Synthesis and characterization of novel donor–acceptor type electrochromic polymers containing diketopyrrolopyrrole as an acceptor and propylenedioxythiophene or indacenodithiophene as a donor

A range of low band gap donor–acceptor conjugated polymers (P1–P3) with backbones composed of diketopyrrolopyrrole (DPP), propylenedioxythiophene (ProDOT) and indacenodithiophene (IDT) units were designed and synthesized using the Stille coupling reaction. The optical, electrochemical and electrochromic properties of the resultant polymers were thoroughly characterized. These polymers showed exceptional solubility in common organic solvents and displayed thermal stability at a high temperature. The optical and electrochemical measurements revealed slight variations in the maximum absorptions and oxidation peaks depending on the intrinsic D–A ratio in each polymer, and narrow band gaps lower than 1.60 eV were found for these polymers. Upon oxidation, the polymer films exhibit distinct color changes (pale violet-red to dark gray for P1, rosy brown to silver for P2, atrovirens to light grey for P3) in the VIS and NIR regions. Moreover, the electrochromic switching studies indicated that these polymers have favorable switching properties, such as rapid response speed and high optical contrast and coloration efficiency, and are outstanding candidates for electrochromic applications.

Three novel D–A type conjugated copolymers were prepared, illustrating excellent electrochromic properties, such as desirable color switches, high optical contrasts, fast response time, and high color efficiency.     

Implementing the donor–acceptor approach in electronically conducting copolymers via electropolymerization

Electropolymerization has become a convenient method for synthesizing and characterizing complex organic copolymers having intrinsic electronic conductivity, including the donor (D)–acceptor (A) class of electronically conducting polymers (ECPs). This review begins with an introduction to the electrosynthesis of common second-generation ECPs. The information obtainable from electroanalytical studies, charge carriers such as polarons (positive and negative) and bipolarons (positive and negative) and doping will be discussed. The evolutionary chain of ECPs is then presented. ECPs comprising electron-rich D and electron-deficient A moieties have been shown to possess intrinsic electronic conductivity and unique optical and electronic properties. They are third generation ECPs and electropolymerization of mixtures of D and A leads to stoichiometrically controlled block copolymers. These D–A type ECPs are discussed on the basis of selected representative materials. Since the discovery of electropolymerization as a powerful tool to synthesize copolymers of conjugated monomers with a pre-determined ratio of D and A repeat units present in the polymer, the field of D–A type ECPs has grown considerably and the literature available since 2004 to 2021 is summarized and tabulated. Electronic and optical properties of the materials determined by computational chemistry are presented. The data obtained from electrochemical and optical methods are compared with those obtained from computational methods and reasons for discrepancies are given. The literature on the concept of electropolymerization extended to synthesizing triblock and many-block copolymers is reviewed. Finally, applications of D–A polymers in optoelectronic devices (organic solar cells and field-effect transistors) and in bio-imaging are explained quoting appropriate examples.

Electropolymerization has become a convenient method for synthesizing and characterizing complex organic copolymers having intrinsic electronic conductivity, including the donor (D)–acceptor (A) class of electronically conducting polymers (ECPs).     

Theoretical study of D–A′–π–A/D–π–A′–π–A triphenylamine and quinoline derivatives as sensitizers for dye-sensitized solar cells

We have designed four dyes based on D–A′–π–A/D–π–A′–π–A triphenylamine and quinoline derivatives for dye-sensitized solar cells (DSSCs) and studied their optoelectronic properties as well as the effects of the introduction of alkoxy groups and thiophene group on these properties. The geometries, single point energy, charge population, electrostatic potential (ESP) distribution, dipole moments, frontier molecular orbitals (FMOs) and HOMO–LUMO energy gaps of the dyes were discussed to study the electronic properties of dyes based on density functional theory (DFT). And the absorption spectra, light harvesting efficiency (LHE), hole–electron distribution, charge transfer amount from HOMO to LUMO (Q_CT), D index, H_CT index, S_m index and exciton binding energy (E_coul) were discussed to investigate the optical and charge-transfer properties of dyes by time-dependent density functional theory (TD-DFT). The calculated results show that all the dyes follow the energy level matching principle and have broadened absorption bands at visible region. Besides, the introduction of alkoxy groups into triarylamine donors and thiophene groups into conjugated bridges can obviously improve the stability and optoelectronic properties of dyes. It is shown that the dye D4, which has had alkoxy groups as well as thiophene groups introduced and possesses a D–π–A′–π–A configuration, has the optimal optoelectronic properties and can be used as an ideal dye sensitizer.

