. In particular, we employ algebra isomorphisms as a key tool to study this equivalence problem. We then leverage the Quillen-Suslin and Lin-Bose theorems to extend these results to non-square and rank-deficient matrices. Moreover, the verification of our criteria is achievable algorithmically via existing Gröbner basis methods.

math.AC↗

arXiv2024

Further results on equivalence of multivariate polynomial matrices

This paper investigates equivalence of square multivariate polynomial matrices with the determinant being some power of a univariate irreducible polynomial. We first generalized a global-local theorem of Vaserstein. Then we proved these matrices are equivalent to their Smith forms by the generalized global-local theorem.

math.AC↗

arXiv2024

High efficient sunlight-driven CO2 hydrogenation to methanol over NiZn intermetallic catalysts under atmospheric pressure

The synthesis of solar methanol through direct CO2 hydrogenation using solar energy is of great importance in advancing a sustainable energy economy. In this study, non-precious NiZn intermetallic/ZnO catalyst is reported to catalyze the hydrogenation of CO2 to methanol using sunlight irradiation (1sun). The NiZn-ZnO interface is identified as the active site to stabilize the key intermediates of HxCO*. At ambient pressure, the NiZn-ZnO catalyst demonstrates a methanol production rate of 127.5 umol g-1h-1 from solar driven CO2 hydrogenation, with a remarkable 100% selectivity towards methanol in the total organic products. Notably, this production rate stands as the highest record for photothermic CO2 hydrogenation to methanol in continuous-flow reactors with sunlight as the only requisite energy input. This discovery not only paves the way for the development of novel catalysts for CO2 hydrogenation to methanol but also marks a significant stride towards a full solar-driven chemical energy storage.

cond-mat.mtrl-sci↗

arXiv2024

Multi-interface engineering to realize all-solution processed highly efficient Kesterite solar cells

With the rapid development of Kesterite Cu2ZnSn(S, Se)4 solar cells in the past few years, how to achieve higher cost-performance ratio has become an important topic in the future development and industrialization of this technology. Herein, we demonstrate an all-solution route for the cell fabrication, in particular targeting at the solution processed window layer comprised of ZnO nanoparticles/Ag nanowires. A multi-interface engineering strategy assisted by organic polymers and molecules is explored to synergistically improve the film deposition, passivate the surface defects and facilitate the charge transfer. These efforts help us achieve high-performance and robust Kesterite solar cells at extremely low time and energy costs, with efficiency records of 14.37% and 13.12% being realized in rigid and flexible Kesterite solar cells, respectively. Our strategy here is also promising to be transplanted into other solar cells with similar geometric and energy band structures, helping reduce production costs and shorten the production cycle (i.e. increasing production capacity) of these photovoltaic industries.

cond-mat.mtrl-sci↗

arXiv2024

Vacancy enhanced cation ordering enables >15% efficiency in Kesterite solar cells

Atomic disorder, a widespread problem in compound crystalline materials, is a imperative affecting the performance of multi-chalcogenide Cu2ZnSn(S, Se)4 (CZTSSe) photovoltaic device known for its low cost and environmental friendliness. Cu-Zn disorder is particularly abundantly present in CZTSSe due to its extraordinarily low formation energy, having induced high-concentration deep defects and severe charge loss, while its regulation remains challenging due to the contradiction between disorder-order phase transition thermodynamics and atom-interchange kinetics. Herein, through introducing more vacancies in the CZTSSe surface, we explored a vacancy-assisted strategy to reduce the atom-interchange barrier limit to facilitate the Cu-Zn ordering kinetic process. The improvement in the Cu-Zn order degree has significantly reduced the charge loss in the device and helped us realize 15.4% (certified at 14.9%) and 13.5% efficiency (certified at 13.3%) in 0.27 cm2 and 1.1 cm2-area CZTSSe solar cells, respectively, thus bringing substantial advancement for emerging inorganic thin-film photovoltaics.

cond-mat.mtrl-sci↗

arXiv2024

Gradient bandgap enables >13% efficiency sulfide Kesterite solar cells with open-circuit voltage over 800 mV

