Optoelectronic Functional Materials Research Articles

Emerging trends in the development of flexible optrode arrays for electrophysiology.

Optical-electrode (optrode) arrays use light to modulate excitable biological tissues and/or transduce bioelectrical signals into the optical domain. Light offers several advantages over electrical wiring, including the ability to encode multiple data channels within a single beam. This approach is at the forefront of innovation aimed at increasing spatial resolution and channel count in multichannel electrophysiology systems. This review presents an overview of devices and material systems that utilize light for electrophysiology recording and stimulation. The work focuses on the current and emerging methods and their applications, and provides a detailed discussion of the design and fabrication of flexible arrayed devices. Optrode arrays feature components non-existent in conventional multi-electrode arrays, such as waveguides, optical circuitry, light-emitting diodes, and optoelectronic and light-sensitive functional materials, packaged in planar, penetrating, or endoscopic forms. Often these are combined with dielectric and conductive structures and, less frequently, with multi-functional sensors. While creating flexible optrode arrays is feasible and necessary to minimize tissue-device mechanical mismatch, key factors must be considered for regulatory approval and clinical use. These include the biocompatibility of optical and photonic components. Additionally, material selection should match the operating wavelength of the specific electrophysiology application, minimizing light scattering and optical losses under physiologically induced stresses and strains. Flexible and soft variants of traditionally rigid photonic circuitry for passive optical multiplexing should be developed to advance the field. We evaluate fabrication techniques against these requirements. We foresee a future whereby established telecommunications techniques are engineered into flexible optrode arrays to enable unprecedented large-scale high-resolution electrophysiology systems.

Birefringence Regulation by Clarifying the Relationship Between Stereochemically Active Lone Pairs and Optical Anisotropy in Tin-based Ternary Halides.

It is important to establish and clarify the relationship between stereochemically active lone pairs and birefringence, since it is one of the significantly effective routes to explore birefringent crystals by introducing Sn-centered polyhedra with stereochemically active lone pairs. Herein, four tin(Ⅱ)-based ternary halides A3SnCl5 and ASn2Cl5 (A = NH4 and Rb) have been synthesized successfully. The experimental birefringence of Rb3SnCl5 and RbSn2Cl5 is larger than or equal to 0.046 and 0.123@546 nm, respectively. Through investigating the alkali or alkaline-earth metal tin(Ⅱ)-based ternary halides, the structure-performance relationship has been concluded between stereochemically active lone pairs and optical anisotropy. It is beneficial to the analysis and prediction of birefringence in tin-based halides and provides a guide for exploring tin(Ⅱ)-based optoelectronic functional materials.

Birefringence Regulation by Clarifying the Relationship Between Stereochemically Active Lone Pairs and Optical Anisotropy in Tin‐based Ternary Halides

AbstractIt is important to establish and clarify the relationship between stereochemically active lone pairs and birefringence, since it is one of the significantly effective routes to explore birefringent crystals by introducing Sn‐centered polyhedra with stereochemically active lone pairs. Herein, four tin(II)‐based ternary halides A3SnCl5 and ASn2Cl5 (A=NH4 and Rb) have been synthesized successfully. The experimental birefringence of Rb3SnCl5 and RbSn2Cl5 is larger than or equal to 0.046 and 0.123@546 nm, respectively. Through investigating the alkali or alkaline‐earth metal tin(II)‐based ternary halides, the structure‐performance relationship has been concluded between stereochemically active lone pairs and optical anisotropy. It is beneficial to the analysis and prediction of birefringence in tin‐based halides and provides a guide for exploring tin(II)‐based optoelectronic functional materials.

