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Solar reflectance and thermal emissivity are critical benchmarks for evaluating the effectiveness of passive cooling strategies. The integration of three-dimensional (3D) printing techniques with passive cooling materials enables local thermal management of multifaceted objects, offering opportunities for unexplored energy-saving applications. For example, conformal printing of cooling materials can mitigate solar absorption caused by the top metal electrodes in solar cells, thereby improving their efficiency and lifetime. In this study, we report the synthesis of 3D printable hollow silica nanoparticles (HSNPs) designed to induce subambient cooling performance under daylight conditions. HSNPs with diameters of 400–700 nm and silica shell thicknesses of approximately 100 nm were synthesized using an in-situ sol–gel emulsion method. Subsequently, these HSNPs were formulated into printable pastes by carefully selecting the mixture concentration and molecular weight of polyvinylpyrrolidone (PVP). The PVP-linked HSNPs exhibited a solar (0.3–2.5 μm) reflectivity of 0.98 and a thermal (8–13 μm) emissivity of 0.93. In contrast to a single silica nanoparticle (NP), the scattering analysis of a single HSNP revealed a distinctive scattering distribution characterized by amplified backward scattering and suppressed forward scattering. In outdoor daytime experiments, the HSNP-printed sample led to the subambient cooling of a dielectric substrate, surpassing the cooling performance of reference materials such as silica NPs, silver pastes, and commercial white plastics and paints.

Transparent solar cells (TSCs) hold promise for applications in building‐integrated photovoltaics (BIPVs) and vehicles. However, existing TSCs often have compromised color neutrality and efficiency because of the distinctive colors arising from their photoactive materials. The study proposes a novel fabrication method for TSCs based on Si wafers with the average visible transmittance (AVT) controlled by creating a microhole pattern through a combination of nanosecond laser drilling and subsequent wet etching. Through this ambient‐air process, organic–Si hybrid TSCs are successfully realized by integrating an organic PEDOT:PSS layer onto this structure with a neutral color. The power conversion efficiency (PCE) is adjusted by the fraction of the perforated region, and it attained 6.20% at 30% AVT, 5.37% at 40% AVT, and 4.67% at 50% AVT. In this hybrid TSC approach, the CIE color coordinates are closely aligned with the neutral‐color points (0, 0), resulting in color rendering index (CRI) values exceeding 99. The strategy represents a significant step toward the development of efficient color‐neutral TSCs for transparent solar applications. [ABSTRACT FROM AUTHOR]

In this study, we synthesized NaYF4-based downshifting nanophosphors (DSNPs), and fabricated DSNP-polydimethylsiloxane (PDMS) composites. Nd3+ ions were doped into the core and shell to increase absorbance at 800 nm. Yb3+ ions were co-doped into the core to achieve intense near-infrared (NIR) luminescence. To further enhance the NIR luminescence, NaYF4:Nd,Yb/NaYF4:Nd/NaYF4 core/shell/shell (C/S/S) DSNPs were synthesized. The C/S/S DSNPs showed a 3.0-fold enhanced NIR emission at 978 nm compared with core DSNPs under 800 nm NIR light. The synthesized C/S/S DSNPs showed high thermal stability and photostability against the irradiation with ultraviolet light and NIR light. Moreover, for application as luminescent solar concentrators (LSCs), C/S/S DSNPs were incorporated into the PDMS polymer, and the DSNP-PDMS composite containing 0.25 wt% of C/S/S DSNP was fabricated. The DSNP-PDMS composite showed high transparency (average transmittance = 79.4% for the visible spectral range of 380–750 nm). This result demonstrates the applicability of the DSNP-PDMS composite in transparent photovoltaic modules. [ABSTRACT FROM AUTHOR]

We numerically investigate a plasmonic nanobump and upconversion (UC) layer incorporated metal–insulator–metal (MIM) platform as a light absorber. The hemispherical nanobump array situated over a substrate can serve as an optical nanoantenna in a broadband wavelength range. By precisely engineering the design and optical parameters of the insulating spacer layer sandwiched by the top nanobumps and back reflecting metal film, we can manipulate the light absorption inside the upconversion layer. The optical near-field distribution of the nanobump-assembled plasmonic platform is studied using the finite-difference time-domain (FDTD) method to probe the origin of enhanced absorption within the thin UC layer. A suggested mathematical model considering plasmonic and quenching effects of the MIM configuration to analyze the near-field maximum as a function of an insulator thickness is in good agreement with the FDTD result. The 30-fold enhanced light absorption within the UC layer is observed for the MIM plasmonic platform compared to the reference sample. Well-established optical field confinement at the nanoscale gap and excitation of surface plasmons near the nanobumps can be attributed to increased light absorption inside the plasmonic MIM platform. The plasmonic nanobump array platform can be an alternative strategy to apply a highly efficient light absorber to an UC device. [ABSTRACT FROM AUTHOR]

