Associate Professor Xihan CHEN from the Department of Mechanical and Energy Engineering at Southern University of Science and Technology (SUSTech), together with his collaborators, has made a series of important research advances in the modulation of ultrafast dynamics for enhanced energy conversion efficiency. The team proposed several innovative strategies and achieved significant progress in photocatalytic dynamics, spin dynamics, and carrier dynamics in thermoelectric materials. The related studies have been published in leading journals in the fields of materials science and chemistry, including Advanced Materials, Chemical Science, and The Journal of Physical Chemistry Letters.
Achievement 1: Photothermal Synergistic Catalysis for Solar-Driven Hydrogen Peroxide Production
Hydrogen peroxide is an important chemical widely used in medical disinfection, wastewater treatment, organic synthesis, and the paper industry. Photochemical energy conversion based on renewable solar energy is of great significance for future economic transformation and industrial development. In this work, the team constructed a tungsten-centered amorphous metal–organic polymer using hydroxyl-modified terephthalic acid ligands (MIL-2OH-W), enabling photothermal synergistic catalysis for hydrogen peroxide production with a concentration as high as 1.02 g L–1 and a solar-to-chemical efficiency of 2.74%.
Transient absorption spectroscopy under simulated photocatalytic conditions reveals the presence of a photoinduced oxygen reduction reaction (ORR) and demonstrates that elevated temperatures accelerate the decay kinetics. An increased number of hydroxyl groups in MIL-2OH-W leads to a more pronounced photothermal synergistic effect. This study provides important insights for the large-scale and industrial production of hydrogen peroxide. The work, entitled “Solar-driven Ultrafast Production of Gram-per-litre Level Hydrogen Peroxide with 2.74% Solar-to-chemical Efficiency via Synergistic Photothermal Catalysis by W-based Amorphous Metal-Organic Polymers,” was published in Advanced Materials. SUSTech is the first affiliation. Qiushi HU, a joint PhD student from SUSTech and City University of Hong Kong, is the first author, while Prof. Ruquan YE (City University of Hong Kong), Prof. Li LING (Beijing Normal University), and Prof. Xihan CHEN (SUSTech) are the corresponding authors.
Achievement 2: A Machine Learning Framework for Predicting Ultrafast Spin Dynamics in Perovskites
Spintronics exploits electron spin as an information carrier and holds great promise for applications in quantum computing, information storage, and optoelectronic devices. Metal halide perovskites, with their excellent optoelectronic properties and strong spin-orbit coupling, are emerging as promising materials for ultrafast spintronics. However, their complex spin dynamics remain difficult to predict accurately.
To address this challenge, the research team developed a small-data machine learning framework for pre-synthesis screening, using intrinsic molecular descriptors such as molecular weight, HOMO/LUMO energy levels, polarizability, and dipole moment. An artificial neural network was trained on a dataset of 52 perovskite materials, achieving highly accurate predictions of spin relaxation rates with a leave-one-out cross-validation accuracy of R² = 0.99, and demonstrating good generalization in independent tests. Combined with SHAP-based interpretability analysis, the model reveals the dominant roles of molecular weight and frontier orbital energies, linking spin relaxation behavior to underlying physical mechanisms such as spin-orbit coupling, phonon scattering, and electron–hole exchange. This work provides a lightweight, interpretable, and transferable predictive tool for the rational design and high-throughput discovery of spin-functional perovskite materials.
The study, entitled “Machine learning-driven prediction of ultrafast spin relaxation in metal halide perovskites for spintronic applications,” was published in Chemical Science. SUSTech is the first affiliation. Jianhui LI from Prof. CHEN’s group is the first author, while Prof. Xiaodong XIANG (Institute of Physics, Chinese Academy of Sciences) and Prof. Xihan CHEN are the corresponding authors.
Achievement 3: Chirality-Induced Spin-Orbit Coupling and Long Spin Lifetimes in Chiral Perovskites
The team also achieved an important breakthrough in the study of spin-orbit coupling (SOC) and spin dynamics in chiral perovskite materials. By introducing the chiral organic molecule (R/S)-4-(aminoethyl)piperidinium (4AEP) into iodide-lead perovskite frameworks, chiral [(R/S)-4AEP]PbI4 crystals and thin films were successfully synthesized. Circularly polarized pump–probe ultrafast spectroscopy was employed to systematically investigate carrier spin dynamics.
The results show that chirality-induced SOC generates a pronounced spin splitting of approximately 130 meV, enabling spin-polarized lifetimes exceeding 1 ns at room temperature, which is significantly longer than those in conventional perovskites. Although Pb and I intrinsically exhibit strong SOC that typically leads to rapid spin relaxation, this study demonstrates that chirality-induced SOC effectively counteracts the intrinsic SOC field, suppressing spin precession and stabilizing long-lived spin states. Density functional theory (DFT) calculations further reveal that the chiral structure lifts spin degeneracy at the second valence band maximum (VB2), providing the microscopic origin of the large spin splitting and long spin lifetime. This work offers new physical insights and material design principles for chiral perovskites in spintronic applications.
The paper, entitled “Quantification of Chirality Induced Spin-Orbit Coupling for Long Spin Polarized Lifetime in Hybrid Perovskite,” was published in The Journal of Physical Chemistry Letters. SUSTech is the first affiliation. Yuling HUANG (SUSTech) and Zhikang JIANG (Southeast University) are co-first authors, while Prof. Jinzhu ZHAO (South China Normal University) and Prof. Xihan CHEN are the corresponding authors.
Achievement 4: Ultrafast Spectroscopic Revelation of Carrier Scattering Potential in Thermoelectric Materials
The research group has made significant progress in understanding carrier transport mechanisms in thermoelectric materials, quantitatively revealing for the first time the decisive role of carrier scattering potential in thermoelectric performance using ultrafast spectroscopy. Focusing on the strongly cation-disordered thermoelectric material AgSbSe2, the team synthesized high-quality Cd-doped single crystals and employed femtosecond pump–probe transient reflectance spectroscopy to probe carrier dynamics on ultrafast timescales.
The results show that eliminating grain-boundary defects and introducing short-range ordering significantly reduce the total carrier scattering potential, even leading to a negative extrinsic scattering contribution, thereby enhancing carrier mobility and electrical transport performance. Consequently, the average power factor increases by nearly threefold over the temperature range of 323-723 K, and a maximum thermoelectric figure of merit (zT) of 1.7 is achieved at 723 K, representing one of the highest reported values for AgSbSe2-based systems. Meanwhile, local lattice distortions induced by short-range ordering enhance phonon scattering, effectively lowering lattice thermal conductivity while maintaining high electrical conductivity. A single-leg thermoelectric device fabricated from the optimized single crystal exhibits an energy conversion efficiency of 8% under a temperature difference of 423 K.
The study, entitled “Direct Experimental Evidence of Low Carrier Scattering Potential in High Performance Thermoelectric AgSbSe2 Crystal,” was published in Advanced Materials. Kaiqi ZHANG and Shuang LIU (Chongqing University), together with Yuling HUANG (SUSTech), are co-first authors, while Prof. Xihan CHEN (SUSTech), Prof. Xu LU, and Prof. Xiaoyuan ZHOU (Chongqing University) are the corresponding authors.
Paper Links:
https://doi.org/10.1002/adma.202522526
https://doi.org/10.1039/D5SC07406A
Proofread ByNoah Crockett, Junxi KE
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