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Non-emissive CsPb2Br5 was found to convert into a highly efficient green emitter via simple thermal or photothermal annealing, which is ascribed to the thermally induced indirect-to-direct bandgap transition associated with defect formation.

We present an isomerism strategy to study the substitution position of perylene diimides on the performances of aggregation-induced emission (AIE) and two-photon absorption (2PA). Interestingly, enhanced AIE and 2PA have been achieved.

The isomerism effect on the aggregate emission properties of perylene diimide derivatives is studied. Banking on their bright emission, a cellular imaging test based on their nanoparticles is also conducted.

An electrically switchable multi-stable liquid crystal device is demonstrated based on a non-uniform cholesteric liquid crystal (CLC) structure in a single cell. The non-uniform CLC structure consists of a polymer stabilised CLC layer and a non-polymer stabilised CLC layer. By taking advantage of the difference in driving electric field strength of the two layers, the device can be switched electrically to four different states: the reflecting state, the reflecting and scattering co-existing state, the scattering-only state and the transparent state. The optical properties of the four states and the transition conditions between the states were elucidated. Moreover, all states with reflecting and/or scattering properties are stable for an extended period of time after switching off the electric field. Thanks to its multi-stability, this device can be used for energy-saving smart windows of automobiles, buildings and in architectural aesthetics. An electrically switchable multi-stable liquid crystal device is demonstrated based on a non-uniform cholesteric liquid crystal (CLC) structure in a single cell. The device can be switched electrically to four different states. All states with reflecting and/or scattering properties are stable for an extended period of time after switching off the electric field. Thanks to its multi-stability, this device can be used for energy-saving smart windows of automobiles, buildings and in architectural aesthetics.

Summary Sustainably recycling photovoltaic (PV) products at the end of their life cycle is essential for reducing environmental impact and saving costs on raw materials. Halide perovskite PVs currently suffer from a short lifespan, and recycling and remaking could equivalently extend their life cycle. Here, we report an effective and rapid “one-key reset” recycling paradigm to collect all the functional layer components from a used PV device at a high material extraction efficiency. A remade device incorporating all the layers, including recycled indium tin oxide/tin oxide substrate, perovskite, spiro-OMeTAD, and gold, exhibits an average power conversion efficiency of over 20%. This finding that the recycled device exhibits identical performance compared with the original, while providing enormous savings in cost, time, and energy, could lead to a recycling route that will dramatically lower the levelized cost of energy of perovskite PVs and enhance their competitiveness in future energy markets.

Lead halide perovskite nanocrystals (NCs) have been recognized as a rather competitive candidates for potential advanced optoelectronic applications. But the toxicity of lead and the intrinsic instability are the key concerns for their large-scale commercialization. For addressing these tricky issues, we synthesized lead-free all-inorganic Cs2AgBiBr6 double perovskite NCs adopting a facile hot injection approach. The as-prepared NCs could keep their structure stable either in air for more than two months or being heated at 300 °C in ambient atmosphere for 3 h. Moreover, Cs2AgBiBr6 NCs were investigated for photocatalytic NO removal under visible-light irradiation, achieving an exciting removal rate of 97%, which is much higher than the previous reports as we know. In addition, the Cs2AgBiBr6 NCs demonstrated outstanding recyclability for at least four cycles in NO removal. The photocatalytic mechanism of Cs2AgBiBr6 NCs was further proposed. This investigation offers a new environmental photocatalyst to purify the air.

Electronic defects at grain boundaries and surfaces of perovskite crystals impair the photovoltaic performance and stability of solar devices. In this work, we report the compensation of photovoltage losses in blade-coated methylammonium lead triiodide (MAPbI3) devices via passivation with natural amino acid (NAA) molecules. We found that the optoelectronic properties of NAA-passivated perovskite films and the corresponding device performances are closely correlated with the molecular interaction strength. A side-by-side comparative study of four typical NAAs reveals that arginine (Arg) functionalized with a guanidine end group exhibits optimum passivation effects owing to the strongest coordinative bonding with the uncoordinated Pb2+, which markedly suppresses the detrimental antisite PbI deep level defects. As a result, nonradiative charge recombination is significantly reduced, resulting in a substantially increased open-circuit voltage (VOC) of 1.17 V and a high efficiency of 20.49%. A solar module with an active area of 10.08 cm2 is also fabricated, yielding an efficiency of 15.65% with negligible VOC losses. In parallel, the Arg-passivated solar devices exhibit enhanced operational stability due to the formation of a hydrophilic Arg protective layer which encapsulates the perovskite crystals.