Recent Developments of Organic Optoelectronic Functional Materials and Devices Based on Biphenyl Derivatives

Recent Developments of Organic Optoelectronic Functional Materials and Devices Based on Biphenyl Derivatives

Cyano Substituent on the Olefin Linkage: Promoting Rather than Inhibiting the Performance of Covalent Organic Frameworks

It is generally believed that the electron-withdrawing cyano group in the olefin linkage would inhibit the stability and π-conjugation of covalent organic frameworks (COFs), which raises concerns about their optoelectronic properties. However, the structure–activity relationship between the structure of olefin linkages and properties of COFs is still inconclusive. In this work, imine-, vinylene-, and acrylonitrile-linked COFs with identical triphenyltriazine building blocks were designed and synthesized. Our work demonstrated that construction of acrylonitrile linkages not only enhanced the chemical stability and photostability but also led to remarkable optoelectronic properties with a record fluorescence quantum yield of 35.37% in the solid state. Further, the acrylonitrile linkage endows TTAN-COF/Pt NPs with superior and durable photocatalytic activity in both the hydrogen evolution reaction (11.94 mmol g–1 h–1; BET surface area, 739.28 m2 g–1) and aerobic oxidation reaction. This work demonstrates that the acrylonitrile linkage can significantly enhance the optoelectronic properties and photocatalytic activities of COFs compared with the highly π-conjugated vinylene linkage, providing a valuable reference for the design of optoelectronic functional materials.

Recent progress on artificial propeller chirality and related circular dichroism engineering

<p indent="0mm">Chirality, a geometric asymmetry in which a structure cannot coincide with its own mirror image through rotation and translation, is one of the basic properties of nature. It has been involved in all aspects of our life, such as art, architectural design, medicine, pesticides, life, information, chiral optoelectronic functional materials and devices. The interactions of chiral substances with light can differ for left- and right-handed circularly polarized (LCP and RCP) light and rely on the handedness of the enantiomers. Since scientists discovered the optical activity of chiral matter in the 19th century, the study of chiral light-matter interactions has become one of the most cutting-edge research fields in optics. Circular dichroism (CD) is the difference in absorption of LCP and RCP light by chiral substances. Since the chiral optical response of natural chiral matter is weak and difficult to tune, researchers have creatively designed various artificial chiral structures to enhance chiral light-matter interactions and realize many novel physical phenomena. The most common example is the helical configuration, which can be seen as the result of the stretched superposition of multiple split resonator rings. It can obtain much larger CD than natural materials. However, the three-dimensional fabrication process of micro/nanoscale helical structures faces challenges, which limit its application research. Different from common helical chiral structures and based on the nano-kirigami fabrication technique, this review focuses on a new type of artificial propeller-like chiral micro/nanostructures and their applications in chiral optics. This artificial propeller chirality is quite different from the traditional chiral structure in terms of geometric morphology and physical responses, such as the novel out-of-plane stereo twist and the chiral competition mechanism enabled by the hybridization of unit cells with two different chiral centers. The CD responses can be significantly enhanced by the chiral Fano resonance that is caused by the surface lattice resonances (SLRs). The chiral SLRs are formed by the coupling of chiral electric quadrupole modes to the diffractive lattice mode (Rayleigh anomaly). These unique features enable outstanding advantages in the flexible manipulation of optical CD, including the sensitive changes in intensity, sign and wavelength upon structural perturbations. Specially, the counterintuitive sign reversal of CD can be realized under minor structural changes without inverting the handedness of artificial propeller chirality. The work in this review provides a novel design idea for new artificial chiral micro/nanostructures and an ideal platform for in-depth study of chiral physics.

