Advanced Optical Materials最新文献

Multiresonance thermally activated delayed fluorescence (MR-TADF) emitters with high color purity in virtue of their inherent narrowband emission have received great interest in organic light-emitting diodes (OLEDs). However, it remains a big challenge to develop the ultrapure blue MR-TADF emitters with high efficiency. In this work, a novel “dual-MR-core” strategy is proposed by connecting two parent N-B-O-skeletons with non-conjugate 9-position substituted fluorene linkages for high efficient deep-blue MR-TADF emitters, namely H-FOBN and Me-FOBN, which possess the highly twisted structure with suppressed aggregation. Finally, the vacuum-deposited deep-blue OLED exhibits excellent external quantum efficiency (EQE) of 25.1% with small full width at half maximum (FWHM) of 28 nm, as well as CIE of (0.14, 0.08). Furthermore, owing to enhanced solubility, the solution-processed deep-blue OLED based on Me-FOBN shows EQE of 11.3%, with small FWHM of 32 nm and CIE of (0.14,0.09). These outstanding performances confirm that this “dual-MR-core” strategy provides a feasible approach to develop high efficient ultrapure blue MR-TADF emitters.

Nanostructures represent a frontier where meticulous attention to the control and assessment of structural dimensions becomes a linchpin for their seamless integration into diverse technological applications. However, determining the critical dimensions and optical properties of nanostructures with precision still remains a challenging task. In this study, by using an integrative and comprehensive methodical series of studies, the evolution of the depolarization factors in the anisotropic Bruggeman effective medium approximation (AB-EMA) is investigated. It is found that these anisotropic factors are extremely sensitive to the changes in critical dimensions of the nanostructure platforms. In order to perform a systematic characterization of these parameters, spatially coherent, highly-ordered slanted nanocolumns are fabricated from zirconia, silicon, titanium, and permalloy on silicon substrates with varying column lengths using glancing angle deposition (GLAD). In tandem, broad-spectral range Mueller matrix spectroscopic ellipsometry data, spanning from the near-infrared to the vacuum UV (0.72–6.5 eV), is analyzed with a best-match model approach based on the anisotropic Bruggeman effective medium theory. The anisotropic optical properties, including complex dielectric function, birefringence, and dichroism, are thereby extracted. Most notably, the research unveils a generalized, material-independent inverse relationship between depolarization factors and column length. It is envisioned that the presented scaling rules will permit accurate prediction of optical properties of nanocolumnar thin films improving their integration and optimization for optoelectronic and photonic device applications. As an outlook, the highly porous nature and extreme birefringence properties of the fabricated columnar metamaterial platforms are further explored in the detection of nanoparticles from the cross-polarized integrated spectral color variations.

Metal–organic frameworks (MOFs) like the zeolitic imidazolate framework (ZIF-8) have a high surface area, tunable porosity, and robust thermal and chemical stability, making them attractive candidates for various applications. Here, a strategy is shown that spans that functionality and provides strong photoluminescence (PL) emission, unlocking ZIF-8-based materials for chemical and temperature sensors based on PL. The approach is based on laser processing that dramatically boosts the PL response of laser-irradiated ZIF-8 (LI ZIF-8), achieving a 70-fold increase in intensity relative to the pristine material. The PL characteristics of the irradiated material can be easily tuned by varying the laser power and irradiation time with in situ and real-time spectroscopic analysis providing insights into the process dynamics. It is found that the observed PL enhancement is primarily due to the laser-induced transformation of ZIF-8 into nitrogen-doped nanocarbons and ZnO nanostructures. The versatility of this laser processing approach is leveraged to create flexible electronics by integrating the LI ZIF-8/nanocarbon architectures into thermoplastic polyurethane (TPU). The multifunctional composite material shows excellent performance as flexible electrodes for human-body monitoring applications, as well as both temperature and flexure sensors with remarkable mechanical resilience.