We have designed four dyes based on D–A′–π–A/D–π–A′–π–A triphenylamine and quinoline derivatives for DSSCs and studied their optoelectronic properties as well as the effects of the introduction of alkoxy groups and thiophene group on the properties.     

Improved photoelectric performance of all-inorganic perovskite through different additives for green light-emitting diodes

The exceptional optical and electronic properties of all-inorganic cesium lead bromide (CsPbBr₃) perovskite make it an ideal new optoelectronic material, but low surface coverage limits its performance. The morphological characteristics of thin films have a great influence on the performance of perovskite light emitting diodes, especially at low coverage, and an inhomogeneous surface will lead to current leakage. To tackle this problem, the widespread adoption of composite layers including polymers poly(ethylene oxide) (PEO) and organic insulating poly(vinylpyrrolidone) (PVP) and all-inorganic perovskites is an effective way to increase the surface coverage and uniformity of perovskite films and improve the performance of perovskite light emitting devices. In our work, the perovskite thin films are investigated by using PEO and PVP dual additives, and the optimized CsPbBr₃–PEO–PVP LED with maximum luminance, current efficiency, and external quantum efficiency of 2353 cd m⁻² (at 7.2 V), 2.14 cd A⁻¹ (at 6.5 V) and 0.85% (at 6.5 V) was obtained. This work indicates that the method of using additives is not only the key to enhancing the quality of perovskite thin film, but also the key to achieving a higher performance perovskite LED.

Improving the performance of all-inorganic CsPbBr₃–PEO–PVP-based LEDs with the structure of ITO/PEDOT:PSS/Perovskite/TPBI/LiF/Al.     

One-step synthesis of ultra-long silver nanowires of over 100 μm and their application in flexible transparent conductive films

Silver nanowires (AgNWs) >100 μm and even 160 μm in length have been synthesized using a facile and rationally designed solvothermal method by heating preservation at 150 °C. The length of the as-synthesized AgNWs is over 4–5 times longer than those previously reported, while the diameter range is from 40 nm to 85 nm. A transparent conducting film (TCF) was fabricated using hydroxyethyl cellulose (HEC) as the adhesive polymer, and it achieved exceptional and stable optoelectronic properties. Its low sheet resistance of ∼19 Ω sq⁻¹ (on polyethylene terephthalate, PET) and high optical transmittance of ∼88% are superior to that of expensive indium tin oxide (ITO) films. More significantly, the AgNW network demonstrates excellent adhesion to PET substrates. This study indicates that ultra-long silver nanowires can serve as an alternative to ITO, which also demonstrates its potential application in flexible electronic devices.

Ultra-long silver nanowires (100–160 μm) were applied in flexible transparent conductive films showing low sheet resistance and high optical transmittance.     

Size engineering optoelectronic features of C,Si and CSi hybrid diamond-shaped quantum dots

Based on the density functional theory and many-body ab initio calculations, we investigate the optoelectronic properties of diamond-shaped quantum dots based graphene, silicene and graphene–silicene hybrid. The HOMO–LUMO (H–L) energy gap, the exciton binding energy, the singlet–triplet energy splitting and the electron–hole overlap are all determined and discussed. Smaller nanostructures show high chemical stability and strong quantum confinement resulting in a significant increase in H–L gap and exciton binding energy. On the other hand, the larger configurations are reactive which implies characteristics favorable to possible electronic transport and conductivity. In addition, the typically strong splitting between singlet and triplet excitonic states and the big electron–hole overlap make these QDs emergent systems for nanomedicine applications.