First-principles calculations to investigate the polymorph effects of CuAlO2

Polymorphism is a very common phenomenon for optoelectronic functional materials. The in-depth study of polymorph is an important basis for understanding the structure–activity relationship, polymorph effect and multifunctional application of optoelectronic functional materials. In this work, the crystal microstructure, electronic structure and optical properties of 9 polytypes of CuAlO2 are compared and studied in detail by using density functional theory calculation. We found that the structural motif and its connection mode in the polytype determine the stability of crystal phase and the main characteristics of electronic structure. The coordination environment of Cu is the key factor to determine the stability of crystal phase: the delafossite polytype containing two-fold-coordinated Cu is the most stable; followed by chalcopyrite and wurtzite polytype containing four-fold-coordinated Cu; the polytypes containing high-fold-coordinated Cu or more complex connection mode of motif are the least stable. Moreover, the binding energy and stability of these nine crystalline polytypes are mainly determined by the coordination number of Cu atom, the degree of deformity of structural motif and the connection mode of structural motif. When CuAlO2 contains linear two-coordinated Cu and is connected by sharing vertices, the absolute value of binding energy is the largest and most stable. At the same time, the type of Cu containing structural motif and the connection mode between structural motifs are the key factors to determine the fundamental band gap of CuAlO2. These 9 polytypes of CuAlO2 have well-defined indirect bandgap semiconductor characteristics. Finally, according to the main characteristics of electronic structures and optical properties, we also predict the potential applications of these polytypes of CuAlO2 in different optoelectronic fields.

High performance nonlinear optical materials with simple aromatic hydrocarbons

Design of novel functional materials with high-performance and high stability are of great importance in the field of nonlinear optics. In the present work, a new protocol is proposed for designing optical and nonlinear optical (NLO) functional material through proper interplay of functional moieties (in this work, benzene, naphthalene and azulene) by geometric arrangement within the classical D-π-A paradigm. The π-conjugation across the fused aromatic benzene, naphthalene and azulene, and the electronic structure retention of those functional moieties lead to the redistribution of π-electron in azulene-based polar carbon chains and bring about large second order NLO responses. The charge transfer based electron transition at low energy field has a dominant contribution to the large static first hyperpolarizability (<β0>). The strong second order NLO responses under external fields, e.g., sum frequency generation and difference frequency generation, render these azulene-based molecules promising candidates for optoelectronic functional materials with high-performance in visible and near-infrared regions. The protocol of designing optical and nonlinear optical materials through manipulating the interactions among functional moieties is extendable to designing other optico-electronic functional materials.

Hierarchical Nanowire Architectures Self‐Assembled from Ultra‐Deep‐Blue Fluorene‐Based Conjugated Molecules toward Organic Light‐Emitting Diodes with CIEy = 0.06

AbstractOrganic conjugated molecules with a rigid rod‐like π‐backbone structure automatically and easily self‐assemble into an anisotropic nanostructure. However, supersecondary structures obtained from the hierarchical secondary self‐assembly of nanostructures have rarely been reported for non‐amphiphilic conjugated molecules. Here, a nanowire architecture as a supersecondary structure from an ultra‐deep‐blue fluorene‐based conjugated molecule (FCz‐C8‐Am) to improve the emission efficiency and stability is reported. In significant contrast to the four reference molecules, the FCz‐C8‐Am molecules grow into soft nanowires and further self‐assemble into a series of nanowire architectures in the gelation process. This is associated with the synergistic effect of the hydrogen bonds among the amide units, pendant π–π stacking interactions between pendant Cz units, and appropriate soft steric interaction among side‐chains, which are the three design requirements for preparing these nanowire architectures. Interestingly, this supersecondary architecture of FCz‐C8‐Am has a stable ultra‐deep‐blue emission, with an efficiency of ≈77% and a Commission Internationale de L'Eclairage (CIE) value of (0.16, 0.06) in the solid state. These findings provide a profound understanding of the relationship between the inherent molecular structure, supramolecular interaction, and supersecondary nano‐architecture, offering useful information for the development of new functional optoelectronic materials.

Emerging New‐Generation Detecting and Sensing of Metal Halide Perovskites

AbstractThe unique energy conversion characteristics of metal halide perovskite (MHP) materials, which can be hardly observed in conventional semiconductors and metal oxides, have boosted their promising application in detecting and sensing devices, in addition to their famous optoelectronic functions. Herein, the recent progresses of the state‐of‐the‐art applications of MHPs are focused on X‐ray diagnosis, cardiac detection, bionic retina, artificial synapse, cell imaging, and others. Owing to their emerging electrical properties with multifield coupled response effect, and photoelectric, electro‐optical, and all‐optical conversion functions, MHPs demonstrate promising prospects in the diagnosis and treatment of various diseases. As functional optoelectronic materials, MHPs provide a new platform for future biomedical devices. This review article is expected to present the current status on, and further promote the application of MHP materials in detecting and sensing devices.