Two positional isomers (regioisomers) through changing the substituted position of perylenetetracarboxylic diimide and benzanthrone moieties were designed and synthesized. These two regioisomers exhibit totally different aggregation behaviors. The meta (bay)-substituted product shows the aggregation-caused quenching feature as the fluorescence quantum yield in tetrahydrofuran–water mixtures is reduced by 80% with an increase in the water fraction of the medium from 0% to 60%. Interestingly, an aggregation-induced emission is observed for the ortho-substituted product as the fluorescence quantum yield is increased by nearly one order of magnitude with an increase in the water fraction. This fluorescence enhancement effect for the ortho-substituted product is because of the restriction of the intramolecular rotation between the perylene core and the benzanthrone substituent in the aggregated state. The ortho-substituted product also exhibits excellent two-photon absorption performance because the ortho-substitution retains the planarity of the perylene core and improves the intramolecular charge-transfer among the molecules. Moreover, the ortho-substituted product shows two-photon excited aggregation-induced emission, which has potential application in organic two-photon excited fluorescence imaging agents.

Lewis-base polymers have been widely utilized as additives to act as a template for the perovskite nucleation/crystal growth and passivate the under-coordinated Pb2+ sites. However, it is uncovered in this work that the polymer on the perovskite grain boundaries would significantly hinder the charge transport due to its low conductivity, which brings about free carrier recombination and photocurrent losses. To circumvent this issue while fully exploiting the benefits of polymers in passivating the trap states in perovskite, we incorporate highly conductive multiwall carbon nanotubes (CNTs) with Lewis-base polymers as co-additives in the perovskite film. Functionalizing the CNTs with -COOH group enables a selective hole-extraction and charge transport from perovskite to the hole transporting materials (HTM). By studying the charge transporting and recombination dynamics, we revealed the individual role of the polymer and CNTs in passivating the trap states and facilitating the charge transport, respectively. As a result, the perovskite solar cells (PSCs) with polymer-CNTs composites exhibit an impressive PCE of 21.7% for a small-area device (0.16 cm2) and 20.7% for a large-area device (1.0 cm2). Moreover, due to the superior mechanical flexibility of both polymer and CNTs, the polymer-CNTs composites incorporation in the perovskite film encourages the fabrication of flexible PSCs (f-PSCs) with an impressive PCE of 18.3%, and a strong mechanical durability by retaining 80% of the initial PCE after 1,000 times bending. In addition, we proved that the selection criteria of the polymers can be extended to other long-chain Lewis-base polymers, which opens new possibilities in design and synthesis of inexpensive material for this tactic towards the fabrication of high performance large-area PSCs and f-PSCs.

Manipulating the propagation of photons is meaningful for optical data recognition but extremely challenging. Recently, the metal halide perovskite semiconductors present great potential in photoni...

Inhibition of TICT can significantly increase the brightness of fluorescent materials. Accurate prediction of TICT is thus critical for the quantitative design of high-performance fluorophores and AIEgens. TICT of 14 types of popular organic fluorophores were modeled with time-dependent density functional theory (TD-DFT). A reliable and generalizable computational approach for modeling TICT formations was established. To demonstrate the prediction power of our approach, we quantitatively designed a boron dipyrromethene (BODIPY)-based AIEgen which exhibits (almost) barrierless TICT rotations in monomers. Subsequent experiments validated our molecular design and showed that the aggregation of this compound turns on bright emissions with ca. 27-fold fluorescence enhancement, as TICT formation is inhibited in molecular aggregates.

Lower-dimensional quasi-two-dimensional (quasi-2D) halide perovskites have emerged as promising building blocks for multiple optoelectronic applications due to their superior photophysical properties. Recently, there has been a research focus on the terrace edge states (TES) in quasi-2D perovskites, which are thought to provide hypothetical highways to transport the excited states and thus give a new insight into boosting relevant device performance. Nevertheless, there is neither direct evidence of the electronic facets nor an in-depth understanding of these newly observed nontrivial TES. Here, we are the first to directly visualize the highly charged concentrated TES by means of a charge gradient microscopy (CGM) technique and elucidate the nature of TES through a combination of microscopic characterizations, including high-resolution transmission electron microscopy, Kelvin probe force microscopy and confocal fluorescence microscopy coupled with a first-principles density functional theory (DFT) calculation. It is shown that TES of quasi-2D perovskites are highly conductive (in distinct contrast to the insulating flat terrace region) and display a high Fermi-level and small forbidden bandwidth, which is attributed to the unique electron orbitals of the Pb atoms at the terrace edges. This distinctive conductivity of TES is of great importance in distinguishing them from bulk physical properties and inspiring novel nanoscale electronic applications, such as tip-based data storage and triboelectric nanogenerators.

The integration of aggregation-induced emission (AIE) and two-photon absorption (2PA) into one molecule is very important because such combination would endow the material with synergetic effect for diverse and broader applications. Herein, two regioisomers based on perylene diimide and anthracene moieties are designed and synthesized. The as-prepared compounds exhibit distinct AIE and 2PA properties, where the ortho-substituted one not only exhibits enhanced and accelerated AIE performance, but also displays improved 2PA properties. This research would provide a general approach to explore efficient molecules by the marriage of AIE and 2PA that could improve their performance in various areas.

