Emerging-wide bandgap semiconductor Ga₂O₃ shows distinct characteristics for optoelectronic applications and a stable crystal phase of Ga₂O₃ is highly desired. Herein, we have first reported a metal-semiconductor-metal structure photonic synaptic device based on the ε-Ga₂O₃ thin film. The ε-Ga₂O₃ epilayer is grown on the c-sapphire with a low temperature nucleation layer, which presents a crystal orientation relationship with the c-sapphire (ε-Ga₂O₃ <010> // c-sapphire <1-100> and ε-Ga₂O₃ <001> // c-sapphire <0001>). The ε-Ga₂O₃ photonic device was stimulated by UV pulses at different pulse widths, pulse intervals, and reading voltages. Under the UV pulse excitation, the photonic device exhibits primary synaptic functions including excitatory postsynaptic current, short term memory, pair pulse facilitation, long term memory, and STM-to-LTM conversion. In addition, stronger and repeated stimuli can naturally contribute to the higher learning capability, thus prolonging the memory time.

Cherenkov radiation in artificial structures experiencing strong radiation enhancements promises important applications in free-electron quantum emitters, broadband light sources, miniaturized particle detectors, etc. However, the momentum matching condition between swift electrons and emitted photons generally restricts the radiation enhancement to a particular momentum. Efficient Cherenkov radiation over a wide range of momenta is highly demanded for many applications but still remains a challenging task. To this end, we explored the interaction between swift electrons and twisted hyperbolic Van der Waals crystals and observed enhanced Cherenkov radiation at the flatband resonance frequency. We show that, at the photonic magic angle of the twisted crystals, the electron momentum, once matching with that of the flatband photon, gives rise to a maximum energy loss (corresponding to the surface phonon generation), one-order of magnitude higher than that in conventional hyperbolic materials. Such a significant enhancement is attributed to the excitation of flatband surface phonon polaritons over a broad momentum range. Our findings provide a feasible route for highly directional free-electron radiation and radiation shaping.

Electrochemical deposition technique, a method widely recognized for its precision and versatility in the electronics industry, is gaining attraction in the energy field, particularly in developing solid oxide fuel cells (SOFCs). Its ability to deposit metal compounds with nanostructures under simple ambient conditions makes it invaluable for modifying conventional electrodes with refined morphologies and compositions. In this mini-review, we explore the principles of electrochemical deposition and highlight its recent applications in SOFC technology. Our focus lies on its pivotal role in fabricating coating layers or catalysts on electrodes with improved functionalities to build more efficient and durable fuel cells. Furthermore, we discuss emerging strategies for electrode surface modification and the potential of electrochemical deposition in advancing SOFC design and functionality. Our review also outlines future research directions aimed at harnessing and expanding the capabilities of electrochemical deposition in energy conversion applications.

Metal halide perovskites (MHP)-based electrically pumped vertical-cavity surface-emitting lasers (EPVCSEL) are promising candidates in optoelectronics due to low-carbon footprint solution processing method. However, significant challenges impede MHP-EPVCSEL manufacturing: (1) Distributed Bragg Reflectors (DBRs) composed of typical electron transport layers (ETLs) and hole transport layers (HTLs) are not conductive enough. (2) Due to large mobility difference of typical ETLs and HTLs, carriers-unbalanced injection leads to severe performance degradation. Herein, we propose a potential strategy to address such challenges using MAPbCl₃ and CsSnCl₃ as carrier transport layers with mobility 3 orders larger than typical ETLs and HTLs. Via transfer matrix method calculations, we find that the reflectance of DBRs composed of MAPbCl₃ (130.5 nm)/CsSnCl₃ (108 nm) is larger than 91% with 10 pairs of DBRs. Furthermore, the proposed EPVCSEL device simulation shows that MHP-EPVCSEL has the potential to achieve room temperature continuous wave lasing with a threshold current density of ∼69 A cm^-2 and output optical power ∼10^-4 W. This work can provide a deep insight into the practical realization of MHP-EPVCSEL.

Photocatalytic overall water splitting (OWS) can convert solar energy into hydrogen (H₂) and oxygen (O₂), which is significant in reducing the reliance on fossil fuels. Constructing S-scheme heterojunctions is an effective method for facilitating charge transfer, but the huge interfacial charge transfer barrier poses a challenge to advance the efficiency of photocatalytic OWS. Here, a low-interfacial barrier Ce-S bond-enhanced Mo-doped ZnIn₂S₄/oxygen-deficient CeO₂ (Mo-ZIS/O_V-CeO₂) S-scheme heterojunction photocatalyst was designed via a doping-defect coupling strategy. The abundant unsaturated S atoms generated by doping Mo atoms in ZnIn₂S₄ combine with the unpaired electrons on the Ce atom in O_V-CeO₂, forming the interfacial Ce-S bonds, which induce a 43% decrease in carrier transport activation energy and a 2.1-fold increase in build-in electric field intensity compared to ZIS/O_V-CeO₂. Reduced carrier transport activation energy and increased built-in electric field intensity provide a strong driving force for charge separation following the S-scheme pathway. Benefiting from the interfacial Ce-S bonds and the S-scheme transfer path, Mo-ZIS/O_V-CeO₂ exhibits H₂ and O₂ evolution rates of 512.7 and 256.3 μmol g^-1 h^-1, respectively, along with a solar-to-hydrogen efficiency of 0.14%. This study proposes an innovative insight into developing and constructing S-scheme heterojunction photocatalysts with efficient charge migration interfaces.

Owing to its ability to reduce charge recombination and enhance redox capability, the step-scheme (S-scheme) heterojunction has manifested appealing prospect for photocatalysis. In this work, an organic-inorganic S-scheme heterojunction based on CdS nanorods and conjugated polymer 2-hexyl-carbazole-benzothiadiazole (CBT) is constructed. The obtained catalyst exhibited impressive photocatalytic hydrogen production performance (14.02 mmol g^-1 h^-1) with a high apparent quantum efficiency of 5.4% at 420 nm. The charge transfer mechanism and the enhancement of photocatalytic hydrogen production in S-scheme heterojunctions were investigated by density functional theory calculations, in situ X-ray photoelectron spectroscopy, and in situ Kelvin probe force microscopy. The successful construction of organic-inorganic S-scheme heterojunctions and the formation of Cd-S bonds at the interface effectively promoted the separation and transfer of charge carriers.