Stability and fundamental properties of Cu x O1-x as optoelectronic functional materials.

Binary CuxO1−x compounds have some advantages as optoelectronic functional materials, but their further development has encountered some bottlenecks, such as inaccurate bandgap values and slow improvement of photoelectric conversion efficiency. In this work, all possible stoichiometric ratios and crystal structures of binary CuxO1−x compounds were comprehensively analyzed based on a high-throughput computing database. Stable and metastable phases with different stoichiometric ratios were obtained. Their stability in different chemical environments was further analyzed according to the component phase diagram and chemical potential phase diagram. The calculation results show that Cu, Cu2O and CuO have obvious advantages in thermodynamics. The comparison and analysis of crystal microstructure show that the stable phase of CuxO1−x compounds contains the following two motifs: planar square with Cu atoms as the center and four O atoms as the vertices; regular tetrahedron with O atoms as the center and four Cu atoms as the vertices. In different stoichiometric ratio regions, the electron transfer and interaction modes between Cu and O atoms are different. This effect causes energy differences between bonding and antibonding states, resulting in the different conductivity of binary CuxO1−x compounds: semi-metallic ferromagnetic, semiconducting, and metallicity. This is the root of the inconsistent and inaccurate bandgap values of CuxO1−x compounds. These compositional, structural, and property variations provide greater freedom and scope for the development of binary CuxO1−x compounds as optoelectronic functional materials.

Circularly Polarized Organic Room Temperature Phosphorescence from Amorphous Copolymers.

Organic optoelectronic functional materials featuring circularly polarized emission and persistent luminescence represent a novel research frontier and show promising applications in data encryption, displays, biological imaging, and so on. Herein, we present a simple and universal approach to achieve circularly polarized organic phosphorescence (CPP) from amorphous copolymers by the incorporation of axial chiral chromophores into polymer chains via radical cross-linked polymerization. Our experimental data reveal that copolymers (R/S)-PBNA exhibit a maximum CPP efficiency of 30.6% and the largest dissymmetric factor of 9.4 × 10-3 and copolymers (R/S)-PNA show the longest lifetime of 0.68 s under ambient conditions. Given the CPP property of these copolymers, their potential applications in multiple information encryption and displays are demonstrated, respectively. These findings not only lay the foundation for the development of amorphous polymers with superior CPP but also expand the outlook of room-temperature phosphorescent materials.

Rewritable PEDOT Film Based on Water-Writing and Electroerasing.

Rewritable paper has greatly promoted the sustainable development of society. However, the hydrophilicity/lipophilicity of the poly(3,4-ethylenedioxythiophene) (PEDOT) film limits its application as the rewritable paper. Herein, we constructed a repeatable writing/erasing pattern on a PEDOT film (rewritable PEDOT paper) by combining wettability control, water-induced dedoping, and an electrochemical redox reaction. The treatment with a medium-polarity/high-volatility solvent (MP/HVS) adjusted the wettability of the PEDOT film (water contact angle increased from 6.5° to 146.2°), contributing to the formation of a hydrophobic writable substrate. The treatment with a high-polarity solvent (HPS) induced the dedoping of anions in the PEDOT chain, resulting in the film's color changed from blue to purple and serving as a writing process. The intrinsic electrochemical redox (elimination of color change by doping/dedoping of lithium ions in the PEDOT chain) of the PEDOT film enabled the erasing process. This writing/erasing process can be repeated at least 10 times. The patterned PEDOT film maintained excellent stability to standing diverse solvents (low-polarity solvent (LPS) and MP/HVS), high temperatures (350 °C), and irradiation of different light wavelengths (wavelengths of 365, 380, 460, 520, and 645 nm). Additionally, the conductivity of the PEDOT film was quantitatively measured (impedance: LPS, increased 8.84%; MP/HVS, decreased 6.67%; and HPS, increased 27.97%) by fabricating a micropatterned PEDOT electrode. This work will provide a method for the fabrication of PEDOT-based optoelectronic functional materials.