Formaldehyde (FA) is one of the most common pollutants, which has tremendous harm to humans and environment. In this work, 4-amino-3-pentene-2-one (Fluoral-p) and S i O 2 coated quantum dot ( Q D @ S i O 2 ) were combined to implement a new ratiometric fluorescence probe Q D @ S i O 2 -Fluoral-p for FA detection. In addition, by utilization of polyvinyl alcohol (PVA) and S i O 2 microsphere (SM), a kind of PVA-SM microstructure was assembled with Q D @ S i O 2 -Fluoral-p to composite a signal enhanced sensing film. The Q D @ S i O 2 -Fluoral-p exhibited good response to 0-400 mg/L FA solution and an enhancement around 15 folds was realized after introducing PVA-SM. In both situations, the probe showed linear relationship to FA concentration ( C F A ), with detection limits of 14 and 0.5 mg/L, respectively. Also, the sensing film showed a good linear response to FA gas in the range of 0 to 2 ppm, with a detection limit 0.03 ppm. As a result, the PVA-SM enhanced ratiometric fluorescence probe features high sensitivity, low detection limit, good selectivity, as well as portable, which can serve as a useful tool for investigating FA in solution and gas at room temperature.

Nanoparticle-sensitized photoporation for intracellular delivery of external compounds usually relies on the use of spherical gold nanoparticles as sensitizing nanoparticles. As they need stimulation with visible laser light, they are less suited for transfection of cells in thick biological tissues. In this work, we have explored black phosphorus quantum dots (BPQDs) as alternative sensitizing nanoparticles for photoporation with a broad and uniform absorption spectrum from the visible to the near infra-red (NIR) range. We demonstrate that BPQD sensitized photoporation allows efficient intracellular delivery of both siRNA (>80%) and mRNA (>40%) in adherent cells as well as in suspension cells. Cell viability remained high (>80%) irrespective of whether irradiation was performed with visible (532 nm) or near infrared (800 nm) pulsed laser light. Finally, as a proof of concept, we used BPQD sensitized photoporation to deliver macromolecules in cells with thick phantom tissue in the optical path. NIR laser irradiation resulted in only 1.3x reduction in delivery efficiency as compared to photoporation without the phantom gel, while with visible laser light the delivery efficiency was reduced 2x.

Alignment layer plays a critical role on liquid crystal (LC) conformation for most LC devices. Normally, polyimide (PI) or polyvinyl alcohol (PVA), characterized by their outstanding thermal and electrical properties, have been widely applied as the alignment layer to align LC molecules. Here, we used a semi-conductive material poly(N-vinylcarbazole) (PVK) as the alignment layer to fabricate the cholesteric liquid crystal (CLC) device and the polymer-stabilized cholesteric liquid crystals (PSCLC)-based infrared (IR) reflectors. In the presence of ultraviolet (UV) irradiation, there are hole–electron pairs generated in the PVK layer, which neutralizes the impurity electrons in the LC–PVK junction, resulting in the reduction in the built-in electric field in the LC device. Therefore, the operational voltage of the CLC device switching from cholesteric texture to focal conic texture decreases from 45 V to 30 V. For the PSCLC-based IR reflectors with the PVK alignment layer, at the same applied electric field, the reflection bandwidth is enhanced from 647 to 821 nm, ranging from 685 to 1506 nm in the IR region, which makes it attractive for saving energy as a smart window.

One major challenge in the commercialization of halide perovskite solar cells is the device instability against moisture. Efficient perovskite solar cells usually incorporate the ionic dopants within the charge transfer material to secure their electrical conductivity. Typical ionic dopants are hygroscopic, resulting in significant moisture adsorption and accelerated perovskite degradation. Herein, we report a nonionic dopant, Sc3N@C80, consisting of a hydrophobic fullerene cage that encapsulates the metal salt to achieve a moisture resistive and highly electrically conductive hole transfer layer (HTL). The direct electronic transaction between Sc3N@C80 and spiro-OMeTAD renders a drastically improved conductivity and a lower Fermi-level of the HTL to minimize the Schottky barrier. The hydrophobicity of Sc3N@C80 also decreases the moisture wettability. Perovskite solar cells using the Sc3N@C80-doped HTL exhibit an efficiency surge from 18.15 to 20.77% (champion cell exhibiting 21.09%) and improved device s...

Organic semiconductors for photocatalytic application have received wide attention recently. However, developing organic photocatalysts for highly efficient photocatalytic hydrogen evolution is a great challenge. Herein, we show highly efficient photocatalytic hydrogen evolution from a series of novel conjugated polyelectrolytes (CPEs) by modulating their interaction with co-catalysts. The water-soluble CPEs greatly enhance the photocatalytic performance with 50-fold improvement over that of their non-dissolved precursor conjugated polymer. More importantly, the photocatalytic activity of these CPEs can be optimized by regulating their interaction with Pt co-catalysts through molecular engineering on the side chain species and counterions of CPEs. The cationic CPEs perform better than anionic CPEs due to the robust interaction between quaternary ammonium side chains in cationic CPEs and Pt co-catalysts. It is found that the optimized interface contact between cationic CPEs and Pt co-catalysts can result in more efficient charge transfer and higher photocatalytic activity.

