ABSTRACT Halide double perovskites have emerged as chemically versatile alternatives to lead halide perovskites, yet their functional behavior cannot be understood through simple structural analogy. In these materials, orbital decoupling at the band edges reconstructs electronic dispersion and defect energetics, establishing a distinct regime of exciton localization and symmetry sensitivity. Dimensional reduction amplifies dielectric confinement, while chirality introduces controlled inversion asymmetry. When combined with spin–orbit interaction, these structural parameters enable polarization‐sensitive optical responses under ambient conditions. This Review integrates electronic structure, dimensional architecture, and chiral symmetry into a unified design framework. We show that performance arises from a coupled parameter space rather than isolated optimizations: confinement enhances chiroptical effects but increases disorder sensitivity; heavy‐element substitution strengthens spin‐dependent transitions but modifies defect energetics; and bio‐adjacent deployment requires structural containment rather than compositional substitution alone. By defining realistic performance envelopes and clarifying the distinction between polarization control and long‐lived spin coherence, this work positions double perovskites as solution‐processable, polarization‐aware photonic materials. Within this framework, their functional capabilities are best understood in the context of quantum‐enabled photonics, where spin‐selective optical responses can be achieved without requiring extended coherence times. The resulting design map provides guidance for compositional selection, symmetry engineering, and scalable device integration.
ABSTRACT Although laser‑processed hierarchical micro‑nano structures hold great potential for silicon antireflection, it remains difficult to quantitatively correlate complex multi‑scale morphological features with optical response. This work addresses this bottleneck by developing a multi‐scale semi‐analytical reflectance model. Utilizing three‐level micro‐nano structures reported in our prior study, which were fabricated by our two‐step nanosecond laser‐assisted waterjet and femtosecond laser processing, we reveal the respective antireflection mechanisms of each structural level. The microscale V‐grooves provide a light‐trapping effect; laser‐induced periodic surface structures (LIPSS) promote light absorption via multi‐order grating diffraction inside the silicon substrate while resulting in negligible non‐zero‐order reflection toward air; and random nanoparticles mitigate the abrupt change in interfacial refractive index via the effective medium effect. Integrating ray tracing, grating diffraction, effective medium layer thin‐film interference and nanoparticle scattering, the proposed model predicts that structure reflectance drops with rising V‐groove aspect ratio while being nearly insensitive to groove width. The model establishes a quantitative relationship between hierarchical structural parameters and reflectance, enabling parameter‐guided design of laser‐textured silicon antireflection surfaces. Experimental validation confirms the predictive capability of the model, with the optimized structure achieving a minimum reflectance of 4.5% within 300–1000 nm.
ABSTRACT Short‐distance color mixing from spatially separated red, green, and blue (RGB) emitters is challenging in compact display optics. Here, we demonstrate an adjoint‐designed, fabrication‐constrained mosaic optical Fourier surface (OFS) for RGB homogenization at a 5 mm observation distance. A 3 mm 3 mm aperture comprises 225 sinusoidal tiles with independently optimized period, orientation, and depth. The numerical demonstration uses a publicly documented 3030 RGB package as a reproducible separated‐emitter proxy for compact micro‐LED backlight applications, rather than a sub‐100‐ pixel. A differentiable finite‐source model is followed by direct full‐vector rigorous coupled‐wave analysis (RCWA) of 102,756 local conditions. The optimized OFS reduces from 0.03039 to 0.01429. Replacing 13,766 kernels from 30 high‐risk tiles with ultrafine RCWA or independent finite‐difference time‐domain results gives 0.014293 and 0.014266, with 99.95% and 99.74% dominant‐order agreement. Complementary reduced‐supercell RCWA and full‐size two‐tile FDTD checks directly bound inter‐tile coupling, while first‐order fabrication and material perturbations remain below . The validated library spans 0.90–5.80 periods, 0–350 nm depths, and , linking inverse design, electromagnetic validation, and scalable holographic manufacturing.
ABSTRACT Terahertz (THz) metasurfaces offer strong electromagnetic modulation, yet efficient thermal tunability remains challenging. Here, we investigate the heating‐dependent THz response of metasurfaces integrated with strip‐patterned, square‐patterned, and continuous GaN thin films. The strip‐patterned and continuous samples were characterized from 33°C to 172°C, whereas the square‐patterned sample was measured from 33°C to 130°C. Within the common comparison range up to 130°C, the strip‐patterned configuration exhibited the strongest overall transmittance modulation. These results indicate that GaN pattern geometry modifies the effective electromagnetic loading and interaction with localized resonant fields. When heating was extended to 172°C, the strip‐patterned metasurface exhibited the largest resonance transmittance contrast variation of 11.12%, a phase‐shift range from −334° to 8°, and a maximum transmittance modulation depth of 49.15%. These findings demonstrate semiconductor patterning as an effective strategy for enhancing thermally driven THz modulation.
ABSTRACT Colloidal tin oxide (c‐SnO x ) is the dominant electron transport layer (ETL) used in efficient n–i–p perovskite solar cells (PSCs), yet intrinsic oxygen‐related vacancies undermine operational stability. Here, we report a fluorinated SnO x electron transport layer (ETL) fabricated by SF 6 plasma‐assisted atomic layer deposition (ALD), in which plasma‐generated fluorine species chemisorb preferentially at oxygen vacancy (O v ) sites. Density functional theory calculations show that F and F − bind at a bridging O v with adsorption energies of −5.66 and −4.95 eV, respectively, whereas neutral SF 6 , SF 5, and SF 4 species bind weakly (−0.04 to −0.45 eV). Bader charge analysis confirms electron transfer from the SnO x surface to the adsorbed fluorine. Experimentally, the fluorination induces a surface dipole that shifts the vacuum level and elevates the work function without altering the intrinsic valence band onset of the F‐containing SnO x . This dipole‐induced vacuum level shift influences the interfacial energetics governing directional charge extraction and suppresses interfacial charge accumulation, which enhances device performance and operational stability. PSCs with SF 6 ‐plasma ALD SnO x achieve a power conversion efficiency of 21.0%, retaining 17.29% after 1400 h without encapsulation and sustaining stable power outputs for nearly 7000 min under continuous tracking. These results demonstrate superior performance and operational stability compared to thermal ALD‐grown SnO x without fluorination. The results establish plasma‐enabled interfacial fluorination as a strategy to engineer surface electrostatics and enhance the long‐term stability in perovskite photovoltaics.