Investigation of mesomorphic, photophysical and gelation behavior in aroylhydrazone based liquid crystals: Observation of mesophase crossover phenomena

Five series of substituted aroylhydrazones having two alkoxy chains at 3- and 5- positions at amide end of the molecule have been synthesized; wherein each series differ from each other in terms of number and position of alkoxy chains at imine end. The compounds of first series with the single alkoxy chain at 4-position at imine end self-assembled into columnar hexagonal mesophase. The lower homologues of the series with alkoxy chains at 3- and 5- positions at imine end showed a transition from columnar hexagonal to columnar rectangular mesophase in cooling cycle while the higher homologues exhibited columnar hexagonal mesophase. The series with alkoxy chains at 3- and 4- positions exhibited columnar rectangular mesophase. All the homologues of series with alkoxy chains at 2-, 3- and 4- positions showed a transition from columnar rectangular to columnar oblique mesophase in cooling cycle. The series with alkoxy chains at 3-, 4- and 5- positions exhibited transition in columnar hexagonal mesophase. The mesophase crossover from one columnar mesophase to the other was found to be dependent on the chain length as well as on the temperature during the self-assembly process in these molecules. The temperature dependent columnar mesophase crossover has been observed for the first time in these systems. The substitution pattern showed an influence on the photophysical properties. The number and position of alkoxy chains played a critical role in the formation of gel in these molecules. These liquid crystalline gelators have application potential in organic optoelectronic functional materials and devices.

A Cathodic Electrochromic Material Based on Thick Perylene Bisimide Film with High Optical Contrast and High Stability

A Cathodic Electrochromic Material Based on Thick Perylene Bisimide Film with High Optical Contrast and High Stability

Cs2ZnSn3S8: A Sulfide Compound Realizes a Large Birefringence by Modulating the Dimensional Structure.

Birefringence, an important optical performance parameter for optoelectronic functional materials, is mainly influenced by the types of anion groups and their spatial arrangement. Inspired by the relationship between the structure and properties of chalcogenides, combined with the dimensional transformation, we successfully synthesized a sulfide compound (Cs2ZnSn3S8) with a two-dimensional layered structure and a large birefringence. The experimental results showed that, compared with Rb10Zn4Sn4S17, Cs2ZnSn3S8 achieved the structural transition from a zero-dimensional arrangement to a two-dimensional lamellar arrangement and achieved a breakthrough of birefringence from 0 to 0.12, which was determined by both experiments and first-principles calculations. These findings demonstrated that Cs2ZnSn3S8 was a potential birefringent material and provided instructions for the study of the synthesis of birefringent materials.

Preparation, modification and nonlinear optical properties of semiconducting MoS2 and MoS2/ZnO composite film

In this work, ZnO, MoS2-power, MoS2-time and MoS2/ZnO composite films with excellent linear-nonlinear absorption properties were obtained by magnetron sputtering (MS) method. The structure, nucleation process and optical properties of MoS2 and MoS2/ZnO composite films were studied. The scanning electron microscopy (SEM) images showed that the morphology of the MoS2 film transferred from granular to worm-like. This phenomenon can be attributed to that the energy of Mo and S particles increases with increasing of sputtering power. The UV–Visible absorption spectroscopy and Z-scan technique were used to study the linear-nonlinear absorption characteristics of the samples. Interestingly, it is found that nonlinear absorption behavior of the samples depends on the input energy of laser. When the input energy of laser was increased, the nonlinear absorption mechanism of the MoS2/ZnO composite film changes from saturated absorption (SA) to reverse saturated absorption (RSA). In addition, the results showed that the NLA coefficient of the MoS2/ZnO composite film was 2–5 times higher than that of the ZnO film, which means that the MoS2 film significantly promotes the NLA characteristics of the ZnO. The MoS2/ZnO composite film with controllable morphology and excellent RSA characteristics may be used to optical limiting devices which in the field of nonlinear optoelectronic functional materials.