Sulfide Kesterite Cu2ZnSnS4 (CZTS), a nontoxic and low-cost photovoltaic material, has always being facing severe charge recombination and poor carrier transport, resulting in the cell efficiency record stagnating around 11% for years. Gradient bandgap is a promising approach to relieve these issues, however, has not been effectively realized in Kesterite solar cells due to the challenges in controlling the gradient distribution of alloying elements at high temperatures. Herein, targeting at the Cd alloyed CZTS, we propose a pre-crystallization strategy to reduce the intense vertical mass transport and Cd rapid diffusion in the film growth process, thereby realizing front Cd-gradient CZTS absorber. The Cd-gradient CZTS absorber, exhibiting downward bending conduction band structure, has significantly enhanced the minority carrier transport and additionally improved band alignment and interface property of CZTS/CdS heterojunction. Ultimately, we have achieved a champion total-area efficiency of 13.5% (active-area efficiency: 14.1%) in the cell and in particular a high open-circuit voltage of >800 mV. We have also achieved a certified total-area cell efficiency of 13.16%, realizing a substantial step forward for the pure sulfide Kesterite solar cell.

cond-mat.mtrl-sci↗

arXiv2023

Defect Regulation by Palladium Incorporation towards Grain Boundaries of Kesterite solar cells

Kesterite Cu2ZnSn(S, Se)4 (CZTSSe) solar cell has emerged as one of the most promising candidates for thin-film photovoltaics. However, severe charge losses occurring at the grain boundaries (GBs) of Kesterite polycrystalline absorbers has hindered the improvement of cell performance. Herein, we report a redox reaction strategy involving palladium (Pd) to eliminate atomic vacancy defects such as VSn and VSe in GBs of the Kesterite absorbers. We demonstrate that PdSex compounds could form during the selenization process and distribute at the GBs and the absorber surfaces; thereby aid in the suppression of Sn and Se volatilization loss and inhibiting the formation of VSn and VSe defects. Furthermore, Pd(II)/Pd(IV) serves as a redox shuttle, i.e., on one hand, Pd(II) captures Se vapor from the reaction environment to produce PdSe2, on the other hand, PdSe2 provides Se atoms to the Kesterite absorber by being reduced to PdSe, thus contributing to the elimination of pre-existing VSe defects within GBs. These effects collectively reduce defects and enhance the p-type characteristics of the Kesterite absorber, leading to a significant reduction in charge recombination loss within the cell. As a result, high-performance Kesterite solar cells with a total-area efficiency of 14.5% have been achieved. This remarkable efficiency increase benefited from the redox reaction strategy offers a promising avenue for the precise regulation of defects in Kesterite solar cells and holds generally significant implications for the exploration of various other photovoltaic devices.

cond-mat.mtrl-sci↗

arXiv2023

Multinary Alloying Suppresses Defect Formation in Emerging Inorganic Solar Cells

The Cu2ZnSn(S, Se)4 (CZTSSe) emerging inorganic solar cell is highly promising for accelerating the large-scale and low-cost applications of thin-film photovoltaics. It possesses distinct advantages such as abundant and non-toxic constituent elements, high material stability, and excellent compatibility with industrial processes. However, CZTSSe solar cells still face challenges related to complex defects and charge losses. To overcome these limitations and improve the efficiency of CZTSSe solar cells, it is crucial to experimentally identify and mitigate deep defects. In this study, we reveal that the dominant deep defect in CZTSSe materials exhibits donor characteristics. We propose that incomplete cation exchange during the multi-step crystallization reactions of CZTSSe is the kinetics mechanism responsible for the defect formation. To address this issue, we introduce an elemental synergistic alloying approach aimed at weakening the metal-chalcogen bond strength and the stability of intermediate phases. This alloying strategy has facilitated the kinetics of cation exchange, leading to a significant reduction in charge losses within the CZTSSe absorber. As a result, we have achieved a cell efficiency of over 14.5%. These results represent a significant advancement for emerging inorganic solar cells and additionally bring more opportunities for the precise identification and regulation of defects in a wider range of multinary inorganic compounds.

cond-mat.mtrl-sci↗

arXiv2023

Heterojunction interface regulation to realize high-performance flexible Kesterite solar cells

