Advanced Optoelectronic Materials Research Articles

Optimizing optoelectronic properties and energy harvesting potential of Co-doped LaFeO3: A DFT-based investigation

In response to the growing demand for advanced optoelectronic materials, this comprehensive investigation explores the effects of Co substitution on LaFeO3 using density functional theory. The study provides novel insights into the mechanical and optical properties of the doped structures. Structural stability is assessed through structural optimization, elastic stability tests, and enthalpy of formation calculations. The doped compounds exhibit significant improvements in electronic and optical properties, including enhanced thermal conductivity and reflectivity. Band structure analysis reveals metallic attributes and the Moss-Burstein effect, while magnetic property assessments indicate a decrease in magnetic moment due to Fe-Co degeneracy resulting from higher Co content. Mechanical analysis of elastic moduli B, G, and Y demonstrates enhanced durability and strength with metal-like conductivity, attributed to reduced anharmonicity. The study also highlights increased bond flexibility, suggesting potential applications in flexible electronics and UV light reflectors for effective shielding against photon radiation.

Synergistic enhancement of optical properties in erbium-doped borate glasses through copper nanoparticle incorporation

The present study investigated the impact of incorporating copper nanoparticles (CuNPs) on the optical properties of erbium-doped borate glasses. Through melt-quenching and heat treatment techniques, glasses with varying Cu2O concentrations (x = 0–5 mol%) were synthesized. Physical and structural analyses revealed that Cu ions serve as effective network modifiers. They foster the formation of a greater proportion of BO4 tetrahedra and thus enhancing glass homogeneity. Optical absorption spectra demonstrate a distinct modulation of Er3+ absorption bands with Cu2O embedding, indicating the formation of CuNPs, as validated by the emergence of surface plasmon resonance bands. This structural evolution results in a noticeable reduction in the bandgap energy, signifying improved semiconducting behavior. Judd-Ofelt analysis highlighted the profound influence of CuNPs on hypersensitive transitions, thereby affecting oscillator strength. Photoluminescence measurements revealed amplified emission in the visible red and near infrared (NIR) region, attributed to the synergistic effects of CuNPs and Er3+ ions, with 5 mol % Cu2O exhibiting the highest emission intensity. Analysis of the radiative properties validates the enhancement of the emission cross-section, gain bandwidth, optical gain and radiative transitions. These enhancements contribute to a notable increase in the branching ratio from 0.91 % to 5.41 % accompanied by an increase in the quantum efficiency from ∼79 % to ∼90 %. Moreover, decay analysis revealed a notable enhancement in lifetime from 3.03 ms to 15.74 ms, which is indicative of enhanced radiative transitions. Overall, the incorporation of CuNPs into erbium-doped borate glasses facilitates significant enhancements in physical, structural, and optical properties. This positions them as promising materials for a wide array of optoelectronic applications. This comprehensive study sheds light on the complex interplay between CuNPs and erbium-barium borate glasses, offering valuable insights for the development of advanced optoelectronic materials with enhanced performance and functionality.

End-to-End Bent Perylene Bisimide Cyclophanes by Double Sulfur Extrusion.

Bending inherently planar π-cores consisting of only six-membered rings has traditionally been challenging because a powerful transformation is required to compensate for the significant strain energy associated with bending. Herein, we demonstrate that sulfur extrusion can achieve substantial molecular bending of a perylene structure to form a substructure of a Vögtle belt, a proposed yet hitherto elusive carbon nanotube fragment. Bent perylene bisimide (PBI) derivatives were synthesized through a double-sulfur-extrusion reaction from the corresponding sulfur-containing V-shaped precursors with an internal alkyl tether. The effect of bending the inherently planar PBI core, which is a recent topic of interest for the design of advanced organic electronic and optoelectronic materials, was investigated systematically. Increasing the curvature leads to a red shift in the absorption and emission spectra, while the fluorescence quantum yields remain high. This stands in contrast with the nonemissive features of previously reported nonplanar PBI derivatives based on conjugative tethers. Detailed photophysical measurements indicated that the increasing curvature with shorter alkyl tethers (i) slightly facilitates intersystem crossing and (ii) significantly suppresses the internal conversion in the excited state of the present bent PBI derivatives. The latter characteristics originate from the restricted dynamic motion associated with the charge-transfer (CT) character between the core chromophores and the N-aryl units.