Based on the density functional theory and many-body ab initio calculations, we investigate the optoelectronic properties of diamond-shaped quantum dots based graphene, silicene and graphene–silicene hybrid.     

Nanopatterned silk fibroin films with high transparency and high haze for optical applications

Simultaneous high transparency and high haze are necessary for high-efficiency optical, photonic, and optoelectronic applications. However, a typical highly transparent film lacks high optical haze or vice versa. Here, we report a silk fibroin-based optical film that exhibits both ultrahigh optical transparency (>93%) and ultrahigh optical transmission haze (>65%). Also, in combination with the soft lithography method, different nanostructured silk fibroin films are presented and their optical properties are characterized as well. To demonstrate its exceptional performance in both high transmission and high optical haze, we combine the silk fibroin with the silicon photodiode and show that the efficiency can be increased by 6.96% with the silk fibroin film without patterns and 14.9% with the nanopatterned silk fibroin film. Silk provides excellent mechanical, optical, and electrical properties, and the reported high-performance silk fibroin can enable the development of next-generation biocompatible eco-friendly flexible electronic and optical devices.

Nanopatterned silk fibroin-based optical films exhibit both ultrahigh optical transparency and ultrahigh optical transmission haze.     

First-principles prediction of chemically functionalized InN monolayers: electronic and optical properties

In this work, we consider the electronic and optical properties of chemically functionalized InN monolayers with F and Cl atoms (i.e., F–InN–F, F–InN–Cl, Cl–InN–F, Cl–InN–Cl monolayers) using first-principles calculations. The adsorption of the F and Cl atoms on the InN monolayer is determined to be chemically stable and the F–InN–F monolayer is most likely to occur. Our calculations show that the chemical functionalization with Cl and F atoms not only breaks the planar structure of InN monolayer but also increases its band gap. By using both Perdew, Burke, and Ernzerhof (PBE) and the Heyd–Scuseria–Ernzerhof (HSE06) hybrid functionals, all four models of chemically functionalized InN monolayers are found to be semiconductors with direct energy gaps and these gaps depend on the constituent species. When the spin–orbit coupling (SOC) was included, the energy gap of these monolayers was reduced and an energy splitting was found at the Γ-point in the valence band. Chemically functionalized InN monolayers can absorb light in a wide region, especially the F–InN–F and Cl–InN–F monolayers have a strong ability to absorb the visible light. Our findings reveal that the chemically functionalized InN monolayers have potential applications in next-generation optoelectronic devices.

In this work, we consider the electronic and optical properties of chemically functionalized InN monolayers with F and Cl atoms (i.e., F–InN–F, F–InN–Cl, Cl–InN–F, Cl–InN–Cl monolayers) using first-principles calculations.     

First principles study of electronic and optical properties and photocatalytic performance of GaN–SiS van der Waals heterostructure

The vertical stacking of two-dimensional materials via van der Waals (vdW) interaction is a promising technique for tailoring the physical properties and fabricating potential devices to be applied in the emerging fields of materials science and nanotechnology. The structural, electronic and optical properties and photocatalytic performance of a GaN–SiS vdW heterostructure were explored using first principles calculations. The most stable stacking configuration found energetically stable, possesses a direct staggered band gap, which is crucial for separating photogenerated charged carriers in different constituents and is efficacious for solar cells. Further, the charge transfer occurred from the SiS to GaN layer, indicating that SiS exhibits p-type doping in the GaN–SiS heterobilayer. Interestingly, a systematic red-shift was observed in the optical absorption spectra of the understudy heterobilayer system. Moreover, the conduction band edge and valence band edge of the monolayers and corresponding heterostructure were located above and below the standard redox potentials for photocatalytic water splitting, making these systems promising for water dissociation for hydrogen fuel production. The results provide a route to design the GaN–SiS vdW heterostructure for the practical realization of next-generation light detection and energy harvesting devices.

