Advanced Optical Materials最新文献

Tin (Sn)-based perovskites are promising materials for perovskite-based light-emitting diodes (PeLEDs) that avoid toxic lead. However, the performance of Sn-based PeLEDs lags behind that of their lead analogues due to uncontrolled crystallization, the susceptibility of Sn(II) to oxidation, and high defect densities. In this study, ammonium thiocyanate (NH₄SCN) is used as an additive in DMSO-free perovskite precursor solution to afford Sn-based perovskites that are evaluated in PeLEDs. NH₄SCN modulates the crystallization process in the solution phase to improve the morphology and crystallinity of the resulting 2D perovskite films and inhibits the oxidation of Sn(II) to Sn(IV), a problem observed in DMSO. Transient terahertz spectroscopy reveals that NH₄SCN-based perovskite films have a higher free carrier density compared to the control films, indicative of reduced defect density. Consequently, pure-red Sn-based PeLEDs with an emissive peak of 629 nm achieve an external quantum efficiency of ≈1.4%, with an operating half-life of >11 min. These findings provide valuable insights into the preparation of lead-free perovskite materials avoiding DMSO for application in optoelectronic devices.

Nowadays, luminescent information remains limited to multicolor static or single-color dynamic change driven by high-energy UV, still facing a significant challenge in achieving multilevel luminescent encryption. Here, a visible light irradiation-triggered dynamic multicolor luminescent material of Na₂Ba₆(Si₂O₇)(SiO₄)₂:Eu with multi-coordinated sites is reported. The system possesses three emission centers of red (Eu³⁺), green [Eu²⁺(2)], and blue [Eu²⁺(1)], and can realize a large luminescence contrast (ΔR_t = 96.6% at 444 nm) by 405 nm irradiation-induced oxidation reactions. By adjusting the excitation wavelengths or light irradiation time, the luminescence color and contrast can be dynamically tuned. The unique optical tunable luminescence properties endow them with potential applications in multilevel anticounterfeiting and combined information encryption. The results provide a novel approach for realizing multicolor luminescence modulation under a light field, greatly improving the security level of encrypted information.

Materials with broadband high solar absorptance and excellent thermal stability are crucial for solar energy utilization. The distinct spectral separation between electronic transitions and carrier absorption leads to limited broadband absorption efficiency in ceramics. Strategic design of structural units with tunable absorption and bandwidth is essential to overcome spectral limitations for broadband solar harvesting. This study establishes an engineering strategy that synergistically exploits cation disorder and Jahn-Teller distortions in spinel to achieve enhanced absorption. Through strategic incorporation of [CuO₆] and [CuO₄] structural units into MgAl₂O₄, Mg_0.4Cu_0.6Al₂O₄ achieves a remarkable solar absorptance of 94.9% over 0.2–8 µm and demonstrates impressive thermal stability with less than 1.5% absorptance loss after annealing at 1300 °C for 100 h. The enhanced absorption is attributed to Jahn-Teller distortions in both [CuO₄] tetrahedra and [CuO₆] octahedra, which induce significant multiple splitting of Cu-3d orbitals, enhancing electronic transitions and carrier absorption. The developed material exhibits broadband solar absorptance, high-temperature stability, and low density among oxide ceramics, making it a promising candidate for concentrated solar absorbers. These findings provide fundamental insights into the design of high-performance solar absorbers through targeted manipulation of structural units and coordination environments.

Localized quantum emitters in transition-metal dichalcogenides (TMDs) have recently emerged as solid-state candidates for on-demand sources of single photons. Due to the role of strain in the site-selective creation of TMD emitters, their hybrid integration into photonic structures such as cavities and waveguides is possible using pick-and-place methods. Here, quantum emission from a hybrid structure consisting of a monolayer of WSe₂ interfaced with horizontally aligned InP nanowires (NWs) is investigated. These experiments reveal multiple narrow and bright emission peaks in the 715–785 nm spectral range and g⁽²⁾(0) as low as 0.049, indicating strong antibunching and good single photon purity. The well-defined facets of the InP NWs shape the local strain landscape, enabling controlled formation of localized emitters in the WSe₂ monolayer.

Organic photodetectors operating in the deep-ultraviolet region are crucial for environmental monitoring, biomedical imaging, and sterilization systems. Two novel indolo[2,3-b]indole derivatives with systematic alkyl chain variation: 5,6-didodecyl-5,6-dihydroindolo[2,3-b]indole (ID23b-C12) and 5,6-dihexadecyl-5,6-dihydroindolo[2,3-b]indole (ID23b-C16) are reported. Both compounds exhibit wide bandgaps (>3.5 eV), high thermal stability (decomposition temperature >410 °C), and form aggregates in water:THF mixtures with distinct morphological characteristics. Using simple planar FTO/molecule/FTO devices, films prepared from pre-aggregated solutions achieve photoresponsivities of 32.5 mA W⁻¹ (ID23b-C12) and 74.8 mA W⁻¹ (ID23b-C16) at 254 nm under 2 V bias, representing 6.1 × and 20.8 × enhancements compared to molecularly dispersed films. Detectivity values reach 2.8 × 10¹⁰ Jones and 1.3 × 10¹¹ Jones, respectively. This single-component approach achieves performance competitive with complex donor-acceptor heterojunctions, demonstrating solution-state molecular organization as an effective strategy for efficient deep-UV photodetection without elaborate device engineering.

