Huanjun Lu

Bio: Huanjun Lu is an academic researcher from Soochow University (Suzhou). The author has contributed to research in topics: Materials science & Liquid crystal. The author has an hindex of 5, co-authored 13 publications receiving 93 citations. Previous affiliations of Huanjun Lu include University of Sheffield.

Reducing Energy Disorder in Perovskite Solar Cells by Chelation.

Abstract: In inverted perovskite solar cells (PSCs), the fullerene derivative [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) is a widely used electron transport material. However, a high degree of energy disorder and inadequate passivation of PCBM limit the efficiency of devices, and severe self-aggregation and unstable morphology limit the lifespan of devices. Here, we design a series of fullerene dyads FP-Cn (n = 4, 8, 12) to replace PCBM as an electron transport layer, where [60]fullerene is linked with a terpyridine chelating group via a flexible alkyl chain of different lengths as a spacer. Among three fullerene dyads, FP-C8 shows the most enhanced molecule ordering and adhesion with the perovskite surface due to the balanced decoupling between the chelation effect from terpyridine and the self-assembly of fullerene, leading to lower energy disorder and higher morphological stability relative to PCBM. The FP-C8/C60-based devices using Cs0.05FA0.90MA0.05PbI2.85Br0.15 as a light absorber show a power conversion efficiency of 21.69%, higher than that of PCBM/C60 (20.09%), benefiting from improved electron extraction and transport as well as reduced charge recombination loss. When employing FAPbI3 as a light absorber, the FP-C8/C60-based devices exhibit an efficiency of 23.08%, which is the champion value of inverted PSCs with solution-processed fullerene derivatives. Moreover, the FP-C8/C60-based devices show better moisture and thermal stability than PCBM/C60-based devices and maintain 96% of their original efficiency after 1200 h of operation, while their counterpart PCBM/C60 maintains 60% after 670 h.

The Solution of the Puzzle of Smectic‐Q: The Phase Structure and the Origin of Spontaneous Chirality

Abstract: The so-called smectic-Q (SmQ) liquid crystal phase was discovered in 1983 in rod-like molecules, but its structure remain unclear in spite of numerous attempts to solve it. Herein, we report what we believe to be the solution: A unique bicontinuous phase that is non-cubic and is made up of orthogonal twisted columns with planar 4-way junctions. While SmQ had only been observed in chiral compounds, we show that this chiral phase forms also in achiral materials through spontaneous symmetry breaking. The results strongly support the idea of a helical substructure of bicontinuous phases and long-range homochirality being sustained by helicity-matching at network junctions. The model also explains the triangular shape of double-gyroid domains growing within a SmQ environment. SmQ-forming materials hold potential for applications such as circularly polarized light emitters that require no alignment or asymmetric synthesis.

A Self-Assembled Bicontinuous Cubic Phase with a Single-Diamond Network.

Abstract: The first single-diamond cubic phase in a liquid crystal is reported This skeletal structure with the F d 3 ‾ m space group is formed by self-assembly of bolaamphiphiles with swallow-tailed lateral chains It consists of bundles of π-conjugated p-terphenyl rods fused into an infinite network by hydrogen-bonded spheres at tetrahedral four-way junctions We also present a quantitative model relating molecular architecture to the space-filling requirements of six possible bicontinuous cubic phases, that is, the single- and double-network versions of gyroid, diamond, and "plumber's nightmare"

Helical Networks of π-Conjugated Rods – A Robust Design Concept for Bicontinuous Cubic Liquid Crystalline Phases with Achiral Ia3¯d and Chiral I23 Lattice

Abstract: Bicontinuous cubic liquid crystalline phases of π‐conjugated molecules, representing self‐assembled 3D‐ordered interpenetrating networks with cubic symmetry, are receiving increasing attention due to their capacity for charge transport in all three dimensions and their inherent spontaneous helicity. Herein, a robust general design concept for creating bicontinuous cubic phases is reported. It is based on a nonsymmetric‐substituted π‐conjugated 5,5′‐diphenyl‐2,2′‐bithiophene platform with one end containing three out‐fanning flexible chains and with a range of substituents at the other end (the apex). The cubic phases are stable over broad temperature ranges, often down to ambient temperature, and tolerate a wide range of apex substitution patterns, allowing structural diversity and tailoring of the cubic phase type and application‐relevant properties. With an increasing number and size of apex substituents, a sequence of three different modes of cubic self‐assembly is observed, following an increasing helical twist. Thus, two ranges of the achiral double network Ia 3d phase range can be distinguished, a long pitch and a short pitch, with the chiral triple network I23 cubic phase in the intermediate pitch range. The findings provide a new prospect for the directed design of cubic phase‐forming functional materials based on spontaneously formed helical network liquid crystals with tunable application specific properties.