The two dimensional GaN–SiS van der Waals heterostructure is a promising candidate for optoelectronic and photocatalytic water splitting.     

Theoretical study of a p–n homojunction SiGe field-effect transistor via covalent functionalization

p–n homojunctions are superior to p–n heterojunctions in constructing nanoscale functional devices, owing to the excellent crystallographic alignment. We tune the electronic properties of monolayer siligene (SiGe) into p/n-type via the covalent functionalization of electrophilic/nucleophilic dopants, using ab initio quantum transport calculations. It is found that the n-type doping effect of K atoms is stronger than that of benzyl viologen (BV) molecule on the surface of SiGe monolayer, owing to the strong covalent interaction. Both of p-type 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ)-adsorbed and n-type 4 K-adsorbed SiGe systems show enhanced optical absorption in the infrared region, indicating their promising applications in infrared optoelectronic devices. By spatially adsorbing F4TCNQ molecule and K atoms on the source and drain leads, respectively, we designed a p–n homojunction SiGe field-effect transistor (FET). It is predicted that the built F4TCNQ-4K/SiGe FET can meet the requirements for high-performance (the high current density) and low-power (low subthreshold swing (SS)) applications, according to the International Technology Roadmap for Semiconductors in 2028. The present study gains some key insights into the importance of surface functionalization in constructing p–n homojunction electronic and optoelectronic devices based on monolayer SiGe.

p–n homojunctions are superior to p–n heterojunctions in constructing nanoscale functional devices, owing to the excellent crystallographic alignment.     

Polyfluorene-based white light conjugated polymers incorporating orange iridium(iii) complexes: the effect of steric configuration on their photophysical and electroluminescent properties

Different kinds of polyfluorene-based white light conjugated polymers with phosphorescent iridium(iii) complexes as orange emission groups and polyfluorene as blue emission groups were designed and synthesized. On the basis of adjusting substituent positions on iridium(iii) complexes, the conjugated polymers exhibited different steric configurations, i.e. hyperbranched and linear structures, and the PL emission peaks of iridium(iii) complexes had a significant change. Compared to linear conjugated polymers, hyperbranched white light conjugated polymers showed the best thermal stability and film forming properties. The white light single-emissive-layer devices with simplified configuration were also prepared in a wet process. All these devices realized good electroluminescence, especially the hyperbranched conjugated polymers in which the roll off phenomenon at high current density was effectively suppressed. Furthermore, EL spectra of hyperbranched polymers exhibited good stability at different driving voltages. A maximum luminance of 2469 cd m⁻², a maximum current efficiency of 1.73 cd A⁻¹ and the commission internationale de l''Eclairage (CIE) coordinates of (0.25, 0.23) showed white light was achieved from the HPF-Ir10 devices.

Owing to large steric hindrance, white light hyperbranched conjugated polymers exhibited the best electroluminescent performance with suppression of triplet–triplet annihilation.     

Structural,electronic and optical properties of pristine and functionalized MgO monolayers: a first principles study

In this paper, we present a detailed investigation of the structural, electronic, and optical properties of pristine, nitrogenated, and fluorinated MgO monolayers using ab initio calculations. The two dimensional (2D) material stability is confirmed by the phonon dispersion curves and binding energies. Full functionalization causes notable changes in the monolayer structure and slightly reduces the chemical stability. The simulations predict that the MgO single layer is an indirect semiconductor with an energy gap of 3.481 (4.693) eV as determined by the GGA-PBE (HSE06) functional. The electronic structure of the MgO monolayer exhibits high sensitivity to chemical functionalization. Specifically, nitrogenation induces metallization of the MgO monolayer, while an indirect–direct band gap transition and band gap reduction of 81.34 (59.96)% are achieved by means of fluorination. Consequently, the functionalized single layers display strong optical absorption in the infrared and visible regimes. The results suggest that full nitrogenation and fluorination may be a quite effective approach to enhance the optoelectronic properties of the MgO monolayer for application in nano-devices.

