Perovskite solar cells (PSCs) employing 3D organic-inorganic hybrid perovskite photoabsorbers have received tremendous progress with state-of-the-art power conversion efficiency (PCE) exceeding 25% during the last a dozen years. [1] However, ambient instability of 3D perovskite materials remains a critical obstacle for realistic applications of PSCs. [2,3] A strategy in addressing the poor stability is to reduce the structural dimensionality of perovskites via the introduction of long-chain organic ligands by forming Ruddlesden-Popper (RP) quasi-2D perovskites. [4,5] The organic ligands are bound to the 3D inorganic framework via coulombic interactions, resulting in a layered structure. The general formula of RP-2D perovskites takes the form of (L) 2 A n−1 Pb n I 3n+1 (n = 1, 2, 3, 4…) where A is the methylammonium (MA +), formamidinium (FA +), or cesium (Cs +) cations, L is the bulky organic ligands, e.g., butylammonium (BA +) or 2-phenylethylammonium (PEA +), and n is the number of layers in the [PbI 6 ] 4− octahedral sheets. [4-7] The incorporation of hydrophobic bulky organic ligands can not only enhance the stability of perovskites with minimized permeation of water molecules but also increase the formation energy of perovskites to mitigate thermal degradation and ion migration. [8-10] These merits alongside the quantum confinement have rendered quasi-2D perovskites great potentials for optoelectronic applications with a wide tunability on the bandgap or photophysical properties. [7] Unfavorably, quasi-2D perovskites are generally associated with a large exciton binding energy (hundreds of meV) due to the insulating nature of bulky organic ligands and the specific layered arrangement. [11,12] As a result, charge transport and extraction are hindered in quasi-2D PSCs. To date, the highest reported PCEs of quasi-2D PSCs (n ≤ 5) remain around 18%, [13-15] showing considerable performance gaps with regard to 3D-PSCs. The PCE (η) of photovoltaic cells is determined by the general relation, J V P FF sc oc light η = × × (V oc is the open-circuit voltage, FF is the fill factor, and P light is the illumination intensity). In quasi-2D PSCs, the relatively low J sc is more restrictive for Organic-inorganic hybrid quasi-2D perovskites have shown excellent stability for perovskite solar cells (PSCs), while the poor charge transport in quasi-2D perovskites significantly undermines their power conversion efficiency (PCE). Here, studies on water-controlled crystal growth of quasi-2D perovskites are presented to achieve high-efficiency solar cells. It is demonstrated that the (BA) 2 MA 4 Pb 5 I 16-based PSCs (n = 5) processed with water-containing precursors display an increased short-circuit current density (J sc) of 19.01 mA cm −2 and PCE over 15%. The enhanced performance is attributed to synergetic growths of the 3D and 2D phase components aided by the formed hydration (MAI•H 2 O), leading to modulations on the crystal orientation and phase distribution of various n-value components, which facilitate interphase charge tr...

Absorption spectra of a supramolecular complex (SC) placed in the proximity of a spherical metal nanoparticle (MNP) are computed. A description of the absorption is used that is based on a density matrix propagation. The applied density matrix theory starts from a microscopic model including the Coulomb interaction between the SC and the MNP. This interaction is dominated by an energy exchange coupling between the excitations of the SC and the multipolar excitations of the MNP. Its nonperturbative consideration results in a shift and a broadening of all Frenkel-exciton levels as well as an oscillator strength change. If a J-aggregate type SC near a MNP is considered, all exciton levels strongly contribute to the absorption what is in contrast to the isolated SC.

The involvement of astrocytes in brain functions rather than support has been identified and widely concerned. However the lack of an effective stimulation of astrocytes hampers our understanding of their essential roles. Here, we employed 800-nm near infrared (NIR) femtosecond laser to induce Ca2+ wave in astrocytes. It was demonstrated that photostimulation of astrocytes with femtosecond laser pulses is efficient with the advantages of non-contact, non-disruptiveness, reproducibility, and high spatiotemporal precision. Photostimulation of astrocytes would facilitate investigations on information processing in neuronal circuits by providing effective way to excite astrocytes.

Chiral Au nanorods (c-Au NRs) with diverse architectures constitute an interesting nanospecies in the field of chiral nanophotonics. The numerous possible plasmonic behaviors of Au NRs can be coupled with chirality to initiate, tune, and amplify their chiroptical response. Interdisciplinary technologies have boosted the development of fabrication and applications of c-Au NRs. Herein, we have focused on the role of chirality in c-Au NRs which helps to manipulate the light− matter interaction in nontraditional ways. A broad overview on the chirality origin, chirality transfer, chiroptical activities, artificially synthetic methodologies, and circularly polarized applications of c-Au NRs will be summarized and discussed. A deeper understanding of light−matter interaction in c-Au NRs will help to manipulate the chirality at the nanoscale, reveal the natural evolution process taking place, and set up a series of circularly polarized applications.

In this context, metal nanostructures with localized surface plasmon resonances (LSPRs) have attracted extensive attention. [2] LSPRs can be excited with wide-field normal-incidence illumination, and the optical setup for sensing can be simply constructed based on standard optical microscopes. [3] Periodic plasmonic nanostructures can offer additional advantages, [4] for example, a much narrower resonance linewidth (compared to LSPRs) that is beneficial for measuring a small spectral shift. However, the intense optical fields on the surface of plasmonic nanostructures can result in dissipative loss and lead to heating. Recently, periodic arrays of high-index dielectric nanostructures with collective resonances have been proposed as an alternative. [5-9] However, for periodic arrays of high-index dielectric nanostructures, even with broken inplane symmetry (so-called quasi-BIC; bound states in the continuum), [7,8] the bulk sensitivity (defined as the spectral shift upon the change in the bulk refractive index of the surrounding environment) is much lower than that of plasmonic arrays with the same lattice spacing. The collective lattice resonance stemming from the diffractive coupling in a periodic array of either metal [10-12] or high-index dielectric nanoparticles [13] requires a symmetric refractive-index environment between the bottom substrate and the upper cladding (e.g., aqueous buffers in sensing). [14-17] An asymmetric environment can inhibit long-range coupling between nanoparticles and suppress lattice resonances. In optical sensing, a periodic array of either metal or high-index dielectric nanoparticles is usually fabricated on a transparent substrate and exposed to solutions with different refractive indices. The index-mismatch between widely used quartz substrates (n ≈ 1.5) and aqueous buffers (n ≈ 1.33) can broaden the resonances and deteriorate the bulk sensitivity. [18] Although for sensing in aqueous buffers, one can find fluoropolymer (Cytop) with refractive index close to water to create a symmetric environment, [18,19] it is highly desirable to have a platform that can maintain high-quality resonances when subjected to a relatively large change in the bulk refractive index. (A symmetric refractive-index environment may not be required in a periodic structure with high-quality resonances of quasi-BIC type, for which the bulk sensitivity, however, is not high in the published literature. [7,8]) We recently reported that a hybrid system composed of low-index dielectric pillar arrays on a metal film can support This article reports refractometric sensing using two optical resonances of different types supported by TiO 2 nanopillar arrays on a gold film, which can be exposed to aqueous or organic environments. One lattice resonance, with enhanced electric fields extending into the surrounding environment, can maintain a quality factor Q > 200 when the bulk refractive index of the surrounding environment varies in a large range from 1.33 to 1.58. This lattice resonance exhibits not only sharp trans...