Photoelectric Functional Materials Research Articles

Donor-acceptor-donor type AIEgens based on thieno[3.4-c]pyrrole-4,6-dione: Synthesis, electropolymerization, and electrochromism.

Photoelectric functional materials with electrochemical reversible activity and fluorescence intensities have attracted significant interest due to their wide range of applications in optoelectronic devices. In this work, a series of photoresponsive and electroactive monomers based on thieno[3.4-c]pyrrole-4,6-dione (TPD) are synthesized and characterized. They possess planar geometry with smaller dihedral angles owing to the existence of a noncovalent conformation lock coming from the S atoms and the O atoms. Crystallographic, spectroscopic, and computational results reveal that the introduction of the TPD unit can endow the monomers with aggregation-induced emission (AIE), reduced energy levels, and increased electrochemical activity. The monomers were successfully polymerized through the electrochemical method, and the corresponding polymers displayed reversible electrochemical activity and stability. Moreover, polymer films based on 3,3-dimethyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepine (ProE)-TPD have electrochromic properties in the near-infrared field with a high value of optical contrast ratio (∆T) of 27.1% at 1000 nm.

Synthesis of thiophene-isoindigo receptor small molecules and its application in photodetectors

Organic photodetectors (OPDs) have attracted wide attention from researchers on account of their characteristics such as easy to manufacture, low cost, lightweight, and flexible detectors. Many efforts have been made to improve the performance of OPDs. Scientists have made many efforts to improve the performance of organic photodetectors. Among them, narrow-band-gap organic photoelectric functional materials with wide spectral response exhibit application prospects in photoelectric detection. In this paper, a series of narrow-band-gap thienoisoindigo receptor small molecules were synthesized by using thienoisoindigo, and electron deficient terminal octyl cyanoacetate, 3-ethylrhodanine, and 2-(3-ethyl-4-oxothiazolidine-2-ylidene) malonitrile as receptor units, and 3-dodecylthiophene as donor unit, The photodetector with wide spectral response and high detection rate is fabricated using a Bulk Heterojunction (BHJ) structure.

Room-Temperature Phase Transition Material with Switchable Second-Order Nonlinear Optical Properties.

Phase transition materials with switchable second-order nonlinear optical (NLO) properties have attracted extensive attention because of their great application potential in photoelectric switches, sensors, and modulators, while metal-free organics with NLO switchability near room temperature remain scarce. Herein, we report a hydrogen-bonded metal-free organic crystal, 2-methylpropan-2-aminium 2,2-dimethylpropanoate (1), exhibiting a room-temperature phase transition and favorable NLO switchability. Through investigations on its thermal anomalies, dielectric properties, and crystal structures, we uncover that 1 holds a near-room-temperature phase transition at 303 K from noncentrosymmetric point group C2v to centrosymmetric one D2h, which is attributed to the order-disorder transformations of both tert-butylamine cations and dimethylpropionic acid anions. Accompanied by symmetry change during the phase transition, 1 exhibits reversible and repeatable NLO "on-off" switchability with a desirable switching contrast ratio of ca. 19 between high and low NLO states. This discovery demonstrates a metal-free organic crystal with NLO switching behavior near room temperature, serving as a promising candidate in smart and ecofriendly photoelectric functional materials and devices.

Cs2Pb4Br10: A layered perovskite shows large birefringence

Birefringent crystal is an important photoelectric functional material widely used in laser polarizationtechnology, optical polarization modulation and detection. The research on the reported Pb-Br-Cs system shows that there is no relevant research on the source of birefringence. Therefore, we have carried out the birefringence study of Pb-Br-Cs series crystals, and found that the birefringence of some Pb-Br-Cs substances are lower than 0.05, but only the layered perovskite Cs2Pb4Br10 has a large birefringence (0.392 @ 550 nm). Therefore, layered perovskite metal halides are expected to be candidates for birefringent crystals.