In this study, heavy-metal-free orange light-emitting ZnSe:Mn2+/ZnS doped-core/shell (d-C/S) quantum dots (QDs) were synthesized using a nucleation doping strategy. To synthesize high quality d-C/S QDs with high photoluminescence (PL) quantum yield (QY), the Mn2+ concentration was optimized. The resulting ZnSe:Mn2+(5%)/ZnS d-C/S QDs showed a high PL QY of 83.3%. The optical properties of the synthesized QDs were characterized by absorption and PL spectroscopy. Their structural and compositional properties were studied by X-ray diffraction, transmission electron microscopy, and energy dispersive X-ray spectroscopy. After doping Mn2+ into a ZnSe core, the ZnSe:Mn2+/ZnS d-C/S QDs showed a large Stokes shift of 170 nm. The ZnSe:Mn2+/ZnS d-C/S QDs were embedded in a poly(lauryl methacrylate) (PLMA) polymer matrix and the ZnSe:Mn2+/ZnS-based polymer film was fabricated. The fabricated ZnSe:Mn2+/ZnS-PLMA film was highly transparent in the visible spectral region (transmittance > 83.8% for λ ≥ 450 nm) and it exhibited bright orange light under air mass (AM) 1.5G illumination using a solar simulator. The optical path-dependent PL measurement of the ZnSe:Mn2+/ZnS-PLMA film showed no PL band shift and minimal PL decrease under variation of excitation position. These results indicate that the highly efficient and large Stokes shift-emitting ZnSe:Mn2+/ZnS QDs are promising for application to luminescent solar concentrators. [ABSTRACT FROM AUTHOR]

We report the focusing of a normally incident plane wave of 405 nm through a Ag/dielectric annular ring structure, using finite-difference time domain analysis. We first study the dependency of the focusing efficiency on slit width when the incident wave is transmitted through a single ring whose slit is filled with a dielectric. Then, light focusing by the multiple-ring structure is investigated as a function of the dielectric thickness. It is observed that the focusing is tunable between near-field and quasi-far-field regimes in the Ag/dielectric layered annular ring structure. Also, the focal intensities are remarkably enhanced by the addition of the dielectric layer, showing a Fabry--Perot-like resonance with respect to the thickness of the dielectric layer. The controllable near-field and far-field focusing offers more flexibility for applications of future nano-optic devices. [c] 2010 Optical Society of America OCIS codes: 240.6680, 240.0240.

Recently, Z-scheme systems have gained immense attention for photocatalytic hydrogen evolution (PHE). Herein, LaFeO3 perovskite (as photosystem II) was shelled by nitrogen-doped graphene (NGr as photosystem I) functionalized with ultralow Pt loading to produce an impactful and stable ternary Z-scheme platform: LaFeO3@NGr–Pt. Under visible-light irradiation, the LaFeO3@NGr3–Pt0.5 entity (a NGr shell thickness of 3 nm and Pt loading of 0.5 wt%) delivered a PHE performance of 3.52 μmol mgcat−1 h−1, superior to those of binary LaFeO3@NGr3 (1.86 μmol mgcat−1 h−1), NGr–Pt0.5 (0.88 μmol mgcat−1 h−1), and free-standing NGr (0.34 μmol mgcat−1 h−1) catalysts. It also showed outstanding PHE performance compared to previous advanced Z-scheme species. In addition, the ternary Z-scheme system exhibited a high maximum apparent quantum yield of 18.25% at 450 nm. This excellent performance of the Z-scheme platform can be attributed to the following. (i) The interfacial contact between LaFeO3 and NGr facilitated charge carrier transfer under light. (ii) The promising direct Z-scheme platform not only preserved the strong redox potentials of the two photosystems but also inhibited charge recombination significantly. (iii) Finally, the Pt cocatalyst attracted the electrons migrating from NGr and assisted the adsorption of hydrogen atoms, thus accelerating the overall catalytic reaction. [ABSTRACT FROM AUTHOR]