Self-Assembled Monolayer-Based Hole-Transporting Materials for Perovskite Solar Cells.

Ever since self-assembled monolayers (SAMs) were adopted as hole-transporting layers (HTL) for perovskite solar cells (PSCs), numerous SAMs for HTL have been synthesized and reported. SAMs offer several unique advantages including relatively simple synthesis, straightforward molecular engineering, effective surface modification using small amounts of molecules, and suitability for large-area device fabrication. In this review, we discuss recent developments of SAM-based hole-transporting materials (HTMs) for PSCs. Notably, in this article, SAM-based HTMs have been categorized by similarity of synthesis to provide general information for building a SAM structure. SAMs are composed of head, linker, and anchoring groups, and the selection of anchoring groups is key to design the synthetic procedure of SAM-based HTMs. In addition, the working mechanism of SAM-based HTMs has been visualized and explained to provide inspiration for finding new head and anchoring groups that have not yet been explored. Furthermore, both photovoltaic properties and device stabilities have been discussed and summarized, expanding reader's understanding of the relationship between the structure and performance of SAMs-based PSCs.

Silicon Tetrapyrazinoporphyrazine Derivatives-Incorporated Carbohydrate-Based Block Copolymer Micelles for Photodynamic Therapy.

Developing nonaggregated photosensitizers (PSs) for efficient photodynamic therapy (PDT) using polymeric micelles (PMs) has been challenging. In this study, axially substituted nonaggregated silicon tetrapyrazinoporphyrazine (SiTPyzPz) derivatives in carbohydrate-based block glycopolymer-based PMs were designed and used as PSs for PDT. To achieve the nonaggregated PSs, SiTPyzPz was axially substituted with trihexylsiloxy (THS) groups to form SiTPyzPz-THS, which exhibited highly monomeric behaviors in organic solvents. Moreover, three block copolymers were prepared via reversible addition-fragmentation chain transfer (RAFT) polymerization. Each copolymer comprised hydrophobic polystyrene blocks and loadable SiTPyzPz-THS, and one or two consisted of two possible hydrophilic blocks, polyethylene glycol or poly(glucosylethyl methacrylate). The self-assembly of SiTPyzPz-THS and the block copolymers in aqueous solvents induced the formation of spherical PMs with core-shell or core-shell-corona structures. The SiTPyzPz-THS in the PMs exhibited monomeric state, intense fluorescence emission, and outstanding singlet oxygen generation; moreover, it did not form aggregates. During the in vitro test, which was performed to investigate the PDT efficiency, the PMs, which consisted of poly(glucosylethyl methacrylate) shells, exhibited high photocytotoxicity and cellular internalization ability. Consequently, the PM systems of nonaggregated PSs and carbohydrate-based block copolymers could become very promising materials for PDT owing to their photophysicochemical properties and considerable selectivity against cancer cells.

Scalable Sub-micron Patterning of Organic Materials Toward High Density Soft Electronics.

The success of silicon based high density integrated circuits ignited explosive expansion of microelectronics. Although the inorganic semiconductors have shown superior carrier mobilities for conventional high speed switching devices, the emergence of unconventional applications, such as flexible electronics, highly sensitive photosensors, large area sensor array, and tailored optoelectronics, brought intensive research on next generation electronic materials. The rationally designed multifunctional soft electronic materials, organic and carbon-based semiconductors, are demonstrated with low-cost solution process, exceptional mechanical stability, and on-demand optoelectronic properties. Unfortunately, the industrial implementation of the soft electronic materials has been hindered due to lack of scalable fine-patterning methods. In this report, we demonstrated facile general route for high throughput sub-micron patterning of soft materials, using spatially selective deep-ultraviolet irradiation. For organic and carbon-based materials, the highly energetic photons (e.g. deep-ultraviolet rays) enable direct photo-conversion from conducting/semiconducting to insulating state through molecular dissociation and disordering with spatial resolution down to a sub-µm-scale. The successful demonstration of organic semiconductor circuitry promise our result proliferate industrial adoption of soft materials for next generation electronics.