In this paper, we present a detailed investigation of the structural, electronic, and optical properties of pristine, nitrogenated, and fluorinated MgO monolayers using ab initio calculations.     

p-MoS2/n-InSe van der Waals heterojunctions and their applications in all-2D optoelectronic devices

A library of two-dimensional (2D) semiconductors with different band gaps offers the construction of van der Waals (vdWs) heterostructures with different band alignments, providing a new platform for developing high-performance optoelectronic devices. Here, we demonstrate all-2D optoelectronic devices based on type-II p-MoS₂/n-InSe vdWs heterojunctions operating at the near infrared (NIR) wavelength range. The p–n heterojunction diode exhibits a rectification ratio of ∼10² at V_ds = ±2 V and a turn-on voltage of ∼0.8 V. Under a forward bias exceeding the turn-on voltage and a proper positive back-gate voltage, the all-2D vdWs heterojunction diode exhibits an electroluminescence with an emission peak centered at ∼1020 nm. Besides, this p-MoS₂/n-InSe heterojunction shows a photoresponse at zero external bias, indicating that it can serve as a photodiode working without an external power supply. The as-demonstrated all-2D vdWs heterojunction which can work as both a light-emitting diode and a self-powered photodetector may find applications in flexible wear, display, and optical communication fields, etc.

A library of 2D semiconductors are prepared providing a new platform for developing high-performance optoelectronic devices. All-2D optoelectronic devices based on type-II p-MoS₂/n-InSe vdWs heterojunctions operate at the near-IR wavelength range.

Optoelectronic devices, including light-emitting diodes (LEDs), lasers, solar cells, and photodetectors, have been extensively studied, because of their potential applications in illumination, communication, energy, and healthcare. With the growing demand for advanced functional optoelectronic devices, such as flexible wear and display, faster communications between devices on microchips, etc., next-generation optoelectronic devices require new optoelectronic materials with characteristics superior to those currently in use. Candidate materials must be flexible for wearable devices, transparent for interactive displays, and efficient for light-emitting and/or solar cells. The emergence of two-dimensional (2D) materials, with atomic layers combined by van der Waals (vdWs) force, has brought a new era to the development of optoelectronic devices, because of their unique structural and physical properties, such as strong light–matter interactions, flexibility, vdWs assembly, etc.^1–6 In addition, the extensive library of 2D materials offers the formation of vdWs heterostructures with a broad range of band alignments, and resultant interfacial physical properties, providing a new platform for developing high-performance optoelectronic devices.^7–12 Specifically, heterojunctions with a type-II band alignment, where the valence band maximum and the conduction band minimum reside in two separate materials, have enabled efficient electron–hole separation at the interface. Therefore type-II 2D heterojunctions have been used in high-performance 2D optoelectronic devices such as photodetectors, photovoltaic devices, and LEDs.^6,13,14 The near-infrared (NIR) optoelectronic devices can be used in a wide range of applications, including night vision, optical communication, and computing. However, due to the limit of 2D materials with a band gap in the NIR range, NIR optoelectronic devices based on type-II vdWs heterojunction are rarely studied.InSe, a group III–VI layered semiconductor with a direct band-gap of 1.25 eV for few-layer one (>10L),¹⁵ has gained various interests due to its unique optical, electronic, and mechanical properties, targeting the applications in memory devices, optical sensors, and thermoelectric implements.^16–19 As a direct band-gap semiconductor, which has an efficient electron–hole radiative recombination rate, the few-layer InSe is also suitable for making NIR optoelectronic devices. Recently, high-performance broadband few-layer InSe photodetectors from the visible to NIR region have been realized.^17–19 Few-layer MoS₂ is with an indirect band-gap of ∼1.28 eV, which can form a type-II band alignment with few-layer InSe. Under a forward bias, the injected carriers recombine to emit photons in the InSe region that has a narrower direct band gap.Here, we present type-II vdWs heterojunctions based on the n-type few-layer InSe and p-type MoS₂ nanoflakes (Fig. 1). The heterostructure was stacked and encapsulated by top and bottom hexagonal boron nitride (hBN) nanoflakes using a spatially controlled dry transfer method,²⁰ which guarantees the clean heterojunction interfaces and prevents contaminations from any polymers or solutions. The p-MoS₂/n-InSe heterojunctions exhibit typical diode characteristic with a rectification ratio of ∼10² at V_ds = ±2 V, and a low turn-on voltage of ∼0.8 V. Under a forward bias exceeding the turn-on voltage, the vdWs heterojunction shows strong NIR electroluminescence (EL) centered at ∼1020 nm, corresponding to the band-edge emission of the InSe. Under the simulated solar illumination, the heterojunction also exhibits typical photovoltaic behavior. Photocurrent mapping at zero external bias indicates that the photoresponse of the diode is from the heterojunction region. Our work provides a new feasible structure of all-2D NIR optoelectronic devices for flexible and microchip communication applications.Open in a separate windowFig. 1Schematic illustration of the p-MoS₂/n-InSe vdWs heterostructure.     