Effect of Block Number and Weight Fraction on the Structure and Properties of Poly(butylene terephthalate)-block-Poly(tetramethylene oxide) Multiblock Copolymers

Abstract: We report here the influence of block number and polyester weight fraction on the properties of a series of poly(ether ester) multiblock copolymers (mBCPs), poly(butylene terephthalate)-block-poly(...

Circularly polarized luminescence from AIEgens

Abstract: Circularly polarized luminescence (CPL) based on aggregation-induced emission luminogens (AIEgens) has received increasing attention owing to the increase of applications to generate CPL devices and biologically active probes. CPL-active materials fabricated from AIEgens exhibit higher photoluminescence quantum yields and larger dissymmetry factors in the solid state in comparison with single molecules in solution. We called the phenomenon of enhanced CPL in an aggregated state aggregation-induced circularly polarized luminescence (AICPL). This review highlights recent research in the CPL generation of AIEgens from (macro)molecular luminogens and supramolecular assemblies based on the AIE mechanism of restriction of intramolecular motion. In addition, some cases in which CPL-active AIEgens have enabled advancement in stimulus response materials and application in CPL devices, especially circularly polarized electroluminescence. Thus, CPL-active AIEgens are highly promising candidates for a wide range of technologically oriented multidisciplinary fields.

Photocatalytic C–H activation and the subtle role of chlorine radical complexation in reactivity

Abstract: The functionalization of methane, ethane, and other alkanes derived from fossil fuels is a central goal in the chemical enterprise. Recently, a photocatalytic system comprising [CeIVCl5(OR)]2− [CeIV, cerium(IV); OR, –OCH3 or –OCCl2CH3] was disclosed. The system was reportedly capable of alkane activation by alkoxy radicals (RO•) formed by CeIV–OR bond photolysis. In this work, we present evidence that the reported carbon-hydrogen (C–H) activation of alkanes is instead mediated by the photocatalyst [NEt4]2[CeCl6] (NEt4+, tetraethylammonium), and RO• are not intermediates. Spectroscopic analyses and kinetics were investigated for C–H activation to identify chlorine radical (Cl•) generation as the rate-limiting step. Density functional theory calculations support the formation of [Cl•][alcohol] adducts when alcohols are present, which can manifest a masked RO• character. This result serves as an important cautionary note for interpretation of radical trapping experiments.

Multi-level chirality in liquid crystals formed by achiral molecules.

Abstract: Complex materials often exhibit a hierarchical structure with an intriguing mechanism responsible for the 'propagation' of order from the molecular to the nano- or micro-scale level. In particular, the chirality of biological molecules such as nucleic acids and amino acids is responsible for the helical structure of DNA and proteins, which in turn leads to the lack of mirror symmetry of macro-bio-objects. To fully understand mechanisms of cross-level order transfer there is an intensive search for simpler artificial structures exhibiting hierarchical arrangement. Here we present complex systems built of achiral molecules that show four levels of structural chirality: layer chirality, helicity of a basic repeating unit, mesoscopic helix and helical filaments. The structures are identified by a combination of hard and soft x-ray diffraction measurements, optical studies and theoretical modelling. Similarly to many biological systems, the studied materials exhibit a coupling between chirality at different levels.

Mirror symmetry breaking in liquids and liquid crystals

Abstract: In the recent two decades liquid crystal science has contributed significantly to the understanding of mirror symmetry breaking and spontaneous emergence of chirality in fluids This accoun

Tunable circularly polarized luminescence from molecular assemblies of chiral AIEgens

Abstract: Circularly polarized luminescence (CPL) is important to chiral photonic technologies In molecular systems, besides their intrinsic chemical structures, architectures of molecular assemblies at the mesoscopic scale also account for the final macroscopic CPL properties Herein, tunable CPL responses can be induced through architectural regulation of these molecular assemblies in suspension and solid states A liquid crystalline assembled system of DPCE-ECh exhibiting a smectic C* phase with a high dissymmetry factor (gCD = −020 and glum = +038) is reported The intense and apparent CD and CPL of the film stem from the intrinsic helical structure of the molecular assembles with a weak contribution of Bragg reflection, where the helical axis is perpendicular to the optical axis and parallel to the direction of the glass substrate To the best of our knowledge, this large glum factor is very rare for organic compounds even in the assembled state formed by annealing at the smectic liquid crystalline temperature Interestingly, a strong CPL signal with a glum value of +018 is still recorded when DPCE-ECh is annealed in a chiral isotropic liquid (Iso*) state On the other hand, DPCE-ACh can form two coexisting phases of chiral hexagonal and smectic liquid-crystalline phases due to intermolecular hydrogen bonding The non-periodic molecular orientations of DPCE-ACh break its helical structure to give a weak negtive CPL signal of the order of 10−3 This work thus provides a new insight for developing efficient chiroptical materials in the aggregate state that have profound implications for high-performance CPL-based devices