Quantum Optoelectronics

Abstract:

Weakly bonded native ligands severely degrade the performance of perovskite quantum dot (PeQD) light-emitting diodes (LEDs). While conventional approaches can be used to strengthen ligand binding, they fail to achieve complete ligand exchange, leaving residual ligands that promote degradation. Herein, we present a dual-functional fluorinated benzyl phosphonic acid (F-BPA) ligand that modulates the acidity and enhances the binding affinity between the phosphonate groups of F-BPA and the perovskite surface compared to BPA due to a significant redistribution of the electrostatic potential of the molecule induced by fluorination. The F-BPA treatment facilitates effective ligand exchange and obtains well-passivated CsPbI3 PeQDs with improved stability under thermal, light, and polar solvent stress. Red-emissive LEDs achieved a maximum external quantum efficiency of 24.0% with improved device stability (half-lifetime of 1,020 min at 100 cd m–2). This study demonstrates a dual-functional ligand strategy and opens a new pathway toward PeQDs for next-generation display technologies.

Abstract:

1D and 2D integrations provide significant promise for machine vision by enabling compact, power‐efficient optoelectronic devices. However, the potential of 1D materials in mixed‐dimensional structures for convolutional image processing remains largely unexplored. Here, high‐quality 1D‐Nb2Pd3Se8 is synthesized and integrated with 2D‐WSe2 to form self‐powered photodetectors, exhibiting gate‐tunable bi‐directional photoresponse for image processing. Utilizing the narrow band gap and favorable work function of 1D‐Nb2Pd3Se8, a type‐I junction and 1D van der Waals interface are established with transition metal dichalcogenides. The gate tunable built‐in electric field enables switching between n‐p and n‐n+ configurations, allowing the drift photocurrent direction to be reversed, achieving both negative and positive photocurrent. Furthermore, efficient conversion of high‐energy photons along one dimension enhances sensitivity at 375 nm. The device achieves a responsivity of 232 mA W−1, external quantum efficiency of 77% at 375 nm illumination, rapid response time of ~3 µs, detectivity of 6.35 × 1010 Jones, and broadband photodetection from ultraviolet to near‐infrared. The demonstrated gate‐controllable, bi‐directional photoresponse with linear power dependence in a 1D heterojunction offers a promising platform for in‐sensor convolutional processing with high integration and portability.

Abstract:

${\text{CoTi}}_2{\mathrm{O}}_5$ has the paradox that low temperature static magnetic order is incompatible with the crystal structure owing to a mirror plane that exactly frustrates magnetic interactions. Despite no observable structural distortion with diffraction, ${\text{CoTi}}_2{\mathrm{O}}_5$ does magnetically order below $T_N\sim 25\mathrm{K}$ with the breaking of spin ground state degeneracy proposed to be a realization of the spin Jahn-Teller effect in analogy to the celebrated orbital Jahn-Teller transition. We apply neutron and Raman spectroscopy to study the dynamics of this transition in ${\text{CoTi}}_2{\mathrm{O}}_5$ . We find anomalous acoustics associated with a symmetry breaking strain that characterizes the spin Jahn-Teller transition. Crucially, the energy of this phonon coincides with the energy scale of the magnetic excitations, and has the same symmetry of an optic mode, observed with Raman spectroscopy, which atypically softens in energy with decreasing temperature. Taken together, we propose that the energetics of the spin Jahn-Teller effect in ${\text{CoTi}}_2{\mathrm{O}}_5$ are related to cooperative magnetoelastic fluctuations as opposed to conventional soft critical dynamics which typically drive large measurable static displacements. Published by the American Physical Society 2025

Abstract:

We demonstrate a novel defect-mediated, thermally-activated emission mechanism in [(CH3)3NPh]2MnBr4 single crystals, driven by the coexistence of temperature-sensitive shallow traps and temperature-independent deep traps introduced by Br vacancies. Through comprehensive temperature-dependent photoluminescence (PL) and time-resolved PL measurements, combined with first-principles calculations, we reveal that the material exhibits exceptional thermal stability, retaining 67 % of its relative PL quantum yield at room temperature and achieving an absolute quantum yield of ∼38.9 % under optimal excitation conditions. The dual-component PL decay dynamics consist of a fast decay (∼hundreds of ps) governed by shallow traps and a long decay (∼350 μs) dominated by deep traps, creating an energy cascade that efficiently promotes radiative recombination while minimizing non-radiative losses. Our findings provide critical insights into defect-mediated, thermally-sensitive delayed emission mechanisms and establish [(CH3)3NPh]2MnBr4 as a lead-free, thermally stable material with high efficiency, making it an excellent candidate for next-generation optoelectronic applications, including solid-state lighting and temperature-sensitive devices.