Flexible Cu2ZnSn(S, Se)4 (CZTSSe) solar cells take the advantages of environmental friendliness, low cost, and multi-scenario applications, and have drawn extensive attention in recent years. Compared with rigid devices, the lack of alkali metal elements in the flexible substrate is the main factor limiting the performance of flexible CZTSSe solar cells. This work proposes a Rb ion additive strategy to simultaneously regulate the CZTSSe film surface properties and the CdS chemical bath deposition (CBD) processes. Material and chemical characterization reveals that Rb ions can passivate the detrimental Se0 cluster defect and additionally provide a more active surface for the CdS epitaxial growth. Furthermore, Rb can also coordinate with thiourea (TU) in the CBD solution and improve the ion-by-ion deposition of the CdS layer. Finally, the flexible CZTSSe cell fabricated by this strategy has reached a high total-area efficiency of 12.63% (active-area efficiency of 13.2%), with its VOC and FF reaching 538 mV and 0.70, respectively. This work enriches the alkali metal passivation strategies and provides new ideas for further improving flexible CZTSSe solar cells in the future.

physics.app-ph↗

arXiv2023

Controlling selenization equilibrium enables high-quality Cu2ZnSn(S, Se)4 absorbers for efficient solar cells

Cu2ZnSn(S, Se)4 (CZTSSe) is one of most competitive photovoltaic materials for its earth-abundant reserves, environmental friendliness, and high stability.The quality of CZTSSe absorber determines the power-conversion efficiency (PCE) of CZTSSe solar cells. The absorber's quality lies on post-selenization process, which is the reaction of Cu-Zn-Sn precursor and selenium vapor. And the post-selenization is dependent on various factors (e.g. temperature, precursor composition, reaction atmosphere, etc).However, synergistic regulation of these factors cannot be realized under a widely-used single-temperature zone selenization condition.Here, in our dual-temperature zone selenization scheme, a solid-liquid and solid-gas (solid precursor and liquid/gas phase Se) synergistic reaction strategy has been developed to precisely regulate the selenization. Pre-deposited excess liquid Se provides high Se chemical potential to drive a direct and fast formation of the CZTSSe phase, significantly reducing the amount of binary and ternary compounds within phase evolution. And organics removal can be accomplished via a synergistic optimization of Se condensation and subsequent volatilization. We achieve a high-performance CZTSSe solar cell with a remarkable PCE of 13.6%, and the highest large-area PCE of 12.0% (over 1cm2). Our strategy will provide a new idea for further improving efficiency of CZTSSe solar cells via phase evolution regulation, and also for other complicated multi-compound synthesis.

cond-mat.mtrl-sci↗

arXiv2022

A precisely regulating phase evolution strategy for highly efficient kesterite solar cells

Phase evolution during the selenization is crucial for high-quality kesterite Cu2ZnSn(S, Se)4 (CZTSSe) absorbers and efficient solar cells. Herein, we regulate kinetic process of phase evolution from Cu+-Sn4+-MOE (MOE: 2-methoxyethanol) system by precisely controlling positive chamber pressure. We found that, at the heating-up stage, Se vapor concentration is intentionally suppressed in low-temperature region, which effectively reduces collision probability between the CZTS and Se atoms, thus remarkably inhibiting formation of secondary phases on the surface and multiple-step phase evolution processes. This strategy enables the phase evolution to start at relatively higher temperature and thereby leading to high crystalline quality CZTSSe absorber with fewer defects, and corresponding CZTSSe solar cell can present 14.1% efficiency (total area), which is the highest result so far. This work provides important insights into selenization mechanism of CZTSSe absorbers and explores a new way of kinetic regulation strategy to simplify the phase evolution path to efficient CZTSSe solar cells.

cond-mat.mtrl-sci↗

arXiv2022

Spontaneous Radiative Cooling to Enhance the Operational Stability of Perovskite Solar Cells via a Black-body-like Full Carbon Electrode

Operational stability of perovskite solar cells is remarkably influenced by the device temperature, therefore, decreasing the interior temperature of the device is one of the most effective approaches to prolong the service life. Herein, we introduce the spontaneous radiative cooling effect into the perovskite solar cell and amplified this effect via functional structure design of a full-carbon electrode (F-CE). Firstly, with interface engineering, >19% and >23% power conversion efficiencies of F-CE based inorganic CsPbI3 and hybrid perovskite solar cells have been achieved, respectively, both of which are the highest reported efficiencies based on carbon electrode and are comparative to the results for metal electrodes. Highly efficient thermal radiation of this F-CE can reduce the temperature of the operating cell by about 10 °C. Compared with the conventional metal electrode-based control cells, the operational stability of the above two types of cells have been significantly improved due to this cooling effect. Especially, the CsPbI3 PSCs exhibited no efficiency degradation after 2000 hours of continuous operational tracking.