Large Scale Synthesis and Light Emitting Fibers of Tailor-Made Graphene Quantum Dots.

Graphene oxide (GO), which is an oxidized form of graphene, has a mixed structure consisting of graphitic crystallites of sp(2) hybridized carbon and amorphous regions. In this work, we present a straightforward route for preparing graphene-based quantum dots (GQDs) by extraction of the crystallites from the amorphous matrix of the GO sheets. GQDs with controlled functionality are readily prepared by varying the reaction temperature, which results in precise tunability of their optical properties. Here, it was concluded that the tunable optical properties of GQDs are a result of the different fraction of chemical functionalities present. The synthesis approach presented in this paper provides an efficient strategy for achieving large-scale production and long-time optical stability of the GQDs, and the hybrid assembly of GQD and polymer has potential applications as photoluminescent fibers or films.

The synthesis and optical properties of fluorescent quinoxalines and of electrospun fibers containing fluorescent quinoxaline.

Heterocyclic fluorophores are useful materials in the search for new biologically active compounds and diagnostic methods. We have been interested in the chemistry of nitrogen-containing heterocyclic molecules for many years. Quinoxaline is a representative fluorophore. We have reported on several quinoxalines in recent years. Quinoxaline can easily change its absorption and emission wavelength by oxidation with the proton base in the nitrogen of the quinoxaline ring. In this study, we designed and synthesized several 2,3-distyrylquinoxaline and thieno[3,4-b]quinoxaline derivatives, Each with different electron-donating capabilities. The designed quinoxalines were substituted for the dodecyloxy groups on the benzene ring and stillbene groups were attached by knoevenagel reaction or Hornor-Wadsworth-Emmons (HWE) reaction on the 2,3-positions of the pyrazine ring. They amplified the electron donating capability of the quinoxaline structure. Thus, the weak base property of nitrogen in the heterocyclic ring was increased, especially in a protonic condition. The property in an acidic condition was revealed by fluorescence quenching. However, fluorescent spectral change was observed, especially when the N,N-dimethylamino group was attached to the stillbene group. These properties were also observed in electrospun fibers containing those synthesized compounds. Electrospun fibers contained quinoxaline colorants are expected to have various applications in chemosensors.

New sensitive moisture getter system by using aluminium complex and polyacetylene containing silyl group for display.

In this study, a novel moisture getter was fabricated from a new desiccant triethylaluminum [TEA] and a porous material poly(1-trimethylsilylpropyne) [PTMSP] as a binder and then was applied to organic light-emitting diode (OLED). After forming a film of 1.5 cm x 2.0 cm with 50 mg of PTMSP by a film-casting method, its property was measured. As a result, PTMSP (Mn:50 K) created a film with a relatively high porosity. PTMSP (60%) and TEA (40%) were mixed to fabricate a getter system with a good transmittance of over 80%. The fabricated getter, adopted in a OLED device, showed excellent features, as a level of commercialization: 490-hour shelf lifetime under the conditions of 60 degrees C and 90% RH.

Core-structure effects of novel indenopyrazine derivatives for blue emitter.

A novel core material, indenopyrazine, has been substituted with ethyl, phenyl, tolyl or fluorenyl groups on the locations 6 and 12, to newly synthesize four blue-emitting materials for OLED. Their electro-optical properties were compared through UV-Vis absorption, PL spectra and cyclic voltammetry, according to substituents of the core system of indenopyrazine. Non-doped OLED devices were fabricated by using the synthesized materials as emitting material layers, and among them, SF-EPY showed a highly-efficient luminescence with EL spectrum of 458 nm, luminous efficiency of 2.62 cd/A and CIE coordinates of (0.152, 0.142) at a current density of 10 mA/cm2.