We report a highly stable humidity sensor based on nanocomposite film obtained by depositing Au nanoparticles on the surface of 3-mercaptopropionic acid (MPA) capped CdTe quantum dots (QDs) and the ...

Two N-alkylated diketopyrrolopyrrole derivatives, namely, FDPP-C8 and TDPP-C8, were prepared and applied in the ratiometric and fluorescent detection of Cu2+ in acetonitrile. The distinct optical changes of two probes were attributed to the fast radical process of diketopyrrolopyrrole triggered by Cu2+. This reaction mechanism was investigated by NMR, MS and EPR experiments and DFT theoretical calculations. The detection of Cu2+ with FDPP-C8 and TDPP-C8 were completed instantaneously, making them convenient for practical real-time operation. The limits of detection of FDPP-C8 and TDPP-C8 for Cu2+ were calculated as 65 and 127 nM, respectively. Relevant competitive ions exerted no effect. In addition, the intrinsic two-photon absorption properties of FDPP-C8 were also investigated and successfully used in the detection of Cu2+. Furthermore, given that Cu2+/Cu+-involved radical process is solvent dependent, TDPP-C8 was used to construct a INHIBIT logic gate at the molecular level with DMF and Cu2+ as inputs.

Plasmon enhanced optical properties achieved by using metal nanoparticles are both fundamentally important and appealing for many biological and photonic applications. Although metal-enhanced one-photon excitation fluorescence and two-photon absorption have been previously demonstrated, up to now there are few reports on the overall two-photon excitation fluorescence enhancement by plasmon resonance. Conjugated polymers and oligomers are known to display large two-photon absorption cross-sections. Here we report plasmon-enhanced two-photon excitation fluorescence and singlet oxygen generation of a conjugated oligomer obtained by using gold nanorods in a core–shell structure. The separation between the metal core and the conjugated oligomer molecules was adjusted by varying the thickness of the spacer from 8.5 to 45 nm to achieve an optimized enhancement effect. The one- and two-photon excitation fluorescence intensities of the conjugated oligomer were found to be strongly dependent on the silica shell thickness. The optimum two-photon excitation fluorescence enhancement occurs at a shell thickness of 15 nm with an enhancement factor of 14.2. These core–shell nanostructures also exhibit significantly improved singlet oxygen generation capability under two-photon excitation. The application of these nanoparticles as effective imaging agents for two-photon cell imaging and as nano-photosensitizers for two-photon photodynamic therapy with improved efficiency has been demonstrated on HepG2 cells using the XTT assay. The remarkable two-photon excitation fluorescence enhancement property of these nanoparticles makes them promising agents for two-photon imaging guided phototherapy.

Two-photon excitation (2PE) photodynamic therapy (PDT) is a non-invasive technique for the treatment of cancer. However, its clinical applications are limited by small two-photon absorption cross section values of conventional photosensitizers. Here we designed multifunctional conjugated polymer based nanoparticles consisting of a conjugated polymer, a photosensitizer and a red-emitting dye, which can realize simultaneous 2PE red emission imaging and 2PE-PDT activities. The working principle is based on a 2PE fluorescence resonance energy transfer strategy from the conjugated polymer to photosensitizing and imaging agents. In these nanoparticles (NPs), the conjugated polymer, PPBF, was chosen as a two-photon light-harvesting material while the photosensitizer (tetraphenylporphyrin, TPP) and the red-emitting dye (TPD) were chosen as energy acceptors. The 2PE emission of TPP and TPD was enhanced by up to ∼161 and ∼23 times, respectively. The 2PE-PDT activity of these NPs was significantly improved compared with those NPs without PPBF by up to ∼149 times. Further surface-functionalization with folic acid (FA) groups allows these nanoparticles to exhibit selective affinity toward KB cancer cells. These NPs could act as novel 2PE conjugated polymer based nanoparticles combined with the advantages of low dark cytotoxicity, selective targeting and imaging-guided 2PE-PDT activities.

Two of the greatest global challenges faced by humankind in the 21st century are (1) the lack of access to a clean and potable water supply, and (2) the need for sustainable energy. As such, scientists from all subject areas have been actively developing methods to solve water shortages and the energy crisis. Herein, we present a photo-redox catalysis desalination generator, which possesses dual functions, acting as both an efficient salt remover and a dye-sensitized solar cell (DSSC)-based photoelectricity energy converter. It consists of dye semiconductor materials, a recirculating redox flow electrolyte between the anode and cathode, and salt feed streams. It utilizes the redox reaction of the electrolyte driven by the photo-excited semiconductor and simultaneously, it captures the salt anions and cations via coupling in the presence of ion exchange membranes. The cell is proposed to possess an unlimited salt removal capacity due to the redox catalysis of the same electrolyte redox species, while energy can be released via photoelectric energy conversion. This method will bypass the limitations of energy consumption in desalination and effectively solve the two major issues outlined. The current research will revolutionize desalination methods and propel desalination to a new era.

