In this paper, we reported the in situ fabrication of highly luminescent formamidinium lead bromide (FAPbBr) nanocrystal thin films by dropping toluene as an anti-solvent during the spin-coating with a perovskite precursor solution using 3,3-diphenylpropylamine bromide (DPPA-Br) as a ligand. The resulting films are uniform and composed of 5-20 nm FAPbBr perovskite nanocrystals. By monitoring the solvent mixing of anti-solvent and precursor solution on the substrates, we illustrated the difference between the ligand-assisted reprecipitation (LARP) process and the nanocrystal-pinning (NCP) process. This understanding provides a guideline for film optimization, and the optimized films obtained through the in situ LARP process exhibit strong photoluminescence emission at 528 nm, with quantum yields up to 78% and an average photoluminescence lifetime of 12.7 ns. In addition, an exciton binding energy of 57.5 meV was derived from the temperature-dependent photoluminescence measurement. More importantly, we achieved highly efficient pure green perovskite based light-emitting diode (PeLEDs) devices with an average external quantum efficiency (EQE) of 7.3% (maximum EQE is 16.3%) and an average current efficiency (CE) of 29.5 cd A (maximum CE is 66.3 cd A) by adapting a conventional device structure of ITO/PEDOT:PSS/TFB/perovskite film/TPBi/LiF/Al. It is expected that the in situ LARP process provides an effective methodology for the improvement of the performance of PeLEDs.

Polymer dispersed liquid crystals (PDLCs) have kindled a spark of interest because of their unique characteristic of electrically controlled switching. However, some issues including high operating voltage, low contrast ratio and poor mechanical properties are hindering their practical applications. To overcome these drawbacks, some measures were taken such as molecular structure optimization of the monomers and liquid crystals, modification of PDLC and doping of nanoparticles and dyes. This review aims at detailing the recent advances in the process, preparations and applications of PDLCs over the past six years.

The in situ fabricated perovskite nanocrystals (PNCs) obtained through spin‐coating a precursor solution are suitable candidates to achieve efficient perovskite light emitting diodes (PeLEDs). In this work, the solvent effects of on‐chip crystallization are investigated by correlating the nucleation and growth process of in situ fabricated formamidinium lead iodide (FAPbI3) nanocrystals with their optical and electronic properties. The FAPbI3 nanocrystals obtained from a precursor solution in γ‐butyrolactone (GBL) are smaller than those obtained from N,N‐dimethylformamide and dimethyl sulfoxide, and the relatively weak coordination between GBL and the precursor molecules enables reduced defect states in the resulted PNCs with enhanced photoluminescence properties. A modified LaMer model is proposed to describe the solvent effects in the on‐chip crystallization process. Based on these understandings, red emissive FA0.87Cs0.13PbI3 nanocrystal films with absolute photoluminescence quantum yields up to 70% are realized. Finally, an efficient PeLED with maximum luminance of 218 cd m−2 and peak external quantum efficiency of 15.8% is achieved with good reproducibility.

Fabrication of hybridized structures is an effective strategy to promote the performances of graphene-based composites for energy storage/conversion applications. In this work, macroporous structured graphene thin films (MGTFs) are fabricated on various substrates including flexible graphene papers (GPs) through an ice-crystal-induced phase separation process. The MGTFs prepared on GPs (MGTF@GPs) are recognized with remarkable features such as interconnected macroporous configuration, sufficient exfoliation of the conductive RGO sheets, and good mechanical flexibility. As such, the flexible MGTF@GPs are demonstrated as a versatile conductive platform for depositing conducting polymers (CPs), e.g., polyaniline (PAn), polypyrrole, and polythiophene, through in situ electropolymerization. The contents of the CPs in the composite films are readily controlled by varying the electropolymerization time. Notably, electrodeposition of PAn leads to the formation of nanostructures of PAn nanofibers on the walls of the macroporous structured RGO framework (PAn@MGTF@GPs): thereafter, the PAn@MGTF@GPs display a unique structural feature that combine the nanostructures of PAn nanofibers and the macroporous structures of RGO sheets. Being used as binder-free electrodes for flexible supercapacitors, the PAn@MGTF@GPs exhibit excellent electrochemical performance, in particular a high areal specific capacity (538 mF cm(-2)), high cycling stability, and remarkable capacitive stability to deformation, due to the unique electrode structures.

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We provide a broad overview of current quantum communication by analyzing the recent discoveries on the topic and by identifying the potential bottlenecks requiring further investigation. The analysis follows an industrial perspective, first identifying the state or the art in terms of protocols, systems, and devices for quantum communication. Next, we classify the applicative fields where short- and medium-term impact is expected by emphasizing the potential and challenges of different approaches. The direction and the methodology with which the scientific community is proceeding are discussed. Finally, with reference to the European guidelines within the Quantum Flagship initiative, we suggest a roadmap to match the effort community-wise, with the objective of maximizing the impact that quantum communication may have on our society.

In this study, hybrid BHJbulk heterojunction polymer solar cells were fabricated by incorporating CdS quantum dots (QDs) in a blend of P3HT (donor) and PCBM (acceptor) using dichlorobenzene and chlorobenzene as solvents. CdS QDs at various ratios were mixed in a fixed amount of the P3HT and PCBM blend. The prepared samples have been characterized by a variety of techniques such as I-V and EQE measurements, atomic force microscopy (AFM), scanning electron microscopy (SEM) and ultraviolet-visible (UV-vis) spectroscopy. The mixing of QDs in the polymer blends improved the PCEpower conversion efficiency of the solar cells under standard light conditions. The improved PCE from 2.95 to 4.41% is mostly due to the increase in the fill factor (FF) and short-circuit current (J sc ) of the devices with an optimum amount of CdS in the P3HT:PCBM blend. The increase in J sc possibly originated from the formation of a percolation network of CdS. The conjugation of QDs has increased the absorption of the active layers in the visible region. These results well matched as reported, conjugation of CdS in the perovskite active layer increased the absorption and PCE of the devices relative to those of the perovskite films. This increment in parameters is attributed to the decrease in charge recombinations that improved the performance of the doped device.Fig. 8 Absorption spectra of the undoped and CdS-doped films of P3HT:PCBM (a) and EQE curves of the devices (b). 18056 | RSC Adv., 2018, 8, 18051-18058 This journal is

Solution‐processed optoelectronic devices based on conjugated polymers, colloidal quantum dots (CQDs), halide perovskites, and so on are now emerging as a new‐generation semiconductor technology which prevails its conventional counterparts in terms of low fabrication cost, ease of scalable manufacturing, and abundant material designability. However, the solution‐processed thin films obtained through spin‐coating, spray, inkjet printing, and doctor blading usually suffer from low film quality and a high defect density especially at the interfaces of different functional layers. Currently, the most significant subject is to address the non‐ideal interfaces for achieving improved performance of the devices. Impedance spectroscopy (IS) is a universal technique that can help to examine the charge behavior at the interfaces in an electrochemical or solid‐state multilayered device. Owing to its ability to elucidate the charge transfer, charge transport, and accumulation within the interfaces of electrochemical or multilayered devices with minimal effects to the devices themselves, the use of IS has increased vividly in the last decades. This review provides the basic principles of IS and its applications on solution‐processed optoelectronic devices.