The ligand passivation is considered an attractive strategy to prepare high-quality perovskite nanocrystals (PNCs) with improved photophysical features in polar media. However, the long-term stabilization of PNCs in these environments is still challenging, being pivotal to understanding the protection mechanism given by prominent surface ligands and avoiding material deterioration in polar solvents. In this work, how the nature of diverse alkylammonium bromides used during surface passivation influences the photophysical properties and quality of CsPbX₃ PNCs fully dispersed in alcohol environments, exhibiting stability up to 10 months are investigated. By adding didodecyldimethylammonium benzyldodecyldimethylammonium and tetrabutylammonium bromides (DDAB, BDAB, and TBAB, respectively), DDAB and BDAB promote a suitable and partial surface coverage are observed, respectively, suppressing defect sites in the nanocrystals. Conversely, TBAB shows poor surface protection, decreasing the PL features of PNCs. The presence of DDAB and BDAB favors the fabrication of color converters, and efficient light-emitting diodes (LEDs) with external quantum efficiencies (EQE) of ≈23%. Interestingly, significant device stability with BDAB capping shows an LED half-life of 20-fold longer than for DDAB. This contribution offers a promising approach for preparing highly luminescent and stable alcohol-dispersed PNCs, useful for fabricating efficient optoelectronic devices.

Discovery of new materials with enhanced optical properties in the visible and UV-C range can impact applications in lasers, nonlinear optics, and quantum optics. Here, the optical floating zone growth of a family of rare earth borates, RBa₃(B₃O₆)₃ (R = Nd, Sm, Tb, Dy, and Er), with promising linear and nonlinear optical (NLO) properties is reported. Although previously identified to be centrosymmetric, the X-ray analysis combined with optical second harmonic generation (SHG) assigns the noncentrosymmetric P$�\overline{6}$ space group to these crystals. Characterization of linear optical properties reveals a direct bandgap of ≈5.61–5.72 eV and strong photoluminescence in both the visible and mid-IR regions. Anisotropic linear and nonlinear optical characterization reveals both Type-I and Type-II SHG phase matchability, with the highest effective phase-matched SHG coefficient of 1.2 pm V⁻¹ at 800-nm fundamental wavelength (for DyBa₃(B₃O₆)₃), comparable to β-BaB₂O₄ (phase-matched d₂₂ ≈ 1.9 pm V⁻¹). Laser-induced surface damage threshold for these environmentally stable crystals is 650–900 GW cm⁻², which is four to five times higher than that of β-BaB₂O₄, thus providing an opportunity to pump with significantly higher power to generate about six to seven times stronger SHG light. Since the SHG arises from disorder on the Ba-site, significantly larger SHG coefficients may be realized by “poling” the crystals to align the Ba displacements. These properties motivate further development of this crystal family for laser and wide bandgap NLO applications.

Self-healing transparent polymers are advantageous for various optoelectronic devices to improve resilience and durability. However, most of these materials have been applied only as flat films and do not address the need for optical structures that can manipulate light. Here optical microstructures embossed on a self-healing polyurea film are presented which can autonomously recover from damage in ambient conditions. The polyurea film have a high optical transmittance above 90% and haze below 1.3%, and Young's modulus of 3.4 MPa. When applied as a protective light-trapping layer for perovskite solar cells, the champion device shows improved short circuit current density from 23.7 to 25.0 mA·cm⁻², and power conversion efficiency from 21.5% to 23.0%. Furthermore, the solar cell with the light-trapping layer has improved impact resistance and can recover its performance after being scratched. It is envisioned that self-healing optical structures can be realized for different geometries and materials in a range of optoelectronic applications to produce resilient and durable devices.