Nanocrystal-in-glass (NIG) is an exciting class of composites, because it can not only combine the advantages of crystal and glass materials but also potentially generate new physical phenomenon in a cooperative manner. Herein, the nonlinear light-matter interaction processes in a broad range of NIG composites homogeneously embedded with LiNbO3 are investigated. It is shown that, by rational control of the organization manner of crystal and glass phases, second-harmonic generation (SHG) can be precisely tuned. Importantly, an unusual SHG phenomenon, transverse SHG (TSHG), can be realized in the special region of the microstructure map combined with the features of high loading, nanoscale size, and homogenous distribution of nanocrystals. Furthermore, NIG composites exhibit broadband optical response, allowing TSHG in a wide waveband region to be achieved. Based on the above effects, the applications of the constructed NIG composite for precise measurement of the group velocity and duration of ultrashort optical pulses with femtosecond time scales are demonstrated. Indeed, the findings outline a fundamental principle to design NIG configurations for creating new properties, providing new directions for expanding the scope of NIG functional materials.

A stable and scalable polymer-stabilized liquid crystal window which electrically switches from transparent to opaque has been fabricated. Scanning electron microscope measurement shows that higher polymer concentration will induce denser polymer network in polymer stabilized liquid crystal system and then stronger anchoring force between polymer network and liquid crystal molecules, which resulting in larger operating voltage. The cell with larger cell gap has a lower saturated transmittance in the voltage-on state, which attributed to a larger number of scattering domains in thick cell. The optimized cell exhibits a highly transparent voltage-off state (3.5% haze) and a voltage-on scattering state (98% haze) with the threshold voltage of around 20 V. The durability test shows that the optical device switches at least 100,000 times without degradation of optical contrast and shows a high temperature tolerance. Meanwhile, a 40 × 50 cm2 window has been developed in an industrial production line showing the same optical properties. Our results demonstrate the fabrication of smart windows with a highly transparent rest state and high optical contrast on a commercial mass production scale, making them attractive for applications in buildings, automobiles, and switchable sunglasses for light management and potentially energy saving.

Simultaneously achieving high efficiency and high durability in perovskite solar cells is a critical step toward the commercialization of this technology. Inverted perovskite photovoltaic (IP‐PV) cells incorporating robust and low levelized‐cost‐of‐energy (LCOE) buffer layers are supposed to be a promising solution to this target. However, insufficient inventory of materials for back‐electrode buffers substantially limits the development of IP‐PV. Herein, a composite consisting of 1D cation‐doped TiO2 brookite nanorod (NR) embedded by 0D fullerene is investigated as a top modification buffer for IP‐PV. The cathode buffer is constructed by introducing fullerene to fill the interstitial space of the TiO2 NR matrix. Meanwhile, cations of transition metal Co or Fe are doped into the TiO2 NR to further tune the electronic property. Such a top buffer exhibits multifold advantages, including improved film uniformity, enhanced electron extraction and transfer ability, better energy level matching with perovskite, and stronger moisture resistance. Correspondingly, the resultant IP‐PV displays an efficiency exceeding 22% with a 22‐fold prolonged working lifetime. The strategy not only provides an essential addition to the material inventory for top electron buffers by introducing the 0D:1D composite concept, but also opens a new avenue to optimize perovskite PVs with desirable properties.

For the first time, a reproducible surface plasmon-enhanced optical sensor for the detection of gaseous formaldehyde was proposed, which was fabricated by depositing a mixture of CdSe@ZnS quantum dots (QDs), fumed silica (FS), and gold nanoparticles (GNs) on the surface of a silica sphere array to meet the urgent requirement of a rapid, sensitive, and highly convenient formaldehyde detection method. Because of the spectral overlap between QDs and GNs, plasmon-enhanced fluorescence was observed in the film of QDs/FS/GNs. When exposed to formaldehyde molecules, the enhanced fluorescence was quenched linearly with the increase of formaldehyde concentration in the range of 0.5-2.0 ppm. The reason is attributed to the nonradiative electron transfer from QDs to the carbonyl of formaldehyde molecules with the assistance of amino groups. Our results demonstrate that the designed sensors are capable of detecting ultralow concentration gaseous formaldehyde at room temperature with a fast response-recovery time and excellent selectivity, stability, and reproducibility. This work provides a simple and low-cost approach for optical formaldehyde sensor fabrication and shows promising applications in environmental detection.

