Advanced Optical Materials最新文献

Tunable polariton lasing is demonstrated from an all-inorganic CsPbBr₃ perovskite microcrystal plate over 23 nm in the green part of the optical spectrum, operating at room temperature. The emission spectrum is controlled by adjusting the effective length of a multi-$��\lambda �$ planar microcavity, whilst observing the hallmarks of polariton condensation under non-resonant excitation. Furthermore, simultaneous condensation is observed into two non-degenerate lower polariton branches of orthogonal polarizations induced by anisotropy of the perovskite crystal.

O-phenylenediamine (OPD) is commonly used as a precursor in the preparation of red emissive carbon quantum dots (R-CQDs) due to the sp² hybridized structure. However, the low fluorescence quantum yield (QY) of the OPD-based R-CQDs limits its application. Although some efforts have been made, the improvement of QY is still limited. In this paper, a strategy is proposed to improve the QY of OPD-based R-CQDs by introducing ethylenediamine (EDA), which plays a key role as a nitrogen (N) dopant due to its high N content. The molar ratio of OPD to EDA (M_OPD/M_EDA), the reaction time (t) and temperature (T), and the amount of concentrated H₂SO₄ (V_H2SO4), are optimized. The R-CQDs with QY as high as 32.65% and full width at half maximum (FWHM) emission as narrow as 25 nm are obtained via a hydrothermal procedure under the optimal experimental conditions (i.e., M_OPD/M_EDA = 1/3, t = 6 h, T = 180 °C and V_H2SO4 = 4 mL). Such a QY is higher than most of the reported OPD-based R-CQDs. Besides, it is found that concentrated H₂SO₄ acts as the catalyst in addition to protonation. The enhancement of QY is attributed to the increase of the aromatic N-containing heterocyclic structures (C═N) after the introduction of EDA and catalysis by H₂SO₄.

The efficiency of solar cells based on organic–inorganic hybrid perovskite materials has already met the standards for commercial applications. However, there remains an efficiency gap of ≈30% between small-area devices and industrial-scale devices. Large-area devices, in particular, tend to exhibit lower optoelectronics and reduced environmental stability. The ink fluid behavior significantly influences the crystal process of large-area perovskite films during printing fabrication, which cannot be disregarded. As the manufacturing area and total solvent volatilization increase, the impact of inhomogeneous migration by perovskite colloidal particles gradually intensifies. This work focuses on elucidating the impact of the rheological properties of perovskite colloidal particles on the crystalline quality and device optoelectronic performance of perovskite films during deposition. It explores the fluid behavior of colloidal particles in the ink and throughout the printing process, the effects of additives on the motion of perovskite colloidal particles, and how the ink's rheological properties change when modifying agents interact with perovskite particles. Additionally, the functional aspects of controlling perovskite film formation and optimizing photovoltaic performance in perovskite solar cells (PSCs) are thoroughly discussed. Ultimately, the preparation process improvement of perovskite precursor solution and the current technical barriers to commercialization are summarized and prospected.

The excitation energy transfer (EET) between two conformers of the deep-blue thermally activated delayed fluorescence emitter DBA-BTICz and the multi-resonance fluorescence emitter ν-DABNA is studied by means of quantum chemistry according to Fermi's Golden Rule. Excitation energies, fluorescence and intersystem crossing rate constants of the individual EET donor and acceptor molecules, determined by a combination of density functional theory and a multireference configuration interaction approach, match the experimental data very well. Interestingly, two different conformers of DBA-BTICz with similar absorption, but distinct emission and transfer properties are found. The vibronic envelopes of the DBA-BTICz emission and the ν-DABNA absorption spectra are computed by means of a vertical Hessian approach. Their overall shapes and peak positions agree well with the experimental data but the widths of the computed vibronic spectra remain a critical factor in the evaluation of the spectral overlap integral. The distance and orientation dependencies of the excitonic coupling matrix elements, evaluated in the ideal dipole approximation (IDA), are carefully assessed by means of the monomer transition density (MTD) approach. Deviations between the IDA and MTD results of at most 20% at typical Förster radii justify the use of the computationally much less demanding IDA for estimating environmental and orientation effects on the EET rate.

Laser-induced structural color technology holds great promise for the mass-production of structural colors of wide color gamut, high stability, and low cost. However, its application to flexible and thermolabile substrates (such as plastics and paper) is currently hindered by the reliance on high-temperature processes or metal substrates. Here, an ultrafast laser inkless printing technology is proposed to address this challenge. By optimizing the magnetron sputtering process with a pre-sintered TiN target, the reflective TiN layer can be prepared at room temperature, on which coated an absorptive TiN layer to produce the TiN hybrid film. Under laser irradiation, this hybrid film is transformed into an “oxide-absorptive-reflective” tri-layer film structure when the upper absorptive TiN layer is oxidized. In this case, the thicknesses of the oxide and absorptive layers can be adjusted by modifying the total accumulated laser fluence. This enables the tuning of the double-absorption wavelength, thereby obtaining basic structural colors for printing. The high durability of the obtained structural colors is verified through various aging tests. Notably, this technology is successfully applied to flexible and thermolabile substrates, including plastics and cardboard paper, which may further promote the practical application of laser-induced structural color technology.