Er3+/Tm3+ co-activated core@shell nanoarchitectures: tunable upconversion luminescence and high-security anti-counterfeiting

Currently, developing advanced optoelectronic materials is of great importance to solving serious problem of fake and shoddy products. Lanthanide-doped nanomaterials are particularly suitable for addressing this issue, but limited by the realization of multiple upconverison (UC) emissions upon a single-wavelength laser excitation. Herein, it is proven that the co-dopant of blue/near-infrared (NIR)-emitting activators (Tm3+) and green/red-emitting centers (Er3+) in a particular designed core–shell nanoarchitecture allows the achievement of multiple luminescence over wide spectral region for optical security. In our study, cubic-phased NaYbF4:Tm/Er@CaF2 nanocrystals have been successfully synthesized through a layer-by-layer coprecipitation strategy, which presents visible multicolor UC luminescence and invisible NIR UC emission upon 980 nm laser excitation by just regulating the laser power and temperature. Significantly, the unique luminescent characteristics enables the designed UC nanoparticles a promising candidate for advanced anti-counterfeiting. This works offers a reference to develop advanced optoelectronic materials for practical application in optical security.

Recent advances in bioinspired vision sensor arrays based on advanced optoelectronic materials

Animals can learn about the outside world in many ways, and the visual organ is a key organ for acquiring information about the outside world. With the continuous development of intelligent technology, artificial vision techniques are becoming easier and more automated; however, the rigidity, process complexity, and complicated optical components of traditional commercial photodetectors have hindered their development in bionic vision. In recent years, a new generation of optoelectronic materials has attracted extensive research due to their simple preparation process, continuously tunable bandgap, and excellent optoelectronic properties. Two-dimensional optoelectronic materials and perovskites have become the most promising and effective optoelectronic materials for next-generation optoelectronic devices. Based on the excellent properties of next-generation optoelectronic materials, they have also triggered intensive exploration by researchers in the field of visual bionics. This paper highlights a review of the latest research progress of next-generation optoelectronic materials, including their preparation methods, working mechanisms, structural designs, and advances in the field of imaging. The applications of new generation optoelectronic materials in visual bionics by simulating biological visual structures are also described. Finally, the prospects and challenges for the development of next-generation optoelectronic materials in the emerging field of bionic vision are discussed.

Rare-earth (Nd and Eu) induced structural transformation and optical properties of brownmillerite-type Sr2ScGaO5 oxide

Towards designing of new advanced optoelectronic materials, we have explored the synthesis of a series of rare earth (RE) substituted (Nd3+ and Eu3+) perovskite compounds, Sr2-x-yNdxEuyScGaO5+δ. The phase purities of three new compounds have been verified by Rietveld refinement, FESEM, EDS and Raman spectroscopic studies. The incorporation of RE ions at A-site leads to the structural transformation from brownmillerite Sr2ScGaO5 to cubic perovskite phase and the additional charge of the RE plays a crucial role for the nonstoichiometric oxygen vacancies in the host system. Interestingly, with the increment of europium dopant percentage, the optical properties significantly changes such as the colour of the emitting light moves from dark blue to red under UV irradiation as well as a change in their decay life time profile is also observed. The density functional theory calculations have been performed to understand the effect of oxygen vacancy in the electronic properties of the title compounds.

Intramolecular charge transfer dynamics in the excited states of diphenylamine substituted 1,3,4-oxadiazole derivatives

The excited state dynamics processes of two diphenylamine substituted symmetric 1,3,4-oxadiazole derivatives in different solvents were studied through femtosecond transient absorption spectroscopy. It was revealed that in cyclohexane, the locally excited (LE) state relaxes to the intramolecular charge transfer (ICT) state within 2 ps timescale, then decays to the ground state. In tetrahydrofuran and acetonitrile, the ICT state can be stabilized via solvation, so besides the LE → ICT conversion within 1 ps, another ICT → solvent stabilized ICT (SSICT) conversion in the 1–200 ps time scale could also be observed, and eventually decay to the ground state. Whereas, ICT → SSICT process in acetonitrile is slower than that in tetrahydrofuran, which leads to radiationless deactivation dominates the ICT state deactivation process and low fluorescence quantum efficiency. These results offer a guidance to understand the relationship of low fluorescence quantum efficiency and excited state deactivation mechanism of organic π-conjugated molecules, which would be very helpful for designing new advanced opto-electronic materials.