An IR reflector based on polymer-stabilized cholesteric liquid crystal (PSCLC) can selectively tune IR light reflection for smart window application. Broadening the reflection bandwidth to block more IR heat radiation requires the expansion of the pitch distribution in the PSCLC. Traditional attempts using ex situ direct current (DC) bias upon an already polymerized PSCLC reflector usually require a sustaining potential difference holding the pitch gradient of the reflector. Removing the DC bias will lead to a reflect bandwidth comeback. Here, we have developed an in situ DC curing strategy to realize an irreversible reflect bandwidth broadening. Briefly, a DC bias was used to drive the redistribution of impurity cations, which can be captured by the ester group of oligomers, during the photopolymerization. During the slow polymerization process, such trapped cations will drag the oligomers towards the cathode and compress the pitch length near the cathode before the oligomers form the long polymer chain. Consequently, a frozen pitch gradient by such an in-situ-electric-field-assisted dynamic ion-dragging effect leads to the formation of a pitch gradient along the electrical field direction. After removing the DC bias, the as-cured polymer is observed to have frozen such a gradient pitch feature without recoverable change. As a result, the PSCLC reflector exhibits steady bandwidth broadening of 480 nm in the IR region, which provides the potential for saving energy as a smart window.

A symmetrical, almost linear and planar motif 2,6-bis(1-phenyl-1,2,3-triazol-4-yl)-4-nitroaniline have been designed and synthesized by click chemistry. The synthesis of this novel structure is straightforward and inexpensive. Two kinds of polymorphic crystals are obtained in different solvents, suggesting the versatile intra- and intermolecular interactions. Theoretical calculation was used to study the linear absorption spectrum, which show good agreement with the experimental results. Linear optical property shows an absorption band centered at 368 nm. Nonlinear optical property displays a two-photon absorption cross sections around 200 GM under different power intensities. Therefore, this novel click-derived chromophore exhibits highly-transparent and stable two-photon absorption property.

Phonon-assisted upconversion is a promising way to generate short-wavelength emissions under excitation of long wavelength based on unique anti-Stokes luminescence properties. Graphene oxide nanosheets (GONs) exhibit excellent optical properties owing to quantum confinement and edge effects, which have driven research into fundamental principles and potential applications. Here, we experimentally demonstrate upconversion emission by exciting an easily fabricated GON hybrid waveguide (GHW) with enhanced photothermal effects. The results reveal different origins of short-wavelength range and long-wavelength range in the upconversion spectra, whereas the emissive surface defects of GONs and GHW structure play significant roles in the behavior of photoluminescence. Introducing other upconversion materials to promote emission efficiency, the hybrid waveguide system might readily provide the possibility for the construction of upconversion fiber lasers and remote control of the upconversion luminescence.

Fluorescent organic nanoparticles (FONs) with dual-emission and two-photon fluorescence emission are promising sensing tools. In this work, novel hybrid FONs with two-photon absorption and dual-emission properties were used to detect Hg2+. The FONs were prepared by the co-self-assembly of amphiphilic furyl diketopyrrolopyrrole (DPP1) and tetraphenylethylene (TPE1) in water. Inside the water-soluble FONs, DPP1 worked as a two-photon absorption material and an effective Hg2+ receptor with emission peak at 540 nm. Meanwhile, TPE1, a typical aggregation-induced emission (AIE) molecule, maintained the nanostructure’s stability and offered another distinguishable fluorescent signal at 470 nm as the internal reference. These hybrid FONs were successfully used in the ratiometric and two-photon fluorescence detection of Hg2+ in water. The FONs showed selective and sensitive Hg2+ detection with a limit of detection of ca. 13 nM. Tests on tap-water samples indicated good reliability of the FONs in practical application. Furthermore, the FONs were used in cell imaging, and results demonstrated their potential application in biological sensing.

Hybrid perovskite materials used for realization of efficient perovskite solar cells have drawn great attention in both academic and industrial sectors. It was reported that the crystallinity of hybrid thin-film perovskite materials plays an important role in device performance. In this study, we report a novel and simple method to tune the crystallinity of CH3NH3PbI3 thin film for device performance of perovskite solar cells. By employing tetraphenylphosphonium chloride on the top of PbI2 thin layer in the two-step perovskite deposition processes, the crystallinity of the resultant CH3NH3PbI3 thin film was tuned. As a result, perovskite solar cells by the CH3NH3PbI3 thin film with tuned crystallinity exhibit an enlarged open-circuit voltage and enhanced short-circuit current, thus boosted efficiency as well as reduced photocurrent hysteresis compared to pristine CH3NH3PbI3 thin film. These results indicate that our study provides a new simple way to boost device performance of perovskite solar cells through tuning the crystallinity of CH3NH3PbI3 thin film.