Lanthanide downconversion nanoparticles (DCNPs) have huge potential in biosensing and imaging applications in the NIR-II window. However, DCNPs inherently suffer from low quantum efficiency, due to low absorption cross-section and the restricted doping concentration of lanthanide ions. In this work, a combined strategy for downconversion luminescence in the NIR-II window is investigated by the integration of Ce³⁺ ions into the conventional NaYF₄: Yb³⁺, Er³⁺ DCNPs and incorporation of periodic silver hole-cap coupled Nanoarrays (Ag-HCNAs) simultaneously. Over two orders of magnitude, luminescence enhancement is achieved by the combination of optimized Ce³⁺ doping and plasmonic effects, compared to NaYF₄: Yb³⁺, Er³⁺ DCNPs immobilized on the glass substrate. Moreover, 3D Finite-Difference Time-Domain (FDTD) simulations and time-resolved luminescence measurements are combined to gain important insights into the mechanism of downconversion luminescence enhancement. The results show that there is a large electric field enhancement between the Ag nanoholes and the Ag hemisphere cap at 980 nm (excitation enhancement), while the lifetime shortening at 1525 nm revealed an increased radiative decay rate and enhanced quantum yield (emission rate enhancement). The strategy for downconversion luminescence enhancement demonstrated in this work holds a significant potential for advancing the next generation biosensing and bioimaging based on DCNPs in the NIR-II window.

Integrating quantum materials with fiber optics adds advanced functionalities to a variety of applications, and introduces fiber-based quantum devices such as remote sensors capable of probing multiple physical parameters. However, achieving optimal integration between quantum materials and fibers is challenging, particularly due to difficulties in fabrication of quantum elements with suitable dimensions and an efficient photonic interface to a commercial optical fiber. Here a new modality for a fiber-integrated van der Waals quantum sensor is demonstrated. A hole-based circular Bragg grating cavity from hexagonal boron nitride (hBN) is designed and fabricated, engineer optically active spin defects within the cavity, and integrate the cavity with an optical fiber using a deterministic pattern transfer technique. The fiber-integrated hBN cavity enables efficient excitation and collection of optical signals from spin defects in hBN, thereby enabling all-fiber integrated quantum sensors. Moreover, remote sensing of a ferromagnetic material and of arbitrary magnetic fields is demonstrated. All in all, the hybrid fiber-based quantum sensing platform may pave the way to a new generation of robust, remote, multi-functional quantum sensors.

Nanowire-based plasmonic lasers are now established as nano-sources of coherent radiation, appearing as suitable candidates for integration into next-generation nanophotonic circuitry. However, compared to their photonic counterparts, their relatively high losses and large lasing thresholds still pose a burdening constraint on their scalability. In this study, the lasing characteristics of zinc oxide (ZnO) nanowires on silver (Ag) and aluminum (Al) substrates, operating as optically-pumped short-wavelength plasmonic nanolasers, are systematically investigated in combination with the size-dependent performance of the hybrid cavity. A nanomanipulation-assisted single nanowire optical characterization combined with high-throughput photoluminescence spectroscopy enabled the correlation of the lasing characteristics to the metal substrate and the nanowire diameter. The results evidence that the coupling between excitons and surface plasmons is closely tied to the relationship between substrate dispersive behavior and cavity diameter. Such coupling dictates the degree to which the lasing character, be it more plasmonic- or photonic-like, can define the stimulated emission features and, as a result, the device performance.

Exploring possible strategy to balance the radiative decay and reverse intersystem crossing (RISC) are of great significance in thermally activated delayed fluorescent (TADF) emitters for enabling both high efficiency and low efficiency roll-off. Herein, by introducing a multi-resonance (MR) type acceptor, two TADF emitters featuring hybridized short-range charge transfer (SRCT) and long-rang charge transfer (LRCT) are designed. LRCT-dominate photoluminescent nature is maintained with a short delayed lifetime of 1.5–3.4 µs. While the incorporated SRCT accelerates the radiative decay. Consequently, both emitters demonstrate remarkable electroluminescent performance with maximum EQE (EQE_max) of 40.8% for IT-BO and 39.0% for IA-BO, respectively, along with ultra-high luminance of up to 120 000 cd m⁻². More encouragingly, both emitters can enable small efficiency roll-off with a minimum value of only 4%, highlighting the significance of enhanced k_r in suppressing the roll-off. Moreover, when served as sensitizers, both compounds can also endow excellent performances with EQE_max ≈38%. This work presents an innovative approach by hybridizing SRCT and LRCT for developing practical TADF emitters.