Enhanced Photovoltaic Property and Panchromatic Photocatalytic by Forming D‐π‐A‐Bacteriochlorin Dyads: A Computational Investigation

The photovoltaic characteristics and panchromatic photocatalysis based on monomers and bithiophene‐chlorophyll dyads is investigated. The optical properties and the electron transport capacity of the titled dyes are explicated by investigating the geometry, electronic structure, electron injection, and recombination, intramolecular charge transfer, regeneration process, dye aggregation, and light‐harvesting. The results manifest that the original 3,3′‐dithioalkyl‐2,2′‐bithiophene (SBT)‐based molecule behaves better with photovoltaic performance and an enhanced JSC and VOC. For molecular design, the designed dyads not only show the enhanced absorption range and prolonged excited lifetimes but also noticeable electron transfer ability. Moreover, the strong interfacial interaction, fast electron transfer process, long recombination distance, inhibition in dye aggregate, enhanced regenerative interaction energy are elucidated, which is beneficial for a better photocurrent response. However, the slight shift of the conduction band edge in dyads significantly reduces the VOC, especially for SBT‐Chl. Among dyads, SBT‐BChl exhibits outstanding photovoltaic performance of 14%. Besides, photocatalysis analysis manifests that the dyad composites behave with red‐shifted spectra, enhanced dipole moments, better interfacial interaction to ensure electron transfer, which significantly improved the photocatalytic performance of TiO2. Our study is expected to offer theoretical guidelines for further screening the promising D‐π‐A‐bacteriochlorin dyads in photoelectric functional materials.

Diestervinyl-functionalized acceptor-acceptor type dithienylethenes with efficient photochromic performance.

Exploring novel dithienylethenes (DTEs) with efficient photochromism has drawn increasing attention in virtue of the potential applications for photoelectric functional materials. In this contribution, we presented two novel acceptor-acceptor (A-A) type DTE derivatives (4a and 4b) by incorporating the diestervinyl moieties with strong electron-withdrawing capacity into two sides of DTE skeleton. The corresponding structures were well confirmed by the NMR (1H and 13C) and HRMS. When irradiated alternately with ultraviolet and visible light, 4a and 4b showed efficient photochromism in toluene, chloroform and DMSO, clearly implying a solvent-dependence feature. Moreover, excellent photoswitching behaviors were also observed in the poly(methyl methacrylate) (PMMA) film. The density functional theory (DFT) calculations suggested that strong Acceptor-Acceptor effect plays a dominative role in the efficient photochromic performance. Hence, this study will provide a useful guidance for developing high-performance DTE derivatives in multi-media.

Visible light-triggered acceptor-acceptor type dithienylethene with aggregation-induced emission for NIR photochromism in aqueous media

Photochromic dithienylethene (DTE) derivatives with aggregation-induced emission (AIE) performance are appealing for photoelectric functional materials and photopharmacology. However, they often have to be triggered by ultraviolet light to induce photoisomerization, severely limiting their potential applications in biological systems. Herein, a novel acceptor (A)-acceptor (A) type DTE derivative (CNSDTE) has been rationally designed and prepared, in which the cyanostilbene moieties as strong electron-withdrawing groups are incorporated into both sides of DTE skeleton. Its chemical structure is fully verified by 1H NMR, 13C NMR and HRMS. Upon alternating irradiation of visible and near-infrared light, CNSDTE shows excellent photochromic properties in toluene, chloroform and DMSO. Before irradiation with visible light, AIE properties and solid state luminescence behavior are observed. Furthermore, CNSDTE-loaded nanoparticles (CNSDTE NPs) are facilely fabricated by taking the amphiphilic Pluronic F127 as the encapsulating matrix. The as-prepared CNSDTE NPs display excellent photoswitching behavior in aqueous media. The experimental results of the excellent AIE properties and photoswitching behaviors in the various media is also confirmed by DFT calculations. In short, it may be employed in functional biomaterials as a novel visible light-triggered fluorescence switch with AIE features.

Target-Oriented Synthesis of Borate Derivatives Featuring Isolated [B3O3] Six-Membered Rings as Structural Features.

Borates provide an excellent platform for investigating the optical nonlinearity and linearity of crystals as photoelectric functional materials. In our work, borate derivatives with isolated [B3O3] six-membered rings as structural features are the preferred system due to their simple functional units and excellent properties. Herein, by utilizing the target-oriented synthesis, a series of borate derivatives, A2[B3O3F4(OH)] (A= NH4, Rb, Cs) (ABOFH), K2.3Cs0.7B3O3F6 (KCsBOF), and Cs3[B3O3(OH)3]Cl3 (CsBOHCl), with novel heteroanionic groups containing [BOxF4-x] (x = 0-3) and/or [BO2(OH)] units were obtained. ABOFH, KCsBOF, and CsBOHCl construct different two-dimensional pesudolayers featuring [B3O3F4(OH)], [B3O3F6], and [B3O3(OH)3] units, respectively. Also, the optical properties and the arrangement information of these anionic groups were studied. Among the total five compounds, (NH4)2[B3O3F4(OH)] and Cs3[B3O3(OH)3]Cl3 with enlarged birefringence and sufficient band gaps were screened out as promising birefringent crystals due to the optimally aligned configuration of birefringence-active heteroanionic units. The successful results of target-oriented synthesis indicate a more profound conclusion that the borate system now has more diversified structural chemistry, and an effective strategy was proposed to modify the arrangement and species of anionic units to optimize the performance of optical crystals.