Light-Responsive Proton Conductor: Record High Gain of Proton Conductivity Achieved by Photoinduced Electron-Transfer Strategy

Light-Responsive Proton Conductor: Record High Gain of Proton Conductivity Achieved by Photoinduced Electron-Transfer Strategy

Data-driven prediction of diamond-like infrared nonlinear optical crystals with targeting performances

Combining high-throughput screening and machine learning models is a rapidly developed direction for the exploration of novel optoelectronic functional materials. Here, we employ random forests regression (RFR) model to investigate the second harmonic generation (SHG) coefficients of nonlinear optical crystals with distinct diamond-like (DL) structures. 61 DL structures in Inorganic Crystallographic Structure Database (ICSD) are selected, and four distinctive descriptors, including band gap, electronegativity, group volume and bond flexibility, are used to model and predict second-order nonlinearity. It is demonstrated that the RFR model has reached the first-principles calculation accuracy, and gives validated predictions for a variety of representative DL crystals. Additionally, this model shows promising applications to explore new crystal materials of quaternary DL system with superior mid-IR NLO performances. Two new potential NLO crystals, Li2CuPS4 with ultrawide bandgap and Cu2CdSnTe4 with giant SHG response, are identified by this model.

Research progress in rare earth doping photoluminescent ferroelectric thin films

Rare earth doping is an important method to improve the properties of optoelectronic functional materials. Combining rare earth doping ferroelectric materials and rare earth photoluminescence can create new functional properties of ferroelectric materials. For example, choosing and using an appropriate rare earth element to be doped into a bismuth titanate ferroelectric material, the bismuth titanate will exhibit good photoluminescent properties as well as ferroelectric properties. Recently, photoluminescence properties originating from rare earth ions in oxide ferroelectric materials have attracted much attention for possible integrated photoluminescent ferroelectric device applications. In this paper, we briefly review the research status and progress of photoluminescence in rare earth photoluminescent ferroelectric materials, and we place the emphasis on our own research work in photoluminescent ferroelectric thin films such as (Bi,Eu)&lt;sub&gt;4&lt;/sub&gt;Ti&lt;sub&gt;3&lt;/sub&gt;O&lt;sub&gt;12&lt;/sub&gt;, (Bi,Er)&lt;sub&gt;4&lt;/sub&gt;Ti&lt;sub&gt;3&lt;/sub&gt;O&lt;sub&gt;12&lt;/sub&gt;, and codoped bismuth titanate thin films, and nanocomposite (Bi,Eu)&lt;sub&gt;4&lt;/sub&gt;Ti&lt;sub&gt;3&lt;/sub&gt;O&lt;sub&gt;12&lt;/sub&gt; ferroelectric thin films. Our results show that the rare earth doped bismuth titanate ferroelectric thin films exhibit good photoluminescent and ferroelectric properties due to unique compositions and layered perovskite structure, that the Eu&lt;sup&gt;3+&lt;/sup&gt; fluorescent structure probe can provide a new path for further studying the relationship between structure and property of Eu-doped ferroelectric thin films, that the rare earth photoluminescence can be used to examine the existence of morphotropic phase boundary in certain ferroelectric thin films such as Pr-doped &lt;i&gt;x&lt;/i&gt;(K&lt;sub&gt;1/2&lt;/sub&gt;Bi&lt;sub&gt;1/2&lt;/sub&gt;)TiO&lt;sub&gt;3&lt;/sub&gt;-(1－&lt;i&gt;x&lt;/i&gt;)(Na&lt;sub&gt;1/2&lt;/sub&gt;Bi&lt;sub&gt;1/2&lt;/sub&gt;)TiO&lt;sub&gt;3&lt;/sub&gt; thin films, and nanocomposite materials of ZnO nanomaterials, and that Au nanoparticles, Ag nanoparticles with Eu-doped bismuth titanate exhibit obviously enhanced photoluminescent properties.