Gold nanoparticles (Au NPs) are renowned for their optical properties, nonetheless, challenges persist for applications in broadband quantitative light harvesting from ultraviolet to the near infrared, for instance matching the emission spectrum of sunlight. The challenges are related to limited spectral coverage, low photothermal conversion efficiency, low photostability, low environmental, and economic sustainability of the NPs synthesis. Here, the optical properties of spherical Au NPs are compared with two anisotropic Au nanostructures, aggregated Au nanospheres and Au nanocorals, purposely designed to exhibit broadband absorption. The anisotropic Au NPs are obtained by a convenient, green, and scalable laser ablation in liquid procedure, with the nanocorals exhibiting flat plasmon absorption extending beyond 2500 nm. The optical and photothermal capabilities of these nanostructures are compared with experimental and numerical calculations. Besides, the Au NPs are tested against the direct transduction of light into electricity by photo-thermoelectric generators (photo-TEGs). In fact, the conversion efficiency of TEGs depends on the presence of a steep temperature gradient, achievable under broadband illumination of the anisotropic NPs. This investigation guides to the optimal anisotropic gold NPs for panchromatic light harvesting, which finds relevance across diverse sectors from sunlight energy conversion to photothermal effects in optoelectronics and biomedical applications.

Organic semiconductors combine excellent optoelectronic properties with simple fabrication to obtain the desired features by tuning their chemical structures. Förster resonant energy transfer (FRET) is in designing blended gain media, but it does not enhance efficient optical gain in most cases. This is due to the competition between polaron pairs and stimulated emission (SE), leading to quenching of SE. Thus a challenge to design efficient optical gain systems via FRET. Here, a series of copolymers, F8_xBT_y, through uniformly inserting benzothiadiazole (BT) units into the 9,9-dioctylfluorene (F8) chain, were synthesized. They consist of both charge transfer (CT) and FRET is synthesized. These copolymers can prevent the local F8 aggregation and lead to efficient polaron pair recombination into singlet excitons. The F8 excitons are thus spatially confined, increasing efficient SE. Efficient light amplification has low amplified spontaneous emission (ASE) thresholds (as low as 5.3 µJ cm⁻²) and significantly enhanced optical gain with gain coefficients up to 37 cm⁻¹. The distributed feedback (DFB) lasers has low lasing thresholds down to 5.4 nJ per pulse. The results suggest that these copolymers provide a organic gain media design strategy with efficient optical gain, introducing a new approach to developing laser materials for electrically pumped lasers.

In the past decades, benefitting from the development of synthesis methodology, Cd-based semiconductor nanocrystals (NCs) have been extensively studied and their structure-dependent properties further inspired diverse applications. However, the high toxicity of Cd in Cd-based semiconductor NCs significantly limits their widespread applications. Colloidal Zn-based semiconductor NCs are one of the most promising candidates for Cd-based semiconductor NCs attributed to their low toxicity, creating high-band gap systems with excellent optoelectronic properties. Herein, an overview of the synthesis, structure engineering, and optoelectronic applications of colloidal Zn-based semiconductor NCs are provided. In the first section, the typical growth mechanisms are introduced, including oriented attachment, templated-assisted growth, and ripening. Then, structure engineering, such as core–shell structure, heterostructure, alloying, and doping, of Zn-based NCs are summarized. Simultaneously, an insight into various applications related to these structures of Zn-based NCs are given, including quantum dots light emitting diodes (QLEDs), catalysts, biological-application, sensors, and solar cells. Finally, although huge progress in both synthesis methodology and applications of colloidal Zn-based semiconductor NCs have been achieved, some issues still hinder the further development of Zn-based semiconductor NCs. Then in the last section, it is elaborated on the challenges and provides the possible solutions to tackle these challenges.

The external quantum efficiencies (EQE) and luminances of red InP-based and blue ZnTeSe-based quantum dot light-emitting diodes (QLEDs) have exceeded 20% and 80 000 cd m⁻², respectively, and the T₅₀@100 cd m⁻² (time for the luminance decreasing by 50%) operational lifetime of red InP-based QLEDs also have exceeded 1 000 000 h, nearing industrial application standards. However, the low EQE, luminance, and inferior lifetime of green InP-based QLEDs restrict the application for their full-color Cd-free display and lighting applications. The large electron injection barrier and severe exciton quenching caused by defect states of ZnMgO (ZMO) nanoparticles (NPs) lead to lower electron concentration in the emitting layer, which results in reduced radiative recombination. Here, with the surface passivation of MgCl₂, the exciton quenching sites are significantly suppressed, and the electron injection barrier is reduced owing to the conduction band minimum (CBM) levels upshift of ZMO. As a result, a high EQE of 21.43%, maximum luminance of 25 5985 cd m⁻², along with a long T₅₀@1000 cd m⁻² (over 4 600 h) and T₅₀@100 cd m⁻² (over 290 000 h) operational lifetime is achieved for green InP-based QLEDs. These values have all exceeded the previous best values of green InP-based QLEDs.

Transparent polymers are low-cost, light, and flexible, making them prospective for a plethora of applications. Still, their usage in photonics is impeded by a low refractive index, usually less than 1.7. In this work, an alternative strategy is proposed for improving optical characteristics by developing poly(ionic liquids) (PILs) with a gradient refractive index (GRIN) in thin films. The obtained PILs are transparent, environmentally friendly, and possess the GRIN effect in thin films. Inspired by the architecture of the animal's eye, PILs are employed for inkjet fabrication of microlenses with a giant GRIN value of 0.8, which is up to several times higher than that in previous studies on nanolayered polymeric and 3D printed GRIN lenses. Furthermore, in terms of focusing power, lens transparency, and depth of field, these microlenses outperform the result of high refractive index polymers. Hence, the findings open a novel platform for compact optical components based on new types of ionic polymers.