For decades, pyrolysis of organic compounds has been pursued to produce graphitic carbon, revealing that structural evolution depends more on reaction dynamics than precursor chemistry. Here, a parallel and previously overlooked pathway is uncovered: the spontaneous formation of nanodiamonds (NDs) at temperatures as low as 220 °C and 2.5 MPa during the earliest stages of carbonization. These transient sp³ clusters, long masked by amorphous carbon, can now be unambiguously identified through the activation of optically addressable nitrogen vacancy (NV⁻) and silicon vacancy (SiV⁻) centers, supported by Raman spectroscopy of 1321 nm and high-resolution transmission electron microscopy (HRTEM) lattice spacings of 0.206 nm consistent with diamond. The resulting NDs exhibit robust quantum-optical signatures, including Optically detected magnetic resonance (ODMR) with a contrast of ≈16%, comparable to values measured in bulk single-crystal diamond, confirming the formation of quantum-grade color centers within these sub-10 nm NDs. This discovery reshapes the understanding of carbon phase evolution and establishes a sustainable, solution-processed pathway for scalable, low-temperature synthesis of quantum-relevant NDs, a capability once thought exclusive to nature or extreme synthesis conditions.

The luminescent efficiency of copper(I) halide cluster-based complexes is frequently diminished by multiple exciton recombination centers, which significantly restricts their optoelectronic applications. Herein, a mild structural rigidity-regulation strategy is proposed to suppress exciton recombination by organizing Cu_xX_x clusters with either the semi-rigid ligand bis(2-diphenylphosphinophenyl)ether (POP) or the rigid ligand 1,2-bis(diphenylphosphino)benzene (dppb). As a proof of concept, sandwich- or butterfly-like Cu_xX_x(L)₂ (x = 2 or 4; X = I or Br, L = POP or dppb) clusters with different structural rigidity and photoluminescence/radioluminescence performance are synthesized. Compared with Cu₄I₄(POP)₂, the Cu₂I₂(POP)₂ and Cu₂I₂(dppb)₂ clusters possess higher structural rigidity and form more compact stacks, effectively suppressing structural relaxation-induced non-radiative transitions during metal-to-ligand or halide-to-ligand charge transfer (M/XLCT). Notably, Cu₂I₂(POP)₂ and Cu₂I₂(dppb)₂ exhibit high photoluminescence/radioluminescence performance, achieving steady-state X-ray light yields nearly 150% higher than those of commercial LuAG:Ce. Furthermore, their corresponding flexible films demonstrate outstanding spatial resolution, reaching 11.5 and 14.0 lp mm⁻¹, respectively. This rigidity-regulation strategy can open a new avenue for the systematically designing of high-performance Cu_xX_x cluster-based X-ray scintillators.

Lead-free metal halide perovskites emerge as promising materials for ultraviolet (UV) photodetectors (PDs), addressing the challenges in cost, fabrication, and performance associated with traditional materials. Nevertheless, critical performance parameters such as responsivity, detectivity, and response speed remain substantially limited. This work demonstrates high-performance, self-powered UV photodetectors based on Cu₂AgBiI₆ (CABI) thin films, achieved through synergistic optimization of the photosensitive layer and interfacial layer. The incorporation of 15% chlorine (Cl) into pristine CABI markedly improves film coverage and crystallinity, reducing defect density and enhancing carrier mobility. Further interface modification with 0.25 m formamidinium iodide (FAI) synergistically refines film quality, leading to superior device performance. The resulting self-powered UV photodetector (CABI:15% Cl / 0.25 m-FAI) achieves a record-high specific detectivity of 3.20 × 10¹³ Jones at 365 nm, coupled with excellent stability and rapid response. This study offers valuable insights for developing high-performance, cost-effective, and solution-processable perovskite photodetectors.

Passive radiative cooling is a promising technology for mitigating global warming by reflecting sunlight and radiating heat into the supercooled outer space. This approach has attracted increasing attention. However, achieving efficient light scattering typically depends on high-refractive-index inorganic materials, such as titanium dioxide. Despite its widespread application, recent research reveals that titanium dioxide may pose a potential carcinogenic risk. As a sustainable alternative, cellulose offers renewability, biodegradability, and biocompatibility. Inspired by the scale structure of the Calothyrza margaritifera beetles, all-cellulose-based highly scattering films are developed to overcome the intrinsic low refractive index of cellulose. These films consist of ethyl cellulose microspheres with optimized size and filling fraction as scattering centers and cellulose nanofibers as a supporting network to anchor these microspheres. Despite their ultrathin thickness (10 µm), these films achieved a reflectivity of 70%. When applied for passive radiative cooling, 300-µm-thick all-cellulose-based films reduced temperature by 8 °C during the day and 2 °C at night. The use of cellulose to achieve thinner, more efficient scattering materials while minimizing material usage, offering a sustainable and safer alternative to titanium dioxide as a scattering material. Such all-cellulose-based highly scattering films hold great promise for the fields of functional coatings, foods, and personal care products.

Photoluminescence properties are important for the application of exciton-polaritons. Photoluminescence from lower polariton is usually observed, whereas that from upper polariton is weak. In this study, the emission angle-resolved photoluminescence properties of the strongly coupled gold plasmonic nanoarray cavities and molecular aggregates of squaraine are investigated. Angle-resolved photoluminescence shows similar dispersion as that of reflectance, with strong PL from both upper and lower polariton branches. This is attributed to the direct relaxation of high-energy excited states to upper and lower polariton branches, followed by radiative relaxation. Weak exciton-vibration coupling and inefficient polariton-polariton interactions may account for the weak inter-branch, intra-branch, and polariton-exciton reservoir scattering. It is further found that the photobleaching rate of J-aggregate excitons is suppressed and accelerated under strong coupling for short and long irradiation times, respectively. This is due to the combined effects of strong coupling-induced polariton wavefunction delocalization and the effect of hot electrons in plasmonic nanoarrays, with the latter accelerating the photobleaching. This study provides insights for a controllable modulation of the photophysical properties of molecular excitons in strong coupling conditions.