Strain-tunable electronic and optical properties of BC3 monolayer

Two-dimensional layered nanostructures with unique electronic and optical properties may hold great potential in nanoelectronics and optoelectronics applications. In this work, structural stability, elastic, electronic, and optical properties of BC₃ monolayers have been investigated using a first-principles study. The BC₃ monolayer can be regarded as a series of hexagonal C rings with the connections of B atoms, which has been tested to be highly dynamically stable. The in-plane stiffness is 316.2 N cm⁻¹, potentially rivalling graphene. A screened hybrid density functional HSE06 is used to calculate the electronic and optical properties. It is found that the BC₃ monolayer is an indirect band gap semiconductor with a moderate gap energy of 1.839 eV. Spatial charge distribution to the valence band maximum and the conduction band minimum is analyzed to explore the origin of indirect band gap features. By calculating the complex dielectric function, optical properties considered as excitonic effects are discussed. Besides, the effects of various in-plane strains on electronic and optical properties are explored. Our results of good structural stability, moderate and tunable band gap, and strain-controllable optical properties suggest that the BC₃ monolayer holds great promise in the applications of nanoelectronic and optoelectronic devices.

The BC₃ monolayer holds great promise in the applications of nanoelectronic and optoelectronic devices due to its good structural stability, moderate and tunable band gap, and strain-controllable optical properties.     

Synthesis and characterization of novel donor–acceptor type neutral green electrochromic polymers containing an indolo[3,2-b]carbazole donor and diketopyrrolopyrrole acceptor

Indolocarbazole bearing donor–acceptor type polymers have rarely been reported in the electrochromic field despite them having considerable development in the applications of organic photoelectric devices. In this paper, two novel soluble electrochromic polymers, namely PDTCZ-1 and PDTCZ-2, were prepared by chemical polymerization including indolo[3,2-b]carbazole (IC) units as the donor, diketopyrrolopyrrole (DPP) units as the acceptor and bithiophene units as the bridging group. Through diverse characterization techniques such as cyclic voltammetry (CV), scanning electron microscopy (SEM), UV-vis spectroscopy and thermogravimetric analysis (TGA), it was found that PDTCZ-1 and PDTCZ-2 exhibited saturated green in the neutral state and pale green in the oxidized state with optical band gaps of 1.44 eV and 1.39 eV, respectively, as well as demonstrating fast switching speed, satisfactory coloration efficiency and favorable thermal stability. In addition, the proportion of donors to acceptors definitely exerted an influence on the electrochromic properties of the polymers. As the thiophene/IC/DPP ratio changed from 4/3/1 (PDTCZ-1) to 5/4/1 (PDTCZ-2), meaning an increase of the donor ratio, the polymer showed a reduced onset oxidation potential, decreased optical band gap and different dynamic parameters. The positive results suggest that PDTCZ-1 and PDTCZ-2 could be promising candidates as neutral green electrochromic materials and deserve more attention and penetrating research.