Janus luminogens with bended intramolecular charge transfer: Toward molecular transistor and brain imaging

<h2>Summary</h2> The ingenious construction of electron donor-acceptor (D-A) systems has been proven to be the major trend for advanced performance optoelectronic materials. However, the related development is undiversified and has become stereotyped in recent years, and the explorations of innovative architecture with both prominent optoelectronic properties and innovatively coined optoelectronic mechanisms are appealing, yet significantly challenging tasks. Here, we exploit a series of unique Janus luminogens, namely TAOs, with unique charge separation in a simple five-membered mesoionic ring. TAOs, having low molecular weight (∼329 g mol⁻¹), present efficient aggregation-induced red/near-infrared emission (550–850 nm) with up to 21.5% of fluorescence quantum yield. An original mechanism, termed bended intramolecular charge transfer (BICT), is proposed to understand the fluorescence behavior. It is experimentally demonstrated that TAOs exhibit great potential for use as molecular transistors and can be efficiently utilized in living cells, bacteria, and brain imaging in a straightforward manner by using intravenous postinjection with outstanding photostability and biocompatibility.

Pluronic-loaded Silver Nanoparticles/Photosensitizers Nanohybrids: Influence of the Polymer Chain Length on Metal-enhanced Photophysical Properties.

Silver nanoparticles (AgNPs) are incredibly versatile nanostructures that more recently have been exploited to create advanced optoelectronic materials due enhancement of local magnetic field after its irradiation. However, the use of AgNPs as nanoantennas to amplify photophysical properties of close photosensitizer (PS) molecules in photodynamic therapy is still underexplored. The reason for that is the difficulty to control crucial parameters such as silver-PS distance in aqueous solution. In this scenario, here we propose a nanohybrid system where AgNP/PS distance is controlled by a thin layer of different Pluronic copolymers. The controllable distance and aqueous stability of proposed nanohybrids allow a tunable enhancement of fluorescence emission and singlet oxygen generation of some selected PS molecules. A detailed mechanism investigation demonstrated that the observed metal-enhanced photophysics is due to magnetic field enhancement close to AgNP surface (AgNP/PS distance-controlled effect) and the resonant coupling of AgNP hot electrons and HOMO-LUMO energies of the PS (AgNP/PS spectral overlap-controlled effect). These results show that the rational design in engineering new nanohybrid structures allowed photophysical improvement of PS molecules in aqueous solution in a tunable way and point out Pluronic-based AgNP/PS nanohybrids as a smart material for further developments aiming at theranostic applications in photodynamic therapy.

Supramolecular Assemblies Showing Thermally Activated Delayed Fluorescence

Supramolecular assemblies based on luminescent components offer significant advantages over their discrete counterparts, including improved quantum yields, stability, and tunability. Following interest as advanced optoelectronic materials, thermally activated delayed fluorescence (TADF) emitters are incorporated into a range of supramolecular structures. Herein, a summary of the known examples of emissive supramolecular systems that operate via a TADF mechanism with comparisons, where possible, with their discrete counterparts is presented. While the types of supramolecular structures are diverse, there are limited examples shown for each class. With the increase in photophysical performance and/or emergence of new photochemical properties upon going from molecular to supramolecular, the potential that these systems hold becomes apparent.

Giant clam inspired high-speed photo-conversion for ultraviolet optical wireless communication

Organisms have evolved the ability to manipulate light for vision, as a means to capture its energy, to protect themselves from damage, especially against ultraviolet (UV) and other high flux radiation, and for display purposes. The makeup of the structural elements used for this manipulation often discloses novel pathways for man-made photonic devices. Iridocytes in the mantle of giant clams in the Tridacninae subfamily manipulate light in many ways, e.g., as reflectors, scattering centers, and diffusers. There is, however, a void in understanding the absorption and photoluminescence (PL) emission dynamics of these cells. In turn, a profound understanding of iridocytes’ photophysics can offer the prospect for a new generation of advanced optoelectronic materials and devices. Here, the structural and optical properties of the iridocytes embedded in the mantle tissue of the Tridacna maxima are investigated and their use as a high-speed color convertor for UV photodetection, well-suited to application in UV optical wireless communication, is demonstrated.

