Herein, the fabrication of a lead-free cesium tin halide perovskite produced via a simple solvothermal process is reported for the first time. The resulting CsSnX (X = Cl, Br, and I) quantum rods show composition-tunable photoluminescence (PL) emissions over the entire visible spectral window (from 625 to 709 nm), as well as significant tunability of the optical properties. In this study, we demonstrate that through hybrid materials (CsSnX) with different halides, the system can be tunable in terms of PL. By replacing the halide of the CsSnX quantum rods, a power conversion efficiency of 12.96% under AM 1.5 G has been achieved. This lead-free quantum rod replacement has demonstrated to be an effective method to create an absorber layer that increases light harvesting and charge collection for photovoltaic applications in its perovskite phase.

This study applies a low-cost solvothermal method to synthesize all-inorganic (lead-free cesium tin halide) perovskite quantum dots (AIPQDs) and to fabricate AIPQD-doped lasers with cholesteric liquid crystal (CLC) lasing cavities. The lasers present highly qualified lasing features of low threshold (150 nJ/pulse) and narrow line width (0.20 nm) that are attributed to the conjunction of the suppression of photoluminescence (PL) loss caused by the quantum confinement of AIPQDs and the amplification of PL caused by the band-edge effect of the CLC-distributed feedback resonator. In addition, the lasers possess highly flexible lasing-wavelength tuning features and a long-term stability under storage at room temperature and under high humidity given the protective role of CLC. These advantages are difficult to confer to typical light-emitting perovskite devices. Given these merits, the AIPQD-doped CLC laser device has considerable potential applications in optoelectronic and photonic devices, including lighting, displays, and lasers.

This work demonstrates the first quantum-dot-embedded cholesteric liquid crystal composite laser with an added chiral-azobenzene moiety which possesses optical stability and reversible tunability.

No abstract

This study systematically investigates the morphological appearance of azo-chiral dye-doped cholesteric liquid crystal (DDCLC)/polymer coaxial microfibers obtained through the coaxial electrospinning technique and examines, for the first time, their photocontrollable reflection characteristics. Experimental results show that the quasi-continuous electrospun microfibers can be successfully fabricated at a high polymer concentration of 17.5 wt% and an optimum ratio of 2 for the feeding rates of sheath to core materials at 25 °C and a high humidity of 50% ± 2% in the spinning chamber. Furthermore, the optical controllability of the reflective features for the electrospun fibers is studied in detail by changing the concentration of the azo-chiral dopant in the core material, the UV irradiation intensity, and the core diameter of the fibers. Relevant mechanisms are addressed to explain the optical-control behaviors of the DDCLC coaxial fibers. Considering the results, optically controllable DDCLC coaxial microfibers present potential applications in UV microsensors and wearable smart textiles or swabs.

637 wileyonlinelibrary.com COMMUNICATION www.MaterialsViews.com www.advopticalmat.deThe development in nanotechnology has enabled the manufacture of quantum dot nanocrystals (QD NCs), which have been extensively investigated. They have unique properties such as large absorption cross-section, high quantum yields, broad excitation spectra, wavelength tunability of fl uorescence emission simply by size, better color purity, high stability, and long lifetime. As a result, QDs are highly promising for a wide variety of applications such as light-emitting diodes (LEDs), photovoltaic and photodetector devices, displays, lasers, spectroscopy, telecommunications, optical information processing, biomedical imaging, quantum computation, and so on. [1][2][3][4][5][6] Because of the benefi ts mentioned above, QDs are especially regarded as a potential replacer for rare-earth phosphors in obtaining photometrically effi cient white LEDs if large-sized, economical and eco-friendly production can be realized. [ 7,8 ] QD lasers are semiconductor lasers that use QDs as a gain medium. In contrast to the colloidal NCs based QDs used in this work, the conventional inorganic QD lasers were primarily pursued by using molecular beam epitaxy (MBE) or metalorganic chemical vapor deposition (MOCVD) for forming selfassembled QDs via Stranski-Kastranow growth mode. In addition, recent works had also shown the possibility of growing the QDs by using selective area epitaxy (SAE) method. [9][10][11][12] QD lasers can lase emissions with improved features of linewidth narrowing, decreased lasing threshold and relative intensity noise, and temperature insensitivity because charge carriers experience the quantum confi nement effect in the confi ned 3D nanoscale space in the QDs. [ 13,14 ] These superior features make QD lasers exhibit lasing performances similar to gas lasers so that the device performances of the QD lasers are superior to those of conventional semiconductor lasers with active media in bulk or in the quantum well. In addition, QDs can be designed to lase with a variety of wavelengths by appropriately selecting the size, shape, and/or composite of the dots. This property indicates that QD lasers can be operated at wavelengths where traditional solid-state lasers cannot lase. The QD laser can lase by amplifying the fl uorescence of QDs in a resonant cavity. Fluorescence emission is induced via the photo-or electro-excitation of the valence electron with a specifi c energy or wavelength to the conduction band. A photon with a lower energy or a longer wavelength is then emitted after the excited electron returns to the ground state and recombines with the hole. In addition to the nanocrystal approach described here, it is important to note that III-Nitride based semiconductors have led to high performance LEDs and lasers emitting in the visible spectral regimes. The advances in III-Nitride semiconductors have been focused on the advances in semi-/non-polar quantum well, [ 15,16 ] quantum well with large optical matrix element, [17][18...

Widely tunable reflection and lasing emission in a dye-doped nematic liquid crystal refilled gradient-pitched enantiomorphic cholesteric liquid crystal polymer template.

This study demonstrates for the first time a continuously tunable photonic bandgap (PBG) of wide spectral range based on a blue phase (BP) wedge cell. A continuously shifting PBG of the BP wedge cell occurs due to the thickness gradient of the wedge cell at a fixed temperature. The wedge cell provides a gradient of boundary force on the LCs and thus forms a distribution of BP crystal structure with a gradient lattice. Additionally, a spatially tunable lasing emission based on a dye-doped BP (DDBP) wedge cell is also demonstrated. The tunable band of the PBG and lasing emission is about 130 nm and 70 nm, respectively, which tuning spectral ranges are significantly wider than those of CLC and DDCLC wedge cells, respectively. Such a BP device has a significant potential in applications of tunable photonic devices and displays.