High Electrochromic Performance of Perylene Bisimide/ZnO Hybrid Films: An Efficient, Energy-Saving, and Green Route.

The composite or hybrid of organic and inorganic materials is one of the common ways to improve the properties of photoelectric functional materials. Perylene bisimide (PBI) derivatives, as large π-conjugated organic small molecules, are a class of photoelectric functional materials with excellent performance. However, there were few reports on PBIs in the electrochromic field due to the difficulty of film-forming caused by their generally poor solubility. Here, water-soluble PBI derivatives (PDI-COOH and PCl-COOH) were synthesized. The hybrid films (ZnO@PDI-COOH/PCl-COOH) formed by the coordination bond and π-π stacking were prepared via a simple solution immersion method. Fourier transform infrared spectrometry and X-ray diffraction as well as scanning electron microscopy, and energy-dispersive spectrometry results further confirmed the formation of hybrid films. At the same time, electrochemical and spectroelectrochemical analyses revealed that the films have reversible redox activity and cathodic electrochromic properties, which can change from orange-red to purple. The ZnO@PDI-COOH hybrid film formed by coordination bonds exhibits fast switching times (1.7 s colored time and 2.6 s bleached time), good stability (retain 92.41% contrast after 2400 cycles), a low driving voltage (-0.6-0 V), and a high coloration efficiency (276.14 cm2/C). The corresponding electrochromic devices also have good electrochromic properties. On this basis, a large-area (100 mm × 100 mm) electrochromic display device with fine patterning was fabricated by using the hybrid film, and the device shows excellent reversible electrochromic performance. This idea of constructing organic-inorganic hybrid materials with coordination bonds provides an effective, energy-saving, and green method, which is expected to promote the large-scale and fine production of electrochromic materials.

Investigation on potential applications of thermal activated delayed fluorescence materials in organic electroluminescent devices

In the past few years, organic battery light emitting devices have attracted a lot of attention, showing great application potential. Fluorescence material, phosphorescence material and thermal activated delayed fluorescence (TADF) material, have attracted more and more attention. However, phosphorescent material is limited by the useage of a heavy metal, Ir. So people want to find a more efficient and environmental-friendly material:TADF. TADF polymer can be used as a new type of organic photoelectric functional materials due to its high exciton utilization. This work focuses on the working principle, advantages, applications of TADF materials and the imagination for future applications. OLED emission of different light colors is also worthy of attention, the differences and efficiency of the three colors have sparked discussion as well. On this basis, starting from the luminescence principle and device structure of TADF, the advantages and disadvantages of TADF materials are summarized. Finally, the solution to “aggregation-caused quenching” problem (ACQ) is found, so as to focus on the application of technology and envisage the future application direction.

Crystallization-induced emission enhancement of alkyl chain-dependent pyrene-based luminogens: Visual detection of nitro-explosives

In view of the widespread applications and urgent need for efficient blue emitting materials, the synthesis of such materials has seen renewed interest. In the present work, three alkyl chain-dependent blue emitting pyrene-based luminogens were synthesized and characterized. The experimental results show that these luminogens exhibited high photoluminescence efficiency both in solution (>86%) and in the solid state (>35%). Interestingly, 1,3,6,8-tetrakis (pentylphenyl)pyrene (TPPy), as a photoelectric functional material, was endowed with higher quantum yield (72%) and competitiveness due to a remarkable crystallization-induced emission enhancement (CIEE) property. More importantly, TPPy exhibits high sensitivity and selectivity for ortho-nitroaniline (o-NA) with low limit of detection (9.99 × 10−8 M), which is mainly due to the distinctive odd-even effects of the terminal alkyl chain. The results demonstrate that this type of luminogen can potentially be utilized for practical applications in the field of contaminant or explosive detection as a sensitive and portable fluorimeter.

