An extensive study on the effect of terminal halogens on the structure–property relationship of polar L-shaped mesogens has been elucidated.

An assembly of quantum dots (QDs) is an ideal system in which coupling between individual dots through their charge, spin, or optical excitation can be studied. [2] Apart from these fundamental aspects of physics, such systematic studies will have important implications in a wide range of fields from photovoltaic to displays and quantum information processing. [3][4][5][6] Specifically, the organic/inorganic hybrid perovskites [7] such as MAPbX 3 (MA = CH 3 NH 3 ; X = Cl, Br, I) QDs, have several attractive features such as high photoluminescence (PL) quantum yield, high diffusion length, low processing temperatures, low cost and scalable fabrication. Obviously, they have received significant attention owing to their excellent photovoltaic device performance. [8] They are also potential candidates for use in white LEDs, as wide-color-gamut backlight for LCDs, information storage, etc. [9,10] QDs of fully inorganic halide perovskite (IHP) materials such as CsPbX 3 (X = Cl, Br, I) are becoming popular due to their relatively better stability, significant photovoltaic performances, and high PL efficiency (≈90%) with concomitant narrow emission line width . [2] In the quest for high-purity green light from LEDs, the all-inorganic cesium lead halide perovskite QDs have shown promise owing to pure green emission with a narrow bandwidth and high quantum efficiency. Recalling that the efficiency of the LEDs is lower in the green/yellow spectral range, [11,12] the system investigated here may be attractive. Nanosoft composites comprising LCs as host and nanostructures as the guest is an emerging area of research that gets benefitted by the unique characters of the latter in the self-assembling features of LCs. A variety of nanoparticles have been employed to alter/tune the LC properties. In fact, QDs have received their fair share of attention in this regard. [40][41][42][43][44][45][46][47][48] Presence of QDs has been found to diminish the threshold voltage, [49] accelerate the electrooptic response, [49] photorefractivity, [50][51][52][53] increase the birefringence, [54,55] and control PL. [52,53,56] While the organic-inorganic QDs have been extensively studied in photovoltaics, it is the inorganic variety that is gaining importance in recent times. [51][52][53][57][58][59] It may be highlighted that in the previous cases of LC-QD composites, the QDs are spherical, while in contrast, IHPs form cuboids. Thus their incorporation into the LC medium can be expected to generate a tendency for self-assembled shape Fast electrically switchable anisotropic photoluminescence from a nano-soft composite comprising a nematic liquid crystal (LC) and quantum cuboids of a cesium lead halide perovskite is reported. The magnitude of the anisotropy in emission appears to be dictated by the anisotropy of the LC and the capability of the cuboids to form a linear chain, the latter being evidenced through optical and electron microscopy. Application of an ac electric field of small amplitude and its consequent coupling to the LC director ...

A polymer stabilized liquid crystal (PSLC) system formed by a nematic contained in a biopolymer network of cellulose nanocrystals, exhibiting many attractive features, is demonstrated. The threshold or the minimum voltage needed to operate the electro-optic device does not depend on the concentration of the polymer, a feature that is in contrast to the standard PSLC systems. A second point, more important from the driving circuit point of view, is that the voltage-off response time drastically reduces and even becomes practically invariant over the thermal range of the nematic phase. A smart window fabricated using this biopolymer network system exhibits good contrast between the scattering and transparent states driven by voltage and shows an exceptionally high haze factor. A highlight of the device fabrication is that the employed protocol is facile, making it appealing for a potentially viable smart window application.

We report the influence of photoisomerization on a guest-host composite comprising a soft-bent dimer exhibiting the presently sought-after twist-bend nematic (NTB) phase, doped with small amounts of a calamitic photoactive azobenzene-based dimer that assumes a bent shape when photo-driven. Trans-cis photoisomerization of the latter compound leads to a substantial decrease in the nematic-isotropic and nematic-NTB transition temperatures. The results bring out the puzzling feature that the thermal stability of the NTB phase, having a helical structure, despite the molecules being achiral, is influenced more than the regular nematic. Differential influence is also seen in the Frank elastic constants of the regular nematic: while the splay elastic constant is significantly diminished its bend counterpart is hardly affected. Molecular conformational aspects of the entities are proposed to explain these features. Through a judicious combination of this photo-driven effect and an AC electric field, an attractive type of optical memory device is demonstrated.

We report photophysical properties of a nanocomposite consisting of perovskite quantum cuboids (QCs) formed by CsPbBr 3 and a wide temperature range nematic liquid crystal. Contrary to observations made with conventional II-VI quantum dots dispersed in a liquid crystal, the used QCs form, under the influence of the nematic orientation, linear assemblies over macroscopic length scales evidenced by polarizing optical microscopy. Interestingly, the linear assembly is actually caused by such an anisotropic arrangement at the nm scale, as seen in TEM images. Thin films of the nanocomposite exhibiting this unique and fascinating character exhibit absorption and emission features, which are quite appealing. These include retention of the sharp bandwidth of emission characteristic of the native QCs and establishment of dual anisotropies, arising from the values being different along the director as well in the two directions orthogonal to it. We also present data on voltage-driven switching between one of the anisotropic limits.