physics.app-ph↗

arXiv2022

TFCN: Temporal-Frequential Convolutional Network for Single-Channel Speech Enhancement

Deep learning based single-channel speech enhancement tries to train a neural network model for the prediction of clean speech signal. There are a variety of popular network structures for single-channel speech enhancement, such as TCNN, UNet, WaveNet, etc. However, these structures usually contain millions of parameters, which is an obstacle for mobile applications. In this work, we proposed a light weight neural network for speech enhancement named TFCN. It is a temporal-frequential convolutional network constructed of dilated convolutions and depth-separable convolutions. We evaluate the performance of TFCN in terms of Short-Time Objective Intelligibility (STOI), perceptual evaluation of speech quality (PESQ) and a series of composite metrics named Csig, Cbak and Covl. Experimental results show that compared with TCN and several other state-of-the-art algorithms, the proposed structure achieves a comparable performance with only 93,000 parameters. Further improvement can be achieved at the cost of more parameters, by introducing dense connections and depth-separable convolutions with normal ones. Experiments also show that the proposed structure can work well both in causal and non-causal situations.

eess.AS↗

arXiv2020

Eliminating the Electric Field Response in a Perovskite Heterojunction Solar Cell to Improve Operational Stability

Intrinsic and extrinsic ion migration is a very large threat to the operational stability of perovskite solar cells and is difficult to completely eliminate due to the low activation energy of ion migration and the existence of internal electric field. We propose a heterojunction route to help suppress ion migration, thus improving the operational stability of the cell from the perspective of eliminating the electric field response in the perovskite absorber. A heavily doped p-type (p+) thin layer semiconductor is introduced between the electron transporting layer (ETL) and perovskite absorber. The heterojunction charge depletion and electric field are limited to the ETL and p+ layers, while the perovskite absorber and hole transporting layer remain neutral. The p+ layer has a variety of candidate materials and is tolerant of defect density and carrier mobility, which makes this heterojunction route highly feasible and promising for use in practical applications.

physics.app-ph↗

arXiv2020

Two-stage model and optimal SI-SNR for monaural multi-speaker speech separation in noisy environment

In daily listening environments, speech is always distorted by background noise, room reverberation and interference speakers. With the developing of deep learning approaches, much progress has been performed on monaural multi-speaker speech separation. Nevertheless, most studies in this area focus on a simple problem setup of laboratory environment, which background noises and room reverberations are not considered. In this paper, we propose a two-stage model based on conv-TasNet to deal with the notable effects of noises and interference speakers separately, where enhancement and separation are conducted sequentially using deep dilated temporal convolutional networks (TCN). In addition, we develop a new objective function named optimal scale-invariant signal-noise ratio (OSI-SNR), which are better than original SI-SNR at any circumstances. By jointly training the two-stage model with OSI-SNR, our algorithm outperforms one-stage separation baselines substantially.

eess.AS↗

arXiv2019

Coordination Engineering of Cu-Zn-Sn-S Aqueous Precursor for Efficient Kesterite Solar Cells

Aqueous precursors provide an alluring approach for low-cost and environmentally friendly production of earth-abundant Cu2ZnSn(S,Se)4 (CZTSSe) solar cells. The key is to find an appropriate molecular agent to prepare a stable solution and optimize the coordination structure to facilitate the subsequent crystallization process. Herein, we introduce thioglycolic acid, which possesses strong coordination (-SH) and hydrophilic (-COOH) groups, as the agent and use deprotonation to regulate the coordination competition within the aqueous solution. Ultimately, metal cations are adequately coordinated with thiolate anions, and carboxylate anions are released to become hydrated to form an ultrastable aqueous solution. These factors have contributed to achieving CZTSSe solar cells with efficiency of as high as 12.2% (a certified efficiency of 12.0%) and providing an extremely wide time window for precursor storage and usage. This work represents significant progress in the non-toxic solution fabrication of CZTSSe solar cells and holds great potential for the development of CZTSSe and other metal sulfide solar cells.

physics.app-ph↗