Synthesis and photoswitching behavior of donor-acceptor type dithienylethene derivatives modified by diestervinyl moieties

Developing novel dithienylethenes (DTEs) with excellent photochromic performance has attracted wide attention due to the potential applications in the field of photoelectric functional materials. Herein, two new donor-acceptor type DTE derivatives (1a and 1b) have been developed, which were decorated by electron-donating dimethylaminobenzene (or anisole) and electron-withdrawing diestervinyl moieties on DTE core. Their chemical structures were well characterized by 1H NMR, 13C NMR and HRMS (ESI). As expected, they presented solvent-dependent photochromic behaviors with good fatigue resistance in the different polar solvents (toluene, chloroform and dimethyl sulfoxide) upon irradiation with UV and visible light. Moreover, these results implied a significantly enhanced solvent dependence of photochromism with increasing electron donor capacity in this D-DTE-A system. Furthermore, they also displayed excellent photochromism and fluorescence switching behavior in the PMMA film upon the same irradiation conditions. The corresponding experimental results were further validated by DFT calculations. In view of the above, they can be utilized as a novel D-A type DTE derivatives integrated into the future smart photoelectric materials.

Linear and Nonlinear Photon-Induced Cross Bridge/Space Charge Transfer in STC Molecular Crystals.

In this work, we theoretically studied the optical absorption properties of a layer-stacked cocrystal heterogeneous material Spe-TCNB cocrystal (STC) which is produced by supramolecular self-assembly of organic conjugated monomers SPE and TCNB. The highly ordered aggregate structure in the cocrystal STC will lead to intermolecular interactions such as π∼π, hydrogen bonds and van der Waals forces, resulting in significant charge transfer characteristics and large cross-sectional two-photon absorption characteristics. The physical mechanism of one-photon and two-photon charge transfer of cocrystal molecules is specifically discussed and the interaction between molecules and their role in charge transfer are quantitatively analyzed. We found that the charge transfer between molecular junctions composed of hydrogen bonds is mainly cross-bridge charge transfer, while the charge transfer between molecular junctions caused by accumulation is mainly cross-space charge transfer. This discovery is of great significance to the design of organic photoelectric functional materials.

Hydrothermal synthesis and controlled growth of group-VIB W metal compound nanostructures from tungsten oxide to tungsten disulphide.

Two-dimensional lateral group-VIB transition metal dichalcogenides (TMDs) have attracted much attention in the fast evolving field of advanced photoelectric functional materials, but their controllable fabrication is challenging. Herein, an emerging synthetic route for sulfurization of tungsten oxide was developed. During the hydrothermal reaction, the optimization of the precursor selection and synthesis parameters led to the tunable properties of WO3-WSxOy-WS2 nanostructures. The vulcanization was thermodynamically favorably at low temperatures and in an environment with a sufficient S source, wherein WO3 was reduced by H atoms to WO3-x, and S atoms were preferentially adsorbed on O vacancies. The WSxOy nanostructures have a narrow band-gap attributed to the effect of S on the valence band top and electronic density of states by density functional theory. The photocurrent response and charge transfer properties of WSxOy were improved due to the charge transport between WS2 and WO3. Understanding the formation and transformation of WS2 nanostructures in solution contributes to the discovery of the important structure-efficiency relationship, which may be extended to other TMDs systems. Hence, extensive research efforts are still needed to develop safer and more efficient synthesis and modification methods to fully utilize the distinctive advantageous properties of TMDs in the photoelectric field.

The optical properties of MoSe2 in bulk and monolayer with different crystal orientation based on first-principles calculations

MoSe2 is a crucial photoelectric functional material with good catalytic activity and two-dimensional layered structure and has a broad application prospect as an essential member of the transition metal chalcogenide (TMDs) family. Different MoSe2 forms have other electronic systems and optical properties. In this paper, based on density functional theory (DFT), bulk MoSe2 and monolayer MoSe2 with different growth directions are taken as research objects to study the band structure, electronic properties, and optical properties of bulk MoSe2 and monolayer MoSe2. According to the calculation results, the band gap of MoSe2 in the (100) crystal direction is the smallest, which can effectively realize ultra-wideband absorption. However, there are significant differences in the dielectric function, absorption coefficient, and reflection coefficient of MoSe2 in the three structures. MoSe2 with different forms has different application fields according to various properties. These results provide reliable data and support for the development of new MoSe2 optoelectronic materials and devices.