Fine structural and photoluminescence properties of Mg2Si nanosheet bundles rooted on Si substrates

Creating vertically aligned 2D nanostructures is a promising approach to achieving advanced electronic and optoelectronic materials. In this study, Mg2Si nanosheet bundles were synthesized by Ca atom extraction from CaSi2 microwalls grown on Si substrates via thermal annealing in a MgCl2/Mg mixed vapor. The nanosheet bundle structure was modified to compound nanosheet bundles from previously reported Si nanosheet bundles. The observed Mg2Si nanosheets consist of thin Mg2Si layers, and well-defined fine-scale Mg2Si superlattice-like structures were achieved in the nanosheet bundles. In addition, the Raman scattering and photoluminescence properties were examined, and structural and electronic modifications of the nanosheet bundle compared with the bulk crystals were suggested. To obtain tailored properties and functionalities of the nanosheet bundles, structural modification of layered crystals is a useful technique.

Tailoring Nanoparticle Morphology to Match Application: Growth under Low-Intensity Polychromatic Light Irradiation Governs the Morphology and Optical Properties of Silver Nanoparticles

Silver nanoparticles (AgNPs) are incredibly versatile nanostructures that present a broad spectrum of applications, from nanomedicine to advanced optoelectronic materials. All AgNP properties stron...

Optoelectronic Properties of Monolayer Hexagonal Boron Nitride on Different Substrates Measured by Terahertz Time-Domain Spectroscopy.

Monolayer (ML) hexagonal boron nitride (hBN) is an important material in making, e.g., deep ultraviolet optoelectronic and power devices and van der Waals heterojunctions in combination with other two-dimensional (2D) electronic systems such as graphene and ML MoS. In this work, we present a comparative study of the basic optoelectronic properties of low resistance ML hBN placed on different substrates such as SiO/Si, quartz, PET, and sapphire. The measurement is carried out by using terahertz (THz) time-domain spectroscopy (TDS) in a temperature regime from 80 to 280 K. We find that the real and imaginary parts of the optical conductivity obtained experimentally for low resistance ML hBN on different substrates can fit well to the Drude–Smith formula. Thus, we are able to determine optically the key sample and material parameters (e.g., the electronic relaxation time or mobility, the carrier density, the electronic localization factor, etc.) of ML hBN. The effect of temperature on these parameters is also examined and analyzed. The results obtained from this study enable us to suggest the appropriate substrate for ML hBN based electronic and optoelectronic devices. This work is relevant to the application to a newly developed 2D electronic system as advanced electronic and optoelectronic materials.

Special issue on selected papers from the Advanced Microelectronic and Optoelectronic Materials session of the Chinese Materials Conference 2019

Special issue on selected papers from the Advanced Microelectronic and Optoelectronic Materials session of the Chinese Materials Conference 2019

Computational functionality‐driven design of semiconductors for optoelectronic applications

AbstractThe rapid development of the semiconductor industry has motivated researchers passion for accelerating the discovery of advanced optoelectronic materials. Computational functionality‐driven design is an emerging branch of material science that has become effective at making material predictions. By combining advanced solid‐state knowledge and high‐throughput first‐principles computational approaches with intelligent algorithms plus database development, experts can now efficiently explore many novel materials by taking advantage of the power of supercomputer architectures. Here, we discuss a set of typical design strategies that can be used to accelerate inorganic optoelectronic materials discovery from computer simulations: In silico computational screening; knowledge‐based inverse design; and algorithm‐based searching. A few representative examples in optoelectronic materials design are discussed to illustrate these computational functionality‐driven modalities. Challenges and prospects for the computational functionality‐driven design of materials are further highlighted at the end of the review.image

Efficient green emission from edge states in graphene perforated by nitrogen plasma treatment

Plasma functionalization of graphene is one of the facile ways to tune its doping level without the need for wet chemicals making graphene photoluminescent. Microscopic corrugations in the two-dimensional structure of bilayer CVD graphene having a quasi-free-suspended top layer, such as graphene ripples, nanodomes, and bubbles, may significantly enhance local reactivity leading to etching effects on exposure to plasma. Here, we discovered that bilayer CVD graphene treated with nitrogen plasma exhibits efficient UV-green-red emission, where the excitation at 250 nm leads to photoluminescence with the peaks at 390, 470, and 620 nm, respectively. By using Raman scattering and spectroscopic ellipsometry, we investigated doping effects induced by oxygen or nitrogen plasma on the optical properties of single- and bilayer CVD graphene. The surface morphology of the samples was studied by atomic force microscopy. It is revealed that the top sheet of bilayer graphene becomes perforated after the treatment by nitrogen plasma. Our comprehensive study indicates that the dominant green emission is associated with the edge defect structure of perforated graphene filled with nitrogen. The discovered efficient emission appearing in nitrogen plasma treated perforated graphene may have a significant potential for the development of advanced optoelectronic materials.