In this study, we report the utilization of low-temperature solution-processed Cs-doped VOX thin films as the hole extraction layers (HELs) in perovskite solar cells (PSCs). It is found that the VOX:yCs (where y is the mole ratio of Cs versus V and y = 0.1, 0.3, and 0.5) thin films possess better electrical conductivities than that of the pristine VOX thin film. As a result, the PSCs incorporated with the VOX:yCs HEL exhibit large fill factors and high short-circuit currents, with consequently high power conversion efficiencies, which is more than 30% enhancement as compared with pristine VOX HEL. Our studies provide a facial way to enhance the electrical conductivity of the hole extraction layer for boosting device performance of perovskite solar cells.

Solution-processable highly transparent and thickness-insensitive hybrid electron-transport layer (ETL) with enhanced electron-extraction and electron-transport properties for high-performance polymer solar cell was reported. With the incorporation of Cs2CO3 into the poly[(9,9-bis(6′-((N,N-diethyl)-N-ethylammonium)-hexyl)-2,7-fluorene)-alt-1,4-diphenylsulfide]dibromide (PF6NPSBr) ETL, the power conversion efficiency (PCE) of resulted polymer solar cells (PSCs) was significantly enhanced due to the favorable interfacial contact, energy-level alignment, and thus facile electron transport in the PSC device. These organic–inorganic hybrid ETLs also exhibited high transparency and high electron mobility. All of these combined properties ensured us to design novel thickness-insensitive ETLs that avoid the parasitic absorption of ETL itself simultaneously. With the conventional device structure with poly{4,8-bis[5-(2-ethylhexyl)thiophen-2-yl]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl-alt-3-fluoro-2-[(2-ethylhexyl)c...

With the advantages of facile one-pot synthesis and THF-irrigating purification, we first developed novel cyclic compounds with deep blue thermally activated delayed fluorescence (TADF) and room-temperature phosphorescence (RTP) dual emission even in the as-spun films. Careful crystal analysis, combined with theoretical calculations, reveal that abundant inter- and intra-molecular interactions, whatsoever the molecular packing, are obligated to unique RTP properties. These results open up a new study of compounds with multiple acceptors and donors, and represent an important step in the further development of deep blue TADF and easy RTP emission.

We developed a novel highly efficient blue-light-emitting polymer (P0) containing the alternating electron-deficient diphenylsulfone and the electron-rich 4-octyloxy-aniline moieties, which was synthesized by a palladium catalyzed C–N coupling reaction. Photophysical and light-emitting device characterization confirmed the delayed fluorescence mechanism of this copolymer. A polymer light-emitting diode based on P0 exhibited pure blue emission with CIE coordinates of (0.16, 0.10), which has a maximum external quantum efficiency of 5.3%. In addition, a series of color-tunable polymers that exhibit delayed fluorescence with light emission ranging from sky blue to bluish green and improved efficiency were developed by incorporating a ditriphenylamine-functionalized triazine unit. Our strategy represents a novel approach for the construction of polymers with delayed fluorescence and high efficiency.

As a rising two-dimensional (2D) nanomaterial, layered black phosphorus (BP) nanosheets have shown promising applications in electronics and photonics. Besides the 2D layered structure, recently black phosphorus quantum dots (BPQDs) exhibiting unique optoelectronic properties had been successfully fabricated. However, the nonlinear optical properties of BPQDs at the telecommunication band have not been investigated. Herein, we synthesized the BPQDs by using a liquid exfoliation method that combined probe sonication and bath sonication. It was found that the evident saturable absorption ability of BPQDs at 1.55 μ m waveband could be clearly observed. As for the applications of ultrafast photonics, we fabricated the BPQDs saturable absorber (BPQDs-SA) and applied it to an ultrafast laser. By virtue of the excellent nonlinear optical properties of BPQDs, the fiber laser delivers the stable pulse train with duration as short as 291 fs, whose performance could, to the best of our knowledge, compete with nowadays’ commercial optical saturable absorber devices. In addition, due to the highly nonlinear optical effect generated by the fabricated BPQDs-SA, the multi-soliton nonlinear dynamics in the fiber laser were also investigated. The obtained results suggest that the BPQDs could be an attractive nonlinear optical material for applications in the field of nonlinear optics.

A new acceptor–donor–acceptor type small molecule acceptor, namely IDT-HN, has been developed, which consists of a newly developed 2-(3-oxo-2,3,5,6,7,8-hexahydro-1H-cyclopenta[b]naphthalen-1-ylidene)malononitrile as the peripheral electron-withdrawing group and indaceno[1,2-b:5,6-b′]dithiophene as the electron-donating core. Compared with the reference molecule (IDT-IC) that bears phenyl-fused indanone as the end groups, IDT-HN exhibited an elevated lowest unoccupied molecular orbital level. By utilizing IDT-HN as the electron acceptor and a wide bandgap conjugated polymer, PBDB-T, as the electron donor, optimized devices exhibited an impressively high power conversion efficiency of up to 10.22% with simultaneously improved open-circuit voltage, short-circuit current and fill factor. The improved photovoltaic performance can be attributed to the widened and intensified absorption spectra, improved electron mobility, more ordered π–π packing structure, and the symmetric carrier transport mobility of the IDT-HN-based blend in comparison to those obtained from devices based on the reference molecule IDT-IC. These results indicate that the cyclic alkyl moiety incorporated into the peripheral groups plays a critical role in improving the performance of the corresponding solar cell devices. In addition, the power conversion efficiency of the devices remains at 91% of its optimum performance with a film thickness of 250 nm, indicating its great potential for future practical application.