High performance perovskite solar cells synthesized by dissolving FAPbI<sub>3</sub> single crystal

In recent years, CH(NH<sub>2</sub>)<sub>2</sub>PbI<sub>3</sub> (FAPbI<sub>3</sub>) has received extensive attention due to the suitable band gap, becoming the most attractive photoelectric functional material in perovskite solar cells. However, the traditional perovskite layer prepared by formamidine iodide (FAI) and lead iodide (PbI<sub>2</sub>) has inaccurate stoichiometric ratio, high defect density, low stability, and low crystallinity, which makes it challenging to improve the performance of perovskite solar cells further. In this paper, the perovskite film prepared by FAPbI<sub>3</sub> single crystal has high crystallinity, high stability, accurate stoichiometric ratio and low defect density. The single crystal derived perovskite film has a large grain size and few grain boundaries, resulting in fewer defects in the grain boundaries, which improves the short-circuit current density (<i>J</i><sub>SC</sub>) and open-circuit voltage (<i>V</i><sub>OC</sub>) of perovskite solar cells, and greatly improves the photoelectric conversion efficiency. This work provides an efficient strategy for fabricating perovskite solar cells with high stability, high crystallinity, and low defect density.

Easily synthesized pyrene-based nonfullerene acceptors for efficient organic solar cells

Pyrene is a commercial fused-ring unit and has attracted much attention in the field of organic photoelectric functional materials. Herein, two non-fullerene acceptors (NFAs) Py-2H and Py-2F based on pyrene core have been developed. Unlike most others NFAs, Py-2H and Py-2F were synthesized via a simple and easy synthesis method, and this is fundamental for commercialization of organic solar cells (OSCs). Compared with Py-2H, fluorinated Py-2F exhibited narrower optical bandgap of 1.66 eV, better π-π stacking, lower frontier molecular orbital levels, and its PBDB-T:Py-2F blend film exhibited triple electron mobility. As a result, PBDB-T:Py-2F solar cells afforded a decent power conversion efficiency (PCE) of 9.73%, with an open-circuit voltage (VOC) of 0.92 V, a short circuit current (JSC) of 15.44 mA/cm2 and a fill factor (FF) of 68.22%. As comparison, PBDB-T:Py-2H cell just achieved only one-half PCE of 5.13%. These results demonstrated that NFAs based on fused-ring pyrene core are promising for organic photovoltaic applications due to the simple synthesis, low cost, and decent photovoltaic performance.

光電変換型光機能性材料の横断的分析;カラーフィルム,光触媒,色素増感およびペロブスカイト太陽電池

光電変換型光機能性材料の横断的分析;カラーフィルム,光触媒,色素増感およびペロブスカイト太陽電池

Titanium Iodates with a Second-Harmonic-Generation Response.

Nonlinear-optical (NLO) crystal is an important photoelectric functional material. In this work, a new NLO titanium iodate, (H3O)2Ti(IO3)6, along with Ti(IO3)4 has been synthesized under facile conditions. The space group of (H3O)2Ti(IO3)6 is the chiral noncentrosymmetric group R3 (No. 146), with an interesting three-dimensional framework, while that of Ti(IO3)4 is the centrosymmetric space group P1̅ (No. 2) containing one-dimensional chains. Thermogravimetric analysis shows that (H3O)2Ti(IO3)6 and Ti(IO3)4 have no weight loss below 220 and 390 °C, respectively. In addition, (H3O)2Ti(IO3)6 not only is thermally stable up to 200 °C in an air atmosphere but also is stable in water. (H3O)2Ti(IO3)6 has a moderate-intensity second-harmonic-generation (SHG) response (1.4×KDP), a large laser-induced damage threshold (46×AgGaS2), and high transmittance in the wavelength ranges of 0.5-1.4 and 2.5-10 μm. Both local dipole moment and systematic theoretical calculations reveal that the SHG response of (H3O)2Ti(IO3)6 is mainly because of the combined effect of [TiO6] octahedra and IO3 and IO4 units. In a word, (H3O)2Ti(IO3)6 exhibits good NLO performances, as well as water resistance and facile growth of a single crystal with high quality, indicating its potential application as NLO materials in the visible and mid-IR regions, especially the visible region.

A3BBi(P2O7)2 (A = Rb, Cs; B = Pb, Ba): Isovalent Cation Substitution to Sustain Large Second-Harmonic Generation Responses

Exploring novel photoelectric functional materials via chemical substitution-oriented design is an effective strategy, which can be expanded to the discovery of high-performance UV nonlinear optica...