Thermally Induced Disorder-Order Phase Transition of Gd2Hf2O7:Eu3+ Nanoparticles and Its Implication on Photo- and Radioluminescence.

Crystal structure has a strong influence on the luminescence properties of lanthanide-doped materials. In this work, we have investigated the thermally induced structural transition in Gd2Hf2O7 (GHO) using Eu3+ ions as the spectroscopic probe. It was found that complete phase transition from the disordered fluorite phase (DFP) to the ordered pyrochlore phase (OPP) can be achieved in GHO with the increase of annealing temperature from 650 → 1100 → 1300 °C. OPP is the more stable structural form for the GHOE nanoparticles (NPs) annealed at a higher temperature based on the energy calculation by density functional theory (DFT). The asymmetry ratio of the GHOE-650 NPs was the highest, whereas the quantum yield, luminescence intensity, and lifetime values of the GHOE-1300 NPs were the highest. Emission intensity of Eu3+ ions increases significantly with the phase transition from the DFP to OPP phase and is attributed to the higher radiative transition rate (281 s–1) of the 5D0 level of the Eu3+ ion in the environment with relatively lower symmetry (C2v) because of the increase of crystal size. As the structure changes from DFP to OPP, radioluminescence showed tunable color change from red to orange. The Eu3+ local structure obtained from DFT calculation confirmed the absence of inversion symmetry in the DFP structure, which is consistent with the experimental emission spectra and Stark components. We also elucidated the host to dopant optical energy transfer through density of states calculations. Overall, our current studies present important observations for the GHOE NPs: (i) thermally induced order–disorder phase transition, (ii) change of point group symmetry around Eu3+ ions in the two phases, (iii) high thermal stability, and (iv) tunability of radioluminescent color. This work provides fundamental understanding of the relationship between the crystal structure and photophysical properties of lanthanide-doped materials and helps design a strategy for advanced optoelectronic materials.

Tunable Physical States and Optical Properties of Bola-Amphiphilic Oligo-(p-phenyleneethynylene)-Based Supramolecular Networks Assisted by Functional Group Modulation

Structural understanding and correlation of physical properties of supramolecular networks can lead to improved design strategies for advanced optoelectronic materials. Herein, we demonstrate via single-crystal X-ray diffraction (SCXRD) analysis how end groups (ester and acid) of bola-amphiphilic oligo-(p-phenyleneethynylenes) (OPEs) lead to different supramolecular network formations and also generate selective polymorphism and mechanochromic luminescence in OPE-Cgly-A and OPE-Cgly-E, respectively. OPE-Cgly-E and OPE-Cgly-A have the same π-conjugated backbones with bistriethyleneglycol side chains, only differing in possessing end-capped ester and acid groups, respectively. OPE-Cgly-E has a less densely packed structure than OPE-Cgly-A. This leads to exclusive mechanochromic behavior in OPE-Cgly-E, whereas OPE-Cgly-A generates reversible polymorphic structures which are not present in OPE-Cgly-E. Density functional theoretical calculations reveal that breakage of weak supramolecular interactions in OPE-C...

Involving Synergy of Green Light and Acidic Responses in Control of Unimolecular Multicolor Luminescence.

Conversion of multicolor luminescence is one of desirable goals in study and development of next-generation molecular emitters, whereas involving visible light into the control of the above-mentioned ability has been poorly addressed due to the need of a relatively complicate molecular design. In this work, we present a novel dyad with a linkage of 4-piperazinyl-1,8-naphthalimide and cyanostyryl-modified azulene moiety, upon which the luminescence signal can be orthogonally controlled by protonation and green light irradiation. The superior features of the protonation induced excited state energy alteration, followed by green light driven photoisomerization led to a progressive luminescent color conversion among blue, yellow and green at the single molecular level. This strategy may bring in novel insights for preparing advanced function-integrated optoelectronic materials.