Affording two semiconductors with one template in one step to construct a composite with delicate structures may endow low-cost photocatalysts with desired characteristics, i.e., high activity, stability and recyclability. Herein, novel sandwich-shelled ZnCdS/ZnO/ZnCdS cages are fabricated with “one stone”—zeolitic-imidazolate-framework-8. ZnS and ZnO are formed simultaneously in the sulfidation stage, where ZnS serves as a barrier to localize the ZnO particles filling up the voids between the ZnS layers. It could therefore be very advantageous in photocatalysis that the ZnCdS, derived from cation-exchanged ZnS, and ZnO with well-defined interfaces also have staggered band structure configurations by virtue of the fine adjustment of the composition. The Zn0.5Cd0.5S/ZnO/Zn0.5Cd0.5S cages exhibit a H2 production rate of 28.6 mmol g−1 h−1 and long-term durability, achieving the highest activities among the ZnCdS and ZnO families under noble-metal-free conditions. This remarkable performance could be ascribed to the unique morphology of the sandwich-shell and hollow interior integrating multiple vital merits for photocatalysis, including the enhanced light-harvesting ability, abundant active sites, shortened charge diffusion distances, and Z-scheme mechanism featuring preserved strong redox ability and improved charge separation and migration. This facile strategy may offer great opportunities in developing highly active metal sulfide/oxide-based photocatalysts for practical applications.

In this paper, we present a nickel complex, [BzPyN(CH 3 ) 2 ] 2 [Ni(mnt) 2 ] 1 (mnt 2 − = maleonitriledithiolate), a cocatalyst for building a photocatalytic system for H 2 generation from water. Under photoirradiation with blue light (λ max = 469 nm), 1 , together with CdS nanorods (CdS NRs) as a photosensitizer, and ascorbic acid (H 2 A) as a sacrificial electron donor in a pH 2.5 aqueous solution, produces hydrogen with a turnover number (TON) of 70,970 mol of H 2 per mol of catalyst during 70 h irradiation and the average value of AQY is ~ 18% during 10 h of irradiation.

In recent years, the use of non-fullerene acceptors in organic solar cells has rapidly advanced with new acceptor materials, which have enabled devices to achieve a power conversion efficiency greater than 13%. In addition to new acceptor materials’ design, device engineering plays an important role in improving the device performance. In this study, we develop effective device engineering strategies, including thermal annealing and interlayer modification, to improve the device performance from 7.39% to 9.39%. With the use of PTB7-Th as the donor and IDT-BT-R as the non-fullerene acceptor, we achieved an efficient non-fullerene organic solar cell based on an inverted device architecture with a power conversion efficiency as high as 9.39%. It is worthy of note that the energy loss of the optimized device is only around 0.5 eV, which can be attributed to weak recombination and the appropriate high energy level of the charge transfer states within the optimized device.

The synergistic integration of optofluidic and surface enhanced Raman scattering (SERS) sensing is a new analytical technique that provides a number of unique characteristics for enhancing the sensing performance and simplifying the design of microsystems. Here, we propose a reusable optofluidic SERS sensor by integrating Au nanoisland substrate (AuNIS)-coated fiber into a microfluidic chip. Through both systematic experimental and theoretical analysis, the sensor enables efficient self-cleaning based on its optical-to-heat-hydrodynamic energy conversion property. Besides, the sensor exhibits the instrument detection limit down to 10 − 13 m o l / L and enhancement factor of 10 6 for Rhodamine 6G. Our optofluidic SERS sensor with such a photothermal microfluidic-assisted self-cleaning method has the advantages of portability, simple operation, and high cleaning efficiency, which will provide a new, to the best of our knowledge, concept and approach for cost-effective and reusable sensors.

Microfluidic techniques have emerged as promising strategies for a wide variety of synthetic or biological sorting. Unfortunately, there is still a lack of sorting with automatic and handy operation. In contrast to passively generated vortices, the thermocapillary vortices produced by temperature gradient have the advantages of flexible manipulation, stable strength, and simple integration. In this Letter, we present a device used for the pump-free separation of particles through vortices interaction without external fluidic control systems required for the majority of existing devices. Specifically, the device induces a different flow type upon the actuation of optical power, and the flow functions, such as simultaneous pumping and sorting, agree with stimulation results very well. More importantly, our developed sorting device can achieve separations by means of tunable cutoff diameter size. Therefore, this versatile device can be utilized to sort complex samples with the advantages of portability, user-friendly control, and automation.