Two novel neutral green D–A type conjugated polymers were synthesized, illustrating satisfactory electrochromic properties, such as low band gaps, desirable color switches, excellent solubility and favorable thermal stability.     

Enhanced optical,magnetic and hydrogen evolution reaction properties of Mo1−xNixS2 nanoflakes

Due to exceptional electronic, optoelectronic and catalytic properties, MoS₂ has attracted extensive research interest in various applications. In the present scenario, the exploitation of noble-metal-free catalysts for hydrogen evolution is of great interest. Herein, we report the structural, optical, magnetic and electrocatalytic properties of pure and nickel-substituted MoS₂ nanostructures synthesized by the hydrothermal method. X-ray diffraction (XRD) analysis reveals that all samples exhibit the hexagonal structure of MoS₂ and the formation of NiS₂ at higher concentrations of nickel. Vibrating sample magnetometer (VSM) measurements of the Mo_1−xNi_xS₂ nanostructures show a hysteresis loop at room temperature with a higher saturation magnetization for 1% Ni-substituted MoS₂ nanostructures, confirming the ferromagnetic behaviour of the sample. The indirect-to-direct band gap transition of few-layered nanostructures was confirmed by the optical absorption spectrum showing bands in the 600–700 nm and 350–450 nm regions. This study also highlights the excitation wavelength-dependent down- and up-conversion photoluminescence of the as-synthesized samples, providing new horizons for the design of MoS₂-based optical and spintronic devices. The electrocatalytic effect of 3% Ni-substituted MoS₂ nanostructures has been found to be higher than that of other deposit concentrations as it corresponds to the efficient hydrogen evolution reaction (HER).

Hydrothermal synthesis of Mo_1–xNi_xS₂ nanostructures as efficient catalyst for hydrogen evolution reaction.     

Well-defined benzoxazine/triphenylamine-based hyperbranched polymers with controlled degree of branching

Well-defined thermally polymerizable hyperbranched polymers (TPA–BZs) containing various numbers of triphenylamine (TPA) and benzoxazine (BZ) units have been prepared using a “click-like” reaction concept, through one-pot Mannich condensations of 4-(bis(4-aminophenyl)amino)phenol (TPA–2NH₂–OH, as the AB₂ branching groups), aniline (as the focal groups), CH₂O, and phenol in 1,4-dioxane, with a unique feeding approach. Two design strategies for the chemical construction were applied: (i) simple hyperbranched TPA–BZs, such as those containing one or three TPA units, developed from the focal or the terminal group direction to form the resultant monomers; (ii) three dendritic TPA–BZs containing four TPA units possessing different degrees of branching (DBs) for the conformation study. The exothermic temperature for the dendritic TPA–BZs decreased upon increasing the DB. The bathochromic shifts of the dendritic TPA–BZs increased upon increasing the number of TPA units, in UV-Vis absorption and PL emission spectra, presumably because of an increase in the effective conjugation length. In addition, the polymerized dendritic TPA–BZ DG1 possessed thermal properties superior to those of the hyperbranched TPA–BZ polybenzoxazines, possibly because the segmental mobility in the polymer network was restricted by the dendrimer core group and because of its symmetrical construction. The hyperbranched TPA–BZ possessed unique photophysical properties, suggesting potential applications in optoelectronic devices.

Different well-defined benzoxazine/triphenylamine based hyperbranched polymers with controlled degree of branching were prepared and discussed.     

Synthesis,chiroptical properties,and self-assembled nanoparticles of chiral conjugated polymers based on optically stable helical aromatic esters

By Suzuki coupling reaction, three pairs of chiral conjugated polymers with optically stable helical aromatic ester subunits as the main-chain were designed and synthesized. Polymers (+)-P-P1 and (−)-M-P1, (+)-P-P2 and (−)-M-P2 showed strong fluorescence emission, strong mirror image CD and circularly polarized luminescence (CPL) signals in THF. For polymers (+)-P-P3 and (−)-M-P3, containing the tetraphenylethene (TPE) moiety, they not only showed obvious aggregation induced enhancement emission (AIEE), but also exhibited mirror image CD signals and aggregation-induced enhancement CPL signals in THF–water mixtures. Moreover, (+)-P-P3 and (−)-M-P3 could also form chiral nanoparticles by solvent evaporation induced self-assembly. Interestingly, it was further found that the size of the nanoparticles could be controlled by the changing of THF/water ratio, and their CPL properties were also shown.

Chiral conjugated polymers based on helical aromatic esters and self-assembled nanoparticles were prepared and showed strong fluorescence and CPL properties.     

Unraveling the microstructural and optoelectronic properties of solution-processed Pr-doped SrSnO3 perovskite oxide thin films

The inorganic stannous-based perovskite oxide SrSnO₃ has been utilized in various optoelectronic applications. Facilitating the synthesis process and engineering its properties, however, are still considered challenging due to several aspects. This paper reports on a thorough investigation of the influence of rare-earth (praseodymium) doping on the microstructural and optoelectronic properties of pure and Pr-doped SrSnO₃ perovskite oxide thin films synthesized by a two-step simple chemical solution deposition route. Structural analysis indicated the high quality of the obtained phase and the alteration generated from the insertion of impurities. Surface scanning illustrated the formation of homogenous and crack-free SrSnO₃ thin films with a nanorod morphology, with an augmentation in size as the dopant ratios increased. Optical properties analysis showed an enhancement in the samples optical absorption with wide-range bandgap tuning. First-principles calculations revealed the exchange interactions between the 3d–4f states and their impact on the electronic properties of the pristine material. Hall-effect measurements revealed an immense decrement in the resistivity of the films upon increment of doping ratios, passing from 7.3 × 10⁻² Ω cm for the undoped sample to 4.8 × 10⁻² Ω cm for 7% Pr content, while a reverse trend was observed on the carrier mobility, rising from 2.5 to 7.6 cm² V⁻¹ s⁻¹ for 7% Pr content. The results emphasized the efficiency of the simple synthesis route to produce high-quality samples. The current findings will contribute to paving the way towards expanding the utilization of simple and cost-effective chemical solution deposition methods for the fast and large area growth of stannous-based perovskite oxides for optoelectronic applications.

Unraveling the optical, electronic and electrical properties of high-quality nanorod morphology spray-coated Pr-doped SrSnO₃ perovskite oxide thin films.     

Spin–orbit coupling effect on electronic,optical, and thermoelectric properties of Janus Ga2SSe

In this paper, we investigate the electronic, optical, and thermoelectric properties of Ga₂SSe monolayer by using density functional theory. Via analysis of the phonon spectrum and ab initio molecular dynamics simulations, Ga₂SSe is confirmed to be stable at room temperature. Our calculations demonstrate that Ga₂SSe exhibits indirect semiconductor characteristics and the spin–orbit coupling (SOC) effect has slightly reduced its band gap. Besides, the band gap of Ga₂SSe depends tightly on the biaxial strain. When the SOC effect is included, small spin–orbit splitting energy of 90 meV has been found in the valence band. However, the spin–orbit splitting energy dramatically changes in the presence of biaxial strain. Ga₂SSe exhibits high optical absorption intensity in the near-ultraviolet region, up to 8.444 × 10⁴ cm⁻¹, which is needed for applications in optoelectronic devices. By using the Boltzmann transport equations, the electronic transport coefficients of Ga₂SSe are comprehensively investigated. Our calculations reveal that Ga₂SSe exhibits a very low lattice thermal conductivity and high figure of merit ZT and we can enhance its ZT by temperature. Our findings provide further insight into the physical properties of Ga₂SSe as well as point to prospects for its application in next-generation high-performance devices.

In this paper, we investigate the electronic, optical, and thermoelectric properties of Ga₂SSe monolayer by using density functional theory.